IN-VIVO RESPONSE OF PHOTOSYNTHETIC APPARATUS OF PHASEOLUS-VULGARIS L TO NICKEL TOXICITY

We investigated the effect of in vivo Ni2+ toxicity on the photosynthetic system of primary bean leaves (Phaseolus vulgaris L. cv. Slowianka). The leaf area, chlorophyll and total carotenoid content showed a distinct decrease strictly related to the metal concentration in the nutrient medium and to the period of treatment. An analysis of the parameters of chlorophyll a fluorescence fast phase of induction kinetics revealed the lack of Ni2+ effect of the primary photochemical processes in photosystem II. The measurements of photosynthetic electron transport under heavy metal influence, both in vivo and in vitro, and comparison with the results obtained from the analysis of the slow phase of the Kautsky curve allow us to postulate an indirect effect of nickel on photosystems related to the disturbances caused by the metal in the Calvin cycle reactions and down-regulation or even feedback inhibition of electron transport by the excessive amounts of ATP and NADPH accumulated due to non-efficient dark reactions.