The study of the hydraulic conductivity of the plasmodesmal transport channels by the pulse NMR method

Radial self-diffusion of water in the absorbing zone of the roots of winter wheat (Triticum aestivum L.) seedlings was studied by the pulse-gradient-s pin-echo NMR method. At the fixed time of diffusion observation, the diffus ion decay of proton spin-echo was nonexponential; however, it could be reli ably separated into three exponential components differing in the self-diff usion coefficients (SDC) of water molecules. Our experimental data corrobor ate the modern concept of two transport channels in plant plasmodesmata, wh ich connect cytoplasmic and vacuolar (endoplasmic) compartments of adjacent cells into the unified supracellular continuums. Two SDC obtained by the k inetic analysis of diffusion decay were shown to depend on the expected cha nges in the hydraulic conductivity of the two above-mentioned plasmodesmal channels. To elucidate the role of ATP-dependent actomyosin proteins in the regulation of the hydraulic conductivity of plasmodesmata, we followed the changes in the water SDC induced by treating the roots with cytochalasin B (5 muM, 30 min), the inhibitor of actin polymerization; 2,3-butanedione mo noxime (10 mM, 1 h), the inhibitor of myosin ATPase activity; and antimycin A (5 muM, 1 h) and sodium azide (10 mM, 30 min), the inhibitors of energy generation. The data thus obtained provided the basis for elaborating a new methodological approach to simultaneously monitoring the functional state of both plasmodesmal channels without any wound effect impairing their func tions.