Abstract

Aiming to evaluate the water relations and gas exchange in castor bean cv. BRS Energia under salinity and cationic nature of irrigation water, an experiment was conducted under controlled conditions in an Ultisol Eutrophic of sandy loam texture. Treatments consisted of six combinations of water salinity (S₁– Control (supply water ECw=0.6 dS m^-1); S₂ - Na⁺, S₃ - Ca²⁺, S₄ - Na⁺+ Ca²⁺, S₅ - K⁺ and S₆ - Na⁺+ Ca²⁺ + Mg²⁺all prepared with chloride salt of respective cation and having ECw=4.5 dS m^-1, distributed in a randomized block design with four replications. The use of saline water of distinct cationic nature affected the water relations of the castor bean, the least deleterious effects were observed in plants irrigated with potassic water The negative effects of the cationic nature of irrigation water were more evident in gas exchange at 40 days after sowing (DAS), the highest values for stomatal condutance, transpiration rate, assimialation of CO₂, instantaneous carboxylation efficiency and intrinsic water use efficiency were observed in case of potassium ion. The castor bean 'BRS Energia' is more sensitive to the presence of sodium ions in the irrigation water, both in terms of water relations as well as for gas exchange.

Key words: Ricinus communis L., salt stress, semiarid.