Main content area

Photoinhibition of photosynthesis in water deficit leaves of grapevine (Vitis vinifera L.) plants

Bertamini, M., Zulini, L., Zorer, R., Muthuchelian, K., Nedunchezhian, N.
Photosynthetica 2007 v.45 no.3 pp. 426-432
D1 protein, Vitis vinifera, biphenyl, chlorophyll, electron transfer, fluorescence, leaves, light intensity, manganese, photoinhibition, thylakoids
Photoinhibition under irradiance of 2 000 µmol m⁻² s⁻¹ (HI) was studied in detached control (C) and water deficit (WD) leaves of grapevine (Vitis vinifera L.) plants. The degree of photoinhibition was determined by means of the ratio of variable to maximum chlorophyll (Chl) fluorescence (Fᵥ/Fₘ) and electron transport measurements. The potential efficiency of photosystem (PS) 2, Fᵥ/Fₘ, marginally declined under HI in WD-leaves without significant increase of F₀. In contrast, Fᵥ/Fₘ ratio declined markedly with significant increase of F₀ in C-leaves. In isolated thylakoids, the rate of whole chain and PS2 activity under HI were more decreased in C-than WD-leaves. The artificial exogenous electron donors diphenyl carbazide, NH₂OH, and Mn²⁺ failed to restore the HI-induced loss of PS2 activity in both C-and WD-leaves. Thus HI operates at the acceptor side of PS2 in both leaf types. Quantification of the PS2 reaction centre protein D1 following HI exposure of leaves showed pronounced differences between C-and WD-leaves. The marked loss of PS2 activity under HI of C-leaves was due to the marked loss of D1 protein of the PS2 reaction centre.