PLANT PHYSIOLOGY , Vol 108, Issue 2 623-632, Copyright © 1995 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
The Physiological Role of Abscisic Acid in Eliciting Turion Morphogenesis
C. C. Smart, A. J. Fleming, K. Chaloupkova and D. E. Hanke
Institute of Plant Sciences, Plant Biochemistry and Physiology, Eidgenossiche Technische Hochschule Zurich, Universitatsstrasse 2, CH-8092 Zurich, Switzerland (C.C.S., K.C.)
The exogenous application of hormones has led to their implication in a
number of processes within the plant. However, proof of their function in
vivo depends on quantitative data demonstrating that the exogenous
concentration used to elicit a response leads to tissue hormone levels
within the physiological range. Such proof is often lacking in many
investigations. We are using abscisic acid (ABA)-induced turion formation
in Spirodela polyrrhiza L. to investigate the mechanism by which a hormone
can trigger a morphogenic switch. In this paper, we demonstrate that the
exogenous concentration of ABA used to induce turions leads to tissue
concentrations of ABA within the physiological range, as quantified by both
enzyme-linked immunosorbent assay and high-performance liquid
chromatography/gas chromatography-electron capture detection analysis.
These results are consistent with ABA having a physiological role in turion
formation, and they provide an estimate of the changes in endogenous ABA
concentration required if environmental effectors of turion formation (e.g.
nitrate deficiency, cold) act via an increased level of ABA. In addition,
we show that the (+)- and (-)-enantiomers of ABA are equally effective in
inducing turions. Moreover, comparison of the ABA; levels attained after
treatment with (+)-, (-)-, and ([plus or minus])-ABA and their effect on
turion induction and comparison of the effectiveness of ABA on turion
induction under different pH regimes suggest that ABA most likely interacts
with a plasmalemma-located receptor system to induce turion formation.
