THE ROLE OF POTASSIUM CHANNELS IN THE TEMPERATURE CONTROL OF STOMATALAPERTURE

Citation
N. Ilan et al., THE ROLE OF POTASSIUM CHANNELS IN THE TEMPERATURE CONTROL OF STOMATALAPERTURE, Plant physiology, 108(3), 1995, pp. 1161-1170
Citations number
49
Categorie Soggetti
Plant Sciences
Journal title
ISSN journal
00320889
Volume
108
Issue
3
Year of publication
1995
Pages
1161 - 1170
Database
ISI
SICI code
0032-0889(1995)108:3<1161:TROPCI>2.0.ZU;2-W
Abstract
We used the patch-clamp technique to examine the effect of temperature (13-36 degrees C) on the depolarization-activated K channels (K-D cha nnels) and on the hyperpolarization-activated channels (K-H channels) in the plasma membrane of Vicia faba guard-cell protoplasts. The stead y-state whole-cell conductance of both K channel types increased with temperature up to 20 degrees C. However, whereas the whole-cell conduc tance of the K-H channels increased further and saturated at 28 degree s C, that of K-D channels decreased at higher temperatures. The unitar y conductance of both channel types increased with temperature like th e rate of diffusion in water (temperature quotient of approximately 1. 5), constituting the major contribution to the conductance increase in the whole cells. The mean number of available K-H channels was not af fected significantly by temperature, but the mean number of available K-D channels increased significantly between 13 and 20 degrees C and d eclined drastically above 20 degrees C. This decrease and the reduced steady-state voltage-dependent probability of opening of the K-D chann els above 28 degrees C (because of a shift of voltage dependence by +2 1 mV) account for the depression of the whole-cell K-D conductance at the higher temperatures. This may be a basic mechanism by which leaves of well-watered plants keep their stomata open during heat stress to promote cooling by transpiration.