Water stress-sensitized photoinhibition in senescing cotyledons of clusterbean: Changes in thylakoid structures and inactivation of photosystem 2 |
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Authors: | P M Deo U C Biswal B Biswal |
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Institution: | (1) Biochemistry Laboratory, School of Life Sciences, Sambalpur University, Jyoti Vihar-768019 Orissa, India;(2) Department of Botany, Panchayat College, Bargarh, P.O/Dist.-Bargarh-768028 Orissa, India |
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Abstract: | Seedlings of Cyamopsis tetragonoloba were grown on Petri dishes either in water or water plus 3 % PEG-6000 to induce water stress. The senescing cotyledons experiencing the stress exhibited loss in contents of leaf proteins and
chlorophyll (Chl) and a decline in oxygen evolution. The effect of PEG treatment was more pronounced at moderate (MI) than
low (LI) irradiance. The stress-induced loss in the activity of superoxide dismutase and increase in the thylakoid lipid peroxidation
accompanied a change in the physical status of the bilayer membrane as demonstrated by an enhancement of room temperature
Chl a fluorescence polarization and decrease in energy transfer efficiency in pigment assembly. This resulted in a sustained decrease
in photosystem 2 activity blocking channels of energy utilization. The absorbed quanta, thus unutilized, were excess even
at MI, leading to photoinhibitory response. |
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Keywords: | Cyamopsis tetragonolobar fluorescence polarization lipid peroxidation malondialdehyde membrane fluidity polyethylene glycol proteins superoxide dismutase |
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