Enhanced antioxidant defense after exogenous application of Ca2+ and K+ in Brassica napus seedlings under water deficit stress

Abstract

Supply of adequate moisture is one of the most important factors limiting agricultural extension and productivity. Ca²⁺ and K⁺ are both essential plant nutrients required in a number of developmental and metabolic processes. Both of these nutrients play an important role in ameliorating drought stress in crop plants. This experiment was designed to study whether exogenous application of Ca²⁺ and K⁺ before the drought could enhance the potential of plants to survive under limiting water conditions. Brassica napus L. cv Bulbul-98 seedlings were exposed to drought stress for 10 days after exogenous application of different concentrations of Ca²⁺, K⁺ and N through irrigation water. Exogenous Ca²⁺ and K⁺ application was associated with increased relative water content, membrane stability and chlorophyll content in seedlings exposed to water deficit. Though the quantity of Pro and activities of APX (EC: 1.11.1.11) and CAT (EC: 1.11.1.6) were increased after K⁺ application, they were strongly induced in seedlings supplemented with Ca²⁺ in a dose dependent manner. Increasing quantity of N application, however, had a negative effect on these parameters.

Key words: Drought, Ca²⁺, K⁺, AOS enzymes, proline, chlorophyll.