Individual and additive effects of Na+and Cl−ions on rice under salinity stress

Abstract

This study was attempted to assess the extent of toxicity contributed by Na⁺ and/or Cl⁻ ions individually, besides their possible additive effects under NaCl using physiological and biochemical parameters. Despite the fact that most annual plants accumulate both Na⁺ and Cl⁻ under saline conditions and each ion deserves equal considerations, most research has been focused on Na⁺ toxicity. Consequently, Cl⁻ toxicity mechanisms including its accumulation/exclusion in plants are poorly understood. To address these issues, effects of equimolar (100 mM) concentrations of Na⁺, Cl⁻ and NaCl (EC ≈ 10 dS m⁻¹) were studied on 15-day-old seedlings of two rice cultivars, Panvel-3 (tolerant) and Sahyadri-3 (sensitive), using in vitro cultures. All three treatments induced substantial reductions in germination rate and plant growth with greater impacts under NaCl than Na⁺ and Cl⁻ separately. Apparently, salt tolerance of Panvel-3 was due to its ability to exclude Na⁺ and Cl⁻ from its shoots and maintaining low ( Na⁺ > Cl⁻ manner. Though Cl⁻ was relatively less toxic than its countercation, its effect cannot be totally diminished.