APPLICATION OF THE NMR METHOD WITH PARAMAGNETIC DOPING TO ESTIMATION THE APOPLASTIC WATER TRANSFER IN THE ROOTS OF INTACT PLANTS UNDER IMPACT OF ABIOTIC STRESSES

Abstract

In this work, the methodological approach based on low-field NMR using the GdDTPA paramagnetic complex for the qualitative assessment of water transport along the apoplastic (extracellular) pathway in the roots of intact wheat plants is proposed. This approach consists in measuring the spin-spin relaxation times of the water magnetization in the roots during simultaneous incubation of the roots in a solution of the paramagnetic Gd-DTPA complex and the impact of a stress factor on the plants. During root incubation, this complex spreads only along the root apoplast system and shortens the apoplast water relaxation times. GdDTPA does not penetrate into the cells and, accordingly, does not change the intracellular water relaxation times. Thus, the rate of decrease in the relaxation times of the magnetization of apoplast water, which directly depends on the intensity of water transfer through the apoplast, can be used to determine the relative contribution of water transfer through the root apoplast during stress exposure. A twofold increase in the concentration of carbon dioxide in the aerial parts of plants was used as an abiotic factor presumably influencing the transfer of water along the root apoplast. Using this methodological approach, it was shown that increase in the CO2 concentration in the leaf zone of wheat plants to 800 ppm leads to decrease in the rate of water transfer through the root apoplast by 2–2.5 times compared with the control at ambient CO2 concentration of 400 ppm.