Photoperiod-induced changes in gibberellin metabolism in relation to apical growth and senescence in genetic lines of peas (Pisum sativum L.) |
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Authors: | William M. Proebsting Peter J. Davies G. A. Marx |
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Affiliation: | (1) Section of Botany, Genetics and Development, Cornell University, 14853 Ithaca, NY, USA;(2) Department of Seed and Vegetable Sciences, New York State Agricultural Experiment Station, 14456 Geneva, NY, USA;(3) Present address: Western Regional Research Center, U.S. Department of Agriculture, 800 Buchanan St., 94710 Berkeley, CA, USA |
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Abstract: | In an early-flowering line of pea (G2) apical senescence occurs only in long days (LD), while growth in short days (SD) is indeterminate. In SD, G2 plants are known to produce a graft-transmissible substance which delays apical senescence in related lines that are photoperiod-insensitive with regard to apical senescence. Gibberellic acid (GA3) applied to the apical bud of G2 plants in LD delayed apical senescence indefinitely, while N6-benzyladenine and -naphthaleneacetic acid were ineffective. Of the gibberellins native to pea, GA9 had no effect whereas GA20 had a moderate senescence-delaying effect. [3H]GA9 metabolism in intact leaves of G2 plants was inhibited by LD and was restored by placing the plants back in SD. Leaves of photoperiod-insensitive lines (I-types) metabolized GA9 readily regardless of photoperiod, but the metabolites differed qualitatively from those in G2 leaves. A polar GA9 metabolite, GAE, was found only in G2 plants in SD. The level of GA-like substances in methanol extracts from G2 plants dropped about 10-fold after the plants were moved from SD to LD; it was restored by transferring the plants back to SD. A polar zone of these GA-like materials co-chromatographed with GAE. It is suggested that a polar gibberellin is synthesized by G2 plants in SD; this gibberellin promotes shoot growth and meristematic activity in the shoot apex, preventing senescence.Abbreviations GA gibberellin - GA3 gibberellic acid - SD short days - LD long days |
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Keywords: | Apical senescence Gibberellins Photomorphogenesis Pisum Senescence |
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