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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Institution: | 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 used
to study the effect of individual components of drought stress, namely high
light intensity stress, heat stress and water stress, on their
photosynthetic 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 and
photo-synthetic oxygen evolution were used as key parameters to assess
photosynthetic performance. The results indicated that photochemical
efficiency of photosystem II (PSII) was severely reduced by all three
stress components, whereas PEPcase activity was more specifically reduced
by water stress. Degradation of Rubisco and chlorophyll loss occurred under
high light and water stress conditions. Of the four drought-tolerant
varieties, E 36-1 showed higher PEPcase activity, Rubisco content and
photochemical efficiency of PSII, and was able to sustain a higher maximal
rate of photosynthetic oxygen evolution under each stress condition as
compared to the other varieties. A high stability to stress-induced damage,
or acclimation of photosynthesis to the individual components of drought
stress may contribute to the high yields of E 36-1 under drought
conditions. In the E 36-1 variety markedly higher levels of the
chloroplastic chaperonin 60 (cpn 60) were observed under all stress
conditions than in the susceptible variety CSV 5.Key words: Chlorophyll
fluorescence, drought stress, oxygen evolution, phosphoenopyruvate
carboxylase, Sorghum.
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