Absence Of Gibberellic Acid Research Articles

Peppermint essential oil volatiles as natural alternative to prevent potato sprouting induced by gibberellic acid.

The objective was to evaluate the effect of peppermint essential oil (PEO) on the inhibition of potato sprouting induced by gibberellic acid (GA) during storage. PEO (0.08 and 0.15mL L-1) was applied in the presence and absence of gibberellic acid (10mg L-1). The presence of phytopathogens and changes in breaking of dormancy, weight loss, moisture content, and total soluble solids were measured during 28days. The inhibition of potato sprouting by the PEO occurred at the lowest concentration, even in the presence of GA. Sprout development was inhibited with PEO addition, delaying the dormancy break and reducing weight loss. However, potato sprouting was still inhibited after the removal of the PEO, evidencing its residual efficacy. PEO application at both concentrations had a satisfactory effect on sprout suppression and can be used as a promising eco-friendly approach for inhibiting the sprouting of potato tubers during storage.

Identification and molecular characterization of novel Rht‐1 alleles in hard red spring wheat

AbstractThe introduction of the semidwarfing alleles, Rht‐B1b and Rht‐D1b, into wheat (Triticum aestivum L.) varieties significantly increased wheat yields beginning in the 1960s. Despite their agronomic advantage, Rht‐B1b and Rht‐D1b are also associated with decreased grain protein content and decreased coleoptile length. Furthermore, there is limited allelic diversity available to wheat breeders beyond Rht‐B1b and Rht‐D1b. We identified 16 ethyl methanesulfonate (EMS)‐induced Rht‐1 alleles, including a nonsense mutation in each Rht‐1 gene: Rht‐A‐Q555stop, Rht‐B‐Q420stop, and Rht‐D‐W559stop. We focused our attention for this study on stop alleles since the Rht‐B1b and Rht‐D1b alleles also contain premature stop codons. We evaluated the new nonsense alleles by measuring their impact on coleoptile length, gibberellic acid (GA) sensitivity, and DELLA/GID1 interaction. Rht‐A‐Q555stop reduced coleoptile length 16% compared with Rht‐1a (wild type) and repressed coleoptile GA perception similarly to Rht‐B1b and Rht‐D1b. Rht‐B‐Q420stop and Rht‐D‐W559stop did not affect coleoptile length. However, Rht‐B‐Q420stop reduced the ability of germinating seeds to perceive GA, but not as much as Rht‐A555stop, Rht‐B1b, or Rht‐D1b. We also tested whether the novel mutations affected the interaction between DELLA/GID1 in the presence and absence of GA. We found that Rht‐A‐Q555stop, Rht‐B‐Q420stop, and Rht‐D‐W559stop inhibited DELLA/GID1 interaction in the absence of GA, but the interaction was restored in the presence of GA. The identification of Rht‐A‐Q555stop, Rht‐B‐Q420stop, and Rht‐D‐W559stop increases the allelic diversity of Rht‐1. This study also indicates that the RHT carboxyl terminus is important for DELLA/GID1 interactions.

Regulation of Seed Germination: The Involvement of Multiple Forces Exerted via Gibberellic Acid Signaling

Regulation of Seed Germination: The Involvement of Multiple Forces Exerted via Gibberellic Acid Signaling

Quebra de dormência de semente de murici

O muricizeiro (Byrsonima cydoniifolia A. Juss) é árvore de pequeno porte que apresenta múltiplas potencialidades na produção de alimentos, de lenha e na medicina popular. Sua reprodução é por sementes que estão contidas em endocarpo pétreo constituindo o pirênio, popularmente denominado caroço, que ocasiona baixa e desuniforme taxa de germinação. O objetivo deste trabalho foi avaliar os efeitos do estádio de desenvolvimento da semente, da temperatura, da integridade do endocarpo e do ácido giberélico na germinação dessa espécie. Para tanto, três experimentos foram instalados em delineamentos inteiramente casualizados. O primeiro considerou dois estádios de maturação do fruto, dois estados de integridade do endocarpo e duas concentrações de ácido giberélico (GA3); o segundo envolveu a utilização de envelhecimento acelerado e a presença ou ausência de ácido giberélico (GA3), e o terceiro, dois estádios de maturação do fruto, duas concentrações de ácido giberélico (GA3) e presença ou ausência de aeração. Os resultados obtidos permitiram concluir que as sementes apresentaram melhor qualidade fisiológica quando oriundas de frutos maduros e que sofreram abscisão natural. A pré-embebição de pirênios íntegros em ácido giberélico, na concentração de 1 g.L-1 por 24 horas sob alternância de temperatura de 25/35 ºC, favoreceu a germinação. Resultados satisfatórios ocorreram sob alternância de temperatura em câmara de germinação ou a céu aberto, em substrato constituído por areia lavada com fornecimento de água no período mais quente do dia.

Efeitos da giberelina e da secagem no condicionamento osmótico sobre a viabilidade e o vigor de sementes de sementes de mamão (Carica papaya L.)

Esta pesquisa teve como objetivo avaliar os efeitos da presença ou ausência de giberelina na solução de condicionamento osmótico e da secagem antes e após o condicionamento sobre a qualidade fisiológica de sementes de mamão. As sementes foram condicionadas em soluções de PEG6000 a -0,1 MPa, -1,0 MPa e em água destilada com dois níveis de GA3, 0 ou 200 mg.L-1. Para cada solução osmótica ou água destilada, utilizou-se o delineamento estatístico inteiramente casualizado, com quatro repetições, em esquema fatorial 3 x 2 + 2, sendo três combinações de condicionamento e secagem: 1. sementes condicionadas logo depois de retiradas do fruto com 67,0% de teor de água; 2. sementes secas até 11,5% e condicionadas; e 3. sementes secas, condicionadas e secas novamente x dois níveis de GA3 (0 e 200 mg.L-1) + dois tratamentos adicionais sem condicionamento, um com sementes úmidas (67%) e o outro com sementes secas (11,5%). Avaliou-se o teor de água (%), a germinação (%) aos 14, 21 e 28 dias, a condutividade elétrica (µs/cm/g), massa seca de plântulas (g) e o comprimento de plântulas (mm). Nas soluções com menor potencial osmótico, a presença de giberelina na solução de condicionamento aumentou a germinação. A secagem das sementes após o condicionamento ocasionou redução na qualidade fisiológica das mesmas, independente da presença ou ausência de giberelina na solução.

Explants of Ri-transformed hairy roots of spinach can develop embryogenic calli in the absence of gibberellic acid, an essential growth regulator for induction of embryogenesis from non-transformed roots

Hairy roots of spinach ( Spinacia oleracea L.) were obtained by inoculation of cotyledon explants with wild-type Agrobacterium rhizogenes A13. Integration of the transfer DNA (T-DNA) of a root-inducing (Ri) plasmid of A. rhizogenes into the plant DNA was confirmed by the polymerase chain reaction. Somatic embryogenesis from explants of hairy roots were induced even when the callus-induction (CI) medium did not contain gibberellic acid (GA 3), which is considered to be a key growth regulator that is critical for induction of somatic embryogenesis in spinach. Proteins extracted from hairy root-derived calli and from non-transformed root-derived calli generated on medium that contained 10 μM naphthaleneacetic acid (NAA), without GA 3, were analyzed by polyacrylamide gel electrophoresis. The proteins from the former calli included appreciably higher levels of a 31-kDa basic protein (BP31) (p I=8.8) than proteins from the latter. This 31-kDa protein also accumulated in embryogenic calli derived from non-transformed roots. Somatic embryos from hairy root explants, grown on medium without growth regulators, yielded regenerated plantlets with actively growing root systems and shoots that did not bolt.

Synthesis of Limit Dextrinase in Germinated Barley Kernels and Aleurone Tissues

The development and secretion of α-amylase and limit dextrinase activities in de-embryonated half-kernels of Harrington barley, incubated in the presence and absence of gibberellic acid (GA3), were studied. Development of the enzymes in germinated barley was also investigated. Enzyme levels in the aleurone and starchy endosperm tissues of half-kernels and germinated barley were measured, and proportions of limit dextrinase in aleurone and starchy endosperm tissues of different barley varieties were determined. Aleurones of de-embryonated barley half-kernels produced low levels of both α-amylase and limit dextrinase in the absence of GA3, although secretion of the enzymes from the aleurones under these conditions did not appear to be significant. Added GA3 enhanced the development of both enzymes in half-kernels as well as in germinated seeds. Secretion of α-amylase from aleurones of germinated seeds and de-embryonated half-kernels in the presence of GA3 was very rapid, but GA3 did not appear to have an effect on the secretion of limit dextrinase from aleurones, which was very slow in both de-embryonated half-kernels and germinated barley. The total limit dextrinase activity, and the proportions of limit dextrinase found in the aleurone and starchy endosperm tissues, varied in different varieties of barley.

Effect of light and gibberellic acid on chromosome endoreduplication in leaf epidermis ofTriticum durum Desf.

The first foliage leaf ofTriticum durum Desf., cvs. Capelli and Creso, was studied for the action of light and gibberellic acid on different aspects of plant growth. Creso is a short-strawed cultivar carrying theRht 1 gene, that influences both plant height and sensitivity to applied gibberellins. In this study, a cytophotometric analysis of chromosome endoreduplication in bulliform cells of the leaf epidermis was undertaken. The bulliform cells are arranged in long rows and comprise 4C, 8C, and 16C cells. The relative percentage of these cells was recorded under different light regimes and in the presence or absence of gibberellic acid (GA3). Our data indicate that light strongly affects the occurrence of chromosome endoreduplication. Although cvs. Cappelli and Creso show the same frequency of endo-reduplicated cells in the dark, all light treatments induce lower endo-polyploidy in cv. Creso whereas, in cv. Cappelli, a reduction in endo-polyploidy is observed when plants are irradiated with blue-lacking lights. This indicates that the action of a blue-light responsive photo-receptor determines high endopolyploidy. With respect to GA3 treatment, cv. Creso is again shown to be insensitive to hormone application, whereas in cv. Cappelli, gibberellic acid influences endopolyploidy level in the dark, causing very high frequencies of 8C cells and relatively high frequencies of 16C cells.

Ca2+-Calmodulin Modulates Ion Channel Activity in Storage Protein Vacuoles of Barley Aleurone Cells.

Many plant ion channels have been identified, but little is known about how these transporters are regulated. We have investigated the regulation of a slow vacuolar (SV) ion channel in the tonoplast of barley aleurone storage protein vacuoles (SPV) using the patch-clamp technique. SPV were isolated from barley aleurone protoplasts incubated with CaCl2 in the presence or absence of gibberellic acid (GA) or abscisic acid (ABA). A slowly activating, voltage-dependent ion channel was identified in the SPV membrane. Mean channel conductance was 26 pS when 100 mM KCl was on both sides of the membrane, and reversal potential measurements indicated that most of the current was carried by K+. Treatment of protoplasts with GA3 increased whole-vacuole current density compared to SPV isolated from ABA- or CaCl2-treated cells. The opening of the SV channel was sensitive to cytosolic free Ca2+ concentration ([Ca2+]i) between 600 nM and 100 [mu]M, with higher [Ca2+]i resulting in a greater probability of channel opening. SV channel activity was reduced greater than 90% by the calmodulin (CaM) inhibitors W7 and trifluoperazine, suggesting that Ca2+ activates endogenous CaM tightly associated with the membrane. Exogenous CaM partially reversed the inhibitory effects of W7 on SV channel opening. CaM also sensitized the SV channel to Ca2+. In the presence of ~3.5 [mu]M CaM, specific current increased by approximately threefold at 2.5 [mu]M Ca2+ and by more than 13-fold at 10 [mu]M Ca2+. Since [Ca2+]i and the level of CaM increase in barley aleurone cells following exposure to GA, we suggest that Ca2+ and CaM act as signal transduction elements mediating hormone-induced changes in ion channel activity.

Photoperiod, gibberellic acid, and kinetin, in potato flower differentiationin vitro

To inducein vitro floral differentiation on potato plantlets, one cm long apical explants cv. Marijke were excised and aseptically cultured in a semi-solid medium containing Murashige-Skoog salts supplemented with 0.3 mg/l indoleacetic acid; with or without one mg/l gibberellic acid (GA); 0.3, 3.0 or 30.0 mg/l Kinetin (K); 20, 40 or 60 g/l sucrose (S) and 8% agar, pH 5.7. After a five week growing period at 26–28 C with daily light PAR 35 μE/m2/sec, 14 or 24 h daylength (DL), flower buds developed with exposed sepals and an abscission zone in the peduncle. Statistical significance was found when the variation factors (GA, K, S, and DL) were analyzed individually or in combination for number and weight of floral buds. Absence of GA favored the number of buds/plant, and the interaction of continuous light with a culture medium containing 0.3 or 3.0 mg/l kinetin and 40 g/l sucrose induced the highestin vitro “yields” in number and weight of flower buds (6 per plant and up to 14 mg/bud), followed by premature abscission. In a similar experiment, to prevent such abscission, plants from five week old tissue culture were transferred to soil and maintained at 24 h DL and 26–28 C, but flower bud abortion could not be avoided. These results demonstrate the importance of manipulating exogenous factors (growth regulators, sucrose, photoperiod) to inducein vitro specific organogenesis in potatoes.

Gibberellic acid stimulates lipid metabolism in barley aleurone protoplasts

Changes in the lipid composition of barley aleurone protoplasts following incubation in the presence or absence of gibberellic acid (GA) were studied and correlated with cell development. Analysis of neutral lipids in protoplast extracts and purified lipid bodies provide evidence for the strong effect of GA on the mobilization of storage lipids. In vivo protoplast staining with the membrane marker N-phenyl-l-naphthylamine (NPN) and phospholipid determinations of protoplast extracts show an increase in membrane lipids during protoplast incubation. GA stimulates phospholipid metabolism by increasing the synthesis of phosphatidyl ethanolamine and phosphatidyl choline, the major phospholipid constituents of the endoplasmic reticulum.

ENERGY METABOLISM OF IMBIBING KALANCHOË SEEDS. RESPONSE TO GIBBERELLIC ACID AND CONTRIBUTION OF RESPIRATION AND FERMENTATION TO ATP PRODUCTION

In Kalanchoe blossfeldiana seeds imbibed in the dark for 10 days at 20°C, very similar energy charge ( EC ) values were measured in the presence and absence of gibberellic acid (GA 3 ). This demonstrates that GA 3 does not prevent or strongly delay the induction of secondary dormancy in Kalanchoe seeds by elevating EC levels. However, GA 3 clearly increased the ATP and AMP content of the seeds. During the first hours of anoxic imbibition, the sodium-fluoride sensitive ATP production still represents 25 to 30% of the ATP amount produced in the air, indicating that in Kalanchoe seeds the fermentative pathway can partly contribute to ATP production. As the oxygen uptake by the seeds is cyanide-sensitive and a severe inhibition of the increase in ATP content by cyanide can be demonstrated during the first hours of aerobic imbibition, our results indicate the participation of the normal cytochromic pathway in ATP synthesis.

Gibberellic-acid-stimulated Ca2+ accumulation in endoplasmic reticulum of barley aleurone: Ca2+ transport and steady-state levels

The steady-state levels of Ca(2+) within the endoplasmic reticulum (ER) and the transport of (45)Ca(2+) into isolated ER of barley (Hordeum vulgare L. cv. Himalaya) aleurone layers were studied. The Ca(2+)-sensitive dye indo-1. Endoplasmic reticulum was isolated and purified from indo-1-loaded protoplasts, and the Ca(2+) level in the ER was measured using the Ca(2+)-sensitive dye indo-1. Endoplasmic reticulum was isolated and purified from indo-1-loaded protoplasts, and the Ca(2+) level in the lumen of the ER was determined by the fluorescence-ratio method to be at least 3 μM. Transport of (45)Ca(2+) into the ER was studied in microsomal fractions isolated from aleurone layers incubated in the presence and absence of gibberellic acid (GA3) and Ca(2+). Isopycinic sucrose density gradient centrifugation of microsomal fractions isolated from aleurone layers or protoplasts separates ER from tonoplast and plasma membranes but not from the Golgi apparatus. Transport of (45)Ca(2+) occurs primarily in the microsomal fraction enriched in ER and Golgi. Using monensin and heat-shock treatments to discriminate between uptake into the ER and Golgi, we established that (45)Ca(2+) transport was into the ER. The sensitivity of (45)Ca(2+) transport to inhibitors and the Km of (45)Ca(2+) uptake for ATP and Ca(2+) transport in the microsomal fraction of barley aleurone cells. The rate of (45)Ca(2+) transport is stimulated several-fold by treatment with GA3. This effect of GA3 is mediated principally by an effect on the activity of the Ca(2+) transporter rather than on the amount of ER.

Identification of an endochitinase cDNA clone from barley aleurone cells

A barley aleurone cDNA library was screened using (32)P-labeled cDNA prepared by reverse transcription of mRNA from aleurone layers treated in the presence or absence of gibberellic acid (GA). Besides α-amylase cDNA clones, another set of clones representing an abundant mRNA in aleurone cells was identified. Messenger RNA hybrid-selected by a prototype clone of this group (clone 10) was translated in vitro to yield a 36 kDa protein. Analysis of the DNA sequence and the predicted amino acid sequence of the protein product of this clone indicates that this gene codes for a protein with homology to endochitinases from tobacco and bean. In addition, the predicted amino acid sequence includes a stretch that is closely related to a cyanogen bromide cleavage fragment from an endochitinase isolated from barley endosperm. The structural genes for endochitinase are present as multiple copies on barley chromosome 1. mRNA detectable by this clone increases in abundance in barley aleurone cells incubated in the absence and in the presence of GA. Western blot analysis of proteins from aleurone and endosperm tissues indicates the presence of multiple endochitinases differing in molecular size. Possible mechanisms for the occurrence of multiple forms of endochitinases and their biological significance are discussed.

Growth and osmoregulation in Pisum sativum subhooks as affected by gibberellic acid and cotyledon excision

Growth stimulation by gibberellic acid (GA) of the Alaska pea (Pisum sativum L.) subhook was observed within 6 h after its application; the stimulation being larger in cuttings with cotyledons than in decotylized ones. The osmotic potential in the subhook increased as it grew, the rate of its increase being faster in cuttings without than in cuttings with cotyledons. GA had no effect on the change in the osmotic potential until 8 h after GA application, but afterwards it suppressed the increase in cuttings with cotyledons. This GA effect was not observed in decotylized cuttings. Changes in the osmotic potential were well correlated with changes in the concentration of soluble sugars, but not with changes in amino acids and K+, Soluble sugars accumulated in the subhook of cuttings with and without cotyledons in proportion to growth, irrespective of the presence or absence of GA. Cotyledon excision suppressed sugar accumulation, and GA promoted it in cuttings with cotyledons but not in decotylized ones. These results suggest that GA stimulates the translocation of sugars from the cotyledons to the subhook and, thereby, maintains the osmotic potential low, resulting in enhanced growth.

Effect of gibberellic acid on the uptake and loss of inorganic phosphate from sweet potato slices

Uptake and loss of irorganic phosphate was determined in sweet potato slices ‘aged’ in the presence or absence of gibberellic acid. Concentrations of uptake medium were varied from 0.1 to 1.2 mM. Slices, aged in gibberellic acid, took up considerably less phosphate, at all concentrations than control, whereas efflux from GA3 treated discs was greater than control. Whether treated or untreated, kinetics proved to be biphasic hyperbolas. The results suggested an alteration in membrane permeability induced by gibberellic acid.

Hydrolysis of Storage Proteins in Barley Endosperms

Soluble products, released by the hydrolysis of hordeins into the media of barley (Hordeum vulgare cv. Perth) half-seeds were analyzed. Large polypeptide fragments (methanol-insoluble) were identified using the Western immunoblot technique with the antibodies prepared against B and C polypeptides of hordein. A number of hordein IgG-reacting bands were noted in the samples from dry kernels. In samples incubated in the absence of gibberellic acid, polypeptide fragments in the size range of 25 to 30 kilodaltons appeared within 24 hours, and those in the size range of 40 kilodaltons became more prominent. In samples incubated in the presence of gibberellic acid, polypeptide fragments in the size range of 45 to 67 kilodaltons were less apparent and those in the size range of less than 15 kilodaltons were more pronounced. The hordein-related polypeptide fragments were present in low amounts after 72 hours in the presence of gibberellic acid. Methanol-soluble peptides were fractionated, on the basis of size, into two broad peaks. In the absence of gibberellic acid, there was no significant change in their profile over a 72 hour incubation period. In the presence of this growth substance, however, there was a decrease in the proportion of large size peptides (50-70 amino acid residues in length), and an increase in the levels of small peptides (15-35 amino acid residues in length) and amino acids. Our interpretation of the results is that the release of the initial large polypeptide fragments from hordein proteins is mediated by a protease(s) whose appearance is not dependent on the exogenously added gibberellic acid. Further hydrolysis is, however, mediated by proteases induced in the presence of this growth substance.

Production of α-Amylase Isozymes in Barley Caryopses in the Absence of Embryos and Exogenous Gibberellic Acid

The isozyme composition and kinetics of production of α-amylase were studied in three samples of barley. Acid-dehusked caryopses and endosperm halves from a sample of Klages and from two samples of Clipper that differed in their ability to produce α-amylase in the absence of added gibberellic acid were incubated on moist sand at two temperatures in the presence or absence of gibberellic acid. The isozyme composition of the extracts was analysed on isoelectric-focusing-polyacrylamide gels and chromatofocusing columns. The endosperm halves of Klages and Clipper (type A) produced very low levels of enzyme in the absence of gibberellic acid while similar amounts of enzyme activity were found in both (+) and (-) gibberellic acid-treated incubates of Clipper (type B) endosperm halves. In these latter incubates, the initial kinetics of production, the proportion of α-amylase 1 to total enzyme activity and the effect of incubation temperature on the kinetics of production in both acid-dehusked caryopses and endosperm halves were similar, and were comparable to those observed in gibberellic acid-treated incubates of Klages and Clipper (type A). Since Clipper (type B) endosperm halves can produce α-amylase in the absence of added gibberellic acid, its role in this process should be reexamined.

Genotype and the production of α-amylase in barley grains germinated in the presence and absence of gibberellic acid

Decorticated barley grains of different genotypes were germinated with and without optimum amounts of gibberellic acid and potassium sulphate. For comparative trials, a standard germination time was chosen such that α-amylase formation was continuing, but substantial destruction of the enzyme had not begun. The influences of grain size, nitrogen content and threshing damage on α-amylase levels were assessed. In the presence of gibberellic acid, enzyme yield was regarded as a measure of the maximum enzyme-forming capacity of the grain tissues. The “α-amylase ratio”, the ratio of α-amylase formed in the presence of added gibberellic acid to that formed in its absence probably reflects the quantities of endogenous gibberellins formed in the germinating grain. When grains of 93 varieties were investigated, a wide range of enzyme levels occurred in the samples of adequate viability grown with gibberellic acid. This study has identified genotypes with unusually high and low α-amylase-forming capacities that are available for breeding purposes. Also a range of “α-amylase ratios” was encountered, suggesting that a spread of genetically regulated, gibberellin-forming capacities was present.

The action of exogenous gibberellic acid on polysome formation and translation of mRNA in germinating castor-bean seeds

The amount of protein synthesis in germinating castor-bean seeds has been estimated by the quantitative and qualitative exmainatin of polysomes from the seeds in the presence and absence of gibberellic acid (GA3). Careful optimisation of polysome extraction procedures was required to minimise the ribonuclease activity in the extracts. Ribonuclease activity in seed extracts increased fourfold over the first 5 d of germination. Gibberellic acid stimulated polysome formation about twofold during the first 4 d of germination. It also stimulated the amount of mRNA associated with polysomes by about twofold during the first 3 d of germination. Between days 1 and 5 of germination, polysome formation was primarily limited by mRNA availability. During the period 0-24 h, polysome formation was independent of mRNA levles. The increase in enzyme activities stimulated by GA3 was probably the result of an increase in the amount of cellular mRNA. No evidence was obtained for an action of GA3 on translation other than on the increased production of RNA. Examination of the recruitment of isocitrate-lyase mRNA into polysomes showed that GA3 did not specifically stimulate production of this enzyme.