Use Of Gibberellic Acid Research Articles

PROPAGAÇÃO SEXUADA DO PEQUIZEIRO (Caryocar brasiliense Camb.) ESTIMULADA POR ÁCIDO GIBERÉLICO

The species Caryocar brasiliense, known as 'pequi', presents low percentage and low average time for plantule emergence. In order to solve this problem, this study aimed to evaluate the levels of gibberellic acid (GA3) on seed emergence of C. brasiliense, without endocarp. Ripe fruits were collected and stored for 27 days in plastic bags. Subsequently, their skin, mesocarp, and thorns were removed. After seven days, the almond was extracted from the endocarp. The treatments were: distilled water, and GA3 at 75 mg L-1, 150 mg L-1,300 mg L-1, and 600 mg L-1, soaked for 24 hours. Twenty-six seeds per plot were arranged in a completely randomized design, with five treatments and five replications. The percentage and average time for plantule emergence, height, diameter, and fresh and dry root and shoot mass of pequi plantules were evaluated. The data were analyzed by variance analysis and linear regression. The gibberellic acid, at the conditions and concentrations evaluated, influenced significantly the percentage and average time for the pequi plantule emergence. Forty days after sowing, the emergence average was 24%. The use of gibberellic acid (GA3) in seeds without endocarp, at the estimated concentration of 345 mg L-1, has provided the highest emergence percentage, as related to the other evaluated treatments. KEY-WORDS: Pequi ; plant hormone; emergence.

Biological and Molecular Analyses of the Acibenzolar-S-Methyl-Induced Systemic Acquired Resistance in Flue-Cured Tobacco Against Tomato spotted wilt virus

Tomato spotted wilt virus (TSWV) is an economically important virus of flue-cured tobacco. Activation of systemic acquired resistance (SAR) by acibenzolar-S-methyl (ASM) in flue-cured tobacco was studied under greenhouse conditions by challenge inoculation with a severe isolate of TSWV. ASM restricted virus replication and movement, and as a result reduced systemic infection. Activation of resistance was observed within 2 days after treatment with ASM and a high level of resistance was observed at 5 days onward. Expression of the pathogenesis-related (PR) protein gene, PR-3, and different classes of PR proteins such as PR-1, PR-3, and PR-5 were detected at 2 days post-ASM treatment which inversely correlated with the reduction in the number of local lesions caused by TSWV. Tobacco plants treated with increased quantities of ASM (0.25, 0.5, 1.0, 2.0, and 4.0 g a.i./7,000 plants) showed increased levels of SAR as indicated by the reduction of both local and systemic infections by TSWV. The highest level of resistance was at 4 g a.i., but this rate of ASM also caused phytotoxicity resulting in temporary foliar spotting and stunting of plants. An inverse correlation between the TSWV reduction and phytotoxicity was observed with the increase of ASM concentration. ASM at the rate of 1 to 2 g a.i./7,000 plants activated a high level of resistance and minimized the phytotoxicity. Use of gibberellic acid in combination with ASM reduced the stunting caused by ASM. Present findings together with previous field experiments demonstrate that ASM is a potential option for management of TSWV in flue-cured tobacco.

Short communication. Secondary dormancy in Diplotaxis erucoides: a possible adaptative strategy as an annual weed

The germination of stored Diplotaxis erucoides seed was studied under controlled conditions of temperature and light by conducting germination tests over three years after collection. The D. erucoides seed was not dormant at harvest, but secondary dormancy appeared during storage as indicated by reduced germination 12 months after collection (from 92% down to 39%). This could be overcome by prolonged storage or by the use of gibberellic acid. Such shifts between dormancy and non-dormancy can be interpreted in terms of the soil seed bank dynamics in relation to intraspecific competition and/or with its adaptation as an annual weed in periodically disturbed soil in cultivated areas.

Aplicación del ácido giberélico en Citrus: revisión de resultados experimentales en Uruguay

En esta revisión se presentan los principales resultados experimentales obtenidos con la aplicación de ácido giberélico (GA3 ) en el control y mejora del ciclo reproductivo de variedades de Citrus en Uruguay. El GA3 asperjado en concentraciones de 20 - 40 mg.L-1 durante el período de ecodormición (otoño-invierno) logra disminuir en forma significativa el número de flores formadas en los híbridos “Ellendale”, “Nova”, “Ortanique”, en mandarina ‘Montenegrina’ y en naranjo dulce “Washington” navel. La eficacia del GA3 se asocia a la intensidad de floración de la variedad en cada ciclo y a la concentración de producto utilizada. En pocos casos, esta reducción de la floración se traduce en un incremento del número de frutos cosechados o en una disminución en la alternancia productiva. La aplicación durante la antesis, en concentraciones de 15 a 50 mg.L-1 con el objetivo de mejorar en forma directa el cuajado en híbridos de bajo índice de partenocarpia, no ha resultado eficaz en ninguno de los cultivares evaluados, con una tendencia adicional a disminuir el tamaño de frutos. La incidencia y severidad del “creasing”, desorden fisiológico que afecta la cáscara de la fruta cítrica, disminuye en forma significativa con la aplicación de GA3 (10- 20 mg.L-1) entre 90 y 120 días después de la floración en naranja “Washington” navel. Se discuten los resultados considerando la información internacional disponible.

Regulating yield and wine quality of minimal prunning systems through the application of gibberellic acid

<p style="text-align: justify;">The use of gibberellic acid to increase berry size and to loosen up bunches in the production of seedless table grape varieties has a long history. The use of gibberellic acid on wine grapes, however, is very limited, mainly because some varieties can show substantial losses in bud fertility and thus in commercial yield. We tried to exploit the feature of decreases in bud fertility as a response to gibberellic acid applications (in the form of GA3) to regulate yield and quality aspects of minimally pruned (MP) White Riesling grapevines where other thinning methods have failed. Single applications of 50 mg L-1 GA3 at 500 L ha-1 were used during full bloom in each year from 2002-2004 (MP GA3-02/03/04) in one MP treatment, while the second MP treatment received no GA3 in 2003 (MP GA3-02/04). Treatments were compared with untreated MP vines and with a standard pruned, vertically shoot positioned system (VSP). GA3 applications reduced inflorescence number by about 30-50% the year following treatment, while shoot number remained unchanged. GA3 treated MP vines responded to this type of « thinning » by a 10-28 % increase in berry weight. Total yield of MP vines was reduced by 26-49% the year after first time application approaching VSP yield. Yield of the continuously treated vines (MP GA3-02/03/04) remained comparable to pruned VSP vines up to now (harvest 2005) (about 9-13 tons per ha). Discontinuing the GA3 treatment for one year caused yield to re-approach the one of untreated MP vines the next year. Despite of the increase in berry weight, bunch structure remained less compact as compared to VSP fruit. Sugar levels at harvest of vines treated with GA3 the previous year were similar to sugar levels of VSP vines and superior to untreated MP vines. We found no treatment effect on glycosyl-glucose (bound secondary metabolites, GG) concentration but a slight increase in phenols and titratable acidity the year after GA3 treatment. Sensory evaluation of the resulting wines revealed no or only minimal differences with a slight preference for the least yielding VSP and MP GA3-02/03/04 wines. The outlined strategy seems promising for the production of quality fruit in a highly economic viticultural system.</p>

Conditions and stimulation for germination in Bromus auleticus seeds

Bromus auleticus Trin. ex Nees is a perennial species with high forage production, good nutritional quality in a critical period of the year (autumn – winter), and long persistence. This work studied: I) the effect of temperature and light on B. auleticus seed germination, II) the effect of laboratory seed treatments on germination stimulation immediately after harvest. In I), three alternating temperatures: 20-30, 15-25 and 10-20°C (the lower temperature maintained by 16 hours), and two constant temperatures: 10 and 20°C were tested. Light treatments were: a) no light, and b) 8 hours of light followed by 16 hours of darkness. The following treatments were tested to stimulate germination: a) control: with distilled water, b) 0.2% potassium nitrate solution instead of water, c) 0.05% gibberellic acid solution instead of water, and d) prechilling at 7°C for 7 days. Results showed that B. auleticus can germinate in a range of temperatures between 10 and 25°C, either constant or alternating, with light or without it. For germination trials, constant temperature at 20°C gave the highest germination velocity. Germination was increased by prechilling and use of gibberellic acid, probably because of the hormonal nature of dormancy in this species.

(426) Evaluation of Pregerminative Treatmentsin Soursop (Annona muricata L.) Seeds

The most common spread of this species is sexual or by seed. In normal conditions, the germination of the seeds of Anonaceae can increase with pregerminative treatments prior to sowing. The objective was to determine the best pregerminative treatment to increase germination of soursop seeds. This study was carried out under the the dry, tropic conditions of Tecomán, Colima, Mexico. The experimental design was completely random with 12 treatments: 1) dip in water for 24 hours; 2) dip in water for 24 hours + gibberellic acid (GA3) at 350 ppm; 3) dip in water for 24 hours + GA3 at 500 ppm; 4) dip in water for 24 hours + GA3 at 1000 ppm; 5) mechanical scarification; 6) dip in water for 24 hours + mechanical scarification; 7) mechanical scarification + GA3 at 350 ppm; 8) mechanical scarification + GA3 at 500 ppm; 9) mechanical scarification + GA3 at 1000 ppm; 10) GA3 at 350 ppm; 11) GA3 at 500 ppm; and 12) GA3 at 1000 ppm; and control. There were four repetitions with 10 seeds in each experimental unit. The evaluated variables were the percentage of germination and the number of days from planting to emergence. To record results, analysis of variance and Tukey's test averages were used. The major percentage of germination resulted from the seeds treated with soaking in water for 24 hours plus GA3 to 350 ppm, dip in water for 24 hours plus scarification and GA3 at 1000 ppm, and equalized statistically to the control. For the number of days from planting to emergence, the treatment with mechanical scarification + GA3 at 500 ppm was statistically better. The use of gibberellic acid with mechanical scarification diminishes the dormancy of soursop seeds, producing plants in a relatively short period.

Conservação refrigerada de lima ácida 'Tahiti': uso de 1-metilciclopropeno, ácido giberélico e cera

A conservação refrigerada da lima ácida 'Tahiti' sob baixa temperatura permite o aumento no período de comercialização dos frutos, entretanto, a perda da coloração verde da casca é o principal entrave que impede este prolongamento. O objetivo do presente trabalho foi verificar o efeito da aplicação do 1-metilciclopropeno (1-MCP), associado ao uso de cera e ácido giberélico (GA), sobre a conservação refrigerada de lima ácida 'Tahiti'. Foram aplicados os tratamentos: T1:Controle; T2: 1-MCP (1 mg. L-1) durante 12 horas a 20ºC; T3: Cera (0,1 mL por fruto); T4: Ácido giberélico - GA (10 mg. L-1); T5: 1-MCP + Cera; T6: 1-MCP + GA; T7: Cera + GA; T8: 1-MCP + Cera + GA; T9: T2 + re-aplicação de 1-MCP após 30 dias de armazenamento. Os frutos foram armazenados durante 30 e 60 dias a 10C e 90% UR. A cera foi suficiente para retardar a perda de coloração verde da casca até 30 dias de conservação a 10ºC. O 1-MCP também mantém a coloração verde até 30 dias de conservação refrigerada, enquanto que a sua reaplicação após este período não apresenta efeito para a manutenção da coloração verde da casca. No presente trabalho não foi pronunciado o efeito do ácido giberélico. Após 60 dias de armazenamento os frutos não se apresentavam comercializáveis.

233 Alteration of Flower Development and Fruit Growth in Summer Squash

Many summer squash hybrids initiate flowering by first producing one or more pistillate flowers before the development of any staminate flowers. These first pistillate flowers have no pollen source unless an earlier squash planting is nearby. The objectives of this study were to measure the loss in yield incurred by the absence of pollination and to determine if sex expression in squash could be altered by use of gibberellic acid (GA). `Cougar' summer squash was planted in 12 isolated plots on 13 May; four plots had adjacent rows planted on 3 May to provide pollen for the earliest developing pistillate flowers in those plots. On 28 May, 0.146 L·ha-1 of GA (ProGibb 4®) was applied to an adjacent row in four of the plots planted on 13 May. The four control plots received no treatment. At anthesis, pistillate and staminate flowers were counted daily for 10 days. The first six pistillate flowers that bloomed in each plot were identified and measured (length and diameter) on the day of anthesis, and at 4 and 7 days after anthesis. Fruit were harvested five times at 2-day intervals and data are reported on fruit ≤5.7 cm in diameter. GA had no effect on squash flowering habit. At 4 and 7 days after anthesis, fruit were smaller in plots where no pollen source was available. Early yields were higher for the first two harvests in plots where pollinators were present. A small, early planting of squash should be made to provide staminate flowers for normal growth and development of early fruit on the main summer squash crop.

Use of gibberellic acid to prolong dormancy and reduce losses during traditional storage of yams

The annual vegetative cycle of the yam (Dioscorea spp) necessitates a long period of storage. Losses during this period are high and are mainly due to germination. Trials on the effectiveness of gibberellic acid (GA3) for controlling storage losses were carried out on the two main species of yam (D cayenensis rotundata and D alata) grown in the Ivory Coast. Methods of application at the apex adapted to the rural environment were tested. Treatment with GA3 prolonged the dormancy period and thus reduced losses. This substance was effective at low concentration with a long soaking duration (75 mg litre−1 for 2 h) and during a soaking of short duration with a higher concentration (0·5 h at 150 mg litre−1). Because of its stability at ambient temperature, the solution was still active 3 days after being prepared and after reuse of the same dip six times. © 1998 SCI.

Chemical regulation of growth, yield, and digestibility of alfalfa and smooth bromegrass

In addition to enabling manipulation of plant growth and development, growth regulators have potential for increasing forage digestibility. This study focuses on the use of gibberellic acid (GA3), α-naphthalene acetic acid (NAA), 6-benzylaminopurine (BA), o-benzylhydroxylamine (OBHA), and monocetyl phosphate (C16P) to alter growth, dry weight (DW) yield, and in vitro digestible dry matter (IVDDM) of forage grasses and legumes grown in a greenhouse. Screening experiments revealed that GA3, NAA, and OBHA at rates of 1.6, 160, and 0.51 g a.i. ha−1, respectively, were more effective in altering regrowth of potted alfalfa (Medicago sativa L.) and orchardgrass (Dactylis glomerata L.) compared with other treatments. Subsequent experiments with increasing dosages of GA3, NAA, and OBHA on alfalfa and smooth bromegrass (Bromus inermis Leyss.) confirmed that these regulators can be used to manipulate forage growth. Increasing concentrations of GA3 increased growth and DW yield but decreased IVDDM, whereas high concentrations of NAA decreased growth and DW yield but increased IVDDM. OBHA treatments resulted in little or negative change in IVDDM. Results generally showed that plant growth regulators can be used to manipulate forage growth, but that there is a trade-off between herbage yield and digestibility of forage tissues.

ChemInform Abstract: Use of Gibberellic Acid to Reduce Citrus Fruit Susceptibility to Fruit Flies.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

QUALITY CHARACTERISTICS OF ‘BING’ AND ‘RAINIER’ SWEET CHERRIES TREATED WITH GIBBERELLIC ACID, FOLLOWING FUMIGATION WITH METHYL BROMIDE

ABSTRACTMethyl bromide (MeBr) fumigation did not significantly influence weight loss, fruit color or soluble solids of either ‘Bing’ or ‘Rainier’ sweet cherries. MeBr increased pitting and reduced objective and subjective stem color of both cultivars. There was a slight advantage in quality (bruising, pitting and stem color) for the 48g/m3 at 12°C over the 64g/m3 at 6°C MeBr treatment. As fumigation temperature increased, bruising and pitting increased and stem color decreased. Use of gibberellic acid resulted in increased firmness for ‘Bing’ cherries and superior fruit and stem color with less pitting for both ‘Bing’ and ‘Rainier’ cherries.

The use of gibberellic acid, ethephon and cold treatment to promote germination of Rhus typhina L. seeds

Germination of Rhus typhina was less than 20%. Treatment with gibberellic acid (GA) (0–1000 mg l−1) or cold stratification (0–30 days at 4°C) improved germination. GA treatment did not improve germination if the stratification period exceeded 10 days. Cold treatment for 30 days increased germination to 45%. Cold treatment at 4°C was limited to 30 days to develop a rapid system for stratification. A combination of ethephon treatment at 200 mg l−1 for 24 h followed by 30 days cold (4°C) treatment increased germination to 60%. This promotion of germination due to ethephon showed a strong interaction with subsequent duration of cold treatment; the effect was more pronounced with increasing duration of cold treatment, while no effect was observed in the absence of a cold treatment.

Dormancy responses to post-harvest application of growth regulators in Dioscorea species. 2. Dormancy responses in ware tubers of D. alata and D. esculenta

SummaryThe effects of post-harvest application of gibberellic acid on dormancy of tubers of Dioscorea alata and D. esculenta were examined. In both species, gibberellic acid extended the dormancy of immature and mature tubers but when GA3 application was made after storage for varying lengths of time, there was a decreasing effect with increased storage time. Dormancy was also reinduced in germinating tubers, that had gone through a normal dormant period, as a result of gibberellic acid treatment. A possible mechanism of dormancy in tropical yams is discussed. It is concluded that use of gibberellic acid as a means of extending the storage life of yam tubers by post-harvest application is a distinct possibility.

Regulation of Cropping and Fruit Quality of Conference Pear by the Use of Gibberellic Acid and Thinning. II. The Effect of Ethephon as a Flower Thinner When Used in Conjunction with Gibberellic Acid Application

SummaryThe number of fruits developing on Conference pear trees treated at flowering with gibberellic acid was reduced by the application of ethephon, and the amount of large fruit increased. Although time of application, from white bud (pre-GA3) to petal-fall, did not influence the response to ethephon, both temperature and the concentration of GA3 affected the response considerably. Although increasing the alkalinity of an aqueous ethephon solution compensated for low temperatures, in terms of the amount of ethylene released into an enclosed space, the result of using this technique with a field spray was inconclusive. The mechanism of action of ethephon as an abscission agent in relation to its breakdown characteristics is discussed.

Regulation of cropping and fruit quality of Conference pears by the use of gibberellic acid and thinning. I. The effect of hand thinning of blossom in conjunction with gibberellic acid application

SummaryTreating Conference pear trees with gibberellic acid induced a crop of small, often misshapen, fruits. Fruit bud formation was inhibited, which was not due to the GA3 per se but was related to the number of fruitlets initially set. Reducing the numbers of flowers prior to GA3 treatment resulted in greater yields of better quality fruit and fruit bud numbers were normal. Within-cluster flower thinning was more effective than reducing the number of clusters. Possible mechanisms underlying these effects are discussed.

Physiology of Seed Dormancy in Heliotropium eichwaldi Steud

Summary Seed dormancy in Heliotropium eichwaldi is dependent on the endogenous level of promoter and inhibitor. These seeds posses a water-soluble inhibitor requiring light for its activity. Indirect evidence also showed the presence of one or more light-activated inhibitors which were not water-soluble. The seed dormancy in H. eichwaldi was broken by the use of gibberellic acid in dark giving the maximum of germination (58 %) with 4000 ppm concentration. Gibberellic acid did not show much response in light in breaking seed dormancy. Bioassay studies with the developing seeds of H. eichwaldi at its various stages till maturity indicated the presence of growth promoter and inhibitor-like compounds. The R F values of growth promoter and inhibitor were 0.50 and 0.68, respectively, using paper chromatography. Results obtained indicated a higher concentration of growth promoter between the period just after anthesis till 20 days, while the inhibitor concentration was higher during the period between 20 days after anthesis and maturity of the seeds in this plant.

The use of gibberellic acid to control alternate cropping of Late Valencia sweet orange

The effect of spraying commercial gibberellic acid (GA) on alternate cropping and yield of Late Valencia orange trees was studied in detail at three sites over three seasons. Two applications of GA were applied at a minimum concentration of 25 ppm (in two experiments 0.75% emulsifiable oil was used as an adjuvant) 3 weeks apart during April and May for Dareton (on the River Murray) or June and early July for Yanco (Murrumbidgee Irrigation Areas) prior to the heavy-crop blossom. These sprays partly inhibited flowering and the subsequent heavy crop was reduced by up to 22% (by fruit number). In the next season there were more flowers and the light crop was increased by up to 57% at Dareton and 228% at Yanco. Some treatments practically eliminated alternate cropping while all reduced considerably the heavyllight crop ratio. Mean weight yields over 2 years were increased by up to 17% at Yanco and 16% at Dareton with mean increases for all successful GA treatments of 12.6% and 7.2% respectively. This represented an increase of 34 and 24 kg fruitltree. No long-term adverse effects on yield were found.Apart from re-greening of the fruit present at the time of spraying, fruit quality was not affected. There were fewer non-saleable small fruit at Yanco in the heavy crop as a result of the GA treatments, and a better range of fruit sizes in both the heavy and light crops. Trees on Rough Lemon rootstock responded well to GA treatments, especially in terms of increased yield in the light crop. Poncirus trifoliata rootstock was less responsive than Sweet Orange. This method might be used for the commercial control of alternate cropping of Late Valencia orange trees.

Mise au point d'un test rapide de germination des faînes (Fagussylvatica)

The use of gibberellic acid (GA3) to break dormancy has enabled us to develop a new and quick germination test for Fagussylvatica L. nuts. The test procedure involves removing the external pericarps, sterilizing the nuts, removing the internal coats, and germinating the bare nuts on cotton wool moistened with a solution of GA3 (200 mg/l) in darkness at 20 °C. Under these test conditions, it was possible to obtain good results after 3 to 4 weeks as compared with those obtained after 3 to 4 months by conventional methods.