Changes in Carbohydrate Metabolism During Transient Senescence of Mustard (Sinapis Alba L.) Cotyledons
Higher plants very often display a transient senescence which occurs under unfavorable environmental conditions (for example in stress situations such as light stress or nitrogen deficiency). This adaptive senescence can be reversed as soon as the stress conditions cease. In fact, adaptive senescence is a characteristic of the flexibility of the plant with respect to the choice between preserving an organ or giving it up which in turn may depend on the actual source-sink situation (Kelly and Davies, 1988). It can be assumed that this process of “differential sacrifice” takes place even in one and the same organ at the level of organelles by means of different controls of either protein degradation or synthesis. In this case, the metabolic state within the cell may be a decisive tool for regulation (Trippi et al., 1989). By determining the activity of ribulose-1.5-bisphosphate carboxylase/oxygenase (Rubisco, E.C. 18.104.22.168) and, in some experiments, the mRNA of its small subunit (SSU) we have tried to find out with mustard seedlings whether chloroplast degradation during adaptive senescence can be correlated with parameters of carbohydrate metabolism such as the levels of glucose, sucrose, and starch. As an experimental approach we used the reversible transformation of chloroplast into amylo-plasts which can be induced by continuous irradiation (cWL) and accelerated by nitrogen deprivation.
KeywordsLight Stress Rubisco Activity Mustard Seed Unfavorable Environmental Condition Acer Pseudoplatanus
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