Physiological mechanisms involved with reduction in the K+ induced by NaCl in cashew roots

Abstract

The objective of this study was to elucidate some mechanisms involved with the salt-induced reduction in the K⁺ content in cashew roots. The seedlings and detached roots of clone CCP 06 were exposed to different NaCl levels (0; 100; 200; 300; 400 mM) and 200 mM NaCl along 0; 12; 24; 36 and 48 hours. The experiments were carryied out in nutrient solution and in a growth chamber under controlled conditions: temperature 27ºC/24ºC (day/night), relative humidity 70%, photosynthetically radiation density 250 µmol m^-2 s^-1 and a 12-h photoperiod. The external NaCl levels caused a prominent and steady reduction in the K⁺ content in roots. These induced salinity caused root membrane damage, with electrolyte leakage to external environment. The external NaCl caused slight increase in the concentrations of K⁺ in shoot and significant decrease in the K⁺ net influx. Taken together, data evidence that NaCl-induced reduction in the K⁺-root content is caused mainly by increase in both K⁺ efflux, due to damage of membrane, and inhibition in the net influx.