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* contain xyloglucan as cell wall storage polysaccharide observed (40 of the species with yields between 10-20 and 30 of the species with yields between 25-35 ) indicating a shift of the mode towards a lower yield (Figure 3B). In Faboideae, a much stronger shift is observed toward lower yields, almost 50 of the species in Faboideae presenting from 0.1-10 of their dry weight as galactomannan. Whereas almost 50 of the species in Caesalpinioideae present M G ratios between 2.5-3.5, in Mimosoideae...

Targeting A Bacillus Fructosyltransferase To The Cytosol

Edelman and Jefford 26 put forward a model in 1968 that would become the basis for exploring plant fructan metabolism over the next three decades. In this model the first enzymatic step, catalyzed by SST, was believed to take place in the cytosol. Chain elongation by FFT and storage of polymer occurred only in vacuoles. The model, therefore, called for transport of low molecular weight fructan, not sucrose, across the tonoplast. The locations of enzymes in this model pathway were not challenged...

In Design And Function During Evolution

Starch Synthesis Plants

According to Polhill et al. 38 , there is an evolutionary trend in the family Leguminosae towards accumulation of reserves in the cotyledons. In general, the seeds from species belonging to the subfamily Caesalpinioideae, which is considered to be the most primitive, tend to accumulate large amounts of galactomannan in their endosperm cell walls. Within this subfamily, it is also possible to observe that some tribes (Amherstieae and Detariae) tend not to have endosperms (normally consumed...

References

Glicksman in Handbook of Food Additives, T.E. Furia, (editor), CRC Press, Boca Raton, 1968. 2.1.C.M. Dea and A. Morrison, Adv. Carbohydr. Chem. Biochem., 31 (1975) 241. 3. J.S.G. Reid and M. Edwards in Food polysaccharides and their applications, A.M. Stephen (editor), Marcel Dekker, Inc, New York, 1995. 4. M.S. Buckeridge, H.P. Santos and M.A. Tin , Plant Physiol. Biochem., 38 (2000) In Press 5. J.S.G. Reid in Biochemistry of the plant cell walls, C.T. Brett and J.R. Hillman...

Carbohydrate Metabolism In Developing Tubers

There is general consensus that SuSy plays an important role in sucrose mobilization in developing tubers. Morrell and ap Rees (55) correlated the maximum catalytic activities of acid invertase, alkaline invertase and SuSy with the net rate of sucrose degradation in vivo in developing tubers of three potato cultivars and found that only SuSy could sustain the rates observed in all cultivars. SuSy activity markedly increases at the onset of tuber formation, remains high during the phase of tuber...

Transport Of Sucrose

Once sucrose is synthesized in mesophyll cells of source leaves, it has to be translocated to sink tissues. This transport occurs through phloem which contains elongated cells joined by sieve plates, consisting of diagonal cell walls perforated by pores. The single cells called sieve elements are surrounded by companion cells. Sieve elements and companion cells, in turn are connected to each other by many plasmodesmata. Photoassimilates generated in mesophyll cells diffuse via plasmodesmata to...

Structure And Composition Of The Starch Granule

Starch is a dominant reserve material of plants and an important component of the human diet. The starch granule is a dense, semi-crystalline, anhydrous structure found exclusively in the plastids of green algae and higher plants and in the cytosol of some red algae. In the potato tuber starch granules are located inside amyloplasts (one per plastid) and have characteristic shapes and structure, but are mostly oval or egg-shaped (126). Starch grain size increases as the tuber matures up to...

The Cell Wall Function In The Mannan Group

It seems quite clear from the information discussed above on the mannan group as a whole, that there is a structure-function relationship which has a central point in the degree and or positioning of the galactose residues on the p-mannan backbone. As the galactose branching approaches zero (pure mannans) their biological function seems to be more related to hardness. This can be clearly seen in Palmae and other non-legume species. Conversely, with higher degrees of galactosylation (fenugreek...

Sucrose Transport In The Sugar Beet Plant

Sucrose Proton Symporter

Sucrose transport is critical for development and growth in most plant species. Biological membranes like the plasma membrane and the tonoplast are almost impermeable to uncharged and charged molecules under normal conditions unless there is a principle realised within these membranes rendering them selectively permeable to certain molecule species. Some specific sort of pores and or transport proteins have to be present to ensure selective permeability of these membranes for sucrose as well....

Starch Metabolism Of Wheat Grain

Degradation And Biosynthesis Starch

The subject matter below will cover the primary issues of starch metabolism as they are relevant to wheat and grain filling, but the reader is encouraged to explore any of several recent reviews which will provide greater detail on the genes, enzymes and mechanisms of starch synthesis in plants 27-33 . Starch granules are composed of two types of glucan polymer. One is amylose, consisting of predominantly linear chains of a 1-4 -linked glucose residues, and the second is amylopectin, a highly...

Factors Affecting Grain Filling And Starch Synthesis

Many factors can influence starch synthesis and grain filling in wheat. Some are intrinsic, such as development of reproductive structures, mechanisms of assimilate utilization, and phytohormones within the seed. Others relate to environmental factors, such as nitrogen N availability and high temperature stress. Regardless of the particular component, these controls are often evaluated for their influence on seed dry matter accumulation, as a whole, and not starch biosynthesis, per se. Because...

Occurrence Of Starch In The Seed And Its Relationship To Grain Development

Starch synthesis in wheat is important because of its direct link to the productivity of the crop. Grain yield can be described as the product of the number of reproductive units per unit of ground area, the number of grains per reproductive unit, and the average weight per grain 2 . Average grain weight is determined by the pattern of seed growth and kernel composition. Hucl and Chibbar 3 measured the concentration of starch in grain of wheat from a number of different market classes and found...

Carbon Fixation

Rubisco Mechanism

All oxygenic organisms from the simplest prokaryotic cyanobacteria to the most complicated land plants reduce atmospheric CO2 to sugar phosphates by a pathway referred to as the Calvin cycle or RPP pathway. This pathway located in chloroplasts is the primary carboxylating mechanism in plants and is comprised of thirteen reactions catalyzed by eleven enzymes. The pathway has four principal features which include i carboxylation, in which CO2 is joined to the acceptor RuBP to form two molecules...

Tuber Induction

Starch Associated Protein

With a few exceptions, modern potato cultivars are all derived from one tuber bearing species of plants of the genus Solarium, i.e. Solatium tuberosum. Typically, the plant forms underground lateral shoots stolons with elongated internodes, hooked tips and characterised by diageotropic growth. Under specific environmental conditions e.g. short photoperiod, high light intensity, cool temperatures or low nitrogen levels, the stolons change their growth habit by dramatically reducing elongation...