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.

α-Amylase production and leaf protein synthesis in a gibberellin-responsive dwarf mutant of ‘Himalaya’ barley (Hordeum vulgare L.)

Abstract: A dwarf mutant, M117, was isolated following sodium-azide mutagenesis of barley (Hordeum vulgare L. ‘Himalaya’). Treatment of the mutant with gibberellic acid (GA3) restored growth to levels of the tall parent, α-Amylase production was examined in germinated grains of the dwarf mutant and in Himalaya plants treated with gibberellin (GA) biosynthesis inhibitors. The mutant showed reduced α-amylase activity relative to the parent when grains were germinated on water, but activities were equivalent to the parent following germination on GA3 solution. Germination of normal or mutant grains in the presence of GA biosynthesis inhibitors led to reduced α-amylase activity levels, but normal levels were restored if GA3 was included in the inhibitor solution. These data are consistent with a model in which α-amylase production in the germinated grain is regulated by the supply of active GAs. Treatment of M117 with GA3 increased the length, fresh weight, dry weight, volume, cell number, and protein content of the first leaf. Proteins being synthesized in the first leaf were labelled with [35S]methionine and fractionated by two-dimensional electrophoresis. No reproducible qualitative or quantitative differences in protein profiles were detected in response to GA3 treatment. In contrast, first leaves from seedlings exposed to dehydration stress had profiles clearly distinguishable from those of control seedlings. Stem sections from dwarf plants maintained on 10 μM GA3 in the presence of sucrose elongated significantly more than controls without GA3, but two-dimensional analysis of the [35S]methionine-labelled radioactive polypeptides again revealed no GA3-induced differences. It was concluded that enhanced elongation rates of leaves or stem segments were not associated with major changes in gene expression.

Changes in the structure of ovary tissues and in the ultrastructure of mesocarp cells during ovary senescence or fruit development induced by plant growth substances in Pisum sativum

Abstract: Structural changes of tissues in unpollinated ovaries of Pisum sativum L. cv. Alaska after treatment with different plant growth substances (gibberellic acid, 2,4-dichlorophenoxyacetic acid, and 6-benzyladenine) or decapitation of the plant were studied. All the treatments resulted in the prevention of cellular disorganization associated with ovary senescence. They effected the enlargement of mesocarp cells and the differentiation of endocarp cells in very similar patterns, suggesting a similar induction of the structural processes involved in fruit development. Ultrastructural changes in mesocarp cells after treatment with gibberellic acid showed that rapid enlargement of mesocarp cells was sustained mainly by a reorganization of the membrane systems directed to the sysnthesis of primary cell wall. Early changes in the subcellular components in mesocarp cells were observed as the first symptoms in ovary senescence.

Exogenous abscisic acid and gibberellic acid elicit opposing effects on Fusarium graminearum infection in wheat.

Abstract: Although the roles of salicylate (SA) and jasmonic acid (JA) have been well-characterized in Fusarium head blight (FHB)-infected cereals, the roles of other phytohormones remain more ambiguous. Here, the association between an array of phytohormones and FHB pathogenesis in wheat is investigated. Comprehensive profiling of endogenous hormones demonstrated altered cytokinin, gibberellic acid (GA), and JA metabolism in a FHB-resistant cultivar, whereas challenge by Fusarium graminearum increased abscisic acid (ABA), JA, and SA in both FHB-susceptible and -resistant cultivars. Subsequent investigation of ABA or GA coapplication with fungal challenge increased and decreased FHB spread, respectively. These phytohormones-induced effects may be attributed to alteration of the F. graminearum transcriptome because ABA promoted expression of early-infection genes, including hydrolases and cytoskeletal reorganization genes, while GA suppressed nitrogen metabolic gene expression. Neither ABA nor GA elicited significant effects on F. graminearum fungal growth or sporulation in axenic conditions, nor do these phytohormones affect trichothecene gene expression, deoxynivalenol mycotoxin accumulation, or SA/JA biosynthesis in F. graminearum-challenged wheat spikes. Finally, the combined application of GA and paclobutrazol, a Fusarium fungicide, provided additive effects on reducing FHB severity, highlighting the potential for combining fungicidal agents with select phytohormone-related treatments for management of FHB infection in wheat.

In vitro rescue of zygotic embryos of sour orange, Citrus aurantium L., and their detection based on RFLP analysis

Abstract: Embryo development in vivo has been studied in four Citrus aurantium L. polyembryonic genotypes. Seeds were collected 65, 85, 105, 125 and 220 days after pollination (DAP). None of the immature seeds harvested 65 and 85 DAP contained visible embryos. A single embryo at a more advanced developmental stage was observed in the central position at the micropylar apex of the embryo sac in about 74% of seeds harvested at 105 DAP, while at 125 and 220 DAP the majority of seeds had two or more embryos at the same developmental stage crowded together. Restriction fragment length polymorphism (RFLP) analysis of low- and high-copy-number nuclear DNA was used to distinguish zygotic from nucellar seedlings. Analysis of plantlets derived from in vitro culture of the bigger embryos, located in the central position at the micropylar apex of the embryo sac of seeds harvested at 105 DAP, established that the frequencies of zygotic embryos ranged from 82 to 88%. Media for immature embryo germination in vitro were based on the nutrients and vitamins of Murashige and Skoog (MS) and Murashige and Tucker (MT) media supplemented with various concentrations of sucrose and growth regulators. A total of 76% of globular stage embryos (<0.3mm) germinated on MT medium containing 150 mM sucrose and 14.4 μM gibberellic acid. Heart stage embryos (0.3-0.8 mm) germinated at 95% on MT medium supplemented with 150 mM sucrose and 2.9 μM gibberellic acid. The addition of 500 mg/l malt extract to MS medium increased the germination of early cotyledon stage (0.8-2.0mm) embryos to 98%. The optimum sucrose concentration for embryo rescue was 150 mM for the three embryo developmental stages. The ability to form plants in vitro strongly increased with increasing embryo developmental stage.

Gibberellin-like Activity of Helminthosporol and Helminthosporic Acid

Abstract: HELMINTHOSPOROL (I) was isolated from a culture of Helminthosporium sativum by Tamura et al.1, and was shown in this and subsequent studies2 to stimulate the growth of the second leaf sheath of rice seedlings. However, (I) did not promote the growth of dwarf maize, nor did it give positive results in some other biological tests. Subsequently, Tamura and Sakurai3 prepared a variety of related compounds and showed that (I) and helminthosporic acid, (II), promoted the elongation of rice seedlings and of lettuce seedling hypocotyls grown in light4. Thus, at high dose levels, these substances sometimes showed gibberellin-like activity. Various substances related to (−)-kaurene are probably on the biosynthetic pathway to gibberellic acid, (III), in Gibberella fujikuroi5,6, and probably in higher plants also7. Some of these substances give positive results in a number of biological tests for gibberellins8,9, as does steviol10. Gibberella converts steviol to an unidentified substance having activity in a wider range of test systems11.