Hormones Gibberellic Acid Research Articles

The Stimulating Effect of a Phytohormone, Gibberellic Acid, on Reproduction of Mus musculus

The plant hormone gibberellic acid (GA3), given in the drinking water to field-caught Mus musculus in the laboratory, almost doubled the proportion of females producing litters. No increase was detected in litter size or number of litters produced by breeding females. In a further experiment, the proportion of females coming into oestrus was more than doubled by treatment with GA3. Present in many plants, especially during germination, growth and seed maturation, gibberellins may be proximate chemical cues to reproduction in some herbivores, and may act as a feedback mechanism between plant and herbivore in some models of demographic cycles.

Effects of temperature, red light and hormones on the accumulation of free amino acids in osmotically growth-inhibited embryonic axes of New York lettuce seeds.

Free amino acids accumulated in non-thermodormant embryonic axes of New York lettuce seeds from the 16th to the 24th hour of imbibition, even when germination was prevented with 0.3 m mannitol. The accumulation of free amino acids in the embryonic axes was affected by temperature, red light and hormones (gibberellic acid, kinetin and abscisic acid), and was correlated with the growth potential of the axes. These data are evidence that the accumulation of free amino acids in the embryonic axes is not the result of axes-growth, but one of its causes.

Action of gibberellic acid in a dwarf maize mutant: an X‐ray microanalysis study

SUMMARYA method is described to prepare plant tissue for X‐ray microanalysis. Model experiments with radioactively labelled ions show that freeze substitution can be used for the retention of soluble ions under controlled conditions. For calculations of absolute values a combination of the ratio method and the continuum method is used with dentine as the only standard.An X‐ray microanalysis study of the action of plant hormones was performed with a dwarf maize mutant, sensitive to minimal amounts of the plant hormone gibberellic acid (GA3). The dwarf corn mutant shows completely different concentrations of K+, Ca++ and Cl in chloroplasts, cytoplasm and vacuoles in comparison with the normal plant. GA3 produces changes of the ion concentrations similar to those of the normal plant. Short‐term experiments (1‐4h action of the hormone) also result in changes in the ion concentrations, specifically due to the hormone. The structurally similar by physiologically inactive GA3 methylester causes a response comparable to that of water.

Control of protein synthesis in barley aleurone layers by the plant hormones gibberellic acid and abscisic acid

The patterns of protein synthesis in barley aleurone layers treated with gibberellic acid (GA 3) and abscisic acid (ABA) are compared with the patterns observed in wheat germ in vitro translation assays directed by RNA isolated from similarly treated layers. When used alone, GA 3 and ABA both induce the formation of new translatable mRNAs and cause new proteins to be synthesized. The effects of GA 3 are more dramatic than those of ABA. In GA 3-treated tissues, overall protein synthesis is redirected to produce large quantities of α-amylase and a few other GA 3-induced proteins, while other protein synthesis is reduced or stopped. Large amounts of new translatable mRNA for α-amylase are also induced such that the dominant in vitro translation product is α-amylase. These changes are blocked by the simultaneous addition of ABA to the tissue. In GA 3 plus ABA-treated layers, few changes in protein synthesis in vivo are observed when compared to protein synthesis in untreated tissue, although the induction of mRNA for α-amylase and the other GA 3-induced mRNAs does occur. This indicates that ABA does not interfere with GA 3 induction of translatable mRNAs but prevents the translation of these mRNAs in vivo. Thus ABA and potentially GA 3 regulate the translation of proteins in vivo in barley aleurone layers.

Quantitative gaschromatographische Bestimmung von ng-Mengen der Gibberellinsäure (GA3) durch den Elektronenanlagerungsdetektor

Using the gibberellic acid-(7)-methylester-bis-(3,13)-trifluoracetylester, a sensitive gas chromatographic method was developed for the determination of the plant hormone gibberellic acid (GA 3 ). The minimum detectable quantity (MDQ), defined as quantity that gives a signal three times the background noise level, was determined as 2 ng. The method was used to quantify gibberellic acid from wheat plants.

Gibberellic acid enhances the level of translatable mRNA for α-amylase in barley aleurone layers

α-AMYLASE is synthesised de novo in response to the plant hormone gibberellic acid (GA3) in the aleurone layers of barley grains1. This enzyme induction depends on RNA and protein synthesis, as determined by the use of inhibitors2–4, and it occurs after a temperature-dependent lag period5. The biochemical events of the lag period have been studied with respect to ionic requirements5–7, early protein synthesis8, RNA synthesis9–12, polysome formation13 and lipid synthesis and turnover14–17. It has been postulated that new mRNA for α-amylase synthesis might be produced in response to the hormone2,3 and there is evidence that GA3 enhances the incorporation of labelled ribonucleosides into poly(A)-containing RNA of barley aleurone layers18–20. Stimulation could be detected about 4 h after hormone treatment and although GA3 probably stimulates synthesis of a limited number of proteins, there was stimulation of a wide size range of poly(A)-containing RNAs. Thus it was not possible to say that GA3 had a selective effect on the synthesis of the mRNA for α-amylase.

Effects of Growth-Regulatory Chemicals on the Action Spectra for 14C Assimilation and Transport in Sugarcane Leaves

Pretreatment of sugarcane with the growth hormone gibberellic acid (GA3) and the growth depressant Polaris [N,N-bis (phosphonomethyl) glycine] significantly altered the action spectra for 14C assimilation and transport by leaf tissues. Leaf segments enclosed in a 14CO2 atmosphere were illuminated with discrete wavelengths of equal quantum flux from 400 to 710 nanometers (nm). Both compounds significantly lowered 14C assimilation in the blue, from 437 to 480 nm. Polaris accentuated a green depression at 550 nm while lowering assimilation peaks in the red at 600-640 nm and at 670 nm. Translocation of 14C, as percentages of the total nuclide assimilated, was vastly increased by both materials in the blue-violet (400 nm) and by GA3 in the blue (437-480 nm). Polaris increased transport from the blue-green to yellow (520-600 nm). A high sensitivity of control plants to far-red light (710 nm) was unaffected by either material. These results support the theory that chemical ripening may involve sugar synthesis and transport processes in addition to growth-regulatory effects in sink tissues.

The effect of gibberellic acid and kinetin on chlorophyll retention in Lemna trisulca L

Plant hormones gibberellic acid and kinetin were applied to the sterile cultures of Lemna trisulca in different concentrations. Gibberellic acid in concentration of 1.0 mg/l had a remarkable effect in preventing the chlorophyll destruction, so that the plants remained green for 2–3 weeks longer than the control ones. Kinetin had no effect on the retention of chlorophyll in any concentration used.

Influence of 2,4-D, Dicamba, and Naptalam on Hormonal Control of Dipeptidase

The plant hormones gibberellic acid (GA) and benzyladenine (BA) stimulated the development of dipeptidase activity in distal-half cotyledons of squash (Cucurbita maximaDuch. ‘Chicago Warted Hubbard’). The herbicides 2,4-D [(2,4-dichlorophenoxy)acetic acid], dicamba (3,6-dichloro-o-anisic acid), and naptalam (N-1-napthylphalamic acid) inhibited the development of dipeptidase activity in this tissue. Herbicide concentrations which inhibited the development of this enzyme activity about 30% were used for the herbicidehormone interaction study. The addition of GA or BA counteracted the inhibition induced by 2,4-D and naptalam. Neither hormone grossly altered the inhibition induced by dicamba; however, BA did significantly reduce the inhibition caused by dicamba.

Early effects of gibberellic acid on barley aleurone layers

The most obvious effects resulting from the application of the hormone gibberellic acid (GA) to cereal aleurone layers are the secretion of metabolites and the de novo synthesis and secretion into the medium of enzymes, mostly hydrolases ( Varner, 1964; Varner et al., 1965; Chrispeels and Varner, 1967 a,b; Jacobsen and Varner, 1967). For that reason research on the mode of action of GA has focused on the elucidation of the roles of protein synthesis and RNA synthesis in the responses. The present report follows observations that the effects of GA occur sequentially ( Pollard, 1968). Furthermore, we have found that GA enhances the secretion of more than 20 metabolites and enzymes. It is desirable to identify the earliest of these reponses since they are most likely to be near the primary action of the hormone. We wish to report (1) the effect of GA on the secretion of soluble carbohydrates and several phosphatases, the earliest effects it has been possible to detect and (2) data relating the effects of the hormone to other aspects of metabolism, especially protein synthesis, RNA synthesis and respiration.

RECIPROCAL EFFECTS OF INSECT AND PLANT-GROWTH SUBSTANCES.

INJECTION of homogenates of active prothoracic glands into fourth instar locust larvae, a day after moulting, causes them to moult again prematurely. The instar is shortened by about 12–18 h (Fig. 1). The active agent appears to be an ecdysone (which we have named ecdysone-λ). Injection of those fractions of extracts of whole locusts that contain ecdysone-λ have a similar effect. The plant growth hormone gibberellic acid likewise shortens the instar when injected at the appropriate time into larvse of both Locusta migratoria migratorioides (R. and F.) and Schistocerca gregaria (Forskal) (Fig. 1).

Replacement of an Alternating Temperature Requirement for Germination by Gibberellic Acid

IN many species of plants, seed-germination does not take place readily except under special conditions. A barrier to germination may be imposed by the seed coats or other coverings, by the presence of germination inhibitors in some part of the seed, by morphological or physiological immaturity of the embryo, by the need for light or for its absence, or by the need for alternating temperatures during germination1. Chemical substances can in some cases substitute for specific environmental factors in effecting seed germination. Nitrates, for example, promote the germination of some light-requiring seeds in the dark1, and the results of recent work indicate that the plant hormone gibberellic acid is particularly effective in overcoming several types of germination inhibition. In the germination of ‘Grand Rapids’ lettuce seeds, the primary light-requirement2,3 and the light-requirement induced by high temperature or dark-osmotic treatments3 can be replaced by gibberellic acid. Gibberellic acid overcomes the inhibiting effect of coumarin on lettuce seed germination4 and of endogenous germination inhibitors present in Avena fatua5 and Betula spp.6 seeds. Kallio and Piiroinen7 found that gibberellic acid has a marked stimulating effect on the germination of seeds of 8 species, including Gentiana nivalis and Geranium sylvaticum; their experiments were conducted in the light at 24°.