Diffusion of the organic cation in root cell walls

摘要

A comparative study of the uptake of cation type dye (methylene blue) of the isolated root cell walls, of the roots of whole transpirating seedlings and of excised roots was performed. Seven day seedlings of the Triticum aestivum L., Zea mays L., Cucumis sativus L., Lupinus albus L. and Vigna radiata L. grown at low concentration of all nutrients (~0.2 mM) were used. We determined the amount of ionogenic groups per 1 g of dry and fresh weight of root cell walls, their swelling capacity, ion exchangecapacity on methylene blue (M_(cw)) depending on adsorption time, diffusion coefficients of organic cation into polymeric matrix of cell walls (D_(cw)), into the roots of whole transpirating seedlings (D_(ts)) and the excised roots (D_(er)) -It was shownthat MCW depended on pH (or dissociation degree of the carboxyl groups), changed in accordance with the amount of the carboxyl groups per 1 g of cell walls dry weight and decreased as follows: cucumber > mungbean > lupin > wheat > corn. The D_(ts) and D_(ts) also depended on plant species. In all cases the D_(er) was 1.5-4 times lower than into the cell walls. The values of D_(ts) were comparable with D_(cw). We concluded that the mechanism of methylene blue absorbing by roots is stipulated by ion exchangeable reactions between the of methylene blue cation and carboxyl groups of cell walls, but the rate of adsorbing process is mainly defined by diffusion methylene blue cation into the cell walls polymeric matrix.