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

Malgorzata Lukowska,Grzegorz Józefaciuk

doi:10.1007/s11738-015-2050-1

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.

Highlights

The response and adaptive mechanisms of plants to drought are under an increasing interest of many researchers (De Micco and Aronne 2012; Zlatev and Lidon 2012), that to high extent is connected with threats of a recent climate changes (Nezhadahmadi et al 2013)
The cation exchange capacity (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
For all studied plants stress induced a decrease of fine roots length practically in each range of their dimensions; the overall shape of the distribution functions was only slightly affected by stress

Summary

Introduction

The response and adaptive mechanisms of plants to drought are under an increasing interest of many researchers (De Micco and Aronne 2012; Zlatev and Lidon 2012), that to high extent is connected with threats of a recent climate changes (Nezhadahmadi et al 2013). Soil moisture deficit environments affect at first the plant roots. The cation exchange capacity (CEC) of the roots, governing the ions ratio and their uptake by plants, changes under different stressing conditions that was reported for aluminum and heavy metals toxicity (Jozefaciuk and Szatanik-Kloc 2004; Szatanik-Kloc 2010). Lukowska and Jozefaciuk (2013) found that low soil moisture and osmotic stresses decreased the CEC and variable charge of barley roots and increased their average values of surface dissociation constants. We hypothesized that drought stress affects roots surface charge properties of other cereal plants, as well, that up to date remains a question. Since roots taken from a soil may loose their finest parts adhered to the soil material and some of the soil colloids adhered to the roots may be sampled, instead of the low soil moisture, we performed hydroponic experiments with mannitol-induced osmotic stress

Methods

Results

Discussion

Conclusion