Potencial fitotóxico do extrato aquoso das folhas de urucuzeiro (Bixa orellana L.) sobre o desenvolvimento inicial de alface (Lactuca sativa L.)

Abstract

Biotic and/or abiotic stresses trigger, in vegetables, the production of secondary metabolites, which are extremely important for acclimatization and defense of the plant. In this context, the objective was to evaluate the phytotoxic effect of the aqueous extract of the leaves of Bixa orellana L. (EABO) on the initial development of lettuce (Lactuca sativa L.). In petri dishes a micro environment was created, in which seeds of Lactuca sativa L. Were exposed to different concentrations of EABO (25%, 50%, 75% and 100%) and acclimated in a germination chamber of the BOD type (Biochemical Oxygen Demand) at 25±2ºC, and followed for seven days. On the seventh day of the experiment, biometric evaluations, germination speed indexes, vigor, tolerance index, chlorophyll content a, b, totals, carotenoids and histochemistry were performed. The number of germinated seeds showed a delay in the highest extract concentrations. The radicle length of the seedlings reduced when 100% EABO concentration was applied. As the concentrations of the extract increased, the content of chlorophylls a, totals and carotenoids underwent changes, as well as, in the metabolism of carbohydrates and lipids. The results revealed that the aqueous extract of Bixa orellana L. Has a phytotoxic effect on the initial development of Lactuca sativa L.