Low night temperature effects on photosynthetic performance on two grapevine genotypes

The functional activities of the photosynthetic apparatus of two grapevine genotypes (Vitis vinifera L. cvs. Muller-Thurgau and Lagrein) were investigated after low night temperature (LNT) treatment for 7 d. LNT caused important reductions of the net photosynthetic rate (PN) of Lagrein plants due to non-stomatal components. These non-stomatal effects were not evident in Muller-Thurgau. At LNT treatment, the contents of photosynthetic pigments decreased significantly in Lagrein, but in Muller-Thurgau the contents of chlorophyll (Chl) remained unchanged whereas the contents of carotenoids (Car) increased. An increase and decrease of Chl a/b was shown in Mu ller-Thurgau and Lagrein stressed plants, respectively. RuBPC activity and content of soluble proteins were also significantly reduced in Lagrein. Under LNT treatment, photosystem (PS) 2 was markedly more inhibited in Lagrein than in Muller-Thurgau. The decrease in PS 2 activity in Lagrein was mostly due to the marked loss of D1, 47, 43, 33, 28-25, 23 and 17 kDa proteins determined by immunological and SDS-PAGE studies.