Competition between drought-tolerant upland rice cultivars and weeds under water stress condition Competi o entre cultivares de arroz de terras altas tolerantes à seca e plantas daninhas sob condi o de estresse hídrico

The objective of this study was to evaluate the competitiveness of two cultivars of upland rice drought-tolerant, cultured in coexistence with weed S. verticillata, under conditions of absence and presence of water stress. The experiment was conducted in a greenhouse at the Experimental Station of the Universidade Federal de Tocantins, Gurupi-TO Campus. The experimental design was completely randomized in a factorial 2 x 2 x 4 with four replications. The treatments consisted of two rice cultivars under two water conditions and four densities. At 57 days after emergence, were evaluated in rice cultivars and weed S. verticillata leaf area, dry weight of roots and shoots and total concentration and depth of roots. Was also evaluated in rice cultivars, plant height and number of tillers. Water stress caused a reduction in leaf area, the concentration of roots and vegetative components of dry matter (APDM, and MSR MST) of rice cultivars and Jatoba Catet o and weed S. verticillata. The competition established by the presence of the weed provided reduction of all vegetative components (MSPA, and MSR MST) of cultivars and Jatoba Catet o. It also decreased the number of tillers, the concentration of roots and leaf area. At the highest level of weed competition with rice cultivars, a greater decrease in vegetative components and leaf area of culture, regardless of water conditions. O objetivo deste trabalho foi avaliar a capacidade competitiva de dois cultivares de arroz de terras altas tolerantes à seca, cultivados em convivência com a planta daninha S. verticillata, sob as condi es de ausência e presen a de estresse hídrico. O experimento foi instalado em casa de vegeta o, na Esta o Experimental da Universidade Federal do Tocantins, Campus Gurupi-TO. O delineamento experimental utilizado foi o inteiramente casualizado, em esquema fatorial 2 x 2 x 4, com quatro repeti es. Os tratamentos foram constituídos de dois cultivares de arroz, sob duas condi es hídricas e quatro densidades. Aos 57 dias após a emergência, foram avaliados nos cultivares de arroz e na planta daninha S. verticillata: área foliar, matéria seca das raízes e da parte aérea e total, concentra o e profundidade de raízes. Também foi avaliada, nos cultivares de arroz, a altura de plantas e o número de perfilhos. O estresse hídrico promoveu redu o da área foliar, da concentra o de raízes e da matéria seca dos componentes vegetativos (MSPA, MSR e MST) dos cultivares de arroz Jatobá e Catet o e da planta daninha S. verticillata. A competi o estabelecida pela presen a da planta daninha proporci