Gibberellic acid

About: Gibberellic acid is a research topic. Over the lifetime, 6597 publications have been published within this topic receiving 109294 citations. The topic is also known as: GIBBERELLIN A3.

Hormonal regulation of gene expression in barley aleurone layers : Induction and suppression of specific genes.

Abstract: As part of our investigation of the mode of action of plant hormones in barley (Hordeum vulgare L.) aleurone layers, we have studied the expression of five identified and three unidentified mRNA species in the presence of exogenous gibberellic acid (GA3) and abscisic acid. Three of the mRNAs are GA3-inducible, three are suppressed by GA3, and two are constitutive. The extent of the GA3 effect differs considerably for both inducible and suppressible mRNAs. For example, a ten-fold higher concentration of GA3 (10-8 M) is required for full induction of the high-pl group α-amylase mRNA than is required for the low-pI α-amylase mRNA (10-9 M). Temporal regulation of mRNA abundance also varies between the two α-amylase isoenzyme groups. The three GA3-suppressible mRNA species studied, alcohol dehydrogenase (ADH1), a probable amylase and protease inhibitor, and an unidentified barley mRNA species also varied in response to GA3. The ADH1 mRNA decreased drastically within 8 h of GA3 treatment, whereas the other two began to decrease in abundance only after 12–16 h of GA3 treatment. Abscisic-acid treatment counteracted the GA3 effects for both the inducible and suppressible mRNA species. Comparison of α-amylase-mRNA levels and α-amylase-synthesis rates showed a strong correlation between the two parameters, the only exception being a lack of α-amylase synthesis in the presence of α-amylase mRNA at low GA3 concentrations. Therefore, the expression of α-amylase seems to be regulated primarily by its mRNA levels.

The petunia homologue of tomato gast1: transcript accumulation coincides with gibberellin-induced corolla cell elongation.

Abstract: Gibberellins (GAs) regulate petunia corolla pigmentation and elongation. To study this hormone's effect at the molecular level, we used the tomato gast1 gene as a probe to isolate a gibberellin-induced gene (gip) from petunia corollas. The deduced sequence of gip exhibited 82% identity with GAST1 protein and contained a short, highly hydrophobic N-terminal region. High levels of gip expression were detected in elongating corollas and young stem internodes. When detached corollas were grown in vitro in sucrose medium, gip expression was strongly induced by gibberellic acid (GA3). GA3-induced gip expression in corollas was inhibited by abscisic acid (ABA). The expression of the gene was also induced by GA3 in detached young stem segments. Sucrose was not essential for GA-induced gip expression in corollas but enhanced its effect. In stems, on the other hand, sucrose inhibited the effect of the hormone. The results of the present work support the possible role of gip in GA-induced corolla and stem elongation.

The Effect of Temperature, Light and Gibberellic Acid (Ga3) on the Germination of Australian Everlasting Daisies (Asteraceae, Tribe Inuleae)

Abstract: Australian everlasting daisies have considerable potential as bedding plants, but little is known about their germination requirements. In ten taxa of everlasting daisies (Asteraceae, Tribe Inuleae) examined, germination in petri dishes was optimum over the temperature range 10-20°C with little or no germination at more extreme temperatures (5 and 30°C). Light stimulated germination in seven of the ten tare; Erymophyllum ramosum (A. Gray) Wilson, Craspedia sp., Leucochrysum fitzgibbonii (F. Muell.) Wilson, Waitzia suaveolens var. flava Wilson, Rhodanthe chlorocephala subsp. rosea (Hook.) Wilson, R. chlorocephala subsp. splendida (Hemsley) Wilson and R. floribunda (DC.) Wilson. In the dark, gibberellic acid (GA3, 50 mg L-1) stimulated germination to similar levels observed in light-treated seed. Schoenia filifolia subsp. subulifolia and S. cassiniana were not affected by light regime, but in both taxa germination was improved by the addition of GA3. By contrast, germination in Rhodanthe humboldtiana, which also had no response to light, was inhibited by GA3. In most species, germination in the dark was similar over the GA3 concentration range 1-100 mg L-1, but 500 mg L-1 was often inhibitory. Germination was optimised under temperature and light conditions related to maximising survival of seedlings which germinate near the soil surface during winter in the arid interior habitat of central Australia.

Kinetic studies on the redistribution of endogenous growth regulators in gravireacting plant organs.

Abstract: The kinetics of redistribution of endogenous indole-3-acetic acid, cis-abscisic acid and gibberellic acid (+gibberellin A7) in gravistimulated plant organs were followed by immunoassay, during the latent period and the phase of gravitropic curvature. Whereas in maize coleoptile tips, endogenous indole-3-acetic acid accumulated in the lower half of the organ (ratio 65:35, in favour of the lower half) before bending occurred, it was not possible to detect any significant lateral asymmetry of any of the growth regulators assayed in gravitropically reacting root tips of Zea mays L. and Vicia faba L. nor in hypocotyls of Helianthus annus L. Also, no indication was obtained for an exchange of growth regulators between peripheral and central cell layers of the sunflower hypocotyl. Evidence is presented that changes in the properties of the epidermal or subepidermal cell layers located in the lower half of the horizontally placed sunflower hypocotyl are largely responsible for the gravitropic reaction. An alteration in the subcellular compartmentation of IAA may be involved in this process.