Giberellic Acid Research Articles

Induction of fruit set and development in pea ovary explants by gibberellic acid

The response of unpollinated ovary explants ofPisum sativum L. cv. Alaska No. 7 to several plant growth regulators and nutrients has been studied. Explants consisted of a segment of stem and an emasculated flower with or without the adjacent leaf. They were made on the day equivalent to anthesis and were cultured in a liquid medium. Growth regulators were applied either in the solution or directly to the ovaries. Giberellic acid (GA3) in the presence of sucrose, but not indole-3-acetic acid or N6-(Δ2-isopentenyl)-adenine (2iP), induced fruit set and development of parthenocarpic fruits, the final length of these being a function of the intensity of the GA3 treatment. The capacity of ovaries to respond fully to GA3 was not lost after incubation of explants in water or 50 mM sucrose for 1 day and was similar in explants made between the day of anthesis and 3 days later. Limited growth was obtained with 100 mM sucrose alone but this effect was counteracted by 2′-isopropyl-4′-(trimethyl ammonium chloride)-5′-methylphenyl piperidine-1-carboxylate (AMO-1618). This inhibitor was ineffective when GA3 was applied to the ovary. The development of the fruit was proportional to the length of the segment of stem up to 5 cm. The presence of the leaf in the explant enhanced the development of the fruit. These results indicate that a gibberellin is necessary for setting and development of fruits from cultured ovaries and that this effect depends on an appropriate source of nutrients. The course of development of parthenocarpic fruits on explants was similar to that of seeded fruits on the intact plant. The cultured pea ovary systemoffers convenient means to investigate the role of gibberellins and nutrients in fruit set and development.

Effects of dewinging, soaking, stratification, and growth regulators on germination of green ash seed

Dewinging stored seed of green ash (Fraxinuspennsylvanica Marsh.) increased speed of and total germination. Fresh seed germinated best with a 4-day warm-water soak followed by 30-day stratification at 3 °C. Best procedures for stored seed were a 4-day soak in 100 ppm giberellic acid or a 2-day soak in 1 – 10 ppm 6-benzyladenine, followed by 30-day stratification at 3 °C.

Host influence on floral variability inOrthocarpus densiflorus (Scrophulariaceae)

This study investigates the influence of host plants on the expression of floral variability in the hemiparasiteOrthocarpus densiflorus (Scrophulariaceae), to determine if interaction with host plants can facilitate the expression of normally hidden genes. Style extension inO. densiflorus is highly uniform in natural populations, with less than 1% of the individuals exhibiting an aberrant extended-style condition. Both seed treatment with giberellic acid and parasitic development with host plants significantly facilitates the expression of extended-style in progenies that show only minimal expression when grown autotrophically. Artificial selection experiments demonstrate the range of potential phenotypic variation to be under genetic control, and differentially influenced by the host environment. Although the biochemical basis of the host influence is unknown, some host plants produce stimuli that apparently disrupt buffering inO. densiflorus and expose normally unexpressed genetic variability to selection. If variation in other traits is similarly affected, the influence of host chemistry may provide parasitic plants with a greater than normal opportunity for rapid selectional change.

Regulation of the Activity of Spinach Phosphoribosylpyrophosphate Synthetase by «Energy Charge» and End Products

Summary The activity of phosphoribosylpyrophosphate synthetase (PRPP synthetase, EC 2.7.6.1), partially purified from spinach leaves, was assayed in the presence of a variety of biological compounds to test for their possible regulatory effects. 1. The activity of spinach PRPP synthetase is influenced by the ≪adenylate energy charge≫, although the response of the enzyme is less than that obtained in typical ATP-utilizing enzymes controlled by the -energy charge-. 2. The enzyme activity is activated by Mg2+, and is probably inhibited by free ATP. 3. A variety of nucleoside monophosphate (NMP) and nucleoside diphosphate (NDP) inhibits the enzyme activity. Nucleoside triphosphates (NTP) are much less effective than NMP and NDP. The inhibition by NMP and NDP is not relieved by inorganic phosphate (Pi). 4. Little or no inhibition of the activity by NAD2+, NADP2+, histidine, and tryptophan was found. 5. The activity of the enzyme is not influenced by certain plant growth regulators, including indoleacetic acid, 2,4-dichlorophenoxyacetic acid, giberellic acid, kinetin, and 3',5'-cyclic AMP. 6. The observed properties of PRPP synthetase is discussed in relation to the regulation of the PRPP synthesis in plant tissue.

The enzymic response of pea (Pisum sativum) stem sections to applied indoleacetic acid, gibberellic acid and Ethrel: Catalase, peroxidase and polyphenol oxidase

Summary Applied indoleacetic acid (IAA), Giberellic acid (GA) and Ethrel (separate and in combination) to excised apical sections of etiolated Alaska pea ( Pisum sativum ) seedlings indicate that both GA and IAA cause a depression in the activities of peroxidase, catalase and polyphenol oxidase, in comparison to untreated controls. Ethrel treatment cause a significant decrease in the activity of both catalase and polyphenol oxidase vs. untreated control tissue. GA plus Ethrel and IAA plus Ethrel both mediate lowered levels of catalase, peroxidase and polyphenol oxidase activities, in comparison to untreated controls. Ethrel treatment causes a depression in peroxidase activity vs. applied GA or IAA. The present study suggests that excised pea stem tissue segments, immediately below the apical area, respond differentially with respect to the activities of catalase, peroxidase and polyphenol oxidase, when treated with GA or IAA alone, or in combination with Ethrel. However, Ethrel, applied together with either GA or IAA, has a depressor effect on all three respective enzyme activity levels. In all instances, the effects of IAA, GA and Ethrel treatments, alone or in combination, were of a lower order of magnitude than the corresponding untreated control stem sections.

Facts and hypotheses on the origin of S mutations and on the function of the S gene in Nicotiana alata and Lycopersicum peruvianum

Fragments in certain pollen-part mutants are suspected to originate from duplications of satellited regions. Linkage tests demonstrate that, if this interpretation is correct, either the specificity segment of the S locus is not on the fragment or two unliked specificity segments operate respectively in pollen and style. As electron microscopy and the effects of giberellic acid on selfing suggest that one manifestation of incompatibility reactions is a cessation of protein synthesis in pollen tubes, it is possible that the fragment does not carry an S locus but ribosomal cistrons necessary for the maintenance of activity. Ancestry tests are under way for testing the hypothesis that different specificity segments are organized as tandem repeats and can be switched on and off in inbred backgrounds. Electron microscopy analyses of self-incompatible hybrids indicate that a single gametophytic factor governs interspecific incompatibility in hybrid pollen and is allelic or linked to the S locus.

An analytical study of the role of various factors causing red tide outbreaks of trichodesmium as deduced from field and laboratory observation.

The marine blue green alga Trichodesmium sp is found in red-tide outbreaks in sub-tropical areas in the Pacific and Indian Oceans, the Arabian Seas and the equatorial currents of the Gulf of Mexico. Giberellic acid stimulated the growth of Trichodesmium cultures to a greater extent than in the diatom Melosira sulcata. While increasing either the nitrate or phosphate above the normal levels in the culture medium did not greatly stimulate the growth of this organism, Trichodesmium did thrive in nitrogen impoverished waters by nitrogen fixation. The relevance of these findings to the hydrological factors which favour red-tide outbreaks is discussed.

Carbohydrate oxidation during Nicotiana tabacum callus growth

Tobacco callus was cultured in light or dark, with or without giberellic acid, and with various carbon sources in the medium, and the growth rate and activities of some enzymes of the Embden-Meyerhof-Parnas and pentose phosphate pathway were determined. No changes in the specific activities of enzymes of either pathway could be correlated with growth but there was a light-dependent stimulation of the pentose phosphate pathway enzymes examined.

Effect of gibberellic acid on mevalonate activation in germinating Corylus avellana seeds

Giberellic acid (GA) induced germination of hazel seeds is accompanied by early increases in the specific and total activities of MVA kinase in the embryonic axes. This is followed by an increase in the activity of decarboxylation of MVA by the whole axes. The activity of MVA kinase in the cotyledons is not affected by GA treatment although increased uptake of MVA results in increased decarboxylation by cotyledon slices. The effects of cofactors and inhibitors on the activities of MVA kinase and MVA decarboxylation in a cell free extract of hazel cotyledons are described.

The effect of (2-chloroethyl)trimethylammonium chloride (CCC) and gibberellic acid on the growth and development of wheat cultivated under red or blue light

The effect of CCC and GA3 on the growth and development of spring wheat (Triticum aestivum L.) cultivated under predominantly red (500–700 nm) or blue (400–500 nm) light was investigated. Red light enhanced the development of wheat during the exponential phase of growth. This effect presumably implicated the promotion of gibberellin synthesis under red light. The strong inhibitory action of CCC under red light (the inhibition was lower under blue light) might be interpreted in a similar way. The growth became more intensive under blue light after caring and was accompanied by increased susceptibility to giberellic acid treatment.

POLINIZACIÓN ESTIGMÁTICA IN VITRO DE FRESA (FRAGARIA VESCA) A PARTIR DE LAS VARIEDADES MONTEREY, ALBEÓN Y DIAMANTE CON MIRAS A LA OBTENCIÓN DE UN NUEVO GENOTIPO

La siembra de fresa es promisoria en el Ecuador y sus cultivos se encuentran en crecimiento. Se ha visto la necesidad de contar con variedades propias para mejorar la producción interna; el objetivo de este estudio es la obtención de un nuevo genotipo, a partir de variedades existentes en campo. Se aisló plantas élite de las 3 variedades Monterey, Albeón y Diamante a condiciones de invernadero y se las sometió a floraciones continuas con ácido giberélico (AG), se emasculó flores semi-abiertas, y se las introdujo a condiciones in vitro con una desinfección previa evaluando los desinfectantes hipoclorito de sodio 0,5% y fungicida al 1,5% en tiempos de 6,8,10 y 15 minutos de inmersión de los pistilos. Posteriormente se eliminó los sépalos, pétalos y anteras, y se los introdujo in vitro en medios M&S, se valoró la oxidación y presencia de exudado en la base del estigma. En los gametos masculinos (polen), se realizó pruebas de viabilidad con la germinación del tubo polínico a partir de anteras que no habían sufrido dehiscencia, el polen in maduro fue capaz de geminar en una solución de medio BK con 50mg/L de H3BO3 y sacarosa al 10%, obteniéndose tubos polínicos largos y vitales a las 12 horas de incubación. Esta investigación constituye el punto de partida para la búsqueda de un nuevo genotipo por medio de una fertilización in vitro que podría permitir mezclar 2 variedades distintas para la obtención de un genotipo nuevo con características de los dos progenitores.

Effect of Various Concentrations and Frequency of Application of Gibberellic Acid on Growth and Formation of Metabolic Products of Datura stramonium

In a 2 × 4 × 5 factorial experiment employing 320 plants in randomized blocks with eight replications the following salient points were noted from a statistical analysis of the data: the greatest increase in height was induced with the 192-mcg. dosage of giberellic acid (GA). All treated plants at the 12, 48, and 192-mcg. dosages of GA grew more rapidly than controls. Height increases were significantly different at each dosage level. The most favorable response on height was between the 12-mcg. and 48-mcg. levels. The total dry weights of treated plants were significantly affected by dosage and age. The growth rate varied with the dose of GA used. The frequency of application (whether one or two installments were given weekly) did not significantly affect the aforementioned variables. Analyses of pooled samples of treated plants indicated the following general trends: reduced concentration of alkaloids in the plant organs, greatest reductions usually noted at the higher dosage levels, decreased per cent of chlorophyll, marked increases in the total sugars and starch content of the leaf-tops, considerable decreases in the petroleum ether extract of the leaf-tops, and qualitative differences in the ether extract of the leaf-tops.

Effect of giberellic acid on leaf form.

RECENT reports1,2 show that gibberellic acid affects the production of the juvenile or adult leaf form in plants. In the course of a study of the effect of physiologically active substances on heteroblastic development in Ipomoea caerulea, plants have been treated with various substances, including gibberellic acid. The observations so far made may be of interest in considering the effect of this substance on leaf form in other plants.