Ion uptake and growth of pinhão-manso under different salinity levels

Abstract

The objective of this work was to characterize the uptake and partitioning of sodium (Na⁺), chlorate (Cl^-) and potassium (K⁺) ions in leaves and roots of physic nut plants exposed to different NaCl levels. 35-day-old seedlings were exposed to 0; 25; 50; 75 and 100 mM of NaCl supplied in the nutritive solution during 15 days under greenhouse conditions (day/night) temperatures from 28 to 36 and 24 to 27 °C, average relative humidity 40-80% (day/night) and maximum PAR 1,200 mmol m^-2 s^-1. The accumulation of Na⁺ and Cl^- in leaves and roots increased proportionally to external NaCl levels. In contrast, the K⁺ content was prominently reduced in both organs as salinity increased. Na⁺ and Cl^- concentrations in leaves were 2,493 and 980 mmol kg^-1 DM while in roots they achieved 1,681 and 1,458 mmol kg^-1 DM, respectively, under 100 mM NaCl treatment. The K⁺ content in leaves and roots was 188 and 1,043 mmol kg^-1 DM, respectively. The K⁺/Na⁺ ratios decreased significantly in leaves and roots as salinity increased, in parallel to the dry matter yield. These data strongly suggest that young plants of physic nut are sensitive to salinity.