Comparative effect of water, heat and light stresses on photosynthetic reactions in Sorghum bicolor(L.) Moench |
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Authors: | Jagtap, V Bhargava, S Streb, P Feierabend, J |
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Affiliation: | Department of Botany, University of Pune, Pune-411007, India; Botanisches Institut, J.W. Goethe Universitat, D-60054 Frankfurt, Germany; Corresponding author |
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Abstract: | Five varieties of Sorghum bicolor (L.) Moench.,differing in their drought tolerance under field conditions have been usedto study the effect of individual components of drought stress, namely highlight intensity stress, heat stress and water stress, on theirphotosynthetic performance. Chlorophyll content, chlorophyll fluorescence,ribulose-1,5-bisphosphate carboxylase (Rubisco, EC 4.1.1.39) content,phosphoenolpyruvate carboxylase (PEPcase, EC 4.1.1.31) activity andphoto-synthetic oxygen evolution were used as key parameters to assessphotosynthetic performance. The results indicated that photochemicalefficiency of photosystem II (PSII) was severely reduced by all threestress components, whereas PEPcase activity was more specifically reducedby water stress. Degradation of Rubisco and chlorophyll loss occurred underhigh light and water stress conditions. Of the four drought-tolerantvarieties, E 36-1 showed higher PEPcase activity, Rubisco content andphotochemical efficiency of PSII, and was able to sustain a higher maximalrate of photosynthetic oxygen evolution under each stress condition ascompared to the other varieties. A high stability to stress-induced damage,or acclimation of photosynthesis to the individual components of droughtstress may contribute to the high yields of E 36-1 under droughtconditions. In the E 36-1 variety markedly higher levels of thechloroplastic chaperonin 60 (cpn 60) were observed under all stressconditions than in the susceptible variety CSV 5.Key words: Chlorophyllfluorescence, drought stress, oxygen evolution, phosphoenopyruvatecarboxylase, Sorghum. |
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