Foliar Application of Salicylic Acid and Calcium Chloride Enhances Growth and Productivity of Lettuce (Lactuca sativa)

Abstract

SALICYLIC ACID (SA) and Ca2+ regulate the physiological and biochemical mechanisms in plants. A factorial experiment was designed to evaluate the effect of foliar application of calcium chloride (0, 10, 20, 30 or 40 mM) and salicylic acid (0, 0.5, 1, 1.5 or 2 mM) on the vegetative growth of romaine lettuce cv. Balady during 2013/2014 and 2014/2015 seasons at the Experimental Farm of Horticulture Department, Faculty of Agriculture, Ain Shams University, Qalubia Governorate, Egypt. Results clearly indicated positive effects of foliar applications of calcium chloride and salicylic acid either alone or in combination on lettuce growth, productivity and some physiological parameters. Foliar application of calcium chloride at 20 mM significantly increased vegetative growth parameters (plant length, head diameter, fresh and dry weights of head, number of leaves/head, average leaf area and leaf area index), chlorophyll (a, b, and total), leaf relative water content, leaf membrane stability index, and macro- and micro-nutrients. Moreover, salicylic acid spraying at 1.5 mM significantly gave the highest significant values of all aforementioned parameters. Exogenous applications of calcium chloride and salicylic acid either alone or in combination reduced nitrate accumulation in the leaves. Spraying of calcium chloride at 20 mM with salicylic acid at 1.5 mM was the most effective treatment which can be used as an applicable practice in romaine lettuce cv. Balady cultivation.