The Roles of Plant Hormones in Style and Stigma Growth in Gaillardia Grandiflora (Asteraceae)

Abstract

Style and stigma elongation and stigma unfolding, and the roles of plant hormones in these processes in Gaillardia grandijlora Van Houtte were investigated. Style and stigma elongation in vivo began just after anthesis, and style elongation was accompanied by epidermal cell elongation (greatest near the stigma) and a fresh weight increase, but not by cell division or a dry weight increase. The stigma unfolded after the style and stigma elongated. Style-stigma units excised from young disc flowers of this composite were measured as they responded to plant growth regulators applied singly, as well as in sequential and simultaneous combinations, in vitro. Style elongation was promoted by auxin, was inhibited by gibberellins and ethylene, and was unaffected by other growth regulators. Stigma elongation followed a similar pattern of response. Endogenous auxin levels and ethylene production showed parallel variation and endogenous gibberellin levels showed inverse variation with style and stigma elongation. Stigma unfolding was more sensitive to auxin applications and was promoted by applied ethylene. Ethylene production showed parallel variation and endogenous auxin levels showed inverse variation with stigma unfolding. AVG and C0 2 + applications decreased auxin-induced style elongation and fusicoccin promoted all of the growth responses of style-stigma units in vitro. A gibberellin-auxin-ethylene-acid growth interaction mode ofcontrol is proposed for these three growth processes.

Application of Trehalose Mitigates Short-Styled Flowers in Solanaceous Crops

“…The roles of plant hormones on style growth have long been acknowledged. , Here, we examined the contents of ten plant hormones in swollen flower buds by LC-MS to seek potential mediators for style elongating action of trehalose (Supplementary Figure S5). In the flower buds of tomato, GA 4 and DHZ were below the detection limits (∼10 pg per sample).…”

Resupination in Flowers of Two Dendrobium (Orchidaceae) Hybrids: Effects of Nodal Position and Removal of Floral Segments

“…Auxin (100 and 500 ppm naphthaleneacetic acid in lanolin) can replace the effect of pollinia on elongation (KAKO and OHNO 1980). In other flowers, styles and stigmas can be a source of auxin (KONING 1983). Altogether, the available evidence suggests that auxin and/ or possibly other substances produced by the gynostemium or pollinia regulate resupination.…”