Water stress-sensitized photoinhibition in senescing cotyledons of clusterbean: Changes in thylakoid structures and inactivation of photosystem 2

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 t...

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Bibliographic Details
Published in:Photosynthetica 2006-06, Vol.44 (2), p.187-192
Main Authors: Deo, P. M., Biswal, U. C., Biswal, B.
Format: Article
Language:English
Subjects:
Chlorophyll
Cotyledons
Energy transfer
Energy utilization
Fluorescence polarization
Inactivation
Irradiance
Lipid peroxidation
Lipids
Peroxidation
Photoinhibition
Photosystem
Room temperature
Seedlings
Superoxide dismutase
Water stress
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Summary: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.
ISSN:0300-3604
1573-9058
DOI:10.1007/s11099-006-0005-x