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Osmotic water permeability of isolated protoplasts. Modifications during development

Ramahaleo, T., Morillon, R., Alexandre, J., Lassalles, J.P.
Plant physiology 1999 v.119 no.3 pp. 885-896
Triticum aestivum, Zea mays, Brassica napus, protoplasts, plant development, osmosis, roots, active transport, membrane permeability, plasma membrane
A transference chamber was developed to measure the osmotic water permeability coefficient (P(os)) in protoplasts 40 to 120 micrometer in diameter. The protoplast was held by a micropipette and submitted to a steep osmotic gradient created in the transference chamber. P(os) was served from the changes in protoplast dimensions, as measured using a light microscope. Permeabilities were in the range 1 to 1000 micrometer s(-1) for the various types of protoplasts tested. The precision for P(os) was <(or)= 40%, and within this limit, no asymmetry in the water fluxes was observed. Measurements on protoplasts isolated from 2- to 5-d-old roots revealed a dramatic increase in P(os) during root development. A shift in P(os) from 10 to 500 micrometer s(-1) occurred within less than 48 h. This phenomenon was found in maize (zea mays), wheat (Triticum aestivum), and rape (Brassica napus) roots. These results show that early developmental processes modify water-transport properties of the plasma membrane, and that the transference chamber is adapted to the study of water-transport mechanisms in native membranes.