RESUMO -Com o objetivo de verificar condições favoráveis de temperatura para a germinação das sementes do maracujá-doce (Passiflora alata Dryander), utilizou-se como tratamento de cinco plantas fornecedoras de sementes e duas temperaturas de germinação, na ausência de luz: 25ºC constante e 20-30ºC alternada. Os arilos das sementes provenientes de frutos maduros, completamente amarelos, foram extraídos com a utilização de liquidificador em baixa rotação. As características avaliadas nas sementes foram: peso, conteúdo de matéria seca, teor de água, porcentagem de germinação (plântulas normais), de plântulas anormais, de sementes dormentes e mortas. Concluiu-se que a temperatura alternada 20-30ºC atuou significativamente na obtenção de maior porcentagem de germinação e reduzida porcentagem de sementes dormentes. Estas últimas, para as sementes de todas as plantas, foi elevada sob temperatura de 25ºC, evidenciando grande influência do fator temperatura na superação de dormência. Termos para indexação: Passiflora alata, maracujá, semente, germinação, temperatura, dormência EFFECTS OF TEMPERATURE ON EVALUATION OF PHYSIOLOGICAL QUALITY Of SEEDS ON SWEET PASSION-FRUIT (Passiflora alata Dryander)ABSTRACT -With the purpose to study favorable conditions of temperature for seeds germination of sweet passion-fruit (Passiflora alata Dryander), it was used, as treatment, five plants for seeds and two germination temperatures, with no light: 25ºC constant and alternate 20-30ºC. Mucilage of seeds, proceeding from mature fruits, completely yellow, were extracted using a mixer at low rotation. The characteristic of the evaluated seeds were: weigh, dried matter contend, water content, germination percentage (of normal seedlings) , of abnormal seedlings, of dormant and died seeds. It was concluded that alternated temperature at 20-30ºC actuated significantly to obtain higher percentage of germination and low percentage of dormant seeds. These last ones, for seeds of all plants, was elevated under temperature of 25ºC, showing great influence of temperature fact, on dormancy surpassing.
O objetivo deste trabalho foi avaliar o efeito de diferentes métodos de remoção do arilo, na germinação de sementes e emergência de plântulas do maracujá-doce (Passiflora alata Curtis). Sementes extraídas de frutos maduros foram submetidas aos métodos de remoção do arilo: manual com fricção sobre malha de arame; manual com fricção de areia grossa sobre malha de arame; mecânico com liquidificador; biológico com fermentação à temperatura de 24ºC, por cinco dias; químico com imersão em solução de cal virgem a 10%; químico com imersão em solução de ácido clorídrico a 37% (1:2), ambos sob agitação por 30 minutos, e sementes sem a extração do arilo. As sementes foram avaliadas pelos testes de germinação, emergência de plântulas e índice de velocidade de emergência. O delineamento estatístico foi inteiramente casualizado, com quatro repetições de 50 sementes. A remoção do arilo com friccão em malha de arame apresentou a maior eficiência de germinação em laboratório. Os métodos com fricção de areia em malha de arame, imersão em solução com cal, imersão em solução com ácido clorídrico, fermentação e a não remoção do arilo conferiram melhor desempenho às sementes em condições de viveiro. A remoção do arilo com liquidificador prejudicou a qualidade fisiológica das sementes. As condições de viveiro proporcionaram percentuais de emergência em plântulas, que superaram os resultados obtidos em condições de laboratório.
The aim of this study was to evaluate the performance of plant regulators on seed germination of different atemoya cultivars: Thompson, Gefner and PR-1. The seeds were extracted from ripe fruits and submitted to the following treatments: 50 mg L -1 gibberellic acid (GA 3 ), 10 ml kg -1 of seeds (Stimulate ® ), 6 ml kg -1 of seeds (Evolust ® ), and control. The experimental design was completely randomized in a factorial 4x3 (three seed treatments + control x three cultivars), using five samples of 25 seeds. The seeds were sowed on paper and placed in a germination chamber, using alternated temperature 20-30 o C (16h -8h) under light absence. There were evaluated the percentage of germinated seeds, normal seedlings, abnormal seedlings, and the germination speed index. The Thompson cultivar presented the highest percentage of germinated seeds, normal seedlings, and germination speed index, followed by the Gefner cultivar. Among the products, the GA 3 promoted greater germination percentage. Using GA 3 and Stimulate ® , as a pre-germination treatment, provided high percentage of normal seedlings. The products utilized did not affect the germination speed index.
Corn has shown different degrees of positive response to inoculation with the nitrogen- fixing bacteria of the genera Azospirillum. Part of it has been attributed to the plant genotypic variation, including the root exudates, that are used by the bacteria as energy source. In this study, we grew two corn hybrids that differ for their response to Azospirillum, to investigate the effect of different exudates profiles on the bacteria growth and nitrogenase activity. Employing high performance liquid chromatography, we identified nine amino acids (asparagine, aspartic acid, serine, glutamic acid, valine, phenylalanine, threonine, tryptophan and alanine), six sugars (glucose, sucrose, xylose, arabinose, fructose and galactose) and four organic acids (citrate, malate, succinate and fumarate). The less responsive corn genotype showed reduced plant growth (root volume, shoot dry mass and shoot N content), a lower concentration of Azospirillum cells within the root tissues, a higher content of asparagine and glucose and a reduced amount of metabolites that serve as bacterial energy source (all organic acids + five sugars, excluding glucose). The genotypes did not interfere in the ability of Azospirillum to colonize the substrate, but the metabolites released by the less responsive one reduced the nitrogenase activity.
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