Affiliation:
1. Kazan Institute of Biochemistry and Biophysics, Federal Research Center Kazan Scientific Center, Russian Academy of Sciences
2. Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS
3. Arbuzov Institute of Organic and Physical Chemistry, Federal Research Center Kazan Scientific Center RAS
Abstract
The paper presents the results of using the NMR spin-echo method with a new type of MRI contrast agents in the form of fluorescent paramagnetic nanoparticles to study the characteristics of water transport in plant root tissues. Double contrasting is provided by the inclusion of both fluorescent and paramagnetic components in silicate nanoparticles. The purpose of using this methodological approach was to selectively assess the intensity of water transport in plant roots selectively by the symplast (from cell to cell via plasmodesmata) and apoplastic (extracellular) pathways of water transport. The fluorescent properties of nanoparticles made it possible to study the rate of their penetration and the nature of their distribution in root tissues. It was shown that the particles penetrate relatively quickly and are distributed over the root apoplast, but do not penetrate into the cells, at least for 1.5-2 hours, which was a necessary condition for the NMR experiments. We used two types of nanoparticles with a paramagnetic core based on manganese and iron oxide. It was shown that aqueous solutions of nanoparticles have relaxivity parameters acceptable for separating extracellular and intracellular water in root tissues according to magnetic relaxation times after one hour of incubation of plant roots in solutions. This made it possible to “turn off” the signal from extracellular water and then, using the gradient NMR technique, to study water transport selectively by the root symplast. The control of the rate of penetration of nanoparticles into the root apoplast using confocal microscopy was used to demonstrate the possibilities for a qualitative assessment of the intensity of apoplastic water transport in the root under the action of various types of stress, for example, water deficiency, change of light intensity and air humidity. Thus, compared with well-known types of MRI contrast agents based on gadolinium, manganese, etc., the obvious advantage of using paramagnetic fluorescent nanoparticles in the study of water transport in plant tissues is the possibility of their visualization in tissues, as well as the absence of toxic effects on plants, which was shown in this work.