Morfologia, fisiologia e controle químico do capim pé-de-galinha em diferentes regimes hídricos

Abstract

The species Eleusine indica (L.) Gaertn. (goosegrass) in the state of Rio Grande do Sul has a prominent presence as a weed in typical areas of upland crops. However, in recent years it has been reported in lowland areas, typical of irrigated rice cultivation. In this different ecosystem little is known about its biology, which often leads to erroneous interpretations by the technical community, regarding its characterization and management. The objective of the work was to characterize the morphology and physiology of Eleusine indica biotypes under different soil water managements and to make a distinction between herbicide performance and developmental stages. For this, two greenhouse experiments were carried out in the year 2016. The first consisted in the submission of two Eleusine indica biotypes to three soil water conditions: flooding, 50 and 100% of soil water-retention capacity. Were evaluated photosynthetic and gas exchange parameters: photosynthetic rate (A), stomatal conductance (Gs), intercellular CO2 concentration (Ci), evapotranspiration (E), water use efficiency and the assimilation ratio by Rubisco (C), as well as the morphological diversity using descriptors. The second experiment submitted the stages of 1-2 and 3-4 tillers to the application of herbicides (clethodim, cyhalofop-butyl, propaquizafop, imazapic + imazapyr and glyphosate) under irrigation management: flooded soil, flooding just after application and no flooding the soil. The assessments were percentage of control and reduction of dry mass. We conclude that the biotypes are able to survive, develop and generate seeds in flooded environment, without reduction of photosynthetic rate or characterizing a lowland biotype. The higher stage of development of 3-4 tillers defavors the effectiveness of herbicides, with emphasis to cyhalofop-butyl and imazapic + imazapyr that interestingly reduced the control in application followed by the flooding. This information emphasizes its invasive potential in different environments and reinforces the problem of the species at a global level.