PLANT PHYSIOLOGY , Vol 101, Issue 1 49-55, Copyright © 1993 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Rapid Induction of Ion Pulses in Tomato, Cucumber, and Maize Plants following a Foliar Application of L(+)-Adenosine
S. Ries, S. Savithiry, V. Wert and I. Widders
Department of Horticulture, Michigan State University, East Lansing, Michigan 48824
Application of picomole quantities of (+)-adenosine, a plant
growth-regulating second messenger elicited by triacontanol, to tomato
(Lycopersicon esculentum Mill.), maize (Zea mays L.), and cucumber (Cucumis
sativa L.) foliage, increased Ca2+, Mg2+, and K+ concentrations in the
exudate from the stumps of excised plants by 20 to 60% within 5 s after
treatment. The change in ionic concentration of the exudate was transitory.
When L(+)-adenosine and triacontanol were applied to different tomato
plants at the same time, the L(+)-adenosine caused an increase in Ca2+ flux
within 3 s, whereas a significant increase from triacontanol was not
detectable until 5 min after application. This was expected because
triacontanol elicits the formation of L(+)-adenosine. The enantiomer of
L(+)-adenosine, D(-)-adenosine, had no effect on the cation concentration
in tomato and inhibited the effect of L(+)-adenosine at equimolar or lower
concentrations. These observations suggest that L(+)-adenosine acts by
eliciting a rapidly propagated signal that increases the concentration of
several ions in the apoplast. We postulate that modulations in apoplastic
ion concentration, especially increases in Ca2+ concentration, constitute a
mechanism by which plants regulate metabolic activity and growth in
response to certain stimuli.