EVALUATION OF THE ROLE OF ASCORBIC ACID IN BARLEY UNDER CADMIUM TOXICITY

Abstract

The Cd accumulation might result disturbances in plant metabolism causing several physio-biochemical and structural changes ultimately declining the crop productivity. The experiments were conducted in two phases (plant and callus) under different combinations of Cd (control, 100, 500, and 700 μM) without or with AsA (0.0 18 and 200 mg L-1) with four genotypes of barley (Jau-83, Jau-87, Paidar 91 and Haider 93). The results revealed variable Cd accumulation pattern in the both culture systems (seedling and callus). Roots showed higher Cd accumulation as compared to shoot and callus. The lower Cd accumulation of callus than root exhibited less sensitivity of callus to Cd-induced stress. A two phase linear concentration-dependent Cd accumulation pattern was observed in root and shoot whereas in callus Cd accumulated in a linear concentration-dependent fashion with the elevating Cd levels in the both culture media. However, protective effect of AsA on root or shoot and the callus inhibited the Cd accumulation from the both media revealing the possibility of occurrence of the formation of stable AsA-Cd complexes. Higher amounts of H2O2 and MDA caused Cdinduced oxidative stress elevating the activities of antioxidants (CAT and POD) which accelerated the accumulation of solutes disturbing mineral nutrients and water status in the both media. The uneven SOD activity exhibited that differences existed among the genotypes to withstand the Cd toxicity. The application of AsA in combination with the elevating Cd stress showed improvements in the SOD activity indicating that higher SOD activity might modulate the activities of other enzymes and regulate the solutes maintaining water relations under Cd-induced oxidative stress and ultimately the growth in the both culture media. Based on Cd translocation factor and the root STI, and the callus BCF and STI factors, Jau-83 showed more tolerance to Cd toxicity followed by Jau-87 and Paidar 91and Haider 93 to Cd toxicity.