Source sink relationship in pulses and legumes

These pathways have been extensively studied in legume seeds, together with the SOURCE-SINK RELATIONSHIPS IN PLANT AND SUGAR In rice, when the expression of a SUTs involved in sucrose efflux from the. Interestingly, ST in legumes contains a unique protein crystalline body, the . that quantified translocation and source/sink relations in the legume white lupin. of an integrated view of translocation in relation to plant growth (Fig. were labeled and injected into the vasculature of intact rice plants through. It is interesting to know in details about the source-sink relationships in soybean. Here Soybean is a grain legume crop. As food cereals and many pulses.

Abstract Source-to-sink transport of sugar is one of the major determinants of plant growth and relies on the efficient and controlled distribution of sucrose and some other sugars such as raffinose and polyols across plant organs through the phloem. In this paper, we summarize current knowledge about the phloem transport mechanisms and review the effects of several abiotic water and salt stress, mineral deficiency, CO2, light, temperature, air, and soil pollutants and biotic mutualistic and pathogenic microbes, viruses, aphids, and parasitic plants factors.

Concerning abiotic constraints, alteration of the distribution of sugar among sinks is often reported, with some sinks as roots favored in case of mineral deficiency.

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Many of these constraints impair the transport function of the phloem but the exact mechanisms are far from being completely known. Phloem integrity can be disrupted e. Photosynthesis inhibition could result from the increase in sugar concentration due to phloem transport decrease. Biotic interactions aphids, fungi, viruses… also affect crop plant productivity. Recent breakthroughs have identified some of the sugar transporters involved in these interactions on the host and pathogen sides.

The different data are discussed in relation to the phloem transport pathways. When possible, the link with current knowledge on the pathways at the molecular level will be highlighted.

Source-to-sink transport of sugar and regulation by environmental factors

In all cases, sucrose is the main form of carbon found in the phloem. In addition to sucrose, polyols mainly sorbitol and mannitol and oligosaccharides of the raffinose family can also be found. This article has been cited by other articles in PMC.

Abstract Considerable interest has been evoked by the analysis of the regulatory pathway in carbohydrate metabolism and cell growth involving the non-reducing disaccharide trehalose TRE.

TRE is at small concentrations in mesophytes such as Arabidopsis thaliana and Triticum aestivum, excluding a role in osmoregulation once suggested for it.

Studies of TRE metabolism, and genetic modification of it, have shown a very wide and more important role of the pathway in regulation of many processes in development, growth, and photosynthesis. It has now been established that rather than TRE, it is trehalose 6-phosphate T6P which has such profound effects.

Source Sink Movement in Hindi/Urdu - Biology Crash Course #417

T6P is the intermediary in TRE synthesis formed from glucosephosphate and UDP-glucose, derived from sucrose, by the action of trehalose phosphate synthase. The concentration of T6P is determined both by the rate of synthesis, which depends on the sucrose concentration, and also by the rate of breakdown by trehalosephosphate phosphatase which produces TRE.

Changing T6P concentrations by genetically modifying the enzymes of synthesis and breakdown has altered photosynthesis, sugar metabolism, growth, and development which affect responses to, and recovery from, environmental factors. T6P inhibits the activity of SnRK1, which de-represses genes encoding proteins involved in anabolism.

Source-to-sink transport of sugar and regulation by environmental factors

Consequently, a large concentration of sucrose increases T6P and thereby inhibits SnRK1, so stimulating growth of cells and their metabolic activity. One mechanism linking the two has been identified: Although T6P and TRE usually occur at very small concentrations compared with many other carbohydrates, T6P increases substantially — albeit over the micromolar range — with greater availability of sucrose and larger fluxes of sucrose to organs and correlates strongly with changes in carbohydrates, e.

It is now very clear that T6P is a signal of sucrose availability with large effects throughout metabolism Nunes et al. The effects of altering T6P on plant development and growth have been well demonstrated by genetic modification. Frequently development of shoot, leaf, and root is altered, giving smaller, thicker organs when T6P exceeds its normal concentration range: Decreases in T6P result in the opposite phenotype, where leaves are paler, larger, and thinner Pellny et al.

Such changes in vegetative phenotype are reminiscent of sun and shade leaves respectively indicating that carbon, via T6P, has an input into leaf development as an indicator of energy and resource availability independent of the light environment. T6P also plays an essential role in regulation of sugar-induced leaf senescence Wingler et al. The effects of altering T6P can be variable.

For example, Yeo et al. However, Han et al. A major consequence of modifying T6P is alteration of carbohydrate balance, with accumulation of carbohydrates, e.