Rela??o entre exsuda??o radicular de carbono organico e variáveis fisiológicas de cultivares de arroz irrigado

摘要

Rhizospheric carbon resulting from root exudation is one of the substrates used by the soil microbiota, and reflects methane (CH 4 ) emissions in anoxic environments such as irrigated rice cultivation. With the increase of the photosynthetic capacity of the plant in the reproductive period, there is greater accumulation of biomass which, in turn, increases the rate of root exudation. However, genotypic variations in the physiological aspects of rice plants may be related to the amount of root exudates. Ten cultivars of irrigated rice were evaluated for the exudation rate of total organic carbon (EXR Toc ), shoot dry matter (SDM), and physiological variables related to photosynthesis during the full flowering (blooming) period. Two experiments were conducted in the greenhouse of the Department of Soils of the UFSM (University of Santa Maria, Santa Maria, RS, Brazil) in a completely randomized experimental design. The cultivars presented significant differences in EXR Toc , SDM, and all physiological variables as well as positive and significant correlations between EXR Toc and physiological variables. Early cultivars were more inefficient in the physiological variables reflecting reduced values of EXR Toc and SDM whereas medium-cycle cultivars were more efficient with larger EXR Toc and SDM reflections.