Water Stress-Induced Responses in the Growth, Cuticular Wax Composition, Chloroplast Pigments and Soluble Protein Content, and Redox Metabolism of Two Genotypes of Ricinus communis L.

The aim of this study was to investigate the physiological and biochemical responses to three different water regimes in two castor bean genotypes (BRS Energia and BRS Nordestina) with different drought tolerance. After 67 days of sowing and 28 days under different water stress levels, some growth parameters were affected by increased stress, resulting in lower height, root, and shoot biomass, leaf area, and number of mature leaves. The increase in cuticular wax load on leaves was prominent under higher water stress. Triterpene and primary alcohols were the main constituent classes identified, but their content did not change under water deficit. Changes primarily occurred in the n-alkane and fatty acid classes. Water stress caused an increase in hydrogen peroxide and malondialdehyde content, a decrease in soluble protein content, and an increase in the activity of key enzymes of the antioxidant defense system (SOD, CAT, and APX). The BRS Nordestina genotype demonstrated a more efficient protection mechanism against drought compared to BRS Energia.