Regulation of growth and antioxidant enzyme activities by 28-homobrassinolide in seedlings of Raphanus sativus L. under cadmium stress.

28-Homobrassinolide (28-HBL), a brassinosteroid is reported to play significant role in diverse physiological processes. It induces a range of cellular and adaptive responses to a range of environmental stresses. Cadmium (Cd) is a non-essential metal which alters various physiological processes and generates ROS, which can oxidize biological macromolecules and causes oxidative stress. This stress is generally overcome by the internal antioxidative defense system and stress shielding phytohormones. In this study, effect of 28-HBL was studied on growth and activities of antioxidant enzymes in known hyperaccumulator Raphanus sativus L. (radish) seedlings grown under cadmium (Cd) metal stress. To determine the influence of 28-HBL (0, 10-11, 10-9, 10-7 M) in radish seedlings subjected to Cd (0, 0.5, 1.0, 1.5 mM) stress, the activities of antioxidant enzymes (APOX, CAT, GR, POD and SOD) were analyzed. In addition, length and biomass of radish seedlings was also recorded. Cd toxicity resulted in reduced length, biomass, protein content and activities of antioxidant enzymes. 28-HBL treatments lowered the Cd toxicity by enhancing the activities of antioxidant enzymes, biomass and seedling length. The present study thus suggests a possible role of 28-HBL in amelioration of metal stress by regulating the activities of antioxidant enzymes in radish.

Chromium in tannery industry effluent and its effect on plant metabolism and growth.

Different dilution levels of tannery treated effluent and their corresponding concentration of chromium (Cr6+) were studied in a petridish culture experiment on seed germination and seedling growth in radish (Raphanus sativus L). The different concentrations of Cr6+ (2, 5 and 10 ppm) and treated tannery effluent (10, 25 and 50%) showed reduction in seedling growth and related enzymatic activities with increase in concentration of Cr6+ in treatments and effluent both. The low concentration of chromium (2 ppm) and effluent dilution (10%) showed significant growth reduction separately. At this concentration of chromium and effluent dilution chlorophyll content, amylase, catalase and protein contents remained unchanged while with increase in Cr6+ concentration (>2ppm) and effluent dilution (> 10%) in treatments showed growth inhibitory effects.