Improvement in growth and physiochemical attributes of Raphanus sativus L. through exogenous application of 28-Homobrassinolide under nickel stress

Nickel (Ni) pollution in agricultural areas is a global problem that has been steadily getting worse. Seed priming increases crop production and quality, which may be related to invoking stress memory in germinating seed under Ni stress. The objective of the current study was to comprehend the mechanism by which Raphanus sativus L. (radish) seeds primed with 28-homobrassinolide (28-HBL) could mitigate Ni stress. The R. sativus seeds primed with 0, 1, 5, and 10 mu mol L-1 concentrations of 28-HBL. The Ni stress caused oxidative damage in R. sativus seedlings by increased ROS biosynthesis which results in impaired morphological characteristics, photosynthetic content and gas exchange parameters. The Ni stress caused a significant decrease in protein (26%), phenolic (37%), total chlorophyll content (29%) and plant height (22%) as compared with control. Seedlings raised from 28-HBL primed seeds exhibited reduced Ni contents besides improved biosynthesis of proline content. Furthermore, 5 mu mol L-1 HBL enhanced shoot height (43%), no. of leaf (58%), and fresh biomass (38%) under Ni stress. Nevertheless, increased proline, DPPH activity and mineral uptake (Na, K, Mg and Zn) was obtained in 5 mu mol L-1 HBL treated plants under control and Ni stress conditions. HBL2 primed seed enhanced metal tolerance index along with transpiration rate (28%), stomatal conductance (20%) and photosynthetic rate (9%) in Ni spiked soil. Briefly, the results of current study suggested that 28-HBL perhaps mitigates the deleterious effect of Ni stress and enhanced the growth of R. sativus.