E P I D E R M A L S T R U C T U R E A N D D E V E L O P M E N T O F S T O M A T A I N S O M E P O L Y G O N A C E A E

BY J. A. INAMDAR (Department of Botany, Sardar Patel University, Vallabh Vidyanagar, Gujarat, lndia)

Received December 3, 1969

(Communicated by Prof. V. Purl, r.A.SC.)

ABSTRACT

In the present paper, epidermal structure and development of stomata are described in 15 species of the Polygonaceae. Epidermal cells of Polygonum species contain druses of calcium oxalate. Parallel cuticular striations are noticed. Six types of glandular, non-glandular trichomes and extra-floral nectaries are observed. The mature stomata are aniso- cytic, ancmocytic and paracytic. The anisocytic and paracytic stomata may be monoeyclic or amphicyclic. The anomocytic stomata are incom- pletely monocyclic. The increase in number of subsidiary cells in anise- cytic and paracytic stomata is due to the divisions of the subsidiaries. The ontogeny of anisocytic and paracytic typos is syndetocheilie or meso- genous, while that of anomocytic is haplocheilic or perigenous. Twin stomata are also noticed.

INTRODUCTION

METCALFE AND CHALK (1950) pointed out that the stomata are nearly always ranunculaceous (anomocyfic), rarely rubiaceous (paracytic)in the meml;ers of the family Polygonaceae. The present author 0969 b) studied the epi- dermal structure and ontogeny of stc~nata in two sFecies of the family and reported anisocytic (cruciferous), anomocytic and paracytic stomata. The present investigation, therefore, was undertaken, as there is no other report on the epidermal structure and development of stomata in the Polygonaceae. The present paper deals with the epidermal structure and ontogeny of stomata in 15 species of the Polygonaceae. Terminologies used here are as defined by Metcalfe and Chalk (1950) and Pant (1965).

MATERIALS AND METHODS

Material of the following 15 species was collected by me during bota- nical excursion to Dharampur forests, Mount Abu, Mahableshwar,

B6 91

92 J . A . INAMDAR

Mussourie and University campus: Fagopyrum cymosum Meissn., Muehlen- beckia platyclada (Muell.) Meissn. (leaf and stem), Polygonum amphibium Linn., P. amplexicaule Don, P. barbatum Linn. var. gracile Steward, P. capitaturn Ham., P. chinense Linn., P. dumetorum Linn., P. glabrum Willd. (stipule, perianth), P. laginerum R.Br. P. plebeium R. Br., P. nepalense Meissn., P. recumbens Royle, Rumex dentatus Linn. and R. hastatus D. Don. The herbarium specimens are deposited in the herbarium, Deparlment of Botany, Sardar Patel University, Vatlabh Vidyanagar.

Epidermal peels of your~g and mature leaves and other organs were taken from fresh as well as fixed material (1 :3 acetic-ethanol) and her- barium specimens. Camera lucida drawings were made from temporary whole mounts of epidermal peels stained with Delafield's hematoxylin.

OBSERVATIONS

Mature Epidermis

The leaves of all the species are amphistomatic except the floating leaves of Polygonum amphibium which are epistomatic. In case of amphistomatic leaves, the number of stomata on the lower epidermis are more than the upper. The cells of the epidermis are polygonal, isodiarnetric or elongated and not arranged in a definite pattern. The anticlinal epidermal walls are either sinuous, :straight or arched. Sinuousities are more pronounced in Polygonum dumetorum (Fig. 8) and P. nepalense (Fig. 12). Druses of calcium oxalate are present in the epidermal cells of Polygonum species (Fig. 9). Surface of the cuticle shows parallel striations radiating from the tdchome bases or guard cells (Figs. 7, 9).

Glandular and eglandular trichomes, some six types and extra floral nectaries are observed in the species investigated, they are:

(i) Peltate glandular trichome (Figs. 15-17);

(ii) Extra-floral nectary with a multiseriate stalk, from the stipule and perianth of Polygonum glabrum (Figs. 11, 19);

(iii) Simple uniseriate filiform trichome of Polygonum amplexicaule (Fig. 20);

(iv) Simple bicellular conical trichome ofFagopyrum cymosum (Fig. 21);

(v) Simple unicellular conical peg-like trichome of F. cymosum (Fig. 22);

Epidermal Structure and Development of Stomata in Some Polygonaeeae 93

(vi) Small shaggy trichome of Polygonum barbatum var. gracile (Fig: 23); (vii) Bizarre shaggy trichomes are present in many Polygonum species

(Fig. 24).

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I

FIGS. 1-10. Fig. 1. Young leaf epidermis of Polygonum plebeium showing meri- stemoids ~n different stages of development. Peels from mature epidermis showing anisoe~tic anomocytic and parasytic stoma,a. Fig. 2. Polygonum plebeium (note twin Stomata). Fig. 3. P. amplexicaule. Fig. 4. P. amphibium. Fig. 5. P. barbatum var. graeile. Fig. 6. P. eapitatum. Fig. 7. P. chinense (note cuticular striations). Fig. 8. P. dttmetorum. Fig. 9. P. glabrum (stipule, note cuticular striations). Fig. 10. P. laginerum.

Fig. I, × 230; Figs. 2-10, × 97.

Mature Stomata

The stomata are irregularly arranged on the Ieaf epidemlis. The stomata are distributed in between the veins. The mature stomata are anisocytic (Figs. 2-18), anomocytic (Figs. 2-18) and paracy, tic (Figs. 2-18). The anisocytic and paracytic stomata may be monocycli¢ (Fig~. 2-14, 16-18) or amphicycli¢ (Fig. 15). Twin stomata aro also observed (Fi$. 2), In

94 J . A . INAMDAR

some cases there are distinct stomatiferous and non-stomatiferous areas (Figs. 9-10, 15-16).

FlOS. 11-24. Fig. 11. P. glabrum (perianth, note extra-floral nectary). Fig. 12. P. nepalense. Fig. 13. P. recumbens. Fig. 14. Fagopyrum cymosum. Fig. 15. Meuhlenbeckia platyclada (stem, note peltate gland). Fig. 16. Meuhlenbeckiaplatyclada 0eaf, note peltate glanda Fig. 17. Rumex dentatus (note peltate gland). Fig. 18. R. hastatus. Fig. 19. Extra-floral neetary from stipule of P. glabrum. Fig. 20. Simple uniseriate flliform trichome of P. amplexi- caule. Fig. 21. Simple biceUular conical trichome of Fagopyrum cymosum. Fig. 22. Simple unicellular conical trichome, peg-like, F. cymosum. Fig. 23. Small shaggy trichome of P. bar. batum vat. gracile. Fig. 24. Bizarre shaggy trichome of P. nepalense.

Figs. 11-24, × 97.

Development of Stomata

In a young organ the epidermal cells are polygonal, isodiametric or elongated and uninucleate with straight or arched anticlinal walls (Fig. 1). The stomatal initial is cut off in a corner of any cell of the epidermis. "Ihe meristemoid can be easily distinguished from the adjacent epidermal cells by its smaller size, rather prominent nucleus and dense staining properties (Fig. 1). The ontogeny of the different types of stomata is as follows;

Epidermal Structure and Development of Stomata in Some Polygonaceae 95

(t) Anisocytic stomata.--The triangular meristemoid divides unequally by a slightly curved wall forming a large more or less flat rectangular cell on one side and a small triangular cj1 in a corner (Fig. 1). The large rectangular cell differentiates into a first subsidiary cell, while the small triangular cell divides again by a curved wall perpendicular to the first so as to form a second subsidiary cell and a middle triangular cell (Fig. 1).. The middle cell then divides on the third side by a straight or slightly curved wall perpendicular to the previous ones, so as to give rise to a third subsidiary cell and a small triangular central cell (Fig. 1). It now functions as a guard mother cell, becomes rounded and divides forming a pair of guard cells (Fig. 1). The guard cells become bean-shaped and develop an intervening pore. In majority of the cases the mature anisocytic stomata are surrounded by a ring of three unequal subsidiary cells of which one is distinctly smaller and arranged in a spiral fashion. In the stem of Muehlen- beckia platyelada all the three subsidiary cells divide once, so that tee stomata are surrounded by six subsidiaries and become amphicyclic (Fig. 15).

(2) Anomocytic stomata.--The triangular meristemoid becomes rounded and directly functions as a guard mother cell without cutting off any sub- sidiary cells. The guard cells become bean-shaped ~nd develop a lenti- cular pore in between. The mature stomata are anomocytic and surrounded by 3-5 ordinary epidermal cells. Sometimes, an anomocytic stoma in Polygonum laginerum (Fig. 10) may be flanked by a parallel subsidiary cell, thus making the stomatal apparatus incompletely monocyclic.

(3) Paracytic stomata.--The meristemoid divides by slightly curved wall forming two unequal cells (Fig. 1). The large cell differentiates as a first subsidiary cell while the smaller lenticular cell which increases in size and divides again by a curved wall intersecting the first so as to form a second subsidiary cell and a central guard mother cell (Fig. 1). Some- times, the second wall intersects at one pole only or both the walls are straight and parallel to each other (Fig. 1). The guard mother cell divides by straight wall to form a pair of guard cells between which an intervening pore develops. Occasionally, as in the stem of Muehlenbeckia platyclada, both the subsidiary cells divide once, so that the mature stoma is flanked by 4 subsidiary cells and the stoma becomes amphicyclic (Fig. 15). The mature stomatal apparatus is paracytic, flanked by 2-4 subsidiary cells which are contiguous at both the poles (Figs. 2-5, 9, 16-18) or non- contiguous at one (Figs. 2, 5, 8, 12, 13) or both the poles (Figs. 6, 7, 10, !1, 14, 15).

96 J .A. INAMDAR

As the sut~sidiary cells and the guard cells originate from the same meristemoid in anisocytic and paracytic stomata, lhe ontogeny of these types conforms to the syndetocheilic type of Florin (1931, 1933) or meso- genous type of Pant (1965). The development of anomocytic type is haplo- cheilic (Florin, 1931, 1933) or perigenous (Pant, 1965).

DISCUSSION

According to Metcalfe and Chalk (1950) the stomata in the members of the family Polygonaceae are nearly always anomocjtic except in Cocco- loba which has distinct subsidiary cells; rubiaceous in Oxythec a and Triplaris. Inamdar (1969 b) reported syndetocheilic or mesogenous aniso- cytic, paracytic and haplocheilic or perJgenous anomocytic stomata in the leaves of Antigonon leptopus and Poiygonum glabrum. As regards the structure and ontogeny of stomata in 15 sFecies of the Polygonaceae, the present observations are in accordance with the previous ones of this author. Abnormality noticed here is twin stomata only. Observatior.s on trichomes and extra-floral nectaries are also in accordance with Metcalfe and Chalk (1950).

The development of anisocytic stomata has been studied in the mem- bers of Crassulaceae (Strasburger, 1866; Yarbrough, 1934), Cruciferae (Tognini, 1897; Paliwal, 1967; Pant and Kidwai, 1967), Compositae (Pant and Verma, 1963), Verbenaceae (Pant and Kidwai, 1964; Inamdar, 1969 a), Convolvulaceae (Pant and Banerji, 1965; Inamdar, 1969d), Malvaceae (Inamdar and Chohan, 1969), Araliaceae (Inamdar etaL, 1969), some Centrospermae and Polygonales (Inamdar, 1969b), Violaceae (Inamdar, 1969c) and Solanaceae (Esau, 1965; Inamdar and Patel, 1969). As repor- ted by these authors, here also the meristemoid l~ehaves !;ke an apical cell with three cutting faces and produces three subsidiary cells in a spiral sequence. Here, the meristematic activity is confined to the smaller cell always and the successive walls laid down are perpendicular to the preceding ones.

The occurrence of three types of stomatal apparatuses has l:een ob- served in the leaves of all the species as well as the stipule and perianth of Polygonum glabrum. Inamdar (1969 b) also reported such a diversity in the leaves of Antigonon leptopus and Polygonum glabrum. A combination of diverse types of stomatal complexes on the same surface of the leaf has also been reported by several workers (Tognini, 1897; Pant and Kidwai, 1964; Paliwal, 1965; Inamdar, 1967, 1968, 1969a, 1969b, 1969c, 1969d, Inamdar and Chohan, 1969; Inamdar et aL, 1969; Inamdar and patel, 1969). Although the mature stomatal complexes are constant from

Epidermal Structure and Development of Stomata in Some Polygonaceae 97

species to species, they show variation in number and orientation of the subsidiary cells as pointed out earlier.

The development of the anisocytic and the paracytic stemata resembles syndetocheilic (Florin, 1931, i933) or mesogenous (Pant, 1965) type as the subsidiary ceils and the guard cells originate from the same stomatal initial. The anomocytic stomata are haplocheilic (Florin, 1931, 1933) or perigenous (Pant, 1965).

ACKNOWLEDGEMENTS

The author's gratitude is due to Principal J. G. Chohan and Prof. V. Puri for their keen interest and encouragement. My thanks are due to Mr. R. C. Patel for his ever-willing help.

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