A Plant Monograph

on Onion

(Allium cepa L.)

Prepared by Hridaya Shrestha Roll No. 11/2004

Submitted to The School of Pharmaceutical and Biomedical Sciences

Pokhara University Simalchaur, Pokhara, Nepal.

2007

Acknowledgement

I would like to thank Prof. Dr. Purusotam Basnet, the Dean, Faculty of Science and Technolgy, Pokhara University (PU) who was the first who advise me to utilize my leisure time on writing a plant monograph. I wish to express my gratitude to Prof. Dr. Natasa Skalko Basnet, the Programme Director of The School of Pharmaceutical and Biomedical Sciences, PU for her frequent expressing of interest on the progress of my work on monograph writing. Special thanks are due to Mr. Hari Prasad Devkota, Teaching Associate, The School of Pharmaceutical and Biomedical Sceinces, PU for his guidance and support.Thanks are also due to all the librarian staffs of the Pokhara University Library for their help and providing me available facilities. I would also like to thank the librarians of Pokhara Forestry Campus, Tribhuvan University for providing me facilities available there. Finally I wish to express my warmest and deepest gratitude to my family as well for their support as for their patience during this work.

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Table of Contents 1. Synonyms and common names .............................................................................................. 5

1.1. Scientific Name: .............................................................................................................. 5 1.2. Local Names.................................................................................................................... 5 1.3. Traditional Names ........................................................................................................... 5 1.4. Language Names ............................................................................................................. 5 1.5. Pharmacopoel Name........................................................................................................ 6

2. Introduction ............................................................................................................................ 6 2.1. Origin............................................................................................................................... 6 2.2. History ............................................................................................................................. 7 2.3. Mythological Importance ................................................................................................ 8 2.4. Social Value .................................................................................................................... 8 2.5. Genetic characters ........................................................................................................... 9

3. Classification .......................................................................................................................... 9 4. Botanical Description/ Habit .................................................................................................. 9 5. Pharamcognostical character and pharmacopoeal standard ................................................. 14

5.1. Macroscopic characters ................................................................................................. 14 5.2. Microscopic characters.................................................................................................. 15 5.3. Identity, purity, strength ................................................................................................ 22

6. Distribution/ Habitat............................................................................................................. 26 7. Cultivation and Harvesting................................................................................................... 27

7.1. Breeding and crop improvement ................................................................................... 27 7.2. Propagation and cultivation........................................................................................... 28 7.3. Disease and Pest ............................................................................................................ 31 7.4. Harvesting and Yield..................................................................................................... 32 7.5. Processing and Storage.................................................................................................. 33

8. Chemical Constituents.......................................................................................................... 33 9. Traditional uses .................................................................................................................... 56

9.1. Traditioanl uses in different countries........................................................................... 56 9.2. Ayurvedic use, Homeopathic use, Cosmetic use, other common uses ......................... 58

10. Clinical Use ........................................................................................................................ 59 11. Pharmacological Action (Animal experiment, cellular experiment, enzymatic experiment).................................................................................................................................................. 59 12. Formulation ........................................................................................................................ 73 13. Commercial value............................................................................................................... 74

13.1. Production ................................................................................................................... 74 13.2. Markets........................................................................................................................ 74 13.3. Trade and economic impact ........................................................................................ 74

14. Perspective.......................................................................................................................... 77 14.1. Status ........................................................................................................................... 77 14.2. Patent ........................................................................................................................... 77 14.3. Diagnostic characters .................................................................................................. 78 14.4. Occurrence................................................................................................................... 78 14.5. Taste and Potency........................................................................................................ 78 14.6. Substitutes and Adulterants ......................................................................................... 78

15. Miscellaneous..................................................................................................................... 79 15.1. Herbarium collection................................................................................................... 79

16. References .......................................................................................................................... 80

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Glossary of Botanical terms ..................................................................................................... 85 Glossary of Medical Terms ...................................................................................................... 88 List of Abreevations ................................................................................................................. 90

List of Tables Table 1: Classification of Allium cepa ....................................................................................... 9 Table 3: Compounds identified in oil of onion ........................................................................ 38 Table 4: FAO Data on Onion ................................................................................................... 75 Table 5: Some other United States Patents related to onion .................................................... 77

List of Figures Figure 1: Bulb of onion .............................................................................................................. 5 Figure 2: Origin of A. cepa......................................................................................................... 7 Figure 3: Root of onion .............................................................................................................. 9 Figure 4: Onion bulbs............................................................................................................... 10 Figure 5: Longitudinal section (L.S.) of Allium cepa bulb ...................................................... 11 Figure 6: Leaves of onion......................................................................................................... 12 Figure 7: Inflorescence of Allium cepa .................................................................................... 12 Figure 8: Flowers of Allium cepa ............................................................................................. 13 Figure 9: Different parts of onion flower including floral diagram ......................................... 14 Figure 10: Longitudinal section of onion root tip .................................................................... 16 Figure 11: Onion leaf under low power ................................................................................... 18 Figure 12: The outer layer of onion skin.................................................................................. 19 Figure 13: Onion epidermis under high power ........................................................................ 20 Figure 14: Seeds of Allium cepa............................................................................................... 22 Figure 15: TLC chromatogram of Allium cepa ........................................................................ 23 Figure 16: TLC chromatogram of Allium cepa ........................................................................ 23 Figure 17: Treatment of Allum vegetables before TLC-analysis ............................................. 24 Figure 18: TLC analysis of Allium vegetables (Sapogenins) ................................................... 24 Figure 19: TLC analysis of Allium vegetables (Sapogenins) ................................................... 25

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Allium cepa Linnaeus, Lilliaceae

Figure 1: Bulb of onion (URL-1)

1. Synonyms and common names 1.1. Scientific Name: Allium cepa L. Synonyms: Allium ascalonicum L.

Allium esculentum Salisb. Allim porrum cepa Rehb. Cepa rotunda Dod. (URL-2)

1.2. Local Names Nepalese Local Names Bhojpuri: Pyaj Chepang: Pyaj Danuwar: Pyaj English: Onion Gurung: Pyaj Lepcha: Ochong Limbu: Makkhang Magar: Pyaj

Mooshar: Pyaj Nepali: Pyaj Newari: Pyaj Sunwar: Pyaj Tamang: Pyaj Tharu: Pyaj Tibetan: Btsong, Ri-sgog (Manandhar, 2002)

1.3. Traditional Names Sanskrit Names Palandu Tiksnagandha Rocana Sudrapriya Kandarpa Ulli Durgandha Pharada

Mukhadusana Krimighna Rudrasangyaka Mukhagandhaka Bahupatra Visvagandha Yavanesta Sikhadhara

Dipana Durbalasya Sikhakandu Sukanda Sikhamani Siroratna Sikhamula Varhini

(Joshi, 2000)

1.4. Language Names Arabic Countries: Basl Brazil: Onion China: Hu-tsung

China: Shallot Egypt: Bassal Egypt: Onion

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Europe: Onion Fiji: Piyaj Fiji: Piyaz France: Cepa France: Cebo France: Oignon Greece: Onion Guatemala: Cebolla Guyana: Onion India: Onion India: Piyaj India: Pyaz India: Sibuyas India: Vengayam Iran: Onion Iran: Piaz Italy: Cepolla Italy: Cipolla Japan: Onion Jordan: Basal Kuwait: Cepa bulb Kuwait: Common onion Kuwait: Onion Mexico: Cebolla morada Mexico: Onion Morocco: Bsal Nepal: Onion Nepal: Pyaz Netherlands: Onion

Nicaragua: Cebolla Nicaragua: Inyan Nicaragua: Onion Nicaragua: Sebuya Peru: Cebolla Rodrigues Islands: Oignon Saudi Arabia: Basl Tanzania: Kitunguu Tanzania: Onion Thailand: Hom khaao Thailand: Hom yai Tunisia: I-bsel Tunisia: Oignon Turkey: Sogan USA: Bermuda onion USA: Onion USA: Red globe onion USA: Spanish onion USA: White globe onion USA: Yellow onion USSR: Onion Vietnam: Cu hanh Vietnam: Hua phak bua Vietnam: Khtim Vietnam: Oignon West Indies: Loignon West Indies: Loyon West Indies: Madras onion Yemen: Basal

(Ross, 2001) 1.5. Pharmacopoel NameBulbus Allie Cepae (Anonymous, 1999) 2. Introduction Allium cepa is one of the edible species of a large genus (Allium) consisting of more than 700 species (Burnie et al., 1999). Among the edible Allium, the onion (Allium cepa L.) stands in the first rank, in the warm- temperate hills of eastern Nepal, followed by garlic (Allium sativum) and shallot (Allium cepa Aggregatum group) (Gautam et al., 1997).

2.1. Origin Although the origin remains debatable, the middle Asiatic countries in the region of Iran and Pakistan are considered the primary centre of origin of onion. The near east Asiatic and Mediterranean regions are considered to be the secondary centres of origin (Anonymous, 2003).

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Figure 2: Origin of A. cepa (URL-3)

2.2. History The onion has been cultivated for over five thousand years and has been used in herbal medicine and as an indispensable flavoring agent or as a vegetable that is cooked or eaten raw. The name Onion is derived from the Latin, unio, meaning one large pearl, and it is interesting to note that the Chinese called the Onion the jewel among vegetable (URL-4). The Greek historian, Herodotus, related that nine tons of Gold were spent purchasing onions to feed the builders of pyramids because the onion was so popular in ancient Egypt, and the Hebrews complained sorely to Moses that the missed the onion when they departed Egypt for the Promised Land (URL-4). Prehistoric remains of cultivated plants are often extremely helpful for reconstructing their evolution and history. This is especially true for seed crops, but much less so for vegetable species like onion, which have little chance of long-term preservation. Therefore, one has to rely mostly upon written records and paintings. Hence, the picture one obtains of the history of such species is fragmentary, at least for the earlier epochs (URL-5). Unfortunately, there are no records from the presumed area of primary domestication. The earliest records come from Egypt, where it was cultivated at the time of the Old Kingdom. Onions appear as carvings on pyramid walls and in tombs from the third and fourth dynasties (2700 B.C.) They are frequently depicted on offering tables since the fourth dynasty. Numerous remains from the era of the Egyptian New Kingdom (since 1580 B.C.) have been found. It was used for funeral offerings and for embalming and has frequently been found attached to, or within, mummies. It must have been important in the daily diet of many people. The biblical records of the Exodus (1500 B.C.), in which the Israelites longed for onion, leek, garlic, and other foods of Egypt, are well known. From Mesopotamia there is evidence of cultivation in Sumer at the end of the third millenium B.C. This, together with the records from Egypt, indicates that the initial domestication began much earlier.

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In India there are reports of onion in writings from the 6th century B.C. In the Greek and Roman Empires, it was a common cultivated garden plant. Reports from this period include poetry, beginning with Homer up to the Roman satirist Juvenal. There are botanical and agricultural books, e.g., Theophrastus, 4th century B.C., and Columella in the first century A.D. Finally, there is the natural history compendium by Pliny from the 1st century A.D. which details cultivation, use and history. Pliny and Theophrastus distinguished different varieties. The Romans cultivated onions in special gardens (cepinae) which had specialized gardeners (ceparii). It is thought that the Romans took onion north of the Alps.

Different cultivars of onion are listed in garden catalogues from the 9th century A.D., e.g., in the famous "Capitulare de villis" from the era of Charles the Great. But the onion became widespread as a crop in Europe only during the Middle Ages. It is said to have been introduced in Russia in the 12th to 13th century. The onion was among the first cultivated plants taken to the Americas from Europe. Columbus took it to the Caribbean. Later it was several times imported and established in the early 17th century into what is now the northern U.S. Europeans took the species to East Asia during the last century. Until now, the indigenous cultivated species of this region, especially Allium fistulosum, are more widespread there. Medicinal literature exists, e.g., Hippocrates, in the 5th century B .C. and Dioscorides in the 1st century A.D. who gives a comprehensive description of medicinal properties (URL-5).

2.3. Mythological Importance There once was a great monk who, out of compassion for all sentient beings, was a strict vegetarian. In fact, he claimed he had never in his lifetime consumed the flesh of any animal. One lady, deciding to test the monks claim, prepared a dish for the monk. She told him it contained only vegetables, but in fact it contained a small piece of meat. The monk gratefully accepted the dish and the lady left, believing she had fooled him. However, the monk saw through her trick, and tossed the dish down to the earth. The next morning he awoke, and found that the food, embedded in the earth, had sprouted into 2 shrubs: one garlic and one onion. This is why Buddhists do not eat garlic and onions. The above story discusses two significant prohibitions regarding Buddhist eating customs: that of meat, and that of pungent vegetables (URL-6).

Egyptians worshipped it believing that its spherical shape and concentric rings symbolized eternal life. Onions were even used in Egyptian burials as they believed that if buried with the dead, the strong scent of onions would bring breath back to the dead (URL-7).

Onion has been used as a charm against evil spirits. It is believed that halved or quartered onions placed in the home absorb negativity. An onion under pillow is said to give prophetic dreams. Magical swords and knives are purified by rubbing them with an onion half (URL-8).

2.4. Social Value Jains do not eat any root vegetables at all, some strict Hindu vegetarians do not eat onions (URL-9). Some avoid onion, as they are regarded as rajasic (URL-10). Buddhists do not eat onions. The reason behind this is already discussed in the mythological importance of onion (URL-6).

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2.5. Genetic characters Chromosome number (2n) =16 (Anonymous, 1999). In Allium cepa, there is one pair of chromosome which, instead of having median fiber-attachment and arms of equal length, has the fiber attached toward one of end and this shorter arm bears a small satellite (Taylor, 1925). A. cepa will cross with A. fistulosum; the F1 is self sterile but backcrosses are possible; amphidiploids are partially fertile. Common onions of A. cepa will cross with the shallots of A. cepa and other forms of A. cepa which have normal flowers (proliferum group varieties do not produce viable pollen). All ordinary varieties will intercross. No crossing with leek or garlic (URL-11). 3. Classification

Table 1: Classification of Allium cepa Kingdom Sub-kingdom Super division Division Subclass Order Genus Species

Plantae Tracheobionta Spermatophyta Liliopodia Liliales Liliaceae Allium L. Allium cepa L.

(URL-12) 4. Botanical Description/ Habit Habit A perennial herb, strong smelling when crushed (Anonymous, 1999). Root Adventitious, fibrous (Ranjitkar, 2003)

Figure 3: Root of onion

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Stem Underground stem modified into tunicated bulb consisting up reduced stem and axillary buds surrounded by inner fleshy scale leaves and outer membranous dry scales (Ranjitkar, 2003). Bulbs are uniform in shape, size and skin color. Shapes ranges from spherical to nearly cylindrical and include flat and cone like bulbs. Skin variations are considerable as is skin color, which may be white, yellow, brown, red or purple (Ross, 2001). Stem is up to 100 cm tall and 30 mm in diameter (Anonymous, 1999).

Figure 4: Onion bulbs

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Figure 5: Longitudinal section (L.S.) of Allium cepa bulb (URL-13)

Leaf Radical, alternate, sessile, simple cylindrical, hollow green, parallel veined foliage leaves with fleshy sheathing base arising from the underground stem (Ranjitkar, 2003). The sheath develops to encircle the growing point and forms a tube that encloses younger leaves and the shoot apex. Young leaves grow up through the center of the sheath of the preceding leaf. The leaf blades are tubular, slightly flattened on the adaxial side, and although hollow are closed at the tip (Ross, 2001). Leaves are up to 40 cm in height and 20 mm in diameter (Anonymous, 1999).

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Figure 6: Leaves of onion (URL-14)

Inflorescence: The terminal inflorescence develops from the ring-like apical meristem. Scapes, one to several, generally elongate well above the leaves and range in height from 30 cm to more than 100 cm. The scape is the stem internode between the spathe and the last foloage leaf. A spherical umbel is borne on each scape and can range from 2 cm to 15 cm in diameter. The umbel is an aggregate of flowers at various stages of development; usually it consists of 200-600 small individual flowers, but this number can range from 50 to more than 1000 (Ross, 2001).

Figure 7: Inflorescence of

Allium cepa

Flower Bracteate, 2-3 membranous spathe like bracts enclosing the flower during young stage, actinomorphic, trimerous, hypogynous, small and white (Ranjitkar, 2003).

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Figure 8: Flowers of Allium cepa

Perianth Stellate (Anonymous, 1999), six tepals in two alternate whorls of three each, polyphyllous, petaloid, white with green midrib, inferior (Ranjitkar, 2003). Androecium Six stamens in two whorls of three each, opposite the tepals; antipetalous, polyandrous, epiphyllous, inferior. Filament- long but slightly dilated at the base. Anther- long, bilobed and basifixed (Ranjitkar, 2003). Gynoecium Tricarpellary, syncarpous. Ovary superior, trilocular with 2 ovules in each locules, axile placentation. Style short and filiform. Stigma minute (Ranjitkar, 2003). Fruit Capsule of about 5 mm (Anonymous, 1999) Floral Formula:

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Figure 9: Different parts of onion flower including floral diagram

5. Pharamcognostical character and pharmacopoeal standard

5.1. Macroscopic characters Underground stem modified into tunicated bulb consisting up reduced stem and axillary buds surrounded by inner fleshy scale leaves and outer membranous dry scales (Ranjitkar, 2003). Bulbs are uniform in shape, size and skin color. Shapes ranges from spherical to nearly cylindrical and include flat and cone like bulbs. Skin variations are considerable as is skin

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color, which may be white, yellow, brown, red or purple (Ross, 2001). The shape and the size of the bulb differ with each variety (from 2 to 20 cm, flattened, spherical, or pear-shaped) (Bruneton, 1999; Anonymous, 1999).

5.2. Microscopic characters Root The epidermis consists of small tabular somewhat radially elongate cells in transverse section. The outer tangential and radial walls are relatively thick and layered at the electron microscope level. A distinct hypodermis is present under the epidermis which possesses casparian strips in the primary wall. In the mature state, it is evident in the electron microscope that each cell is encased with a complex suberin lamella. A cortex is present and consists of isodiametrically shaped parenchyma cells. The endodermis is distinct and in the mature form its cells have thick secondary walls. Presumably, as is tree of other monocotyledons, this wall consists of a suberin lamella covered by layers of lignified cellulose. This thickening is greatest on the inner tangential walls. The steles can be tetrarch, pentarch or hexarch but most commonly are pentarch.

The histogens of the onion root tip consist of two distinct groups of initials, one giving rise to the vascular cylinder or stele, and the other to the cortex, endodermis, and root cap. The root cap is presumably the site of gravitational perception in roots. In particular, the site resides in the central column of cells called the columella. The ultrastructural characteristics of the columella cells are similar. The cells contain large nuclei, amyloplasts, endoplasmic reticulum, and mitochondria. The positioning of the organelles in the columella of both types of roots is also the same; amyloplasts (starch grains) are positioned at the gravitational base of the cells and nuclei at top of the cell away from gravity. However, the size of the columella cells is smaller in short roots than in long roots. The volume of columella tissue is correlated with the gravity response.

Roots are continuously formed in distinct rings at regular intervals in the onion stem. They are formed by the PTM at its more basal level just above the region of the stem where all tissues are mature. Since the apical meristem is sunken at the shoot tip, this is approximately at the level of the apical meristem. The vasculature of the root then matures in connection with that of the stem as well as does the endodermis of the root with the endodermoid layer in the stem. Therefore, there is a continuous vascular and endodermal connection between stem and root from root initiation. The root tip grows through stem cortical tissue and leaf bases to emerge from the plant (URL-2).

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Figure 10: Longitudinal section of onion root tip (URL-15)

In the cells of the root tip of an onion chromosomes can be made visible quite easily. They can be seen during various phases of mitosis: the chromosomes in the cell's nucleus copy themselves (URL-15). Vegetative stem The stem of a mature pre-bulbed plant is heart shaped in median longitudinal section. The apical meristem and youngest leaf primordia are sunken in a "bowl" of surrounding stem tissue. The stem can be divided into two major regions: the cortex and the central cylinder. Pith in the center of the central cylinder, directly below the apical meristem, is devoid of vascular tissue. The central cylinder is congested with vascular bundles and leaf traces. The vascular bundles are often seen to describe an "S" shape in longitudinal section, approaching the pith, and then turning out to form leaf traces. In transverse section, the leaf traces are collateral and the stem bundles are amphivasal in vascular tissue arrangement.

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In the basal regions of the stem where all cells are mature, the cortex is distinguished from the central cylinder by boundary zone of three tissues. They are (1) a uniseriate endodermoid layer of cells with thickened cell walls, (2) a layer of irregularly shaped parenchyma cells, often called a pericycle, and (3) and congested network of vascular bundles which form the vascular connection between the stem and roots. If these layers are followed toward the apex in the stem, they are confluent with a narrow meristematic layer, the primary thickening meristem (PTM). The PTM runs parallel to the stem outline and separates the central cylinder from the cortex and meets up with the apical meristem. The PTM consists of flattened cells which are undergoing rapid cell divisions. The PTM is not only responsible for stem thickening in onion but also is responsible for root initiation. These anatomical and histological features are similar in all respects to those in garlic.

The vegetative stem in onion has a very distinctive pattern of cell alignment which is the result of the pattern of cell division in the PTM. In longitudinal section, the cells are arranged in distinctive files which run from the leaf bases through the PTM to the pith of the central cylinder. The files of cells are not continuous across the pith. The arrangement of cells in the pith is irregular. The files of cells in the stem remain organized during stem growth; however, their angle varies at different levels of the stem. The files are almost vertically oriented in the top of the stem near the apical meristem, but more horizontally oriented in the base of the stem. The leaf traces parallel the cell files at all levels of the stem. In cross section, the cell files form concentric circles in the top of the stem.

Stem development in onion is similar to that in other monocotyledonous species with a short, squat stem and a rosette habit. The stem grows in height by the addition of cell files at the base of the shoot apical meristem. The stem then thickens in width first by increase in length of the cell files due to cell divisions in the PTM and by subsequent cell enlargement and finally by reorientation of the cell files toward the horizontal as the tissues reaches maturity. In conjunction with this, the leaf primordia are initiated at the apical meristem in the "well" and as they increase in diameter they pass up and over the shoulders at the top of the stem as the associated stem cell files increase in length, form the shoulders, and finally are bent away from the vertical (URL-2). Leaf Adult Photosynthetic Leaf Leaves possess a uniseriate epidermis with thickened outer walls with a cuticular layer. The epidermal protoplasts are highly vacuolate. Stomata are frequent in the epidermis. Chlorenchyma is present under the epidermis in the form of palisade cells and isodiametric spongy mesophyll. The chlorenchyma contains abundant intercellular space and chloroplasts are located almost exclusively along the walls adjoining the air spaces. These cells are also highly vacuolate. Chloroplasts have a reniform shape, contain highly developed grana-fretwork systems, and lack starch. Mitochondria and microbodies are present in close association with the chloroplasts.

Internal to the chlorenchyma and in the interveinal regions there is one type of ground parenchyma. It has less intercellular space but the characteristics of the chloroplasts are similar to chlorenchyma except that the chloroplasts are elliptical in shape. Articulated laticifers occur between the ground parenchyma and the chlorenchyma. The second type of ground parenchyma is more internal in position and consists of larger cells. Finally, there is a layer of axially elongate cells which lack protoplasts and line the central lacuna.

The major vascular bundles in the onion leaf are bounded by a uniseriate layer of compactly arranged bundle sheath cells. These cells are highly vacuolate but do contain many organelles including spheriodal chloroplasts which contain starch grains. The conducting cells

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of the vascular bundles are surrounded by vascular parenchyma immediately internal to the bundle sheath cells. The bundles are collateral. The phloem contains sieve tube elements and companion cells.

The leaf primordium is initiated on the flanks of the slightly convex apical meristem and grows erectly as first a rounded and then pointed mound on one side of the apical meristem. When it is 150-200 mm in length, adaxial meristematic activity initiates the radial growth responsible for subsequent dilation of the leaf axis. This establishes the boundary between the sheathing base and the unifacial blade. In transectional view the leaf primordium arises from the shoot apex as a flattened, bifacial pad which appears somewhat indented along its adaxial surface. The sheathing base originates as a circumferential expansion of the leaf primordium entirely around the perimeter of the shoot apex. The sheath then elongates as a tube. The boundary between the sheathing base and the blade is delineated in the young primordium by the adaxial ligular outgrowth which is partially epidermal in origin.

Periclinal divisions and enlargement of the central cells in the leaf axis in combination with adaxial meristematic activity contribute to the increase in thickness in the central portion of the leaf. Subsequently, the intercalaxy cell division and expansion, and schizogenous formation of intercellular spaces, result in a more pronounced rounding of the basal section of the unifacial leaf portion. By contrast with the base, the tip of the leaf does not experience as much thickening growth, and it retains its flattened form into maturity. The initial phase of cell enlargement and vacuolation in the onion leaf is expressed along the entire length of the leaf when it is only 200-300 mm long. Elongation of the central pith cells begins below the leaf tip and spreads down the length of the unifacial blade. Cells derived from periclinal division of hypodermal lineages around the periphery of the leaf, especially in the unifacial zone, will mature as the photosynthetic tissue. These cells are smaller and more densely staining in the early phases of leaf morphogenesis. Ultimately cell growth in the pith region fails to keep pace with division and expansion at the leaf's periphery, resulting in the rhexigenous breakdown of pith tissue and the formation of a central cavity along most of the blade's length (URL-2).

Figure 11: Onion leaf under low power (URL-16)

Bulb scale The bulb scale is the organ which is responsible for the food value in onion. It is morphologically a scale leaf which has an expanded base and an aborted leaf blade. The blade of the photosynthetic leaf elongates before the base. Since the blade elongates much more

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than the base, the final leaf ratio (blade/base) is above 5. After transfer to long day, leaf primordia 1 mm long or less become bulb scales. The blade does not elongate, but the leaf base elongates earlier and longer than that of the photosynthetic leaf. The final leaf ratio of the bulb scale is 0.05.

The external dried leaf scales of the bulbs show a large-celled epidermis with lightly spotted cell walls; the cells are elongated longitudinally. The underlying hypodermis runs perpendicular to the epidermis and contains large calcium oxalate crystals bordering the cell walls. The epidermis of the fleshy leaf scales resembles that of the dried leaf scales, and the epidermal cells on the dorsal side are distinctly longer and more elongated than the epidermal cells on the ventral side. Large calcium oxalate crystals are found in the hypodermis; stomata rare; large cell nuclei conspicuous; and spiral vessel elements occur in the leaf mesophyll.

Figure 12: The outer layer of onion skin (URL-17)

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Figure 13: Onion epidermis under high power (URL-18)

Inflorescence stalk The anatomy of the inflorescence stalk bears more similarities to that of the leaves than to that of the vegetative stem. The epidermis is heavily cutinized with sunken stomata and large accompanying substomatal chambers. The mesophyll has palisade cells to the outside and spongy cells to the inside. There are two rings of vascular bundles embedded in longitudinally elongate parenchyma. The outer ring consists of small bundles closely spaced and is associated with a ring of small parenchyma cells. The bundles are all collateral in vascular tissue arrangement. Collapsed and broken cells line a central lacuna. The cells are not arranged in radial files as they are in the vegetative stem and there is no evidence of a cambial-like zone comparable to the PTM.

At the time of flowering the stem grows up through the ensheathing leaf bases to a height of about 1 to 2 m. The entire inflorescence between the vegetative stem and the head of flowers is a single internode. During the transition to flowering, the apical meristem, through extensive rib meristematic activity, assumes the mantle-core arrangement of cells typical of floral meristems. The flattened vegetative apical meristem becomes rounded and dome shaped as rapid longitudinal growth commences. The apex also produces a spathe that subtends the head of flowers. The spathe is produced immediately after the last vegetative leaf and before histological evidence of the transition to an inflorescence apex occurs. The inflorescence subsequently elongates between the last formed vegetative leaf and the spathe. The PTM does not differentiate into the infiorescence but does into the renewal vegetative bud and maintains essentially the same histological characteristics as it had in the original vegetative stem.

Sections of later stages of inflorescence growth show that, at the base of the inflorescence just above the vegetative stem, the cells are small and little tissue differentiation has occurred. There are many mitotic figures at this level, while approximately 2 cm above the base of the inflorescence, some differentiation occurs in the protoderm and few mitotic

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figures are present. Midway up the internode, no mitotic figures are present and much differentiation has occurred. Finally, at the top of the inflorescence axis the cells are larger and the greatest amount of differentiation has occurred; the epidermis has stomata; the palisade layers are developing; and the protoxylem is present. These observations corraborate the marking experiments and indicate that the inflorescence grows by a basal intercalary meristem. In onion, at the time of flowering, there is an immediate shift from an emphasis on growth in width, characteristic of the vegetative phase, to an emphasis on growth in length in the reproductive phase (URL-2). Seed The seed is convex on one side and flattened on the other and is covered by a black seed coat. The embryo is crescent shaped or curled in a spiral. It consists of a long cotyledon and short shoot-root axis. The epicotyl consists only of an apical meristem and one leaf primordium. The epicotyl faces the slit in the base of the cotyledon through which the first true leaf will emerge during seedling development. The procambium (undifferentiated vascular system) extends from the root tip to the base of the cotyledon, where it forms a short branch towards the epicotyl and a long branch which extends the length of the cotyledon. The cotyledon is a storage organ.

Both the protodermal cells and the internal parenchyma cells store protein in the form of variably sized protein bodies and lipids in the form of very small lipid bodies. The larger protein bodies have small light-staining areas which appear as speckles. Undoubtedly, these consist of phytin crystals (myoinositol hexaphosphate), which are considered to be a storage form of phosphate in seeds. They are well characterized in other seeds. The cells are thin walled and intercellular spaces exist between cells. Nuclei are present in each cell. They are relatively small and irregularly shaped as if they are physically crowded by the protein bodies.

The embryo is buried in a gray, horny endosperm tissue which is the major region of stored reserves in the onion seed. The endosperm consists of living cells with extremely thick, hard cell walls. Unlike the cotyledon there are no intercellular spaces between cells. These walls are not stained with the periodic acid schiffs (PAS) reaction, except for the middle lamella and the innermost region immediately adjacent to the plasmalemma. The major carbohydrate in the thickened region of the cell wall is presumably a mannan ( 1, 4 mannose-linked units as a backbone). The protoplasts are jigsaw puzzle-shaped due to the fact that the walls are not thickened in regions of pit fields between cells. The cells also store protein in the form of small evenly sized protein bodies and lipids in the form of very small lipid bodies. Nuclei are present in each cell. They are large, darkly staining, and relatively spherical in shape.

The early divisions after fertilization lead to the formation of first a club shaped and then a spherical embryo attached to a uniseriate suspensor. A slight depression, or notch, appears on one side which indicates the future position of the shoot apical meristem. The cotyledon extends greatly in length and produces a marginal sheath-like extention which creates a depression. Within this depression the apical meristem forms as a mound. It initiates the first leaf before the seed is mature. The apical meristem of the root becomes organized at the base of the short hypocotyl. The formation of a lateral notch and the precocious development of the single cotyledon is similar to embryogenesis in coconut and in grasses (URL-2).

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Figure 14: Seeds of Allium cepa (URL-19)

Microscopic characteristics of powdered plant material Contains mainly thin-walled cells of the mesophyll with broken pieces of spiral vessel elements; cells containing calcium oxalate crystals are scarce (Anonymous, 1999).

5.3. Identity, purity, strength General identity tests Macroscopic inspection, microscopic characteristics and microchemical examination for organic sulphur compounds; and thin-layer chromatographic analysis for the presence of cysteine sulphoxides have been found to be useful (Anonymous, 1999). TLC Chromatograms of Allium cepa Sulphur and non-sulphur containing constituents have been isolated from Bulbus Allii Cepae; the sulphur compounds are the most characterstic (Anonymous, 1999). A.Freshly prepared extracts of Allium cepa (3) (with solvent system of toluene-ethyl acetate(100:30)show five to seven dark zones in the Range R, range 0.2-0.65 with two prominent zones of thiosulphinates at Rf 0.3 and Rf 0.45. The dipropylthiosulphinate (T1) at Rf 0.45 is the characteristic compound of onion extracts. Allicin with almost the same Rf value is absent. Other thiosuphinates such as dimethylthiosulphinate (T2) at Rf 0.2 are present, which is contrast to garlic thiosulphinates (TS) show bown-red colours (vis.). This is partly due to higher TS concentrations and to compounds which overlap the TS as shown in Fig. 15.

After treatment with the Vanillin-glacial acid reagent (VGA No. 42), the extract of Allium cepa is distinguishable by the characterstic violet-brown major zones at Rf 0.3 and Rf 0.45, with less concentrated zones at Rf 0.6-0.8. Allicin is seen as a grey-brown-coloured zone, the sulfides at the solvent front as blue to grey-blue (Fig. 16) zones in the low R, range of the TLC (Farooq, 2005).

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Figure 15: TLC chromatogram of Allium cepa

Figure 16: TLC chromatogram of Allium cepa

B. A article (actually this article was on the topic How to Distinguish Garlic from

other Allium vegetables whose report was presented at the conference Recent advances on the Nutritional Benefits Accompanying the Use of Garlic as a Supplement held November 15-17, 1998 in Newport Beach, CA) tells us that each Allium vegetables is characteristic and distinguishable. The detail of chromatographic technique for sapogenin according to this article is discussed here.

Twenty six different kinds of Allium vegetables were purchased in markets of Japan and United states. They included Allium sativum L. (garlic), A. ampeloprasum (elephant garlic), A. ascalonicum, A. canadence, A. cepa (10 different types), A. chinense (Rakkyo), A. fistulosum (3 different types), A. porrum (leek), A. shoenoprassum (2 dufferent types), A.tricocum, A.tuberosum, A. victorialis and A. wakegi. Each 10g of vegetables or processed garlic was crushed in 40 ml of methanol. After removal of the solvent by evaporation, a suspension of resulting extract in 30% aqueous methanol was applied to a column of MCI gel

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CHP20P (stepwise elution of 30% aqueous methanol and methanol). The methanol extracts obtained were hydrolyzed using a mixture of 8% sulphuric acid/ ethanol (1:1) for 5h at 100oC. The hydrolyzates were added to 20 ml of water and applied to a column of MCI gel, which was then washed with methanol. The sapogenin fraction from each methanol eluate was analyzed by TLC.

TLC was performed on a HPTLC Silica gel 60 plate and spots were visualized by spraying of anisaldehyde H2SO4 followed by heating of iodine-platinate reagent for sulphur compounds.

Sapogenin is the agycone of saponin, obtained by hydrolysis of saponin. Twenty-eight different kinds of Allium vegetables were treated as shown in Figure17. The sapogenin fractions obtained, corresponding to each vegetable, were analyzed by TLC as shown in Figure 18 and 19. Each chromatogram of Allium vegetables is characteristic and distinguishable (Itakura et al., 2001).

Figure 17: Treatment of Allum vegetables before TLC-analysis

Figure 18: TLC analysis of Allium vegetables (Sapogenins)

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Figure 19: TLC analysis of Allium vegetables (Sapogenins)

Biochemical characterization of landraces through HPLC analysis of endosperm seed proteins:

Water-, salt-, alcohol- and alkali-soluble seed storage proteins, extracted from 21 white onion landraces (Allium cepa L.), were analyzed by anionic exchange-high performance liquid chromatography (AE-HPLC). Chromatographic elution profiles of (time range 0-40 min) at 280 nm of water soluble seed proteins evidenced the presence of 21 peaks, which allowed all the landraces studied to be distinguished from each other. The differences detected were both qualitative and (presence/absence of one or more peaks) and quantitative; the water-soluble proteins were useful in differentiating landraces and cultivars while the other seed protein fractions only showed a weak polymorphism. The cluster analysis, bases on HPLC data, showed that the landraces clustered with a genetic similarity degree ranging between 69% and 94%. The possibility of discriminating among closely related onion landraces during the course of breeding programmes could allow the identification of biochemical markers linked to useful agronomical traits. As observed by chromatographic analysis, the globulin composition of onion water-soluble seed protein appears to be independent of environmental growth conditions. The biochemical characterization of the available typical onion gremplasm may contribute to obtain a community recognition and denomination, such as Denomination of Protected Origin (D.O.P.), Indication of Protected Origin (I.G.P) or Specificity Attestation (A.S.). The biochemical method here developed resulted of high resolution, cost effective and time-saving for characterization and genetic purity assessment of the landraces studied (Mennella et al., 2005).

Purity and Strength: Microbiology: - The test for Salmonella spp. in Bulbus Allii Cepae products should be negative. The maximum acceptable limits of other microorganisms are as follows. Preparations for oral use: aerobic bacteria - not more than 105/g or ml; fungi - not more than 104/g or ml; enterobacteria and certain Gram-negative bacteria - not more than 103/g or ml; Escherichia coli 0/g or ml (Anonymous, 1999). Total ash Not more than 6% (Anonymous, 1999)

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Acid-insoluble ash Not more than 1.0%, Water-soluble extractive - not more than 5.0% (Anonymous, 1999) Alcohol-soluble extractive Not more than 4.0% (Anonymous, 1999) Pesticide residues To be established in accordance with national requirements. Normally, the maximum residue limit of aldrin and dieldrin for Bulbus Allii Cepae is not more than 0.05mg/kg (Anonymous, 1999). Heavy metals Recommended lead and cadmium levels are no more than 10 and 0.3mg/kg, respectively, in the final dosage form of the plant material (Anonymous, 1999). Other purity tests Chemical, foreign organic matter, and moisture tests to be established in accordance with national requirements (Anonymous, 1999).

Mineral concentrations of onions (Allium cepa L.) grown under various conditions,

including factors (fertilization, crop year, variety, and provenance) are different. This can help to develop a technique to determine the geographic origins of onions by mineral composition (Ariyama et al., 2006). 6. Distribution/ Habitat Distribution: It is now cultivated throughout the world. Although temperate in origin, it has been bred to adapt to the tropics (Ross, 2001). It is distributed throughout Nepal to about 3000 m (Manandhar, 2002). They are not found in New Zealand and Australia (Anonymous, 2006). Habitat: A. cepa is cultivated under a wide range of conditions. The environmental conditions are- Latitude It can be grown between 60S and 60N (URL-5). Temperature High temperatures encourage bulb formation, but flower formation and seed production are only possible where the bulbs are subjected to low temperatures. A cool period promotes early leaf production. Germination temperature is between 15-25C, optimal between 20-25. It grows between 4 and 30C, and does not tolerate frost (URL-5). Water A long, dry period is required for bulb repening after the leaves have withered. Optimal rainfall/irrigation requirements are 350-600 mm and it is grown in areas with up to 2800 mm annual rainfall (URL-5). Radiation Range and intensity It is a sun-loving species (URL-5).

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Photoperiodism The production of bulbs is controlled by the photoperiod, the critical day-length varies from 11-16 hours, depending on the cultivar (URL-5). Soil Physical Moist soil is required throughout the growing period, but excessive soil water and high humidity encourage diseases. Best soils are medium deep, well drained, sandy loams with a good content of organic matter; it can in also any soil (URL-5). Chemical Best soils are medium fertility with low salinity and a pH between 6.0-7.0, but also soils with low fertility, some salinity and a pH between 4.3-8.3 are feasible (URL-5). 7. Cultivation and Harvesting

7.1. Breeding and crop improvement Breeding experiments on different varieties of onion showed significance differences for the all characters studied, viz. leaf length, umbel height, number of seed stalks per plant, umbel diameter, weight per umbel, 1,000-seed weight, and seed yield per plant. In general, a character exhibiting a wider range also showed high phenotypic and genotypic coefficients of variability. High heritability was observed for the number of seed stalks per plant, whereas it was low for all other characters. The number of seed stalks gave high values for genetic advance but umbel diameter showed low expectation for genetic gain. Hybrid vigour or heterosis was observed to the extent of 72 per cent on the average of the parents, and up to 37 per cent as measured from the better parent. Highly significant combining ability effects of parents were recorded in the females. For obtaining hybrid vigour in onions, cytoplasmic male sterility is a useful tool. A 13- 53 cytoplasm which remains apparently completely stable in performance, is the main source utilized for producing hybrids. For example, shallot (A. ascalonicum) is easily hybridized with 13-53 (male sterile cytoplasm) onion because it has the male sterile genes. For selecting varieties suitable for dehydration the following characterstics are essential: pale white flesh, small neck and root zones, high pungency, uniform bulb, size of similar composition throughout, long fresh storage life, high yield potential, high solids content (15-20%) and also high drying ratio between 3:1 and 20:1. Selfing and massing method is found to be existed for raising the improved strains of onion. During the first year, bulbs of desired characters such as uniform size, colour and necks are planted for obtaining seeds. The umbels are selfed by covering them with muslin cloth bags and shaking the bags every day to ensure pollination and greater seed-setting. The progeny of these selfed plants are grown separately, selected for desirable characters and the selected bulbs propagated and selfed again. This inbreeding for two successive generations results in homozygosity to a large extent, although the inbred progeny is found to be less vigorous than the open pollinated original crop. Group breeding in the third generation results in restored vigour besides the formation of new strains. By following this procedure of breeding, a number of strains in red, scarlet, and white onions have been evolved (Anonymous, 2003).

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7.2. Propagation and cultivation Onion is important tropical vegetable, grown both as field and garden crop. It is

extensively grown all over India. It is generally grown as irrigated crop throughout the year though the main planting seasons are June-July and Dec-Jan. In the plains, it is sown during Oct-Nov and on the hills during March-May. It can not stand heavy rainfall although it can be grown as a rain-fed crop in certain places. (Anonymous, 2003) Preparation of land Onion grown from seed requires a finer degree of tilth than most other vegetables. The soil should be spread over with decomposed farmyard manure to a depth of 7.5-10.0 cm. Addition of wood or cowdung ashes and compost has a beneficial effect on the crop. The soil is worked smooth to a depth of 15-20 cm by repeated ploughing and raking. Beds or ridges with intervening channels for irrigation are then laid out. In places where onions are to follow rice, excessive water is drained off by making treches 6-9 m apart immediately after harvesting the rice crop. The land is worked with a furrow turning plough and left for drying. Three to four ploughings are given subsequently, clods broken and pulverized by using a roller. Onions being a shallow feeder, most of the roots penetrate to a depth of 5.0-7.5 cm and the crop thrives well on a hard bottom (Anonymous, 2003). Sowing time Depending upon the geographical conditions, the sowing time is found to be different in different places. The bulk of the onion crop is obtained from seed. The seedlings are first grown in the nursery bed and transplanted in the field later (Anonymous, 2003). Selection of seed The viability of the seed is lost in 1-2 years. Good seed is triangular, and black or dark in colour. The loss of germinating capacity can be detected when the seed looks pale, especially along the marginal edges. Such non-viable seed is light in weight. About 25 g of normal seed contains about 7,000 seeds (Anonymous, 2003). Seed production Large-sized bulbs (about 7.5 cm in diameter and about 40 g in wt) are selected from the previous years crop and are planted in the field 30 cm apart in rows spaced at 60 cm during September-October. A furrow 7.5-10.0 cm deep is opened and the bulbs are set in and covered by hand. Prior to sowing half of the top portion of the bulb results in early sprouting, better stand, more seed stalks and larger yield of seed. The upper cut portion may be used for edible purposes. Onion is a cross-pollinated plant and when the seed production of more than on variety is required, the varieties should be separated at least by 200 m. Flowering stalks emerge in 10 weeks, and within 6 weeks the seeds ripen. The seed is harvested when the capsules ripen and the black seeds are seen. The umbels or seed heads are cut from the stalk and collected. After collection the seeds are spread on a canvas cloth kept in a well-ventilated, shaded place and stirred once a day. When thoroughly dried, the seeds are threshed and winnowed clean and dried again before storing in alkathene in a cool place. Seed yield per plant is significantly and positively correlated with the number of seed stalks per plant and the weight per umbel. Seed yield increases with close plant spacing (20 cm), the use of big-sized bulbs (about 50 g) and application of 40 kg N/ha.

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Onion seed loses its viability after one year; high humidity and high temperature cause onion to lose its vitality rapidly. Seed viability is enhanced and the associated fungal flora is eliminated by treatment with Dithan 2-78, Captan, and Brassicol. Onion seed harvested in May shows 90 per cent germination when sown in Sept.-Oct. Seeds treated with 10 ppm NAA and 10 ppm IBA gave over 90 per cent and 85 per cent germination respectively as against about 65 per cent in control (Anonymous, 2003). Propagation Ripe onions are generally produced from transplants raised from seeds sown in the nursery bed 6-8 weeks prior to transplanting, from seeds sown directly in the open field, and by planting medium-sized mature onion sets (Anonymous, 2003). Transplanting The chief advantages of this method are the use of a lower seed rate, early maturation, formation of large and more uniform bulbs, a better stand, better control of weeds and ultimately a higher yield. The main disadvantage is the manual labour required. For the production of healthy seedlings, seed of selected, high yielding varieties should be sown broadcast, or in drills made 10-15 cm apart in the first week of November or preferably before the first week of December. Immediately, after sowing the seed is covered 5 cm deep with fine soil mixed with farmyard manure, and a light irrigation given. Irrigation is repeated every third or fourth day till the plants are well established. The seedlings come up in a weeks time and are ready for transplanting in 7-9 weeks. Larger seedlings give better yield. The fields, where the seedlings are to be transported, are divided into small plots of a convenient size, preferably long and narrow beds, to facilitate weeding and irrigation. The seedlings are set out in rows about 10 cm apart both ways. Wider spacing for the convenience of hoeing without provision for adequate plant population, yields bigger-sized onions at the cost of optimal yield. Transplanting is done in the first week of January. Seedlings are set 2.5-3.5 cm deep. Deep planting of seedlings hampers the proper development of bulbs and lowers the yield. Irrigation is necessary immediately after planting (Anonymous, 2003). Seed propagation Onion is also propagated by sowing the seed directly in the field in rows about 30 cm apart. The seed is dibbled about 1.5 cm deep in heavy soils and about 2.5 cm in sandy soils. For sowing directly the seed bed is prepared thoroughly and laid out in plots. The rows are marked and furrows made. The seed is then dropped by hand in the furrows. Coarse sand mixed with the seed, gives even distribution. A very light irrigation is given immediately after sowing followed by another after 4-5 days. The seedlings push through the surface in about a weeks time. When the plants are 6-8 weeks old they are thinned to about 10-12 cm apart. The thinnings may be transplanted to vacant plots or between other crops, or made use of in a green state during the course of the season (Anonymous, 2003). Propagation from dry sets Onion is also cutivated by planting dry onion sets from the previous years crop, which yields more and matures earlier. The sets are planted in rows 30 cm apart and spaced 10 cm in the rows. The medium-sized sets of 1.5-2.0 cm in diameter are most desirable for planting. About 14-18 qt of sets is required to plant a hectare. The dry onion sets are produced by sowing seeds thickly in rows 22-30 cm apart at the rate of 90-135 kg/ha. Globe-shaped early varieties are chose. The sets are harvested as soon as

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the crop is ripe and before hot weather sets in. They are pulled out by hand, the tops twisted off and the bulbs collected and immediately removed to the shade for curing. The green onions are produced by planting the smallest bulbs from the previous crop during Sept-Oct in rows 22-30 cm apart and 10 cm apart in the rows. They are usually ready to be pulled out in 4-5 weeks after planting (Anonymous, 2003). Manuring Onion needs moisture-retaining soil rich in available plant food, especially humus. Farmyard manure or green manure is used freely to maintain a favourable physical condition of the soil. But the crop does not require much nitrogenous manure which leads to more leaf growth at the cost of bulbs. Manures rich in potash like wood ash, poultry dropping, etc. give increased out-turns. Well-rotted farmyard manure is applied at the rate of 25-50 tonnes/ha after the first ploughing or it may preferably be applied to the preceding crop. When farmyard manure is used in smaller quantities, application of nitrogenous fertilizers proves beneficial, but overdoses are detrimental to the keeping quality of the bulbs and cause the appearance of scallions or bull necks in a high percentage of the crop. At the time of the final ploughing, fertilizer at the rate of 250 kg of calcium ammonium nitrate, 250 kg of superphosphate and 125 kg of muriate of potash per hectare is broadcast and mixed well into the soil. Besides, the crop after transplanting is top-dressed in two split-up doses; the first dose is given one month after transplanting and the second after three months. Soot and ash are also used for top-dressing. Manorial experiments have shown that application of nitrogen, either alone or in combination with P2O5 and K2O in varying proportions, depending on soil condition, gives satisfactory results in onion cultivation. Application of 563 kg of calcium ammonium nitrate, 679 kg of superphosphate and 47 kg of muriate of potash per hecatare gave the best results. In studies on the effect of application of potash and different micronutrient sprays such as zinc, manganese, and copper on the onion crop, the highest yield was obtained with 281 kg of potash with copper spray (Anonymous, 2003). Weeding Onion needs frequent weeding; the crop is hand-hoed and weeded 20-25 days after planting and again 3 weeks later. Chemical weed control by using Tenoran (2.0-2.5 kg/ha in 1,000l of water) after 3-5 weeks of transplanting is very effective and does not affect the yield. Other weedicides like contact herbicides, etc. are also used (Anonymous, 2003). Irrigation Since a steady state moisture supply is required for continuous growth in onion, irrigation is given once every two weeks during the cool growing period and more frequently when the hot weather sets in. In all 8-9 irrigations are sufficient for the crop. When the crop is nearing maturity, it is watered sparingly and when the tops start falling over, irrigation is stopped. Irrigations should be light, as wetting the soil up to a depth of 30 cm is sufficient for the onion crop. The drip method of irrigation gives higher yield of the crop (Anonymous, 2003). Rotation and Intercropping Rotation is very important for onion crop. It usually follows a heavily manure crop like potato, which requires a thorough cultivation and leaves the land comparatively free of weeds. Onion following clovers and cereals thrives well. In irrigated lands, it is rotated with sorghum, ragi, chillies, rice, etc. in the same year. Depending upon the variety of onion, it is found to be

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rotated with wheat, bajra, groundnut, vegetables like chillies, potatoes, fodder crops, maize, etc. Onion is found to be intercropped with garlic, turmeric, sugarcane, etc (Anonymous, 2003).

7.3. Disease and Pest Fungi Leaf diseases Peronospora destructor, the causal agent of downy mildew is widespread on all continents (URL-5). The affected parts attain a peculiar colour, and the foliage and the flowering stalks wither and the bulbs become moist and spongy, thus reducing the yield considerably. Three to four sprayings with Difolatan was found to be beneficial to reduce the intensity of the disease and also to increase the net yield of the crop (Anonymous, 2003). Alternaria porri which causes purple blotch and scald and this is widespread in hot, humid climates as it requires temperatures of 21-30oC for development. Botrytis allii which causes leaf spot, leaf fleck, collar rot, brown stain is the common grey mould fungus ubiquitous in temperate regions (URL-5). The infection usually takes place at curing time, through the exposed moist tissues. The white varieties, scallions, and injured bulbs are more susceptible than the normal ones. The lesions on the bulbs appear as sunken dried areas around the neck but may involve the whole bulb that ultimately rots, giving a stinking smell. The fungus can tide over the winter. The disease can be controlled by proper rotation and sanitation, elimination of late application of fertilizers to avoid scallions, clean tillage, rapid curing, close topping, careful handling and thorough ventilation throughout the storage period. The rotten bulbs should be sorted out and removed (Anonymous, 2003). Cladosporium allii-cepae causes outbreaks of leaf blotch in temperate areas. Puccinia allii, causing rust, is widespread but sporadic in temperate zones. Pleospora herbarum (black stalk mould, leaf spot) occurs in temperate and subtropical parts of the world. Stemphylium vesicarium, Stemphylium leaf blight, normally invades dying tissue. Glomerella cingulata (twister disease, anthracnose, seven curls) is more common in the tropics and subtropics. Cercospora duddiae leaf spot is a tropical disease. The soil bourne smudge caused by Colletotrichum circinans reduces cosmetic quality on the outer scales (URL-5). Root deseases Pink root, caused by Pyrenochaeta terrestris is present in regions with high soil temperatures. Fusarium basal rot caused by Fusarium oxysporum is present almost wherever onions are grown and can cause up to 90% loss of seedlings. Onion smut, caused by the soil bourne Urocystis colchici and U. cepulae is present in most temperate onion growing regions (URL-5). The infected plants become stunted, do not develop bulbs and ultimately die. Onion suffers heavily from bulb rot, caused by Sclerotium cepivorum. Lower moisture content and an alkaline soil seem to reduce the intensity of the desease (Anonymous, 2003). Southern blight is capable of causing serious field and storage losses and is caused by Athelia rolfsii. Fusarium, Pythium and Rhizoctonia spp. cause damping off (URL-5). Viruses Onion Yellow Dwarf Potyvirus (OYDV) is the only important and widespread virus infecting A. cepa. Others may occasionally infect the common onion (URL-5). Insects

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Of the several aphids which attack onion, Myzus ascalonicus is a typical pest of the stored crop and Myzus persicae damages the growing crop; both are virus vectors. The onion thrips, Thrips tabaci is widely distributed and is believed to cause more damage to alliaceous crops than all other pests. Cutworms are major pests of many crops and those which are more important pests of onion include the larval stages of the turnip moth, Agrotis segetum, Agrotis ipsilon- the black cutworm and Peridroma saucia- the variegated cutworm. The almond moth is a cosmopolitan pest of stored products including onion. The leek moth, Acrolepiopsis assectella also attack onion. The onion fly or onion maggot, Delia antique is a major pest attacking bulbing and green onions globally. The bulb fly, Eumerus amoenus is a pest in warmer regions. Several leaf miners (e.g., Liriomyza sativae and other Liriomyza spp.) colonize onion and are polyphagous. Several beetles are important pests of alliaceous crops including flea beetles, chafer beetles, leaf beetles, weevils and click beetles (URL-5). Mites Tetranychus cinnabarius- the carmine spider mite and Tetranychus urticae- the red spider mite are particularly severe pests locally in many parts of the world. Petrobia latens- the stone mite may be the most serious onion pest in some parts of the world. The bulb mites, Rhizoglyphus echinopus and Rhizoglyphus robini are occasionally serious storage pests. The gall mite- Aceria tulipae occasionally damages onions. Gastropods Slugs and snails are troublesome pests of onion- the commonest UK species are Deroceras reticulatum- the field slug, Arion hortensis- the garden slug and Helix aspersa- the garden snail (URL-5). Nematodes Root parasites: These include the sedentary endoparasites (the root knot nematodes- Meloidogyne arenaria, Meloidogyne hapla, Meloidogyne exigua, Meloidogyne incognita, Meloidogyne javanica and Meloidogyne thanesi) and the sedentary ectoparasite includes the reniform nematode (Rotylenchus reniformis). Migratory endoparasites include the lesion and burrowing nematodes (Pratylenchus sp. and Radolphos similes respectively) and the migratory ectoparasites include the stubby root (Trichodorus sp.), lance (Longidorus sp.) and dagger (Xiphinema diversichaudatum) nematodes. Crown parasites: The major crown parasite is the stem and bulb nematodes (Ditylenchus dipasaci) (URL-5).

7.4. Harvesting and Yield Harvesting The green bunching onions are harvested by hand as soon as they attain the required size. The roots are washed and the outer skin is peeled out leaving the onion clean and white. They are then tied into bunches and sold. For the bulb crop, the flower heads are not allowed to set as they affect the formation of bulbs. The onions are ready for harvest when they are fully mature, which is indicated by the falling over of the tops while the leaves are still green. When these leaves turn yellow the onions should be pulled out. Harvesting can be advanced by a process called necking in which the tops of the onions are broken with the help of a plank or the crop is trampled 2-3 times at intervals of a few days. Necking does not affect the yield or the keeping quality of the

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produce. The bulb crop is ready for harvest in three months after planting. The entire plants can be pulled out easily from the light soils, but in heavy soils they have to be dug out with the aid of a sharp-edged hand tool (Khurpa). The tops are cut off 2.5-3.0 cm from the bulbs as soon as possible after they are removed from the field. The bulbs are then spread out in shade in thin layers for curing. They are cured for a week or ten days till the necks are completely dry. A well-cured onion is firm and the top of the bulb is not readily dented with the thumb. After curing the onions are kept in heaps till they are sent to the market. The small bulbs can be kept in stacks for two months (Anonymous, 2003). Yield The average yield of a transplanted crop varies from 90 to 270 qt/ha. Yields are usually high when the crop is raised from sets. A seed crop gives c 400-660 kg of seeds per hectare. When all conditions are optimum it is possible to get yields up to 900 qt/ha (Anonymous, 2003).

7.5. Processing and Storage Mature onions are cured and dried before storage. They are usually stored by spreading on the floor or on racks or keeping them in baskets in well-ventilated, thatched sheds or rooms. Frequent removal of rotted bulbs and loose skins and thinning over of the stored product is done. Occasionally, they are stored in small thatched pyramids of wheat straw, sorghum straw or sarkanda constructed in the open on roofs or under shade. This method is probably the cheapest and the most efficient. Onions can be stored in cold storage at 0.0-2.2 and low humidity approximately for six months without affecting their pungency (Anonymous, 2003). The ideal condition of the relative humidity for storage of onions is 70-75% (URL-5).

Heavy losses in onions occur during storage, the chief causes sprouting, rotting, shrinkage and driage. Sprouting is enhanced by increase in temperature whereas rotting increases with increase in humidity. Losses are also influenced by varieties, seasonal variations, stage of harvest of bulb, etc. Onions having a closed neck and tight fitting scales have better keeping quality. A pre-harvest spray with maleic hydrazide (600 ppm of 40% maleic hydrazide) considerably inhibits rooting and spoiling during storage. Dipping onions in a mixture of Fernate and Senesan fungicides and DDT before storing reduces rotting significantly (Anonymous, 2003). Onions sprayed with maleic hydrazide can not be used for planting purposes next year, because they will not sprout (URL-5). 8. Chemical Constituents Bulb Analysis of the onion (big) gave the following values: moisture, 86.6; protein,1.2; fat,0.1; carbohydrates,11.1; fibre,0.6; and minerals, 0.4g/100g; calcium ,47.0; phosphorus,50.0; iron,0.7; thiamine,0.08; riboflavin,0.01; niacin,0.4; and vitamic C, 11.0mg/100g. The Vitgamic C content decreases on cooking and storage. The essential amino acid composition of a sample of Indian onion (protein, 1.19%) was as follows (g/16g N):arginine,2.72; histidine,1.12; lysine,4.64; tryptophan,1.44; phenylalanine,2.88; methionine, 1.12; threonine, 1.44; leucine, 2.72; isoleucine, 1.44; and valine, 2.24 (Anonymous, 2003). The constituents identified are listed below (ppm unless otherwise indicated): (+)L-S-Prop-1-enyl-cysteine-s-oxide: 25.8 1(F)-beta-fructosyl-sucrose 2-Methyl-but-2-en-1-al 2-Methyl-butyr-2-aldehyde

33

4-Alpha-methyl-zymostenol 4-S-Oxide(trans)dec-2-ene,5-ethyl-4,6,7-Trithia (diastereomer) 4-S-Oxide(trans)dec-2-ene,5-ethyl-4,6,7-trithia 4-S-Oxide(trans/cis)deca-2,8-diene,5-ethyl-4,6,7-thithia (diastereomer) 4-S-Oxide(trans/trans) deca-2,8-diene,5-ethyl-4,6,7-thithia (diastereomer) 4-S-Oxide(trans/trans)deca-2,8-diene,5-ethyl-4,6,7-thithia 6(G)-Beta-fructosyl-sucrose 2,3-Dimethyl-bicyclo(2,2,1)hexane-5-oxide-5,6-dithia(1,2,3,4-alpha-5-beta) 2,3-Dimethyl-thiophene 2,4-Dimethyl-thiophene 24-Methylene cycloartanol 28-Iso-fucosterol 31-Nor-cycloartenol 31-Nor-lanostenol 9,10,13-Trihydroxy-octadec-11-enoic acid 9,12,13-Trihydroxy-octadec-10-enoic acid Abscisic acid Acetal Acetic acid Adenosine Allicin Alliin gamma-glutamyl-peptide Alliin Allium cepa polysaccharide Allyl-propyl-disulfide Alpha amyrin Alpha linolenic acid Alpha-sitosterol Arabinose Ascorbic acid Benzyl-iso-thiocyanate Beta carotene Beta-sitosterol Butane-cis-1-cis-4-dithial-S-S-dioxide,2,3-dimethyl Caffeic acid Calcium oxalate Catechol Cepaene 1 Cepaene 2-A Cepaene 2-B Cepaene 3 Cepaene 4-A Cepaene 4-B Cholest-7-en-3-beta-ol Cholesterol Choline Cis-Propanethial-s-oxide Cis-zweibelane Citric acid

34

Cyanidin bioside Cyanidin diglycoside Cyanidin monoglycoside Cyanidin-3-O-laminariobioside Cyclo-(2,1,1)-heptane-5-oxide,cis-2,3-dimethyl-5,6-dithia Cyclo-(2,1,1)-heptane-5-oxide,trans-2,3-dimethyl-5,6-dithia Cycloalliin Cycloartanol Cycloartenol Cycloeucalenol Cysteine Di-n-propyl-disulfide Dimethyl-trisulfide Diphenylamine DNA Ethanol Ferulic acid Fructose Gamma-gultamyl leucine Gamma-glutamyl-S-(Beta-carboxy-Beta-methyl-ethyl)-cysteinyl glycine Gamma-L-glutamyl cysteine Gamma-L-glutamyl-L-iso-leucine Gamma-L-glutamyl-L-valine Gamma-L-glutamyl-S-(2-carboxy-N-propyl)cysteine Gamma-L-glutamyl-S-(2-carboxy-propyl)-L-cysteinyl glycine ethyl ester Gamma-L-glutamyl-S-propenyl cysteine sulfoxide Glucofructan (Allium cepa) Glucose Glutamic acid Glutathione Glycine Glycolic acid Gramisterol Iso-quercitrin Iso-rhamnetin 4-O-beta-D-glucoside Iso-rhamnetin Kaempferol Kaempferol-3,4-di-O-beta-D-glucoside Kaempferol-4,7-di-O-beta-D-glucoside Kaempferol-4-0-beta-D-glucoside L-2-Propenyl-cysteine sulfoxide L-Gamma-glutamyl-phenylalanine ethyl ester L-Gamma-glutamyl-phenylalanine Gamma-L-glutamyl-L-arginine L-Methyl-cysteine sulfoxide Lophenol Leutein: 0.02 Malic acid Melatonin: 31.5 pcg/gm

35

Methanol Methionine methylsulfonium salt Methionine sulfone Methionine Methyl, 1-(methyl-sulfinyl)-propyl-disulfide Mevalonic acid: 0.5 N-Propyl mercaptan Nonadecanoic acid Oleanolic acid Oleic acid: Onion coat colorant Oxalic acid Palmitic acid Para-coumaric acid Para-hydroxybenzoic acid Pelargonidin monoglycoside Phloroglucinol carboxylic acid: 100 Phloroglucinol: 100 Prop-cis-enyl-disulfide Prop-(trans)-enyl propyl-trisulfide Propan-1-ol Propane-1-thiol Propional Propionaldehyde Prostaglandin A Prostaglandin A-1 Prostaglandin B Prostaglandin E-1 Prostaglandin F Protocatechuic acid: 0.45% Pyrocatechol Pyruvic acid Quercetin: 0.01-4.8% Quercetin-3,4-di-O-Beta-D-glucoside Quercetin-4,7-di-O-Beta-D-glucoside Quercetin-4-di-O-Beta-D-glucoside Raffinose Rhamnose Ribose Rutin S-(2-Carboxy-propyl) glutathione: 125mcg/g S-(beta-carboxy-beta-methyl-L-ethyl)cysteine S-1-cis-propenyl ester methyl sulfinothioic acid S-1-Cis-propenyl ester propyl sulfinothioic acid S-1-Propenyl ester n-propyl sulfinothioic acid(cis) S-1-Propenyl ester n-propyl sulfinothioic acid(trans) S-1-Trans-propenyl ester methyl sulfinothioic acid S-1-Trans-propenyl ester propyl sulfinothioic acid S-Allyl-cysteine

36

S-Methyl-cysteine sulfoxide S-N-Propyl ester N-propyl sulphinothioic acid S-Propyl ester propyl sulfinothioic acid S-Propyl-cysteine sulfoxide Satiomem Sinapic acid Sodium prop-(cis)-1-enyl-thiosulfate Sodium prop-(trans)-1-enyl-thiosulfate Sodium propyl-thiosulfate Spiraeoside: 1.13% Stearic acid Stigmasterol Succinic acid Sucrose Sugars Thiopropanal-S-oxide Thiopropional-S-oxide Valine Xylitol Xylose Zeaxanthin (Ross, 2001) When an onion is bruised; the sulphoxides are degraded by allinase and release puruvic acid and alkyl-thiosulfinates, which rapidly form into disulfides (Bruneton, 1999).

The organic sulphur compounds of Bulbous Allii cepae including the thiosuphinates, thiosulphonates, cepaenes, S-oxides, S,S-dioxides, monosulfides, disulphides, trisulfides, and zwiebelanes occur only as degradation products of the naturally occurring cysteine sulphoxides (eg. (+)-s-propyl-L-cysteine sulphoxide). When the onion bulb is crushed, minced, or otherwise processed, the cysteine sulfoxides are released from compartments and contact the enzyme allinase in adjacent vacuoles. Hydrolysis and immediate condensation of the reactive intermediate (Sulphenic acids) form the compounds.

The odorous thiosuphonates occur (in low concentrations) only in freshly chopped onions, whereas the sulphides accumulate in stored extracts or steam-distilled oils. Approximately 90% of the soluble organic-bound sulphur is present as gamma-glutamyl cysteine peptides, which are not acted on by allinase. They function as storage reserve and contribute to the germination of seeds. However, on prolonged storage or during germination, these peptides are acted on by gamma-glutamyl transpeptidase to form cystine sulphoxides, which in turn give rise to other volatile sulphur compounds (Breu and Dorsch, 1994). Essential oil The bulbs on steam distillation yield an essential oil (0.005%) known as ONION OIL (d9, 1.041, []D, -0.5) having an acrid taste and an unpleasant odour. The characteristic odour of the oil is attributed to the presence of several unstrurated sulphur and other organic compounds. The alkyl di- and tri-sulphides are primarily responsible for the cooked onion flavour which is characteristic of steam distilled onion oil. Gas chromatrography of the steam distilled onion oil showed the presence of several flavour constituents (Table 2). Other compounds identified are cepanone, nor-cepanone and neodecanoic acid. A lachrymatory principle, thiopropanal-S-oxide, is also present.

37

Table 2: Compounds identified in oil of onion

Thiophene dervatives 2,5-Dimethylthiophene 2,4-Dimethylthiophene 3,4-Dimethylthiophene 3,4-Dimethyl-2,5-dihydrothiophen-2-one

Monosulphides Dimethyl sulphide Allyl methyl sulphide Methyl propenyl sulphide (2 isomers) Allyl propyl sulphide Propenyl propyl sulphide (2 isomers) Dipropenyl sulphides (3 isomers)

Oxygen compounds Propanal Dimethylfuran 2-Methylpentanal 2-Methyl-pent-2-enal Tridecan-2-one 5-Methyl-2-n-hexyl-2,3-dihydrofuran-3-one

Trisulphides Dimethyl trisulphide Methyl propyl trisulphide Allyl methyl trisulphide Methyl cis-propenyl trisulphide Methyl trans-propenyl trisulphide Diisopropyl propyl trisulphide Isopropyl propyl trisulphide Dipropyl trisulphide Allyl propyl trisulphide Diallyl trisulphide cis-Propenyl propyl trisulphide trans-Propenyl propyl trisulphide

Thiols Hydrogen sulphide Mehanethiol Propanethiol Allylthiol

Disulphides Dimethyl disulphide Methyl propyl disulphide Allyl methyl disulphide Methyl cis-propenyl disulphide Methyl trans-propenyl disulphide Isopropyl propyl disulphide Dipropyl disulphide Allyl propyl disulphide cis-Propenyl propyl disulphide trans-Propenyl propyl disulphide Diallyl disulphide Allyl propenyl disulphide ( 2 isomers) Dipropenyl disulphide (3 isomers)

Tetrasulphide Dimethyl tetrasulphide

(Anonymous, 2003) Root Caffeic acid Ferulic acid Gibberellin A-4 Para-hydroxybenzoic acid Tuliposide A Tuliposide B (Ross, 2001) Leaf and Flower The leaf and flower from Japan on steam distillation yielded an essential oil (0.006%). The oil contain two new cyclic cis- and trans-3,5-diethyl-1,2,4-trithiolanes (Anonymous, 2001). The flower also contains carotene. The other compounds identified as constituents of leaf are as follows: Ascorbic acid

38

Caffeic acid Citric acid Ferulic acid Fructose Glucose Malic acid Methanol Oxalic acid Para-coumaric acid Para-hydroxybenzoic acid Propionaldehyde Protocatechuic acid Raffinose Sinapic acid Succinic acid Sucrose (Ross, 2001) The presences of quercetin, sterol glycosides are reported. The presence of gibberllin is also reported. Analysis of onion stalks gave the following values:moisture, 87.6;protein, 0.9; fat, 0.2; fibre, 1.6; carbohrdrates, 8.9; and minerals, 0.8g/100g; calcium, 50.0; phosphorus,50.0; iron,7.5; riboflavin, 0.03; niacin, 0.3; and vitamin C,17.0 mg/100g. The carotene content is 595mg and calorie value, 41 Kcal/100g (Anonymous, 2003). Skins Dried onion skins are the best natural source of quercetin. The skin of the pink onion cotains stigmasterol, cholesterol, -sitosterol, kaempferol, quercetin, and quercetin-3-glucoside. The phenolic acids reported to be present are p-hydroxy-benzoic acid, protocatechuic acid and vanillic acid. The onion skin is also used in the preparation of pectic substances (11-12%) as reported in the skin of white onion (Anonymous, 2003). Seed 5-Dehydroavenasterol Beta-sitosterol Beta-tocopherol Brassicasterol Cholesterol Fixed oil (17.3-18.1%) Stigmast-7-en-beta-ol Trigonelline Tseposide A Tseposide B Tseposide C Tseposide D Tseposide E Tseposide F (Ross, 2001) The seed yield an oil (18%) (Anonymous, 2003) with following composition (ppm unless otherwise indicated):

39

Alpha-tocopherol Arachidic acid Eicosen-1-ol Hexadecen-1-ol Linoleic acid (57.5-59.1%) Myristic acid Oleic acid (26.29%) Palmitic acid (7.3%) Stearic acid (3.5%) Stigmasterol (Ross, 2001)

O2-Methylpentanal

H

O2-Methyl-but-2-en-1-al

S CH3

CH3

2,3-Dimethyl-thiophene

S2,4-Dimethylthiophene

S2,5-Dimethylthiophene

S3,4-Dimethylthiophene

OHO

Abietic acid

O

HO

OHO

Abscisic acid

40

O OH

Acetic acid

N N

NN

H2N

O

HO

HOOH

Adenosine

SS

Allyl methyl disulphide

S

Allyl methyl sulphide

SS

S

Allyl methyl trisulphide

S

Allyl propenyl disulphide

SS

Allyl propyl disulphide

S

Allyl propyl sulphide

Allyl propyl trisulphide

SS

S

S

SAllyl-methyl-disulfide

SS

Allyl-propyl-disulfide

S

Allyl-propyl-sulfide

SS

S

Allyl-propyl-trisulfide

HS

Allylthiol

41

HH

H

HO

Alpha amyrin

OHO

Alpha linolenic acid

Alpha-sitosterol

SSO

Allicin

S

OHO

H2N

O

Allin

O

OH OHOH

OHArabinosealpha-D-Pyranose form

O

OH

OH

O

HO

HOAscorbic acid

NC

S

Benzyl-iso-thiocyanate

42

Beta carotene

Beta sitosterol

O

OHHO

HOCaffeic acid

OCa

OO

OCa

Calcium oxalate

OH

OHCatechol

O

O

Cepanone

43

HO

Cholesterol

HOCholest-7-en-3-beta-ol

Cis-Propanethial-s-oxideH3C

SO

+-

O

OH

OHO

OH

O OH

Citric acid

OH

N

Choline

44

OHO

OHO

OHOH

O

OH

OH

OH

OH

Cyanidin 3-glucoside

O

HOOH

OH

OHO

O

O

OHOH

OHOH

HO

OH

OH

Cyanidin-3,5-diglucoside

45

OHO

OHO

O

OH

OH

OOHOH

O

OH OHOH

OH

Cyanidin 3-laminariobioside

NHS

O

O OH

Cycloallin

HOCycloartenol

46

HO

Cycloeucalenol

OH

Cycloartanol

HSCO2H

NH2Cysteine

Diallyl disulphide

SS

Diallyl trisulphide

SS

S

Dimethyl disulphide

SS

S

Dimethyl sulphide

Dimethyl tetrasulphide

SS

SS

Dimethyl trisulphide

SS

S

Dimethyl-disulfide

SS

Dipropyl disulphide

SS

Dipropyl trisulphide

SS

S

47

HO

Ethanol

O

HO

O

HO

Ferulic acid

OHOMe

COOH

Ferulic acid(E)-form

O

OH

CH2OH

OHOH

OHFructosealpha-D-Pyranose form

OOH

OH

OH

OH

CH2OH

Galactosealpha-D-Pyranose form

OHOO

OHO

Gibberllin A-4

O

OH OH

OH

OH

CH2OH

Glucosealpha-D-Pyranose form

48

H2N O

HO O

OH

Glutamic acid

HS O

HN

HNO

NH2O

OH

O

OH

Glutathione

ONH2

OH

Glycine

OOH

OH

Glycolic acid

OH

Gramisterol

SS

Isopropyl propyl disulphide

Isopropyl propyl trisulphideS

SS

OO

HO

HOO OH

OH

Iso-rhamnetin

OHO

OH OOH

OHKaemferol

49

OH

Lophenol

SCO2H

H NH2

S-Allyl-cysteine

SCO2HH3C

O H NH2S-Propyl-cysteine sulfoxide

OHO

Stearic acid

HO O

OH

HO

O

Malic acid

O

HN

HN

O

Melatonin

SH

Methanthiol

OH

Methanol

S N 2

HO OMethionine

H

50

SO O

NH2

HO O

Methionine sulphone

Methyl propenyl sulphide

S S

Methyl propyl disulphide

SS

SS

S

Methyl propyl trisulphide

OH

OH

OH

OMevalonic acid

OH

O

Nonadecanoic acid

HO

OH

O

Oleanolic acid

OHO

Oleic acid

OH

OO

OHOxalic acid

51

HO O

Palmitic acid

OH

CO2H

Para-coumaric acid

HO

OH

O

Para-hydroxybenzoic acid

O

HO OH

O

OHO

O

HO OH

OH

OH

Peonidin-3-glucoside

OH

OH

HO

Phloroglucinol

52

CO2H

HOOH

Prostaglndin E-1

OHHO

O

OHProtocatechuic acid

O

Propanal

HOO

OH

OO

OH

Pyruvic acidTautomeric structures

53

OOH

OH

HO

OH OOH

Quercetin

O

OHHO

HOO

O O

HO

OH

OH

OH

O OH

OHHO

HO

Raffinose

O

OH OHOHOH

CH3

Rhamnosealpha-D-Pyranose form

O

OH OH

OHOHRibosealpha-D-Pyranose form

54

OHHO

OO

O

OHHO

O

HO OH

OH

OO

HO OH

OH

Rutin

O

OHO

O OH

Sinapic acid

CO2HH3C

O H NH2S-Methyl-cysteine sulfoxide

HOStigmasterol

OHOHO

OSuccinic acid

55

OOHOH

OHO

HO

O

HO

OH

OHOHSucrose

HO O

H2N

Valine

HO OH

HOOH

OH

Xylitol

O

OH OH

OH

OH

Xylosealpha-D-Pyranose form

HO

OH

Zeaxanthin

S

SO

Zwibelene

9. Traditional uses

9.1. Traditioanl uses in different countries Arabic countries. The dried bulb is used orally as a co