DETERMINATION OF RELATIVE PORE SIZE IN LIVING MEMBRANES OF NITELLA BY THE TECHNIQUES OF ELECTROOSMOSIS AND RADIOACTIVE TRACERS

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Abstract
By measuring the number of water molecules per ion moved electroosmotically through living membranes of Nitella flexilis before and after the addition of chemicals to a solution of 10−4 M KCl, the effect of the chemical upon electroosmotic transport was investigated. Carbon tetrachloride and chloroform reduced slightly the amount of water transported per ion. On the other hand 10−5 M indoleacetic acid caused major changes in electroosmotic transport, increasing it in cells tested in July–August, but decreasing it in cells tested in October–November. Different ions also carry different amounts of water with them electroosmotically. These changes can be interpreted in terms of changing pore size.The relative pore size was also determined by measuring the permeation of glucose-14C and sucrose-14C in the absence and presence of electroosmotic transport and in cells treated with indoleacetic acid. Both the plasmalemma and tonoplast were freely permeable to glucose-14C but not to sucrose-14C. However, in the presence of electroosmotic transport sucrose did permeate the cell membrane. Indoleacetic acid enhanced this permeation of sucrose-14C.

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