Abaxial and adaxial stomatal density, stomatal conductances and water status of bean primary leaves as affected by paclobutrazol
2003
Tari, I. (University of Szeged (Hungary). Dept. of Plant Physiology)
The present paper describes the effects of a plant growth retardant, paclobutrazol (PB), on the stomatal development of bean primary leaves and the sensitivity of the stomatal conductance to exogenous abscisic acid (ABA) in PB-treated plants. The PB at 8.5 or 17.0 microM concentrations effectively inhibited the stem elongation and primary leaf expansion of bean seedlings. Although the retardant reduced the relative water content in well-watered plants, the water and pressure potentials remained high in the primary leaves. K+, Na+, Mg2+ and Ca2+ contents in the primary leaves were not significantly different from those in the control. The stomatal density increased on both surfaces but the length of guard cells was not reduced significantly on the adaxial epidermis. The transpiration rate on a unit area basis did not change significantly or increased in the treated leaves thus the reduced water loss of PB-treated plants was due to the reduced leaf area. Stomatal conductances of the adaxial surfaces responded more intensively to ABA and the total leaf conductance decreased faster with increasing ABA concentration in the control than in the PB-treated leaves. Paclobutrazol, an effective inhibitor of phytosterol biosynthesis, not only amplified the stomatal differentiation but increased the differences between the adaxial and abaxial stomatal conductances of the primary leaves.
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