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.

Hormone-directed Transport of Metabolites and its possible Role in Plant Senescence

Abstract: The movement of metabolites and nutrients towards developing seeds, and their accumulation there, appears to play an important role in the regulation of senescence of the shoot in annual plants. The possibility that the directed-trans port of nutrients towards developing fruits is regulated by growth hormones has been studied in French bean (Phaseolus vulgaris). Application of 3-indolyl acetic acid (IAA), in lanolin, to peduncles from which the fruits had been removed, re sulted in significantly greater accumulation of 32P (applied to the lower part of the stem) in the region of hormone application than in peduncles treated with lanolin only. When gibberellic acid (GA) or kinetin were applied alone to defruited ped uncles they had no significant effect on the accumulation of 32P at the point of application of hormone, but when either was applied with IAA they greatly enhanced the effect of the latter on movement of 32P. The greatest effect was obtained when all three hormones were applied simultaneously. This hormone-directed transport was also demonstrated for the movement of I4C-labelled photosynthates from the leaves to the peduncles. It is suggested that hormone-directed transport may play an important role in directing the movement of nutrients towards de veloping seeds, which are rich sources of endogenous hormones.

Effects of Gibberellins on Plant Growth and Development

Abstract: Summary 1The gibberellins are metabolic products of the fungus Gibberella fujikuroi (conidial state Fusarium moniliforme). Three gibberellins are known: gibberellic acid (C19H22O6), gibberellin A1 (C19H24O6) and gibberellin A2 (C19H26O6). A structure for gibberellic acid has been proposed. Gibberellin A1 is a dihydro derivative of gibberellic acid. The structure of gibberellin A2 has not yet been established. 2The biological activity of all three gibberellins is, as far as is known at present, zqualitatively similar; no truly quantitative comparisons have been reported. In describing biological results below, the abbreviation GA may refer to any one gibberellin or to mixtures. 3The most characteristic effects of GA on shoot growth are increased inter-node extension, increased leaf-growth and enhanced apical dominance. 4Under some circumstances, with some plant species, treatment with GA does not stimulate growth of intact roots, though some root sections do respond by increased growth. High concentrations of GA are only slightly inhibitory, results in increased dry weight. This is mainly due to increased carbon fixation and is believed to be a secondary effect of increased leaf growth. 5Not all plants respond to GA by increased shoot growth and the effect on some species is greater than that on others. In species in which dwarf mutants are known, the dwarf may frequently be induced by GA to grow in a form in-distinguishable from that of the tall phenotype, genetically tall plants themselves being unaffected. 6Many forms of dormancy are broken by GA. These include seed dormancy, dormancy of potato tubers and dormancy of shoot internodes and buds. 7GA will induce flowering of long-short-day plants kept permanently in short-day photoperiods. I t will induce stem growth and, in long-day photoperiods but possibly not in short days, flowering in cold-requiring biennial long-day plants. 8It inhibits flowering of short-day plants in inductive short-day photoperiods. I t will induce stem growth and, in long-day photoperiods but possibly not in short days, flowering in cold-requiring biennial long-day plants. It inhibits flowering of short-day plants in inductive short-day photoperiods. 9In its effects on vegetative cell extension GA has certain similarities to the auxins but there are also differences. The most important differences are: (a) auxins greatly increase cell-extension in excised tissue sections, whereas GA has little effect; (6) GA induces marked cell extension in shoots of some intact plants, whereas exogenous auxins have little effect; (c) auxins inhibit root growth strongly, but GA does not. 10There is evidence from several sources that GA only influences cell extension if auxin is present. 11Comparison of the growth rate of excised pea internode sections with the growth rate of comparable tissues in intact plants, using untreated and GA-treated plants as sources of both types of material, has led to the conclusion that the endogenous auxins of plants are limited in their effects, and that growth is correspondingly limited, by 'an inhibitory system'GA acts by neutralizing the effects of this inhibitory system. 12The work of Galston (1957) suggests that this inhibitory system might be an auxin-destroying enzyme. Not all experimental observations are completely compatible with this view. 13In its effects on leaf expansion and on some forms of dormancy, GA simulates light. In most photoperiodically sensitive plants, light, particularly in the form of long-day photoperiod, induces increased shoot growth; GA has a similar effect. The internode-inhibiting effects of light are not simulated by GA, which always promotes growth; on the other hand, GA does not physiologically reverse such inhibitions. 14GA also breaks certain forms of dormancy broken in natural conditions by exposure to low temperature (vernalization). 15In its effects on flowering GA also simulates light. By inducing flowering of long-day plants and long-short-day plants in short days it acts as if by extension of the light period; in inhibitory flowering in short-day plants in inductive short-day photocycles it simulates a light break in the dark period. The action spectrum of he light-induced effects mentioned in this paragraph and in paragraph 13 is similar, red light (650 mp) being most active. Characteristically an inducing exposure to red light may be reversed by an exposure to far-red (735 mμ). 16In cold-requiring biennials GA simulates vernalization. 17GA is not florigen, the postulated flowering hormone common both to short-day plants and long-day plants. 18Hormones with physiological properties similar to those of GA have been detected in several plant tissues. The active material has been isolated from Phaseolus seeds and shown to be gibberellin A,. It is suggested that growth regulation in plants is based on a balance of auxins, GA-like hormones and a growth-inhibitory system. 19Effects of photoperiod on plants are not confined to flowering. In general, short-day photoperiods tend to induce retarded shoot extension and dormancy; shoot extension is accelerated and dormancy broken by exposure to long-day photoperiods, to low temperature, or to exogenous GA. 20There is thus a fundamental unity in the effects of GA on plant development, in which GA closely simulates effects usually induced in nature either by exposure to light or by vernalization. Accordingly, the explanation already offered (paragraphs 11 and 18 of this Summary) of the effects of GA on vegetative growth of day-neutral plants, may be extended to cover phenomena of flowering and dormancy. 21A hypothetical scheme is presented to explain regulation of growth and flowering, based primarily on the activity of GA-like hormones; this scheme is a modification of those proposed by Borthwick et al. (1952) and Liverman & Bonner (1953). It may be summarized as follows: In response to light, GA-like hormones are formed in leaves, a physiologically inactive, or less active, precursor (P) being an intermediary. The hormone is converted slowly back to P in darkness, more rapidly if the leaves are exposed to far-red light. If the leaf is then exposed to red light once more, the hormone is again formed from P. Thus in long-day conditions increasing concentrations of the hormone will be built up but in short-days concentrations will be much lower. If it is supposed that high levels of GA-like hormone induce flowering in long-day plants but that flowering of SDP only takes place when levels of the hormone are low, the flowering and vegetative responses of both types of plant to light and to exogenous GA can be accounted for. This scheme can be adapted to explain other light-induced responses, and also the effects of vernalization if it is assumed that low-temperature treatments also are concerned with synthesis of GA-like hormones.

The effects of gibberellic acid and abscisic acid on α-amylase mRNA levels in barley aleurone layers studies using an α-amylase cDNA clone.

Abstract: Two cDNA clones were characterized which correspond to different RNA species whose level is increased by gibberellic acid (GA3) in barley (Hordeum vulgare L) aleurone layers On the criteria of amino terminal sequencing, amino acid composition and DNA sequencing it is likely that one of these clones (pHV19) corresponds to the mRNA for α-amylase (1,4-α-D-glucan glucanohydrolase, EC 3211), in particular for the B family of α-amylase isozymes (Jacobsen JV, Higgins TJV: Plant Physiol 70:1647–1653, 1982) Sequence analysis of PHV19 revealed a probable 23 amino acid signal peptide Southern hybridization of this clone to barley DNA digested with restriction endonucleases indicated approximately eight gene-equivalents per haploid genome The identity of the other clone (pHV14) is unknown, but from hybridization studies and sequence analysis it is apparently unrelated to the α-amylase clone Both clones hybridize to RNAs that are similar in size (∼1500b), but which accumulate to different extents following GA3 treatment: α-amylase mRNA increases approximately 50-fold in abundance over control levels, whereas the RNA hybridizing to pHV14 increases approximately 10-fold In the presence of abscisic acid (ABA) the response to GA3 is largely, but not entirely, abolished These results suggest that GA3 and ABA regulate synthesis of α-amylase in barley aleurone layers primarily through the accumulation of α-amylase mRNA

Cadmium and nickel accumulation in rice plants. Effects on mineral nutrition and possible interactions of abscisic and gibberellic acids

Abstract: Rice plants accumulate high quantities of Cd and Ni when grown for 10 days in a medium containing these heavy metals. Accompanying Cd and Ni uptake, a decrease in shoot and root length was observed, though dry matter accumulation was not affected accordingly. Metal treatments also induced a decrease in K, Ca and Mg contents in the plants, particularly in the shoots, indicating that Cd and Ni interfered not only with nutrient uptake but also with nutrient distribution into the different plant parts. Addition of abscisic acid (ABA) or gibberellic acid (GA3) to the external solution could not overcome the depressing effects of the metals on nutrient acquisition, and even induced a further decrease of Ca content in Ni-treated plants. Both hormones also reduced, significantly, heavy metal incorporation into the plants. Additionally, hormonal applications affected the transport of Cd and Ni to the shoots, resulting in a higher percentage of the metals taken up remaining in the roots.