Carbohydrate Metabolism of Rice Seedlings Grown in Oxygen Deficient Solution |
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Authors: | ATWELL, B. J. GREENWAY, H. |
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Abstract: | Atwell, B. J. and Greenway, H. 1987. Carbohydrate metabolismof rice seedlings grown in oxygen deficient solution.J.exp. Bot. 38: 466478. Rice seedlings (Oryza sativa L.) were grown in the dark forup to 4 d in solutions containing various concentrations ofO2. The rate of depletion of the endosperm was most rapid inaerated solution (0·25 mol O2 m3), largely dueto the inhibition of growth of seedlings at very low O2 concentrations.Earlier suggestions that there is a deficit of sugars for growthand energy generation in O2 deficient coleoptiles were tested. Coleoptiles, shaking in aerated solution, respired about one-thirdof the endogenous sugars to CO2 and incorporated the rest intostructural compounds. In contrast, the proportion of carbonwhich went to growth in anoxia was very low. Consistent withthese results, endogenous sugar levels were generally highestat low O2 concentrations. Even so, coleoptiles grown and testedas low as 0·03 mol O2 m3 showed appreciable metabolismof exogenous 14C-glucose to CO2, soluble and insoluble compounds,suggesting that a minimal O2 supply was sufficient to sustainsome growth. Furthermore, glucose feeding caused little or norise in O2 uptake or tissue sugar levels. Similarly, the specificactivity of the evolved CO2 was not markedly different in coleoptilesgrowing at 0·03 and 0·25 mol O2 m3 Further evidence was obtained to show that endogenous substrateswere adequate for growth and respiration at both low and highO2 concentrations. Exogenous glucose and malate did not stimulateO2 uptake at any stage of growth in aerated coleoptiles. Therewas sufficient endogenous substrate to sustain a 3545%rise in O2 uptake induced by uncoupling and enrichment withO2. Exogenous glucose did not stimulate growth of intact seedlingsat any O2 concentration. Key words: Rice seedlings, carbohydrate metabolism, oxygen deficient solution |
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