Hıyar (Cucumis sativus L.) Bitkilerinde Kadmiyum Toksisitesinin Fotosentetik Aktivite Üzerindeki Etkileri

Abstract

In this study, the effect of different cadmium [Cd(NO3)2.4H2O] concentrations (0.1 and 1 mM) on photosynthetic activity in a cucumber genotypes (Cucumis sativus L. cv. Beith Alpha F1) was investigated by chlorophyll a fluorescence technique. Photosynthetic pigment (chlorophyll a, chlorophyll b, total chlorophyll and total carotenoid) content was decreased by cadmium toxicity in the leaves of cucumber plants in a dose dependent manner. This result may be explained by the absence of the protective mechanism provided by carotenoids. The decreased level of photosynthetic pigment content in the leaves of cucumber led to the impaired photosynthetic activity as demonstrated by chlorophyll a fluorescence measurement and JIP test. Changes in the chlorophyll fluorescence and JIP test parameters clearly showed that Cd toxicity did not result in the structural damages in reaction center of photosystem II but inhibited the photosynthetic electron transport reactions both in the donor and acceptor side of photosystem II. In addition, it has been observed that Cd toxicity inhibited carbon fixation reactions more strongly in the leaves of cucumber than photochemical reactions. Thus, it may be concluded that photosynthetic activity is impaired primarily due to inhibition of carbon reactions in the leaves of cucumber plants under Cd toxicity.