A water-soluble, ethanol-insoluble extrad of autolytically inactive tomato (Lycopersicon esculentum Mill.) pericarp tissue contains a series of galacturonic acid-containing (pectic) oligosaccharides that will elicit a transient increase in ethylene biosynthesis when applied to pericarp discs cut from mature green fruit. l h e concentration of these oligosaccharides in extracts (2.2 pg/g fresh weight) is in excess of that required to promote ethylene synthesis. Oligomers in extracts of ripening fruits were partially purified by preparative high-performance liquid chromatography, and their compositions are described. Pectins were extracted from cell walls prepared from mature green fruit using chelator and Na2C03 solutions. lhese pectins are not active in eliciting ethylene synthesis. However, treatment of the Na2C03-soluble, but not the chelator-soluble, pectin with pure tomato polygalacturonase 1 generates oligomers that are similar to those extracted from ripening fruit (according to high-performance liquid chromatography analysis) and are active as elicitors. The possibility that pectin-derived oligomers are endogenous regulators of ripening is discussed. ~~~ ~ ~~Work of the last 20 years has shown that many aspects of plant development can be influenced by application of cell wall-derived carbohydrates (Ryan and Farmer, 199 1). Fruit ripening has received a considerable amount of attention in this regard (Baldwin and Pressey, 1988; Brecht and Huber, 1988; Tong and Gross, 1990; Campbell and Labavitch, 1991b), probably because cell wall digestion is such a prominent feature of this process (Huber, 1983; Fischer and Bennett, 1991). Most studies showing an effect of carbohydrates on ripening have utilized the tomato (Lycopersicon esculentum Mill.) fruit. Active fractions have been extracted from fruits and added to immature tissues, which then display aspects of ripening in advance of controls.Oligosaccharides produced during the digestion of pectins have been shown to be active in many developmental systems (Ryan and Farmer, 1991), and this is certainly true for tomato ripening (Baldwin and Pressey, 1988; Brecht and Huber, 1988; Campbell and Labavitch, 1991a). This is not surprising, since the production of PG is a prominent early 575feature of ripening in tomatoes (Fischer and Bennett, 1991). If pectin fragments are a part of the endogenous regulation of ripening, then they must be present as ripening begins or proceeds, and this has not been convincingly demonstrated. Huber and Lee (1988) have demonstrated the in vitro production of pectic oligomers that are apparently (Brecht and Huber, 1988) able to promote tomato ripening, but the presente in vivo of active fractions is less clear. Huber and O'Donoghue (1993), using conventional chromatographic techniques, found no pectin oligomers in extracts of cell walls from ripening tomato fruits prepared under conditions that inactivated PG. The present work presents a contrasting result. Extracts of ripening tomato pericarp that had been pretreated with hot e...
ABSTRACT:The muscadine grape (Vitis rotundifolia Michx.) is native to Florida and has been cultivated for many years in U.S.A. It is harvested as single berries instead of in bunches and has small leaves. The fruit skin is thicker than those of bunch-type grapes. One reason for its popularity is that the muscadine is seldom seriously affected by diseases or insects. The muscadine grape is not readily propagated by hardwood cuttings, therefore the present work was carried out to develop a method for commercial propagation of its cuttings, using treatments with growth regulators (auxins) and low temperature. The results showed that the rooting of both basal and middle shoots of muscadine grape is better than the rooting of terminal sections of the shoots. Cuttings treated with low temperature (4°C) during 24 hours, or immersion of the cutting's bases in solutions of Exuberone 10 and 20 ml.l -1 , promoted rooting of middle and basal cuttings, respectively. The growth of leaves in both basal and middle cuttings was superior in the treatment with low temperature. Key Words: Vitis rotundifolia Michx., cutting, growth regulators ESTIMULAÇÃO DO ENRAIZAMENTO DE ESTACAS DE Vitis rotundifolia MICHX RESUMO:A videira muscadínia, nativa da Flórida, têm-se distinguido pela produtividade, resistência a pragas e doenças e pela característica de desbastar-se facilmente na colheita, possibilitando sua comercialização em cestas, de forma semelhante ao morango. As dificuldades na propagação desse grupo de videira têm impedido sua disseminação na região tropical úmida, em áreas onde a exploração de outras videiras tem sido dificultada pela alta incidência de doenças. O objetivo desse trabalho foi estabelecer o sistema mais adequado de propagação vegetativa de Vitis rotundifolia Michx., utilizando estacas a picáis, medianas e basais, tratamentos com auxina e com baixa temperatura. Verificou-se que o enraizamento de estacas basais e medianas da videira muscadínia foi mais eficiente do que o de estacas apicais. Tratamento das estacas com temperatura de 4°C por 24 horas, ou imersão das estacas em solução de Exuberone 10 e 20 ml.l -1, promoveram o enraizamento de estacas medianas e basais, respectivamente. O desenvolvimento da parte aérea das estacas basais e medianas da videira mostrou-se superior no tratamento com baixa temperatura.
Aplicou-se ethephon nas dosagens de 0,2 e 3 l/ha em cana-de-açúcar NA 56-79, 31 dias antes da colheita. Dos colmos colhidos foram efetuadas avaliações referentes a: infestação da broca da cana; gemas danificadas,entumescidas e brotadas; altura dos colmos; comprimento do ápice; número total de gemas e por último, análises tecnológicas para Pol, Brix, pureza e teor de fibras. Os toletes obtidos desses colmos foram plantados combinando-se as três dosagens de ethephon com três densidades de plantio: colmos simples, cruzados e duplos. Foram coletados dados semanais e posteriormente mensais de brotação e dados mensais de altura dos colmos. Dados de produção e número de colmos produzidos foram tomados por ocasião do 1º, 2º e 3º cortes da cana-de-açúcar. Os resultados revelaram que a aplicação de ethephon 2 l/ha, no estágio que antecede a colheita, promoveu um aumento do número de gemas e na altura dos colmos, e a dosagem 3 l/ha reduziu o teor de fibras na região apical da cana-de-açúcar em relação ao controle. Observou-se um aumento na velocidade de emergência de gemas obtidas de colmos tratados com o produto na dosagem 2 l/ha, antes do início do perfilhamento. Quanto à densidade de plantio, colmos duplos possibilitaram maior velocidade de emergência, seguidos de colmos cruzados, com relação a colmos simples. O crescimento, perfilhamento e produção de três anos consecutivos da cana-de-açúcar proveniente de toletes obtidos de plantas tratadas com ethephon não diferiram do controle. Notou-se um maior número de colmos produzidos no 1º ano, na densidade de plantio colmos duplos, quando comparados a colmos simples, sem, contudo, haver um aumento correspondente na produção.
Termos para indexação: arroz, estimulante vegetal,
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