Leaf pigments, ribulose-1,5-bisphosphate carboxylase, nitrate reductase and photosynthetic efficiency of grapevine (Vitis vinifera L. cv. Pinot noir) grown under different light conditions

Changes of leaf pigments, ribulose-1,5-bisphosphate carboxylase (Rubisco), nitrate reductase and photosynthetic efficiency were determined in leaves of Vitis vinifera L. cv. Pinot noir plants grown at full sunlight (2000 µmol m -2 s -1 ) and 40 % of sunlight (800 µmol m -2 s -1 ). The contents of chlorophyll and carotenoids per fresh mass were higher in 40 % sunlight than in full sunlight-grown leaves. In contrast, Rubisco activity, in vivo nitrate reductase activity (indicator of nitrate utilisation) and soluble proteins were significantly reduced in 40 % sunlight-grown leaves. In isolated thylakoids, a marked inhibition of whole chain (PSI+PSII) and PSII activity were observed in 40 % sunlight-grown leaves. Smaller inhibition of NI activity was also observed in 40 % sunlight-grown leaves. The artificial exogenous electron donors, DPC and NH 2 OH, significantly restored the loss of PSII activity in 40 % sunlight-grown leaves. The same results were obtained when Fv/Fm was evaluated by chlorophyll fluorescence measurements. The marked loss of PSII activity in 40 % sunlight-grown leaves was due to the loss of 47, 33, 28-25 and 23 kDa polypeptides. This conclusion was confirmed by immunological studies showing that the content of the 33 kDa protein of the water-splitting complex was diminished significantly in 40 % sunlight-grown leaves.