Photoinhibition of photosynthesis in leaves of grapevine (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L. cv. Riesling). Effect of chilling nights |
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Authors: | M?Bertamini K?Muthuchelian M?Rubinigg R?Zorer Email author" target="_blank">N?NedunchezhianEmail author |
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Institution: | (1) Istituto Agrario di San Michele all'Adige, 38010 San Michele all'Adige, Italy;(2) Centre for Biodiversity and Forest Studies, School of Energy Sciences, Madurai Kamaraj University, Madurai, 625 021, India;(3) Present address: Govt. HSS. Vellimedupettai, 604 207, India |
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Abstract: | Photoinhibition of photosynthesis was investigated in control (C) and chilling night (CN) leaves of grapevine under natural
photoperiod at different sampling time in a day. The degree of photoinhibition was determined by means of the ratio of variable
to maximum chlorophyll fluorescence (Fv/Fm) and photosynthetic electron transport measurements. When the potential efficiency of photosystem (PS) 2, Fv/Fm was measured at midday, it markedly declined with significant increase of F0 in CN leaves. In isolated thylakoids, the rate of whole chain and PS2 activity were markedly decreased in CN leaves than
control leaves at midday. A smaller inhibition of PS1 activity was also observed in both leaf types. Later, the leaves reached
maximum PS2 efficiencies similar to those observed in the morning during sampling at evening. The artificial exogenous electron
donors diphenyl carbazide, NH2OH, and Mn2+ failed to restore the PS2 activity in both leaf types at midday. Thus CN enhanced inactivation on the acceptor side of PS2
in grapevine leaves. Quantification of the PS2 reaction centre protein D1 following midday exposure of leaves showed pronounced
differences between C and CN leaves. The marked loss of PS2 activity in CN leaves noticed in midday samples was mainly due
to the marked loss of D1 protein of the PS2 reaction centre. |
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Keywords: | acceptor side chlorophyll fluorescence D1 protein diurnal course of photosynthetic activities electron transport Mn NH2OH photosystems 1 and 2 photoinhibition |
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