The effect of salinity stress on ions and soluble sugars distribution in leaves, leaf sheaths and roots of rice (Oryza sativa L.) seedlings

Abstract

In order to investigate the solutes accumulation associated with salt tolerance of rice (Oryza sativa L.), two rice genotypes including IR651 (salt-tolerant) and IR29 (salt-sensitive) were grown hydroponically in the Youshida nutrient solution. Salinity treatment was imposed 3 weeks after sowing using NaCl in two levels 0 and 100 mmol. Samples were separately collected from the youngest (sixth) leaves, leaf sheaths and roots at 72 and 240 h after salinization; then Na<sup>+</sup>, K<sup>+</sup>, Ca<sup>2+</sup>, Mg<sup>2+</sup>, P, Mn<sup>2+</sup>, Cl<sup>–</sup> and total soluble sugars concentration and Na+/K<sup>+</sup> ratio were determined. Total dry weight of both genotypes decreased with the application of NaCl. Salinity caused higher accumulation of Na<sup>+</sup> and Cl<sup>–</sup> in the sixth leaf and leaf sheath of IR29 than in IR651 while their concentration in root of IR651 was higher. K<sup>+</sup> concentration was decreased in the sixth leaf and leaf sheath of IR29 under NaCl stress. Reduction in Ca<sup>2+</sup> and Mg2+ concentrations were observed in sixth leaves of both genotypes. P concentration was increased in leaf sheath and root of IR29 under saline conditions while it showed no changes in IR651. Our results indicated that the tolerant genotype had mechanisms to prevent high Na<sup>+</sup> and Cl<sup>–</sup> accumulation in the sixth leaf. High total soluble sugars concentration in shoot of IR651 is probably for adjusting osmotic potential and better water uptake under salinity. These mechanisms help plant to avoid tissue death and enable to continue its growth and development under saline conditions.