Showing papers on "Gibberellic acid published in 1997"

Sugar Repression of a Gibberellin-Dependent Signaling Pathway in Barley Embryos.

Abstract: Increasing evidence shows that sugars can act as signals affecting plant metabolism and development. Some of the effects of sugars on plant growth and development suggest an interaction of sugar signals with hormonal regulation. We investigated the effects of sugars on the induction of [alpha]-amylase by gibberellic acid in barley embryos and aleurone layers. Our results show that sugar and hormonal signaling interact in the regulation of gibberellic acid-induced gene expression in barley grains. The induction of [alpha]-amylase by gibberellic acid in the aleurone layer is unaffected by the presence of sugars, but repression by carbohydrates is effective in the embryo. [alpha]-Amylase expression in the embryo is localized to the scutellar epithelium and is hormone and sugar modulated. The effects of glucose are independent from the effects of sugars on gibberellin biosynthesis. They are not due to an osmotic effect, they are independent of abscisic acid, and only hexokinase-phosphorylatable glucose analogs are able to trigger gene repression. Overall, the results suggest the existence of an interaction between the hormonal and metabolic regulation of [alpha]-amylase genes in barley grains.

Effects of gibberellic acid on hairy root cultures of Artemisia annua: Growth and artemisinin production

Abstract: Artemisinin (AN), a potent antimalarial drug that has been used for centuries as a folk remedy in China, is an effective treatment against quinine-resistant strains of Plasmodium. It can be produced through the in vitro culture of genetically transformed (hairy) roots. The effect of gibberellic acid (GA3) on the growth and secondary metabolite production of hairy roots of Artemisia annua was investigated. Six different concentrations of GA3 were tested in shaker flasks to determine the optimum concentration. GA3 levels of 0.01–0.001 mg/l (28.9–2.89 µM) provided the most significant increase in biomass, and 0.01 mg/l (28.9 µM) produced the highest amount of AN. Investigation of growth kinetics showed that the use of GA3 at 0.01 mg/l (28.9 µM) increased the growth rate of hairy roots of A. annua by 24.9%. Thus, the cultures treated with GA3 reached stationary phase faster than control cultures.

Hormonal Regulation of Dormancy in Developing Sorghum Seeds

Abstract: The role of abscisic acid (ABA) and gibberellic acid (GA) in determining the dormancy level of developing sorghum (Sorghum bicolor [L.] Moench.) seeds from varieties presenting contrasting preharvest sprouting behavior (Redland B2, susceptible; IS 9530, resistant) was investigated. Panicles from both varieties were sprayed soon after pollination with fluridone or paclobutrazol to inhibit ABA and GA synthesis, respectively. Fluridone application to the panicles increased germinability of Redland B2 immature caryopses, whereas early treatment with paclobutrazol completely inhibited germination of this variety during most of the developmental period. Incubating caryopses in the presence of 100 [mu]M GA4+7 overcame the inhibitory effect of paclobutrazol, but also stimulated germination of seeds from other treatments. IS 9530 caryopses presented germination indices close to zero until physiological maturity (44 d after pollination) in control and paclobutrazol-treated particles. However, fluridone-treated caryopses were released from dormancy earlier than control and paclobutrazol-treated caryopses. Incubation in the presence of GA4+7 stimulated germination of caryopses from all treatments. Our results support the proposition that a low dormancy level (which is related to a high preharvest sprouting susceptibility) is determined not only by a low embryonic sensitivity to ABA, but also by a high GA content or sensitivity.

Rapid clonal propagation of three mulberries,Morus cathayana HemsL,M. lhou Koiz. andM. serrata Roxb., through in vitro culture of apical shoot buds and nodal explants from mature trees.

Abstract: High-frequency bud break and multiple shoots were induced in apical shoot buds and nodal explants ofMorus cathayana, M. lhou andM. serrata on Murashige and Skoog (MS) medium containing 0.5-1.0 mg/l 6-benzylaminopurine (BAP). Addition of gibberellic acid (0.4 mg/l) along with BAP induced faster bud break both in apical shoot buds and nodal explants and also enhanced the frequency of bud break in all three species. Shoot culture initiation was greatly influenced by explant type, explant age and explanting season. The shoots were successfully rooted on half-strength MS medium containing a combination of indole-3-acetic acid, indole-3-butyric acid and indole-3-propionic acid, each at 1.0 mg/l. The plantlets were successfully acclimated and eventually established in soil.

The role of gibberellins A 1 and A 3 in fruit growth of Pisum sativum L. and the identification of gibberellins A 4 and A 7 in young seeds

Abstract: Gibberellins A1 and A3 are the major physiologically active gibberellins (GAs) present in young fruit of pea (Pisum sativum L.). The relative importance of these GAs in controlling fruit growth and their biosynthetic origins were investigated in cv. Alaska. In addition, the non-13-hydroxylated active GAs, GA4 and GA7, were identified for the first time in young seeds harvested 4 d after anthesis, although they are minor components and are not expected to play major physiological roles. The GA1 content is maximal in seeds and pods at 6 d after anthesis, the time of highest growth-rate of the pod (Garcia-Martinez et al. 1991, Planta 184: 53–60), whereas gibberellic acid (GA3), which is present at high levels in seeds 4–8 d after anthesis, has very low abundance in pods. Gibberellins A19, A20 and A29 are most concentrated in seeds at, or shortly after, anthesis and their abundance declines rapidly with development, concomitant with the sharp increase in GA1 and GA3 content. Application of GA1 or GA3 to the leaf subtending an emasculated flower stimulated parthenocarpic fruit development. Measurement of the GA content of the pods at 4 d after anthesis indicated that only 0.002–0.5% of the applied GA was transported to the fruit, depending on dose. There was a linear relationship between GA1 content and pod weight up to about 2 ng · (g FW)−1, whereas no such correlation existed for GA3 content. The concentration of endogenous GA1 in pods from pollinated ovaries is just sufficient to give the maximum growth response. It is concluded that GA1, but not GA3, controls pod growth in pea; GA3 may be involved in early seed development. The distribution of GAs within the seeds at 4 d post anthesis was also investigated. Most of the GA1, GA8, GA19, GA20 and GA29 was present in the testa, whereas GA3 was distributed equally between testa and endosperm and GA4 was localised mainly in the endosperm. Of the GAs analysed, only GA3 and GA20 were detected in the embryo. Metabolism experiments with intact tissues and cell-free fractions indicated compartmentation of GA biosynthesis within the seed. Using 14C-labelled GA12, GA9, 2,3-didehydroGA9 and GA20 as substrates, the testa was shown to contain 13-hydroxylase and 20-oxidase activities, the endosperm, 3β-hydroxylase and 20-oxidase activities. Both tissues also produced 16,17-dihydrodiols. However, GA1 and GA3 were not obtained as products and it is unlikely that they are formed via the early 13-hydroxylation pathway. [14C]gibberellin A12, applied to the inside surface of pods in situ, was metabolised to GA19, GA20, GA29, GA29-catabolite, GA81 and GA97, but GA1 was not detected. Gibberellin A20 was metabolised by this tissue to GA29 and GA29-catabolite.

Gibberellic acid production using different solid-state fermentation systems

Abstract: Gibberellic acid production in liquid fermentation was compared with production of this compound in solid-state fermentation systems using cassava flour, sugar cane bagasse and low density polyurethane. Gibberella fujikuroi produced 23 mg of gibberellin/ml in 120h of liquid fermentation. Solid-state fermentation on bagasse showed excellent growth but presented gibberellin extraction problems. Very low production and growth was observed in solid-state fermentation with low density polyurethane as an inert support. Solid-state fermentation on cassava flour showed high production (250 mg/kg of dry solid medium) in a very short time (36h).

Alleviation of salt stress by plant growth regulators in Triticum aestivum L.

Abstract: Seedlings of the salt sensitive wheat cultivar C-306 evolved more ethylene than the salt tolerant cultivar Kharchia-65 under different levels of both chloride- and sulphate-dominated types of salinity. Pre-sowing seed soaking treatments with kinetin, gibberellic acid and to a lesser extent indole-3-acetic acid alleviated salt stress effects as apparent from seedling dry mass. Treated seedlings also evolved more ethylene both under saline and non-saline conditions. Ethrel did not affect seedling growth as well as ethylene production. Abscisic acid inhibited seedling growth and ethylene production under both types of salinity.

Effect of salinity, gibberellic acid and Azospirillum inoculation on growth and nitrogen uptake of Zea mays

Abstract: Pot experiments were conducted to evaluate the possible interaction of salinity (osmotic potential -0.3, -0.9 and -1.2 MPa) and occurrence of Azospirillum lipoferum or exogenous gibberellic acid (GA3) (100 µg g-1) on growth and some physiological parameters of maize. 15N-uptake as well as the percentage of nitrogen derived from 15N-fertilizer were decreased by increasing the NaCl concentrations and completely inhibited at concentrations corresponding to osmotic potentials -0.9 and -1.2 MPa. The percentage of nitrogen originating from N2 fixation was significantly correlated to the total counts of Azospirillum cells that colonized the histosphere. At high NaCl concentrations although no significant changes in N % in shoot dry mass either in inoculated or uninoculated plants were observed, the total N-yield [mg(N) pot-1] was decreased. Fresh and dry shoot mass significantly increased by Azospirillum inoculation. Azospirillum and GA3 treatments were positively correlated with most of the parameters analysed. Azospirillum inoculation or GA3 application at NaCl concentrations up to -1.2 MPa significantly increased the chlorophyll, K, Ca, soluble saccharides and protein contents as compared with control plants.

In vitro response of encapsulated somatic embryos of camellia

Abstract: Somatic embryos of Camellia japonica were hydrogel encapsulated using 3% sodium alginate and 01 M calcium chloride to produce synthetic seeds Both germinability and repetitive embryogenesis capacity of the encapsulated embryos were investigated The frequency of in vitro germination into plants of artificial seeds was affected by various nutrient additives included in the encapsulating matrix The addition of Ca-free Murashige and Skoog basal medium plus 3% sucrose plus 144 µM gibberellic acid and 285 µM indole-3-acetic acid to the alginate capsule resulted in 63% plant recovery rate, which was similar to that of non-encapsulated embryos Encapsulation of somatic embryos did not negatively affect the maintenance of their embryogenic competence, the mean number of secondary embryos being significantly increased when the alginate beads included the growth regulators of the secondary embryogenesis medium (444 µM 6-benzyladenine and 041 µM indole-3-butyric acid) Storage at 4°C significantly reduced the survival and germination into plants frequencies of both encapsulated and non-encapsulated embryos, but the reduction was much greater for non-encapsulated embryos Plant recovery of encapsulated embryos was 40% and 30% following storage for 30 and 60 days, respectively

Endo-[beta]-Mannanase Activity Present in Cell Wall Extracts of Lettuce Endosperm prior to Radicle Emergence.

Abstract: Lettuce (Lactuca sativa L.) endosperm cell walls isolated prior to radicle emergence underwent autohydrolysis, the rate of which was correlated with whether radicle emergence would subsequently occur. Extraction of endosperm cell walls with 6 M LiCl suppressed autohydrolysis, and the desalted extract possessed activity that was capable of hydrolyzing purified locust bean galactomannan but not arabinogalactan, carboxymethylcellulose, glucomannan, polygalacturonic acid, tomato galactomannan, or native lettuce endosperm cell walls. Some hydrolytic activity was detected on endosperm cell walls if they were modified by partial trifluoroacetic acid hydrolysis or pretreatment with guanidinium thiocyanate. In extended incubations the cell wall enzyme extract released only large molecular mass fragments from locust bean galactomannan, indicating primarily endo-activity. Galactomannan-hydrolyzing activity in the cell wall extract increased as a function of imbibition time and was greatest just prior to radicle emergence. Thermoinhibition (imbibition at 32[deg]C) or treatment with abscisic acid at a temperature optimal for germination (25[deg]C) suppressed both germination and endosperm cell wall mannanase activity, whereas alleviation of thermoinhibition with gibberellic acid was accompanied by significant enhancement of mannanase activity. We conclude that a cell wall-bound endo-[beta]-mannanase is expressed in lettuce endosperm prior to radicle emergence and is regulated by the same conditions that govern germination.

Shoot regeneration from cultured root explants of spinach (Spinacia oleracea L.): a system for Agrobacterium transformation.

Abstract: A reliable plant regeneration system is described for the production of adventitious shoots from root explants of spinach. Explants from roots of axenic shoots and roots induced on cultured hypocotyl explants were used for adventitious shoot induction. Explants from apical, middle and basal root regions were incubated on Nitsch and Nitsch medium supplemented with α-naphthaleneacetic acid, gibberellic acid and kinetin. Optimum shoot regeneration was from explants of apical and middle root regions on medium with 20 µm α-naphthaleneacetic acid and 5.0 µm gibberellic acid. Shoots originated directly from root tissues without an intervening callus phase. Adventitious shoots were rooted and were grown to maturity in the glasshouse. This plant regeneration procedure has been exploited in preliminary studies of Agrobacterium-mediated transformation.

Molecular characterization of L2 lipoxygenase from maize embryos

Abstract: We investigated the expression and accumulation pattern of lipoxygenase isoforms throughout the maize plant life. Two forms of lipoxygenase L1 and L2 have been identified as acidic proteins of 100 kDa (pI 6.4) and 90 kDa (pI 5.5-5.7) which accumulate in dry embryos and in various organs of maize seedlings. In young embryos, only the L2 form was detected and accumulation of L2 mRNA decreased during embryo development. Identification of lipoxygenases from in vivo and in vitro synthesized proteins indicates that similar levels of both L1 and L2 forms accumulated during treatment with abscisic acid, (ABA) gibberellic acid (GA3) and jasmonic acid (JA). However, differences in the activity of both enzymes were detected. By using an antiserum directed against purified L2 we isolated and characterized a partial cDNA clone of maize embryos encoding a lipoxygenase. The deduced amino acid sequence of L2 cDNA shares 78% identity with the rice L2 protein, and 51-56% identity with lipoxygenases from the dicotyledonous plants soybean and Arabidopsis. DNA blot analysis indicated that maize contains a family of lipoxygenase genes which are presently being characterized.

Hormonal regulation of expression of two cysteine endopeptidase genes in rice seedlings.

Abstract: Two cDNA probes (pRP60 and pRP80) were used to examine the hormonal regulation of expression of two cysteine endopeptidase genes in germinated whole seeds and de-embryonated seeds of rice. The pRP60 protein is a major rice cysteine endopeptidase named REP-1 that digests rice glutelin, the main seed storage protein. The pRP80 protein has features of a cysteine endopeptidase but has not yet been confirmed to be one. Neither mRNA was detectable in dry seeds, and the levels per seed increased sharply upon imbibition, reached peaks at d 6 to d 9, and then decreased. Both mRNAs were expressed in a seed-specific manner, but the accumulation of pRP60 mRNA was about ten times greater than the other. When seeds were de-embryonated and incubated, the amounts of both mRNAs were reduced to very low levels, but in the presence of 0.01 to 1 microM gibberellic acid (GA3) both again reached high levels. Addition of abscisic acid (ABA) or uniconazole, an inhibitor of gibberellin biosynthesis, partly eliminated the effect of GA3. Protein immunoblot analysis showed that the accumulation of the REP-1 protein in seeds was regulated by GA3 and ABA similarly to that of pRP60 mRNA, but the change in pRP60 mRNA with time after the onset of imbibition preceded that of the REP-1 protein.

Somatic embryogenesis from chickpea ( Cicer arietinum L.) inmature cotyledons: The effect of zeatin, gibberellic acid and indole-3-butyric acid

Abstract: Studies were conduced to test the effects of various cytokinins on somatic embryogenesis from chickpea (Cicer arietinum L.) immature cotyledons. Zeatin (13.7 µmol) added, to B5 basal medium, supplemented with 1.5 % sucrose and 0.2 µmol indole-3-acetic acid, was the most effective cytokinin. Lobular structures obtained from cotyledons cultures were transferred to B5 basal medium supplemented with gibberellic acid and indole-3-butyric acid at different concentrations. The most effective treatment was B5 medium containing 14.4 µmol gibberellic acid plus 1.0 µmol indole-3-butyric acid in which 42.8 % of lobular structures cultured formed normal somatic embryos. High conversion of embryos into plantlets (61.0–65.2 % embryos regenerated plants) was observed when germinated embryos were placed on plant development medium.

Gibberellic Acid3 Modifies Some Growth and Physiologic Effects of Paclobutrazol (PP333) on Wheat

Abstract: Gibberellic acid3 (GA3) modification of some growth and physiologic effects of paclobutrazol (PP333) was studied by applying PP333 alone and in combination with GA3 at the tillering stage of wheat. Results showed that GA3 weakened the effect of PP333 on tillering and shortening the plant, increased the dry matter accumulation of different tillers, improved plant nitrogen metabolism by favoring nitrogen translocation into tillers at late growth stage, and stimulated tiller development. All of these reduced the difference in spike weight among tillers and the main stem. Compared with control, there were more spikes per plant and fewer grain per spike in the PP333 treatment, but all yield components developed positively in the treatment consisting of the mixture of GA3 and PP333.

Regeneration ofSolanum tuberosum cv. Katahdin from leaf expiantsin vitro

Abstract: A previously published medium has been found to be effective for plant regeneration from leaf expiants ofSolanum tuberosum cv. Katahdin. A number of combinations of thidiazuron and naphthaleneacetic acid, along with a medium previously published for shoot regeneration from protoplast-derived calli ofSolanum phureja, which contained zeatin, indoleacetic acid and gibberellic acid (ZIG), were tested for callus induction, and all calli were transferred to ZIG for shoot induction. We conclude that leaf expiants cultured on ZIG medium at all stages of culture were the most effective at shoot production. A mean of over six shoots were produced per expiant after four months in culture.

Application of gibberellic acid to the surface of soybean seed (t Glycine max (L.) Merr.) and symbiotic nodulation, plant development, final grain and protein yield under short season conditions

Abstract: In short-season soybean production areas, low soil temperature is the major factor limiting soybean establishment, nodulation and nitrogen fixation. Gibberellic acid (GA) pretreatment of crop seeds can overcome low soil temperature inhibition of seed germination and seedling development. However, previous studies have found that the application of GAs decreased legume nodulation and nitrogen fixation under optimal growth conditions. A field experiment was conducted under short season conditions in eastern Canada to determine whether the application of GA3 to soybean seed could accelerate germination, and increase plant nodulation and nitrogen fixation. The results indicated that GA3 application accelerated seedling emergence but decreased plant nodulation and nitrogen accumulation at early plant growth stages. However, these initial negative effects were overcome as the plants developed. Gibberellic acid applied to soybean seed at the time of planting did not influence final grain and protein yield.

Role of benzyladenine and gibberellic acid in alleviating water-stress effect in gram (Cicer arietinum)

Abstract: Two gram (Cicer aerietmum L.) genotypes,'C 235' (susceptible) and 'RSG 143-1' (moderately tolerant to water stress), were grown in earthen pots. One set of plants were subjected to water stress only once (S 1 ) at days after sowing and another set twice (S 2) at 45 and 80 days after sowing. Both the control (non-stress) and stressed plants were sprayed with benzyladenine and gibberellic acid separately at the time of imposing stress. Water stress increased the proline, amino acids and total and total soluble sugars but decreased the soluble proteins and starch content in the leaves. Spray of hormones stimulated accumulation of all these metabolites, especially under water stress in both the genotypes. Stress-induced increase in amino acids, particulary of proline and soluble sugars, might be responsible for osmotic adjustment. Spray of benzyladenine and gibberellic acid could alleviate adverse effect of water stress partly in both the genotypes especially in 'RSG 143-1',Gibberellic acid was more effective in ameliorating water-stress effect than benzyladenine in both the genotypes.

Effect of temperature, scarification and gibberellic acid on the seed germination of three shrubby species of Coronilla L. (Leguminosae)

Abstract: The germinative behaviour of several seed samples belonging to Coronilla juncea L., C. minima L. and C. valentina L. ssp. glauca (L.) Batt., was studied under controlled laboratory conditions. A remarkable intra-, as well as interspecific variability was shown by germination percentages, significantly different between samples of every species. The influence of incubation temperature was significant in C. valentina ssp. glauca and C. juncea. Germination rates were always lower in C. minima than in other species. Mechanical scarification of the seed coat was the most effective method for promoting germination in C. valentina ssp. glauca and C. minima, specially under certain incubation temperatures. The hot-water treatment, studied in one sample of C. juncea, had a clearly negative effect on seed germination. The application of gibberellic acid at different concentrations did not increase significantly the germination rate of most samples.

Accumulation of ferulic acid in cell cultures of Ajuga pyramidalis metallica crispa

Abstract: Cell cultures of Ajuga pyramidalis Metallica Crispa accumulate ferulic acid, a potent antioxidant cinnamic acid. Most of the ferulic acid was found in a soluble form in the cultures. Maximum accumulation of ferulic acid was found in highly pigmented cultures (138 mg/100 g of fresh weight). The leaves from greenhouse-grown plants had lower levels of ferulic acid (24 mg/100 g of fresh weight) compared to the cultures. A close relationship was observed between anthocyanin and ferulic acid accumulation in the cultures. Supplementation with gibberellic acid, a specific anthocyanin inhibitor, at 10, 100, and 1000 μM reduced the levels of both anthocyanins and ferulic acid in the cultures. Keywords: Ajuga pyramidalis; cell culture; ferulic acid

Induction of Seedlessness in `Triumph' Muscadine Grape (Vitis rotundifolia Michx.) by Applying Gibberellic Acid

Abstract: Gibberellic acid (GA 3 ), a plant growth regulator used routinely in the production of seedless bunch grapes, was sprayed on the seeded muscadine grape cultivar Triumph. GA 3 at 100,200, and 300 mg.L -1 was sprayed on the leaves and fruit clusters at late bloom; a second spray followed 1 week later. The sprayed vines produced more than 20% seedless berries and the size of the berries with seeds increased significantly. GA 3 application in commercial muscadine grape production may have potential benefits.

Germination in Photosensitive Seeds: Does Phytochrome Stimulate Metabolism of GA19 and GA20 to GA1?

Abstract: The effect of light on gibberellic acid (GA) metabolism was investigated in Asteraceae seeds. White light (80 mmol m-2 s-1 PAR) increased seed germination in Craspedia sp., Erymophyllum ramosum and Rhodanthe chlorocephala subsp. splendida compared with darkness. In these taxa, red light (R, 640 nm, 8 mmol m-2 s-1) stimulated and far red light (FR, 720 nm, 4 mmol m-2 s-1) inhibited germination, indicating the involvement of phytochrome. Paclobutrazol, a GA biosynthesis inhibitor, reduced light-stimulated germination and this was overcome by exogenous GA3. GA3 and GA1 promoted germination in the dark, but GA19 and GA20, which are precursors to GA1, generally did not. GAs were applied to paclobutrazol-treated seeds which were incubated under either R or FR. Very few paclobutrazol-treated seeds germinated without GAs under FR, and exposure to R only marginally improved germination. Application of GA19 or GA20 to paclobutrazol-treated seeds increased germination in Rhodanthe chlorocephala subsp. splendida under R, with no germination under FR. This trend was observed in Craspedia sp., but not in Erymophyllum ramosum or Rhodanthe floribunda. CGA 163′935, a 3b-hydroxylation inhibitor, and R and FR were used to investigate phytochrome-stimulated conversion of GA19 and GA20 to GA1. It could not be shown that R was required for 3b-hydroxylation in light stimulated germination of these species.