Effects of phytoplasma [stolbur-subgroup (Bois noir-BN)] on photosyntheticpigments, saccharides, ribulose 1,5-bisphosphate carboxylase, nitrate and nitrite reductases, and photosynthetic activities in field-grown grapevine (Vitis vinifera L. cv. Chardonnay) leaves

in leaves of field-grown grapevine, the contents of chlorophyll, carotenoid s, and soluble proteins and the activities of ribulose-1,5-bisphosphate car boxylase (RuBPC) and nitrate (NR) and nitrite (NiR) reductases were decreas ed in phytoplasma-infected leaves, but the contents of soluble sugars and t otal saccharides were markedly increased. In isolated thylakoids, phytoplas ma caused marked inhibition of whole chain and photosystem 2 (PS2) activiti es. The artificial exogenous electron donor, diphenyl carbazide, significan tly restored the loss of PS2 activity in infected leaves.