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.

Phytohormone-regulated beta-amylase gene expression in rice.

Abstract: The expression of β-amylase genes in rice (Oryza sativa) and its regulation by phytohormones gibberellic acid (GA) and abscisic acid (ABA) were examined. Upon germination β-amylase is synthesizedde novo in aleurone cells and (GA) is not required. Exogenous addition of GA does not enhance the β-amylase activity, while ABA inhibits the β-amylase activity, mRNA accumulation, and the germination of rice seeds. GA can reverse ABA inhibition of β-amylase expression, but not ABA inhibition of seed germination. Such regulation represents a new interaction of ABA and GA.

Micropropagation of the critically endangered Western Australian species, Symonanthus bancroftii (F. Muell.) L. Haegi (Solanaceae)

Abstract: A micropropagation protocol was developed for the conservation of the critically endangered Western Australian shrub,Symonanthus bancroftii. It was necessary to screen antioxidant treatments to prevent the occurrence of lethal browning of explants upon excision. Potassium citrate and citric acid (0.1% w/v in a 4:1 ratio) prevented oxidative browning and was superior to the untreated control or other antioxidant treatments tested. Half strength Murashige and Skoog (MS) medium containing 0.5 μM kinetin and 0.25 μM benzyladenine produced three-fold multiplication compared to 1.75×, 1.5×, 1.8× and 1× multiplication for 2.5 μM kinetin + 0.25 μM benzyladenine, 0.5 μM kinetin + 5 μM gibberellic acid, 1 μM kinetin + 3 μM gibberellic acid and half strength MS with no plant growth regulators, over 4 weeks. Root production was achieved with indole-3-butyric acid (IBA) and α-naphthaleneacetic acid (NAA) at 0.5/0.5 μM (31% rooting) and 1.0/1.0 μM (36% rooting), after four weeks. Paclobutrazol (PBZ) at 0, 3.4 (1 mg 1−1), 10.2 (3 mg 1−1), or 17 μM (5 mg 1−1) improved tolerance to desiccation after transfer ofin vitro rooted shoots to soil. PBZ at 10.2 μM increased survival to 90% compared to 50% for those plantlets not treated with PBZ. The acclimatisation period from the glasshouse to the shadehouse was 1 week for plantlets treated with PBZ compared to 4 weeks for plantlets without any PBZ. PBZ at 3.4 μM increased the number of roots per shoot compared to untreated controls.

Genetic and physiological evidence for the role of gibberellic acid in the germination of dormant Avena fatua seeds.

Abstract: germinating soon after they fall to the soil (Naylor, 1983; Cavers et al., 1992). The combination of dormancy and Genetic and physiological data indicate that gibberellic seed longevity allows viable wild oat seeds to infest acid does not have a primary role in the regulation of agricultural soils for several years (Naylor, 1983). Better seed dormancy in wild oat (Avena fatua L.). The gibberel- understanding of seed dormancy may enhance integrated lic acid sensitivity threshold of dormant caryopses weed management strategies, allow the development of imbibed for 7 d was 1 mM. Intact dormant seeds were predictive seed germination models, and provide insights after-ripened for 0, 2, 4, 8, 12, 16, and 20 weeks at into developmental arrest in plants. 40°C and imbibed in H 2 0, 100 nM or 1 mM gibberellic A dormant wild oat seed fails to germinate under acid. The length of the after-ripening interval was conditions which normally favour germination, but afterinversely related to the mean base gibberellic acid con- ripening in warm and dry conditions releases the seed centration (the concentration resulting in 50% germina- from dormancy. Germination of dormant wild oats can tion). Thus, after-ripening, not gibberellic acid, is the be stimulated by treatment with exogenous gibberellic principal factor that regulates the release of seed dorm- acid (GA) (Adkins et al., 1986). Thus, GA may play a ancy in wild oat. F 2 caryopses (dormant◊non-dormant) role in releasing dormancy. However, there is no generally classified by germination response to progressively accepted hypothesis to explain the role of after-ripening higher gibberellic acid concentrations, were pooled or GA in the breaking of seed dormancy (Simpson, 1990). according to their gibberellic acid requirement: low, Our hypothesis is that after-ripening regulates genes or medium and high. Germination responses of the F 3 pro- gene products that control the germination response of geny from the low, medium, and high gibberellic acid dormant wild oat seeds and the activities of these factors requirement pools were regressed on to the F 2 parent are largely independent of GA. The overall objective was values, and a heritability for germination response to to characterize the role of GA in the dormancy of wild gibberellic acid, h2=0.24, was calculated. Random amp- oat seed. Specific objectives were to (1) establish the lified polymorphic DNA analysis of DNA samples from mean GA base concentrations for dormant and partially F 2 pools requiring low and high gibberellic acid concen- after-ripened caryopses, (2) determine if there is genetic trations were screened with 200 decamer primers and evidence for the role of GA in releasing dormancy, and no polymorphisms were found. The findings of this (3) screen for polymorphic DNA markers between F

Secondary dormancy (skotodormancy) in seeds of lettuce (Lactuca sativa cv. Grand Rapids) and its release by light, gibberellic acid and benzyladenine

Abstract: Lettuce seeds (Lactuca sativa L. cv. Grand Rapids) imbibed in darkness at supra-optimal temperatures (23 ± 1°C) develop a secondary dormancy, termed skotodormancy. The seeds first lose their ability to be promoted to germinate by gibberellic acid, and then lose their ability to be promoted by red light. A combination of red light and gibberellic acid will break skotodormancy for longer than either alone, but red light and benzyladenine together are much more effective. Desiccation of skotodormant seeds does not diminish their dormancy. Embryos dissected from skotodormant seeds will germinate, and are as capable of radicle expansion in the osmoticum polyethylene glycol as are newly-imbibed seeds. Hence skotodormancy is a whole seed dormancy and does not reside within the embryo as an inherent block to germination processes, but as an inability to respond to the stimulation of red light or to hormone.

Modification by gibberellin of the growth-temperature relationship in mutant and normal genotypes of several cereals

Abstract: High-resolution growth measurements were conducted using a linear variable displacement transformer in conjunction with a temperature-programmed meristem-cooling collar. Chilling and rewarming profiles were determined for a range of Gramineae, in the presence and absence of varying concentrations of gibberellic acid (GA3). In wheat (Triticum aestivum L.) seedlings, the growth-constraining temperature (Pe) was progressively lowered by increasing GA3 concentration, with a difference of-4.8°C between controls and material treated with 10−4 M GA3. Dwarf-5 maize (Zea mays L.) seedlings had a higher Pe than tall segregates and the difference was markedly reduced by exposure to a saturating concentration of GA3. A similar effect was observed with Tanginbozu dwarf rice (Oryza sativa L.). The growth ratetemperature responses of Rht3 gibberellin-insensitive dwarf wheat seedlings were unaffected by GA3 and the Pe values for these segregates were around 5° C higher than for normals. Slender (s1) barley (Hordeum vulgare L.) genotypes had Pe values of-7° C, compared with +4° C for wild-type material, and did not show positive hysteresis for growth rate during the rewarming phase. These studies indicate that GA3 modifies the thermal sensitivity of meristem function in Gramineae in a manner which enhances low-temperature growth.