Sodium Ions Can Eliminate the Normal Disparity in Abaxial and Adaxial Stomatal Opening on Isolated Epidermes

Abstract

SUMMARY A comparative study was made of the effects of KCl and NaCl on abaxial and adaxial stomatal responses to light, CO2 and indole‐3‐acetic acid (IAA) on isolated epidermes of Commelina communis. Although K+ and Na+ were equally capable of promoting opening, NaCl masked the responses to light, CO2 and IAA normally occurring in KCl; thus a specific requirement of K+ for normal stomatal responses is suggested. NaCl produced equally wide abaxial and adaxial stomatal apertures, so eliminating the disparity in their opening normally found in KCl; the Na+‐stimulated opening was not a result of a stimulation of K+ accumulation in the guard cells. The results suggest that the normal disparity in abaxial and adaxial stomatal opening is specifically linked with differential K+ accumulation in the guard cells.