Photosynthetic responses for Vitis vinifera plants grown at different photon flux densities under field conditions
Bertamini, M.(Istituto Agrario di San Michele all' Adige (Italy))E-mail:[email protected] | Nedunchezhian, N.(Istituto Agrario di San Michele all' Adige (Italy))
The leaves collected from a selected 10-years-old grapevine grown under field were classified into three groups according to the mean irradiation they received on the surface as follows: 200, 850, and 1,750 microM/square m/s, i.e low, moderate and high photon flux densities (PFD), respectively. Leaf chlorophyll (Chl) a and Chl b and carotenoid concentrations were higher in plants grown at low PFD than in those grown at moderate and high PFD. The highest Chl a variable to maximum fluorescence ratio Fv/Fm was observed in plants grown at medium PFD whereas the minimum fluorescence was highest in those at high PFD. In isolated thylakoids, both high and low PFD caused marked inhibition of whole chain and photosystem 2 (PS2) activities. The artificial exogenous electron donor diphenyl carbazide significantly restored the loss of PS2 activity in low PFD leaves.
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