Efeitos alelopáticos do pau pedra (Luetzelburgia auriculata (Allemão) Ducke) sobre a germinação e o desenvolvimento da alface (Lactuca sativa L.).

Abstract

Allelopathic effects from studies of plant species are of great importance to the knowledge of species of Caatinga, so the aim of this study was to evaluate the allelopathic effects of the “pau pedra” (Luetzelburguia auriculata) through the use of aqueous extracts of roots and leaves and soil of a stand of this kind, on germination and growth of the lettuce. Three experiments were performed on DIC: the first two installed in a germination chamber TE 402 for seven days, photoperiod of 12 hours light and constant temperature of 20°C, using lettuce seeds germitest paper, at first with an aqueous extract of leaves of L. auriculata and the second with aqueous extract roots of L. auriculata. In both analyzed germination speed index (GSI), germination percentage (%G) and length of radicle and hypocotyl of lettuce seedlings. The results were submitted to analysis of variance and quadratic regression model, they expressed that the seeds germinated in extract of roots and leaf extract, compared to the control, were negatively affected by these statements. In the third experiment, in pots, conducted in nursery, seeded lettuce seeds in soil collected at 0-20 cm depth of a settlement L. auriculata, with or without cattle manure and soil in an area outside the settlement (0-20 cm), in order to verify the development of plants lettuce. After 63 days of sowing, he held the harvest and measured the length of shoot, root, fresh weight of shoot weight, leaf area and number of leaves from each plant and the chemical analysis of substrates (soil and soil + manure). It applied to ANOVA, Tukey's test at 5% probability and observed significant differences between plants grown in the soil of the area outside the settlement (SAO) and plants grown in soil settlement of L. auriculata (SAS) with and without manure, fact justified by the high amount of nutrients in SAS. In the treatments with the proportions of 50 and 75% of manure there was no development of plants lettuce, due to the high toxicity caused by the amount of nutrients present in these substrates. The results obtained in the first two experiments suggest that extracts of leaves and roots L. auriculata have negative allelopathic effect on lettuce seed germination and in the third experiment, the data suggest that soil the L. auriculata settlement not have any effect allelopathic, positively influencing the development of plants lettuce at high nutrient content.