Phytochrome Regulation of the Response to Exogenous Gibberellins by Epicotyls of Vigna sinensis |
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| Authors: | García-Martínez J L Keith B Bonner B A Stafford A E Rappaport L |
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| Affiliation: | Instituto de Agroquimica y Tecnologia de Alimentos, Jaime Roig 11, 46010 Valencia, Spain. |
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| Abstract: | The elongation rate of cowpea epicotyls from whole cowpea (Vigna sinensis) seedlings and derooted and debladed plants (explants) increased after the main light period (8-hour duration) was extended with either continuous low intensity tungsten light or brief (5 minutes) far-red (FR) irradiation. This end-of-day FR effect was reversed by red (R) irradiation suggesting the involvement of phytochrome. These results confirm and extend those obtained previously with other species. Localization studies indicate the epicotyl to be the site of the photoreceptor. Treatment of cowpea seedlings with paclobutrazol, a gibberellin (GA) biosynthetic inhibitor, abolished the FR promoted epicotyl elongation, indicating a role for GAs in this process. There was no significant difference in epicotyl elongation rates of R plus FR irradiated explants treated with GA1 or GA20 and R irradiated explants treated with GA1. However, R irradiation inhibited subsequent epicotyl elongation of GA20 treated explants. Moreover, the observation, using GC-MS, that GA1 and GA20 are native GAs in cowpea lends support to the concept that phytochrome may control the conversion of endogenous GA20 to GA1 in cowpea. |
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