Efeito alelopático do extrato aquoso de sementes de Cumaru (Amburana cearensis S.) sobre a germinação de sementes, desenvolvimento e crescimento de plântulas de alface, picão-preto e carrapicho.

Abstract

The objective of the present work was to evaluate methods (maceration, decoccion and infusion) and times (30, 60 and 120 min. ) of extraction, besides the substances: fractions chloroform and acetate, and pure coumarin, in different concentrations, of the aqueous extract of cumaru seeds (Amburana cearensis S. ) on the germination, the development and the growth of lettuce seedlings (Lactuca sativa L. ). For “picão-preto” (Bidens pilosa L.) and “carrapicho” (Cenchrus equinatus L.) the effect of the concentration of the extract was evaluated and of the pure coumarin on seeds and seedlings. The experiments were accomplished at the laboratory of Analyses of Seeds, Department of Fitotecnia of the Federal University of Ceará, in Fortaleza-Ce. The aqueous rude extract was prepared starting from the flour of cumaru seeds, being used in the following concentrations: 0.19, 0.39, 0.78, 1.56, 3.13, 6.25, 12.5, 25 and 50 mg/mL, and water distilled as control. The seeds, of the tested species, they were distributed in plates of Petri on three disks of filter paper, previously humidified with the extract in the proportion of 2,5 times the weight of the substratum. Later the plates were conditioned in germination camera regulated to the temperature of 25° C and of 8h luz /16h dark, for seven days. The variables were analyzed: germination, length of the root and of the aerial part of the seedlings, in a in a casual interlay delineation, with four repetitions (50 seeds/repetition for lettuce and 25 for “picão-preto” and “carrapicho”). The most efficient method was the maceration. The time of extraction with better results was it of 30 min. The most potent substance was the pure coumarin. It was verified although starting from 6.25 mg/mL of the extract it happened an inhibition in 100% of the germination of the lettuce seeds. Starting from the concentration 3.13 mg/mL the bun of hair germination was totally inhibited. For “picão-preto” the concentrations 1.56, 3.13 and 6.25 mg/mL were the most harmful. The pure coumarin was plenty phytotoxicans for “picão-preto” and “carrapicho”, because it inhibited the germination of your seeds in the tested concentrations. All the concentrations of the extract presented toxicant effects to the seedlings of the tested species, in adult or smaller intensity.