ABSTRACT
ABSTRACT: Due to the scarcity of information related to the effect of fertilizers on production and quality of vegetable seeds, mainly on species which present an increase in the cycle, like cauliflower, more studies are necessary about the influence of nutrients rates which provide high production of high-quality seeds. This research aimed to evaluate the influence of rates of phosphorus (P) on the production and quality of cauliflower seeds. Five rates of phosphorus were studied (0, 300, 600, 900 and 1200kg ha-1 of P2O5), in a randomized complete block design, with four replications. Production and quality (weight of a thousand seeds, germination test, first count of germination test and emergence in substrate) of the seeds and soil chemical characteristics were evaluated. The higher the rate of phosphorus, the higher P content in the soil and values of sum of bases, cation exchange capacity and saturation of bases were observed at the end of the cycle. Seed quality was not affected by P fertilization, with the exception of the weight of a thousand seeds which was adjusted to a linear model. For seed production quadratic effect was obtained. The highest weight of seeds per plant was estimated for the rate of 862kg ha-1 of P2O5.
RESUMO: Devido à escassez de informações relacionadas com o efeito de fertilizantes na produção e qualidade de sementes de hortaliças, principalmente de espécies que apresentam aumento no ciclo, como a couve-flor, são necessários mais estudos sobre a influência das doses de nutrientes que fornecem alta produção de sementes com alta qualidade. Este trabalho teve como objetivo avaliar a influência de doses de fósforo sobre a produção e qualidade de sementes de couve-flor. Foram estudadas cinco doses de fósforo (0, 300, 600, 900 e 1200kg ha-1 de P2O5), em delineamento em blocos casualizados, com quatro repetições. Foram avaliadas a produção e a qualidade (massa de mil sementes, germinação, primeira contagem de germinação e emergência em substrato) das sementes e características químicas do solo. Quanto maior a dose de fósforo, maior o teor de P no solo e os valores de soma de bases, capacidade de troca catiônica e saturação de bases foram observados no final do ciclo. A qualidade das sementes não foi afetada pela adubação com P, com exceção da massa de mil sementes, que ajustou-se ao modelo linear. Foi obtido efeito quadrático para a produção de sementes. Maior massa de sementes por planta foi estimada para a dose de 862kg ha-1 de P2O5.
ABSTRACT
ABSTRACTThis work studied the acid phosphatase (APase) activity from culture medium (extracellular, eAPase) and mycelial extract (intracellular, iAPase) ofAspergillus niger F111. The influence of fungus growth and phosphate concentration of the media on the synthesis and secretion of phosphatase was demonstrated. The effects of pH, substrate concentration and inorganic and organic compounds added to the reaction mixture on APase activity were also studied. Both enzymes were repressed by high concentrations of phosphate. Overexpression of iAPase in relation to eAPase was detected; iAPase activity was 46.1 times higher than eAPase. The maximal activity of eAPase was after 24h of fungus growth and for iAPase was after 96h. Optimal pH and substrate concentrations were 4.5 and 8.0 mM, respectively. Michaelis-Menten constant (Km) for the hydrolysis of p-nitrophenyl phosphate was 0.57 mM with Vmax = 14,285.71 U mg-1 mycelium for the iAPase and 0.31 mM with V max = 147.06 U mg-1 mycelium for eAPase. Organic substances had little effect on acid phosphatases when compared with the salts. Both the APases were inhibited by 10 mM KH 2PO4 and 5 mM (NH4)2MoO4; eAPase was also inhibited by 1 mM CoCl2.