Competição entre arroz e arroz vermelho em ambiente natural e sob influência da quantidade de radiação

Abstract

In reducing the amount of light condition, weedy rice biotypes and rice crop may have morphophysiological variation. The aim of the research was to investigate the competitive ability between IRGA 424 cultivar and weedy rice biotype 32B in two light conditions by replacement series method. Experiments were conducted in a greenhouse at the Federal University of Pampa, campus Itaqui - RS, in 2014. The experimental design was completely randomized with four replications, a preliminary experiment in additive series and the other treatments were arranged in a replacement series where the proportions of cultivated rice plants and red rice were 100: 0, 75:25, 50:50, 25:75 and 100: 0, with a total population of 240 plants m-². Competitive analysis was performed using diagrams usually applied to replacement series and use of relative competitive indices. To simulate the environment with reduction of radiation was built a shaped structure as a coated tunnel in order to prevent the penetration of direct light. The variables studied were shoot dry mass, plant height, stomatal conductance of water vapor, photosynthesis and transpiration. In natural condition, weedy rice biotype showed greater competitive ability in relation to rice crop. There was no difference between the crop and weedy biotype in radiation reduction condition. Weedy rice had a transpiration rate about three times higher when in low radiation condition; rice crop was also greater transpiration rate, however, about two times greater when in the natural condition.