Germination of Borreria densiflora var. latifolia under Controlled Conditions of Light and Temperature

Germination is a fundamental process in weed population dynamics. Thus, this research aimed to evaluate the interaction between temperature and light upon the germination of a new variety of the weed vassourinha-de-botao (Borreria densiflora var. latifolia), under germination chamber conditions. The influence of five temperatures (20, 25, 30 and 35 degrees C constant and alternated 20-30 degrees C), in presence of 12h-photoperiod and constant dark conditions upon the germination was studied, under a randomized complete-block design, with four replications. Accumulated germination percentage and germination speed were evaluated, being the latter evaluated through the germination speed index. Data were submitted to analysis of variance through F test, followed by Tukey test at probability of 0.05. Germination occurred preferentially in presence of light, with significant interaction only between temperature and presence of light. We observed, thus, the positive photoblastism of this new variety of B. densiflora. The highest germination percentage occurred under the alternated temperature 20-30 degrees C, followed by the temperatures 25, 30 and 35 degrees C, and the germination speed increased with the increase of the temperature. The results obtained in this research show that the population dynamics of this weed is influenced mainly by thermic amplitudes, higher temperatures (over 25 degrees C) and conditions of presence of light, explaining, therefore, its occurrence in the North and Northeastern tropical regions of Brazil.