Protective action of abscisic acid against the inhibition of photosynthesis of barley leaves by bisulphite

The inhibition of photosynthetic activity by bisulphite was studied in inta ct leaves of abscisic acid (ABA)-treated and non-treated (control) barley p lants. ABA inhibited the photosynthetic process as evidenced by lower value s of chlorophyll fluorescence kinetic parameters F-v/F-m (photosystem 2 act ivity) and R-fd (vitality index, related to the whole photosynthetic activi ty) compared with ABA-non-treated plants. After bisulphite treatment, the e xtent of inhibition was smaller in ABA-treated plants than in the control o nes indicating a protective effect of ABA. The protective action sites of A BA were the Q(A) reduction and the Calvin cycle.