Control of Flower Opening By Plant Hormones in Gaillardia Grand iflora.

Abstract

The role of plant hormones in the control of the flower opening phase of flowering was determined through the application of established rules. The flower opening processes in Gaillardia grand iflora were described in terms of organ elongation, cell elongation, and fresh and dry weight changes. These processes included ray corolla elongation; filament, style, and stigma elongation; and stigma unfolding. The effects of applied hormones (auxin, gibberellins, cytokinins, abscisic acid, and brassinolide) upon these processes were observed. The role of hormones was verified by the effects of applications of hormone inhibitors (PCIG, TIBA, AMO 1618, CCC, AVG, and Co('2+)). Ray corolla elongation responded to gibberellins. Filament, style, and stigma elongation were promoted by auxin. Stigma unfolding was promoted by ethylene. The natural levels of auxin, ethylene, and gibberellins were measured by the double standard isotope dilution assay, gas chromatography, and the 'Tan-ginbozu' dwarf rice bioassay, respectively. The timing and amount of gibberellin increases corresponded to those predicted for corolla elongation. The timing and amount of auxin increases corresponded to those predicted for filament, style, and stigma elongation. Ethylene production increases correlated with stigma unfolding. Based upon these results, a model for flower opening in Gaillardia is proposed. This model leads to further questions for future research.