Gibberellic Acid and Salinity Affected Growth and Antioxidant Enzyme Activities in Castor Bean Plants at Early Growth Stage

Abstract

Salinity is a severe environmental factor that has limited the growth and productivity of crops. External application of regulating substances is a useful strategy to minimize the inhibitory effects of salinity on seedling growth. A controlled study was conducted to assess the interactive effects of exogenous gibberellic acid (GA3) addition and salinity on plant growth and antioxidant enzymes of castor bean (Ricinus communis L.) plants. The 50 mM level did not negatively affect the early growth of castor seedlings. At the 100 mM salinity level, however, seedling growth and physiological parameters were severely affected. Plant height, leaf area, and the weight of root, stem, leaf, and the whole plant was reduced by up to 21.7, 27.9, 33.3, 37.5, 33.2, and 34.5%, respectively. The activity of superoxide dismutase (SOD), peroxidases (POD), catalases (CAT), and proline content were also decreased by up to 32.0, 34.3, 53.6, and 212.4% at such a high salinity level. Presoaking seeds with 250 uM GA3 increased plant height, stem diameter, and the weight of leaf and the whole plant by up to 13.3, 7.4, 66.7, and 39.1%, respectively. The activity of SOD and POD and the content of proline and soluble protein were also significantly increased when GA3 was applied at 250 uM. This study indicated that exogenous addition of GA3 at appropriate concentrations can be a useful strategy to promote early seedling growth of castor bean plants grown under saline conditions.