PLANT PHYSIOLOGY , Vol 107, Issue 3 751-756, Copyright © 1995 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Zinc Requirement for Stomatal Opening in Cauliflower
P. N. Sharma, A. Tripathi and S. S. Bisht
Botany Department, Lucknow University, Lucknow-226 007, India
Zn deficiency induced increases in epicuticular wax deposits, lamina
thickness, degree of succulence, water saturation deficit, diffusive
resistance, and proline accumulation and decreases in carbonic anhydrase
activity, water potential, stomatal aperture, and transpiration in the
leaves of cauliflower (Brassica oleracea L. var botrytis cv Pusa) plants.
Restoration of Zn supply to the deficient plants increased stomatal
aperture, transpiration, and carbonic anhydrase activity significantly
within 2 h. However, leaf water potential in the Zn-deficient plants did
not recover within 24 h after resupply of Zn. The guard cells in epidermal
peels from the Zn-deficient leaves had less K+ than those from the
controls. Stomatal aperture in the epidermal peels from Zn-deficient leaves
was 64% less than in the controls when the epidermal strips were floated on
125 mM KCl. Supplementing the ambient medium 25 mM KCl with ZnCl2 enhanced
stomatal aperture in both control and Zn-deficient peels, and the effect
was significant in the latter. The observations indicate involvement of Zn
in stomatal opening, possibly as a constituent of carbonic anhydrase needed
for maintaining adequate [HCO3-] in the guard cells, and also as a factor
affecting K+ uptake by the guard cells.
