KERANGKA TEORI

STRATEGI MENINGKATKAN RENDEMEN TEBU

bahan kajianDiabstraksikan oleh

Prof Dr Ir Soemarno MSPM PSLP PPSUB Agustus 2010

TEORI FOTOSINTESIS

Saccharum officinarum is particularily efficient in producing an excess amount of sucrose. In fact  This

process of taking in light energy and converting it into other substances is called photosynthesis.

FOTOSINTESIS TEBU TANAMAN C4

PENAMPANG DAUN TEBU TANAMAN C4

PHOTO-IONIZATION

The excited chlorophyll-protein complex reacts with water and splits the water into hydrogen ion (OH-). 

This phenomenon is called photoionization.

Chlorophyll-protein complex (Excited) + H2O          ------- Chlorophyll – Protein complex + H* _ OH –

(Ground state)

BIOSINTESIS KARBOHIDRATThe CO 2 acceptor in C 4 plants is phosphoenolpyruvate

(PEP). PEP reacts with CO 2 to form oxaloacetic acid which is reduced by NADPH to form malic acid. The malic acid then

reacts with RUBP to form pyruvic acid..

BIOSINTESIS GLUKOSE

TEORI KHLOROFILPhotochemical Reaction Centre of the Light Harvesting

AntennaWhen a chlorophyll molecule in the thylakoid membrane is

excited by light, the energy level of an electron in its structure is boosted by an amount equivalent to the energy of the absorbed light and the chlorophyll becomes excited. The packet of excitation energy (The Exciton) now migrated rapidly through the light harvesting pigment molecules to the reaction centre of the photosystem where it causes an

electron to acquire the large amount of energy.

KHLOROFIL : PHOTOSYSTEM

Light, in the form of photons, excite the chlorophyll molecules until it reaches the reaction center of

Photosystem II. This allows an electron from one chlorophyll molecule to jump to a higher energy level within the same chlorophyll

molecule.

MOLEKUL KLOROFIL INTI Mg

Chlorophyll is synthesized in chloroplasts from 8 molecules of 5-aminolevulinic acid.  The 8 red lines indicate the location

of the parts of 5-aminolevulinic acid in the finished molecule.  Position 3 that is a methyl group in chlorophyll a

(illustrated) is a formyl (CHO) group in chlorophyll b. 

Molekul khlorofil

BIOSINTESIS KHLOROFIL

In higher plants 5-aminolevulinic acid is synthesized from glutamic acid as illustrated in

Figure of von Wettstien et al. (1995):                                                                             

                                         

BIOSINTESIS KHLOROFILA) An outline of the chlorophyll biosynthetic pathway. The

shaded area represents the region of the pathway under control of ChlM.

B) The methyltransferase reaction catalysed by ChlM. Abbreviations: ALA, d-aminolaevulinic acid; proto,

protoporphyrin IX; GGPP, geranyl-geranoyl pyrophosphate; ChlM, magnesium protoporphyrin IX

methyltransferase; SAM, S-adenosyl-l-methionine; SAH, S-adenosyl-l-homocysteine.

The biosynthetic pathway of chlorophyll and heme.

BIOSINTESIS SUKROSE

BIOSINTESIS SUKROSEPossible sites of sodum involvement in C4 photosynthesis:

stomatal conductance (A), carbonic anhydrase (B), activity of PEP carboxylase (C) were all unaffected by sodium nutrition.

By contrast, leaves of sodium-deficient plants had high levels of alanine and pyruvate and low levels of PEP in the

mesophyll chloroplasts (Original unpublished diagram courtesy P.F. Brownell)

Pathway of starch synthesis in chloroplasts

Carbon assimilated via the Calvin cycle is partitioned with a fraction exported to the cytosol for sucrose synthesis and a

fraction retained in the chloroplast for starch synthesis.

Redox activation and allosteric regulation of AGPase controls the flux of carbon into starch. Abbreviations: Fru6P, fructose 6-phosphate; Glc1P, glucose 1-phosphate; Glc6P,

glucose 6-phosphate; TPT, triose-phosphate/phosphate translocator.

The role of Fru-2,6-P2 in feedforward control of sucrose synthesis.

Reactions shown are catalysed by the following enzymes: 1, Rubisco; 2, chloroplastic PGK and chloroplastic TPI; 3, chloroplastic

Fru-1-6-P2 aldolase; 4, chloroplastic FBPase; 5, transketolase, sedoheptolase-1,7-bisphosphatase aldolase, sedoheptolase-1,7-

bisphosphatase, phosphopentoepimerase, phosphoriboisomerase and phosphoribulokinase; 6, triose phosphate transporter; 7, cytoslic PGK

and cytosolic TPI; 8, cytosolic Fru-1-6-P2 aldolase; 9, cytosolic FBPase; 10, cytosolic PGI ; 11, cytosolic PGM , 12, UGPase, 13, SPS,

14, sucrose phosphatase.

TRANSPORT SUKROSEPathways of sugar metabolism and compartmentation within

sink cells. Sugars can be delivered to sink cells through either apoplasmic or symplasmic pathways.

Within the sink apoplasm, sucrose can be hydrolysed to hexoses by an extracellular invertase.

TRANSPORT SUKROSE

In photosynthetic tissues sucrose is predominantly exported from cells, most probably by facilitated

diffusion and subsequently taken up by the phloem complex by a specific sucrose/H+ co transport

mechanism

Once in the phloem complex sucrose is transported to cells in heterotrophic “sink“ tissues.

At least two distinct classes of sink tissues can be differentiated:

(i) “utilisation sinks“, highly metabolically active, rapidly growing tissues like meristems and immature

leaves, (ii) “storage sinks“, such as tubers, STEM, roots or fruits

which deposit imported carbohydrates as storage compounds (e.g. starch, sucrose, lipid or protein).

Sucrose obtained through translocation, by sink tissues, can enter a cell directly via the symplasm or the apoplasm (whereby it is transported by specific sucrose or, following cleavage to its component

hexoses, monosaccharide transporters.

Several studies using asymmetrically labelled sucrose suggest that carbon obtained by heterotrophic cells moves primarily through the symplastic route and is not cleaved to glucose and fructose during transport.

Mobilisation of Sucrose in sink tissues

Sucrose delivered to the sink tissue can be cleaved in one of three ways:

(i)in the apoplast, as described above, by the action of an acid invertase or in the cytosol by either

(ii)alkaline invertase or

(iii)sucrose synthase (SuSy).

The predominant route of sucrose unloading and subsequent mobilization.

SUKROSE DALAM JARINGAN SIMPANAN

The possible fates of sucrose unloaded apoplastically in sink tissues.

(1) Sucrose that enters the apoplast can be split into glucose and fructose by a wall invertase before entering a cell from a

sink tissue, or (2) sucrose can be taken up into the cell unaltered. (3) Once in the symplast of the cell from the sink tissue, sucrose can be split into glucose and fructose by a cytoplasmic invertase, or (4) sucrose can enter the vacuole unaltered. (5) Once in the vacuole, sucrose can be split into

glucose and fructose by a vacuolar invertase, or it can remain unaltered.

METABOLISME SUKROSE

KATABOLISME SUKROSE

Sucrose is split by either invertase (β-fructofuranosidase) or sucrose synthase .

Dashed arrows at the top differentiate alternative ‘starting points’ for sucrose catabolism.

Products of sucrose breakdown contribute to a pool of cytosolic glucose 6-P and fructose 6-P , which are freely

interconvertible in what is labelled ‘hexose-P pool’.

In the cytosol, fructose 6-P can be converted to fructose 1,6-P2 by two different reactions, one catalysed by 6-

phosphofructokinase and the other by PPi–fructose-6-P 1-phosphotransferase .

Dashed arrows indicate alternative sources of fructose 1,6-P2. [PPi–fructose-6-P 1-phosphotransferase is confined to cytosol , so if fructose 6-P is phosphorylated in plastids,

only one reaction is available.]

Fructose 1,6-P2 is converted to 2 phosphoenolpyruvate (PEP) in glycolysis. As drawn, glycerone-P moves from

cytosol to plastid, although other glycolytic intermediates (e.g. glucose 1-P, 3-P-glycerate and PEP) can also move from

cytosol to plastids .

The Pi exchanged for glycerone-P during cytosolic-plastidic countertransport is balanced by net Pi releases in the

plastid. As drawn, the hexose-P pool supplies glucose 6-P to plastids, where erythrose 4-P (E4P) is produced by cyclic

operation of the oxidative pentose phosphate pathway (OPPP).

RESPIRASI

Respiration begin with breakdown of sucrose to the hexose phosphates (hexose-P) glucose

6-P and fructose 6-P.

Sucrose breakdown is assumed to occur in the cytosol, though it can also occur in the

apoplast. Sucrose can be cleaved by invertase or

sucrose synthase .

The products of invertase action are glucose plus fructose, which can be directly

phosphorylated to form glucose 6-P and fructose 6-P, respectively.

Sucrose breakdown by sucrose synthase yields fructose plus UDP-glucose.

This fructose can be phosphorylated directly, giving fructose 6-P, and the UDP-glucose can

be converted to glucose 6-P in two steps.

STABILISASI UREA

Urea bersifat higroskopis dan mudah larut dalam air

(Urea optimally hydrated: about 6 - 8 moles water per mole urea )

Molekul Urea mengikat Molekul Air

Molecular 'embrace' of an urea and a water molecule

The water molecule is bonded to the urea molecule by two water bonds (dotted lines). The hydrogen atoms are indicated in white, the oxygen atoms in red, the nitrogen atoms

in blue and the carbon atom in black .

H2O

NH2

CO

Molekul Urea higroskopis dan mudah larut air

Solvation structure of the urea molecule from our experiments.

One of the water molecules in the solvation shell shares two hydrogen bonds with urea.

Geometri Kristal Urea

HIDROLISIS UREA SECARA ENSIMATIS

UREASE: ENSIM HIDROLISIS UREA

Some microorganisms excrete an enzyme, Urease.

This highly effective enzyme rapidly hydrolyzes urea to one molecule of Carbon Dioxide, and two molecules of

ammonia.

Because Carbon Dioxide is subject to evaporation, this reaction rapidly increases environmental pH by the production of Ammonium Hydroxide. Once in the

environment, Urease will hydrolyze urea to Ammonia even though the excreting microbe is no longer alive.

If microbes have an abundance of energy-rich carbon foods, and plenty oxygen, they will rapidly oxidize toxic ammonia to harmless nitrates. These nitrates become

available for plant or microbe metabolism or if in excess, decomposition to molecular Nitrogen.

On the other hand, if energy food to support microbe growth is lacking, or if conditions go anaerobic, the

microbes are unable to detoxify ammonia by transformation to nitrate.

When this sequence occurs, ammonia buildup can quickly kill plants.

Biuret is formed by the controlled decomposition of urea; condensing two

molecules of urea into a single molecule of biuret, which retains three of the nitrogen

atoms.Biuret is less soluble than urea. 

ASAM HUMATExample of a typical humic acid, having a variety of components including quinone,

phenol, catechol and sugar moieties

STRUKTUR ASAM HUMAT

The hypothetical structure for humic acid is shown below.

It contains free and bound phenolic OH groups, quinone structures, nitrogen and oxygen as bridge

units and carboxylic acid groups variously placed on aromatic rings.

ASAM HUMAT MENGIKAT KATION TERSEDIA

Because of the variable molecular composition of humic acids, a wide range of dissociation constants exists for

the metals that are chelated by humic acids .

In addition, different metals are bound to humic acids with varying strength, and this would mean that a particular

chelate-bond cation will modify the binding stability of the other metal linkages.

This peculiar metal binding capacity of humic acids is exemplified by the fact that when some alkali metals,

such as K and Na, are bound by previously empty functional groups, then the chelated bonds of Fe and Al

may rupture easier than if the humic acid molecule contains an alkali earth metal, such as Ca .

This peculiar metal binding capacity also protects plants by the ability of water-soluble fractions of humic

substances (humic and fulvic acids) to form precipitates with a number of metals (Ca, Cd, Hg, Pb, Ba), forming

insoluble complexes.

The complexes formed are not available to plants and the concentration of toxications in the soil solution is

reduced .

KIMIAWI ASAM HUMAT

A typical humic substance is a mixture of many molecules, some of which are based on a motif of aromatic nuclei with phenolic and carboxylic subsituents, linked together; the

illustration shows a typical structure. The functional groups that contribute most to surface

charge and reactivity of humic substances are phenolic and carboxylic groups.

Humic acids behave as mixtures of dibasic acids, with a pK1 value around 4 for protonation of carboxyl groups and

around 8 for protonation of phenolate groups. There is considerable overall similarities among individual

humic acids. For this reason, measured pK values for a given sample are average values relating to the constituent

species. The other important characteristic is charge density.

The molecules may form a supramolecular structure held together by non-covalent forces, such as Van der Waals force

, H-H, and CH-H bonds.

The presence of carboxylate and phenolate groups gives the humic acids the ability to form complexes with ions such as Mg2+, Ca2+, Fe2+ and Fe3+. many humic acids

have two or more of these groups arranged so as to enable the formation of chelate complexes.

Pembentukan khelate merupakan aspek penting dari peranan biologis dari asam humat dalam mengendalikan

ketersediaan hara logam.

Asam humat : Khelator

Asam humat mempunyai kemampuan menjadi khelator.

A chelator is a molecule that binds metals, including toxic heavy metals. It is able to

scavenge for these heavy metals and eliminate them from the body.

It also seems to increase the permeability of cell walls, allowing for easier transfer of

nutrient metals.

Research indicates that humic acid can bind to essential metals as well; much like soil humic acid did millions of years ago it can

provide nutrients to living things growing in the soil.

Khelat Cu-asam humat

Bagan berikut menyajikan bagaimana kation Cu++ dikhelate oleh asam humat.

Kation Cu++ pada posisi sentral (pusat) dikhelat oleh asam humat yang ukuran molekulnya lebih besar.

Kation ini diikat secara ionik oleh dua gugusan asam karboksilat yang bermuatan negatif dan dikompleks

dengan satu gugus asam amino netral. Secara bersama-sama ketiga gugusan ini mengikat kation dengan kekuatan yang jauh lebih besar daripada kekuatan

masing-masing gugusan.

Skema pembentukan khelat logam M oleh asam humat

MANFAAT ASAM HUMAT?

Mereduksi jumlah air yang diperlukan untuk tanaman yang sehat.

Mereduksi penggunaan pupuk.

Mereduksi kebutuhan pestisida. Helps control pollutant contamination.

Makes plants more drought, heat and cold resistant.

Adds incredible diversity to the Soil Food Web. Reduces the amount of water needed for healthy

plant.

Berfungsi sebagai bio-stimulant. Memperbaiki sifat fisika tanah.

Menahan hara dalam bentuk dapat ditukar.

Memperbaiki kondisi lengas tanah.

Affects the release of plant nutrients through slow decomposition.

Improves trace element nutrition through chelation of metallic & non-metallic ions.

Chlorosis in plants has been prevented or corrected by humate application.

ASAM HUMAT MEMPERBAIKI STRUKTUR TANAH

ASAM HUMAT BLOCKER VIRUS

Humic acid's mechanism of action in these cases is believed to be the blockage of a virus particle

from attaching to and entering a healthy cell. Viruses can't replicate or divide without entering and taking over the cell's DNA for the making of

more virus particles. By keeping one virus particle from becoming thousands, it effectively blocks

the infection from happening.