Efeito da luz e temperatura na germinação de sementes de plantas daninhas

Abstract

Yield loss in agricultural crops may occur due to biotic and abiotic factors. Among the biotic factors, weeds are considered the main factor. These plants show important characteristics such as: high seed production; dispersal in time and space; and dormancy in seeds. The germination of weeds responds to luminosity and temperature, factors that determine the capacity of adaptation and the potential of infestation. Based on the above, the aim of this work was to evaluate the influence of light and temperature on the germination of five weed species present in crops of Rio Grande do Sul state. The experiment was carried in the Seeds Laboratory of the Agronomy course of the Federal University of Pampa - Itaqui Campus. The seeds were obtained from Agro Cosmos Ltda. The germination tests were carried out in previously sterilized gerbox and the base lined with germitest germinating paper, moistened with distilled water equivalent to 2.5 times the mass of the dry paper. The experiment was carried out in a 2 x 2 x 5 factorial scheme, in a completely randomized design with four replicates, consisting of Factor A: two temperatures, Factor B: two light conditions (with and without light), and Factor C, was composed of five weed species. The temperatures were of 20 and 30 ºC, considering the photoperiod of 12 hours day, and with presence and absence of light. For the absence of light, aluminum foil paper was used to wrap the gerbox boxes. The species used were Eleusine indica, Euphorbia heterophylla, Ipomoea purpurea, Oryza sativa and Urochloa plantaginea. The evaluated variables were: germination, germination speed index and germination speed, for species with presence of light. Germination, shoot length and root length at 14 days after sowing for all experimental units. The data were submitted to the F test (≤ 0.05) and when it presented significance, they were submitted to the Fisher DMS test (p ≤ 0.05). The seeds of the studied species present greater germination in the presence of light and at the temperature of 30 ⁰C. For Eleusine indica, Euphorbia heterophylla and Ipomoea purpurea light interferes positively on germination. Ipomoea purpurea presents higher germination speed index (GSI) and Eleusine indica, higher germination speed (GS). The absence of light factor gives greater root length for Eleusine indica, Oryza sativa and Urochloa plantaginea.