Changes in net photosynthetic rate and chlorophyll fluorescence in potato leaves induced by water stress

Abstract

Net rates of photosynthesis (P(N)) saturated by irradiance of >500 μmol m-2 s-1 (PAR) significantly decreased in water-stressed potato (Solanum tuberosum L. cv. Kufri Sindhuri) plants. The quantum yield of photochemical energy conversion (F(v)/F(m)), relative electron transport rate (ETR), and photochemical quenching (Q(p)) exhibited a parallel decline at high irradiance. A slight decrease in relative water content (RWC) was accompanied by a drastic decline in leaf water potential (Ψ(w)) from -0.2 to -1.0 MPa. Dehydrated leaves showed an increase in the amount of total soluble sugars per unit leaf area which inhibited the photosynthesis in a feedback manner. After rewatering, P(N) and F(v)/F(m) were restored to the values of control plants within 24 h, and the restoration was accompanied by a proportionate lowering of content of total soluble sugars in the leaves.