Alleviation of Adverse Effects of Water Stress on Zea mays (Cv Azam) by Exogenous Application of CaCl²

An experiment was conducted to study the effect of foliar application of CaCl² on alleviation of the adverse effects of water stress on maize (CV. Azam). The experiment was conducted in completely randomized design (CRD) using pots in a glass house and comprised of 2 irrigations (irrigated and water stress) and three concentrations of CaCl² (5, 10 and 15 mM CaCl².2H²O) as foliar spray on maize seedlings 20 days after emergence (DAE). Water was sprayed as untreated control on maize seedlings 20 DAE. After foliar application, the plants were regularly irrigated upto one week and water stress was imposed by withholding water from half of the pots for 20 days. Data were recorded on the relative water content (RWC), proline, sugar content and transcripts abundance of Lhcb2 gene in the selected leaves. Application of CaCl² increased the RWC, proline and sugar content as well as the Lhcb2 expression in the leaves under both irrigation conditions; however, the effect was more prominent under water stress. In the control plants, water stress decreased RWC (-57%) and Lhcb² transcript abundance (-44.37%) but increased proline (9.02 fold) and sugar content (3.42 fold) after 20 days. Significantly higher RWC (82.00 and 55.67%), proline (4.13 and 13.29 nmol·gˉ¹ FW) and sugar content (51.19 and 102.00 mg·gˉ¹ FW) under irrigated and water stressed conditions, respectively, was noted when 10 mM CaCl2 was applied as foliar spray. Furthermore, 10 mM CaCl² application enhanced the Lhcb² transcripts by 18 and 62% under irrigated and water stress conditions, respectively. These results demonstrate the importance of CaCl² foliar application on the improvement in the water relations and biochemical adaptation, resulting in improvement in the performance of plants under water deficit conditions. These results also demonstrated that senescence, which is a type of cell death program that could be inappropriately activated during drought, was also delayed in the supplemented seedlings as highlighted by a high RWC and expression of the Lhcb² gene.