Osmotic stress induces severe decrease in cation exchange capacity and surface groups of medium acidity in roots of cereal plants

Abstract

Huge amount of information on the plants response to drought is available throughout the literature; however, extremely rare information concerns effects of limited water availability on cation exchange capacity (CEC) and surface acidity of plant roots despite their importance for cations uptake by plants. As it is known, the CEC and acidity of barley roots markedly decrease under a low soil moisture and osmotic stresses, so we studied the behavior of the other cereal plants. Surface charge properties of roots of wheat, triticale, rye, oats and barley grown in hydroponics under osmotic stress induced at tillering stage by various mannitol concentrations were determined using a back-titration method. Roots size distributions were measured also. The osmotic stress caused down to a fivefold decrease in the CEC and a twofold decrease in the relative amount of surface functional groups of medium acidic strength, whereas no well-defined trends were observed for surface acidity. The above changes were the highest for rye and the lowest for oats. The general root’s architecture remained roughly same; however,’ the roots length markedly decreased under stress. The smallest decrease in roots length was observed for barley. Decrease in CEC and roots length may be the primary reasons for severe limitation in nutrient uptake by plants during drought.