Hormonal Aspects of Seed Dormancy in Yellow Foxtail

Abstract

Investigations with exogenous test solutions showed that abscisic acid (ABA) inhibited germination of nondormant seeds and that gibberellins (GA) promoted the germination of yellow foxtail (Setaria lutescens (Weigel) Hubb.) The effect of the promoters was much more readily demonstrated with excised caryopses than with intact seeds. Cytokinins reversed ABA inhibition of germination; GA did not, but the two promoters in combination were more effective than the cytokinin alone. The reversal occurred only at one end of the embryonic axis, the shoot end. An endogenous inhibitor was extracted from dormant and nondormant yellow foxtail seeds and compared with ABA by chromatography, electrophoresis, and bioassays. The extracted inhibitor was very similar to ABA in six paper-chromatography solvent systems, three paper electrophoresis runs at different pH values, and three bioassays. Paper electrophoresis was an effective means of separating the two plant hormones, ABA and gibberellic acid (GA3).

Resource Allocation and Reproduction in Populations of Amphicarpum Purshii (Gramineae)

“…Stratification significantly increased the germination of aerial caryopses; other studies of panicoid grasses, e.g., Setaria lutescens (Kollman and Staniforth, 1972), have also noted a stratification response. Amen (1968) believes that such a low-temperature requirement provides the warm-season plant with a safety mechanism against imprudent germination.…”

Seed dormancy characteristics in six weed species as affected by after-ripening temperatures and field conditions

“…One is imposed by the caryopsis and the other one imposed by the hull. Thereafter, Kollman and Staniforth (1972) studied the response of SETLU seeds to homones and found that exogenous applications of gibberellic acid promoted germination, abscisic acid inhibited germination and cytokinins reversed such inhibition. On the basis of this evidence, it is suggested that the primary dormancy in this species is caused by an hormonal imbalance and thus, the effect of natural stratification would be to promote a favorable equilibrium among such hormones (Sutcliffe, 1977), which, according to the promoter/inhibitor theory (Amen, 1968), is necessary for germination to take place.…”

Physiological and ultrastructural investigations of caryopsis dormancy in Setaria lutescens (Gramineae)

“…Several investigators have suggested that caryopsis dormancy is caused by an unfavorable balance between the endogenous content of abscisic acid and gibberellins (Kollman, 1970;Rost, 1971b;Kollman and Staniforth, 1972). This inhibitor-promoter hypothesis is based primarily on the effect of exogenous applications of these ti70 plant hormones on the germination of dormant and nondormant caryopses.…”

“…This inhibitor-promoter hypothesis is based primarily on the effect of exogenous applications of these ti70 plant hormones on the germination of dormant and nondormant caryopses. Exogenous applica tions of gibberellins have been shown to relieve caryopsis dormancy, whereas exogenous application of abscisic acid has been shown to prevent germination in nondormant caryopses (Kollman, 1970;Kollman and Staniforth, 1972). Rost (1971bRost ( , 1975 reasoned that, since embryos excised from dormant caryopses germinate readily, abscisic acid was probably not con centrated in the embryo, but in the caropsis coat.…”

“…Although the inhibitor-promoter hypothesis of caryopsis dormancy is credible, there are a number of observations that do not substantiate it. First, imbibition of nondormant caryopsis in the presence of exogenous abscisic acid does not prevent swelling of the embryo axis and partial growth and differentiation of the coleorhiza, events which do not occur in imbibed, but dormant caryopses (Kollman, 1970;Kollman and Staniforth, 1972). This suggests that, while abscisic acid is certainly inhibitory to germination, this inhibition is on processes that occur later in the germination sequence than those that are inhibited by dormancy imposition.…”