Journal of Experimental Botany, Vol 50, 399-404, Copyright © 1999 by Oxford University Press
C Willmer, K Padmasree and A Raghavendra
A quick and accurate method of monitoring changes of volume of mesophyll
cell protoplasts (MCP) of pea was devised using the difference in
absorbance of the protoplasts at 440 nm and 750 nm (OD 440-750); when
protoplasts expanded in response to changing the external medium from 0.4 M
sorbitol to 0.3 M sorbitol OD 440-750 values increased and, conversely,
when protoplasts were transferred from 0.4 to 0.5 M sorbitol, protoplasts
contracted. The kinetics of expansion or contraction of the protoplasts
could also be monitored using this method and the half-time for water
exchange for expanding protoplasts (about 10 s) was slightly higher than
that for contracting protoplasts. A study of the effects of the water
channel blocker, mercuric chloride, on swelling protoplasts showed that 500
ARTICLES
Short communication. A novel method of measuring volume changes of mesophyll cell protoplasts and the effect of mercuric chloride on their osmotically-induced swelling
Department of Biological and Molecular Sciences, University of Stirling, Stirling FK9 4LA, UK; Institute of Life Sciences, University of Hyderabad, Hyderabad 400046, India; Corresponding author e-mail: c.m.willmer@stir.ac.uk
M irreversibly damaged protoplasts, 5-10
M had a negligible inhibitor effect on
swelling while 100
M had a large inhibitory effect often
completely inhibiting swelling. A preliminary study indicated that
mercapto-ethanol reversed the inhibitory effect of mercuric chloride on
protoplast swelling.Key words: Aquaporins,
endocytosis, exocytosis, osmosis, protoplasts.
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