Effect of Gibberellin A₄ and GA Biosynthesis Inhibitors on Growth and Flowering of Stock [Matthiola incana (L.) R. Br.]

Abstract

Effects of gibberellin A₄ (GA₄) and three GA biosynthesis inhibitors, uniconazole (UCZ), prohexadione-calcium (PCa), and trinexapac-ethyl (TNE) on growth and flowering of Matthiola incana (L.) R. Br. were investigated. In an early flowering 'Sourei', UCZ inhibited stem elongation and flowering. GA₄, PCa and TNE promoted flowering at 20°/15°C and 25°/20°C (day/night) under 12-hr photoperiod as compared to the control. However, only PCa and TNE induced flowering of a late flowering 'Banrei' at 20°/15°C. Flowering was not induced in any treatment at 25°/20°C and 30°/25°C but stem elongation of both cultivars was promoted by GA₄ and PCa at all temperatures. Under green house conditions in the winter, PCa promoted flowering of 'Banrei'. Although GA₄ and PCa promoted stem elongation, they did not induce flowering in the summer. These results indicate that biosynthesis of GA₄ and its deactivation are important factors that control stem elongation and flowering.