ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
It has been shown previously that gibberellins (GAs) mediate the phytochrome (Phy) control of cowpea (Vigna sinensis L.) epicotyl elongation induced by end-of-day (EOD)-far-red light (FR). In the present work, the EOD-FR effect on GA metabolism and GA levels in cowpea has been investigated. GA1, GA8, GA19 and GA20 were identified in epicotyls, and GA1, GA19, GA20 and GA29-catabolite in leaves of 6-day-old cowpea seedlings. The content of GA1 in the epicotyl paralleled the decrease of its growth rate, supporting the hypothesis that this is the GA bioactive in controlling cowpea epicotyl elongation. FR enhanced both the amount of [3H]GA1 in the epicotyl produced from applied [3H]GA20, and that of applied [3H]GA1 that remained unmetabolized in epicotyl explants, suggesting that Phy may regulate the inactivation of GA1. In agreement with this effect of light on GA1 metabolism, the contents of GA1 in the epicotyl remained higher in FR-treated than in R-treated explants. Moreover, in intact seedlings EOD-FR treatment increased both epicotyl elongation and GA1 content in the responsive epicotyl, whereas it was not altered in the leaves. These results show, for the first time, that photostable Phys modulate the stem elongation in light-grown plants by locally controlling the GA1 levels through regulation of its inactivation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1034/j.1399-3054.2000.t01-1-100413.x
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