Abstract
Industrial and anthropogenic activities are the major source of heavy metal toxicants in agricultural soils. Among, heavy metal toxicants, hexavalent chromium is the most toxic toxicant that negatively affects plant’s metabolic activities and yield. It reduces the plant growth and development by influencing the antioxidant defence system’s activities. In the present experiment, two different soil applied dozes of GB viz. 50 and 100mM, and AMF, both individually and in combination were tested for their capability to ameliorate Cr toxicity in sorghum. The promotive behaviour of these treatments for antioxidant defence system was analysed at vegetative (35 DAS) and grain filling stage (95 DAS) in three varieties of sorghum viz. SSG 59-3, HJ 513 (multi-cut) and HJ 541 (single-cut) under 2 and 4 ppm Cr toxicity. At the same time resultant effects of this behaviour on Cr accumulation, grain yield and indices of oxidative stress was also studied. In this experiment antioxidant defence system includes enzymes viz. SOD, APX, CAT, GR, POD and metabolites viz. glutathione, ascorbate, proline, β-carotene and indices of oxidative stress includes parameters viz. PPO, H2O2 and MDA. The results delineated that Cr accumulation and indices of oxidative stress were increased with increasing concentration of Cr stress in all the varieties at both growth stages. Chromium stress at high concentration (4 ppm), decreased the grain yield (71.69 %) as compared with control. Due to 4 ppm Cr stress, PPO activity, MDA and H2O2 accumulation increased significantly (72.29 %, 73.15 %, 79 % respectively, at 35 DAS and 70.36 %, 74.78 %, 79.83 % respectively, at 95 DAS). GB and AMF individually increased antioxidant activity but in combination, further significantly increased antioxidant defence system’s activity which in turn decreased indices of oxidative stress and reduced the Cr toxicity and increased grain yield of sorghum in all varieties at both the growth stages. However, treatment of 100mM GB with AMF was observed most significant in decreasing oxidative stress and improved antioxidant system’s activities and grain yield as compared with all other treatments at both growth stages in all the varieties. SSG 59-3 cultivar showed lowest chromium content (1.60 and 8.61 ppm), indices of oxidative stress and highest antioxidant system’s activity as compared to HJ 513 followed by HJ 541 variety, at 35 and 95 DAS respectively. Thus, among the varieties SSG 59-3 was found most tolerant as compared to HJ 513 followed by HJ 541 variety. These findings suggest that both GB and AMF, either individually or combined can play a positive role to reduce oxidative stress and increased yield attributes under Cr toxicity in sorghum.
THE EFFECTS of HEAVY METAL APPLICATIONS on ANTIOXIDANT DEFENCE ACTIVATION in BARLEY and WHEAT VARIETIES
