Seedling emergence, growth, and leaf mineral nutrition of Ricinus communis L. cultivars irrigated with saline solution

Abstract

Two greenhouse experiments were conducted to evaluate the salt tolerance of five cultivars (‘Brigham’, ‘Energia’, ‘Hale’, ‘Memphis’, and ‘Ultra dwarf’) and one hybrid (‘HCastor’) of castor (Ricinus communis L.) by germinating seeds in saline substrate and irrigating plants with saline solutions. Seeds were sown in substrate that was moistened with reverse osmosis water [Electrical conductivity (EC)=0.02dSm−1, control), wastewater (EC=1.9dSm−1), or saline solution (EC=10.3 or 17.5dSm−1). Both wastewater at EC of 1.9dSm−1 and saline solution at EC of 10.3dSm−1 increased the seedling emergence of ‘Brigham’, ‘Hale’, and ‘Memphis’, but decreased that of ‘HCastor’ and ‘Ultra dwarf’. Saline solution at EC of 17.5dSm−1 significantly inhibited seedling emergence of all cultivars, except ‘Memphis’. The results indicated that ‘Memphis’ was the most tolerant cultivar, and ‘Brigham’, ‘Hale’, ‘HCastor’, ‘Energia’, and ‘Ultra dwarf’ were less tolerant to salinity stress. In the 2nd experiment, plants were irrigated with nutrient solution (no addition of salts, control) or saline solution at EC of 10dSm−1 for 69 days. All plants irrigated with saline solution were shorter than those irrigated with nutrient solution. The reduction in height was 40%, 39%, 44%, 38%, 51%, and 50%, respectively, for ‘Memphis’, ‘Brigham’, ‘HCastor’, ‘Ultra dwarf’, ‘Energia’, and ‘Hale’, compared to their respective controls. The fruit dry weight (DW) of ‘Brigham’, ‘HCastor’, ‘Ultra dwarf’, and ‘Hale’ irrigated with saline solution was significantly reduced by 65%, 66%, 60%, and 78%, respectively. Although a reduction of 57% and 55% in the fruit DW was recorded for ‘Energia’ and ‘Memphis’, respectively, there was no significance between saline solution and nutrient solution. Total DW of the plants irrigated with saline solution decreased by 60% for ‘Memphis’ and 70–78% for other cultivars as compared with those irrigated with nutrient solution. Salt treatment significantly increased leaf Na+, Ca2+, and Cl− concentrations, while decreased K+ concentration. However, leaf Na+ and Cl− concentrations were relatively low compared to other salt sensitive crops. Based on the results from both experiments, ‘Memphis’ was more tolerant to salinity than other cultivars.