Experiments were run in a greenhouse where samples of Eragrostis pilosa and Eragrostis plana, species that infest rice crops, were subjected to three soil moisture conditions (50% of soil water retention capacity (WRC), 100% of WRC, 10 cm water depth), simulating three different environments (upland, lowland and irrigated rice farm, respectively), with the aim of studying how these conditions affect the morphology and vegetative cycle of these plants, by means of development and growth assessments. Results show that each species responds differently when subjected to varying amounts of water in the soil. Soaking the soil with 10 cm of water was the treatment that most negatively influenced the development of E. plana plants, reducing the formation of panicles per plant, as well as the aerial part dry mass. The responses of E. pilosa plants to the waterlogged environment manifested as reductions in tillering parameters, number of panicles per plant, root and aerial part dry mass, changes in flag leaf formation, and vegetative cycle increases, which allows inferring that these plants are more sensitive to hypotoxic environments. Thus, the water depth treatment is possibly what caused negative effects on the development of the study plants, which indicates that water management in irrigated rice farming is of uttermost importance for management of invasive plants.

The experiment was accomplished in a greenhouse, where the mechanisms adaptive to the hypoxic environment of Eragrostis plana and Eragrostis Pilosa where evaluated when submitted to three conditions of humidity of the soil (50% of CRA, 100% of CRA and soil with sheet of water of 10 cm). The plants morphologic-anatomical indexes were appraised, and the aerenchymal formations and adventitious roots in the surface of the soil were quantified. In addition, the photosynthetic pigments and the electron transport capacity of the photosynthetic chain were quantified. It was noticed that the answers were similar among the species when submitted to an environment of water removal, showing more aerenchymal formations in the roots and adventitious roots in the surface of the soil. Negative effects on the electron transport and chlorophyll pigment formation were verified when submitted to the hypoxic environment showing reduction in dry mass of aerial and aerial parts, as well as a reduction in the emission of profiles. The evaluation of the plastic capacity of growth and development of the studied plants allows to conclude that the irrigation water management and water removal in rice crop are important in its control, due to the negative effects caused to the growth and development of the crop.

This work aimed at determining possible resistance of three biotypes of Cyperus iria to inhibiting herbicides of acetolactate synthase enzyme (ALS). An experiment at greenhouse was conducted out where suspected resistance biotypes were multiplied through seeds in pots filled with soil. The treatments were arranged in a trifactorial (AxBxC) design, where factor A consisted of three biotypes of Cyperus iria, from three locations of the state of Rio Grande do Sul (named Santa Maria 1, São Borja 3 and Cachoeira do Sul 7). Factor B corresponds to three herbicides (pyrazosulfuron-ethyl, ethoxysulfuron and bentazon). Factor C refers to herbicide doses (zero, 50% of registered dose; registered dose, two, four and eight times registered dose of herbicides). For resistance measurement, it was used resistance factor calculation (RF) and for dose-response curves through regression analysis, RF on dry mass (DM) of plants. It was observed that São Borja 3 and Cachoeira do Sul 7 biotypes have a low resistance factor (1 < RF < 10) to pyrazosulfuron-ethyl and ethoxysulfuron herbicides. These showed lower susceptibility to ethoxysulfuron (RF = 5.49-6.76) than pyrazosulfuron-ethyl (RF = 2.21-2.47). The clear distinction in the susceptibility of biotypes, include responses of chemical control to field due to the long period of use of ethoxysulfuron herbicide. It is concluded that this factor characterizes low-level resistance, being a cross-resistance type, thus demonstrating the ineffectiveness of ALS-inhibiting herbicides to control this species.

The development of Eragrostis plana and Eragrostis pilosa was evaluated in a greenhouse when submitted to different soil moisture conditions. The design was completely randomized, consisting of a factorial 2x3, with the following factors: Eragrostis accessions and soil moisture levels (50% of water retention capacity (WRC), 100% of WRC and soil with water depth of 10 cm). The morphological-anatomical parameters of the plants were evaluated and the aerenchyma and adventitious roots were quantified. In addition, the photosynthetic pigments and the electron transport capacity of the photosynthetic chain were quantified, with the intention of verifying if the amount of water in the soil interferes with these parameters. Similar responses were observed between the two species when submitted to a water table environment, where there were larger aerenchymal formations in the roots and stems, as well as adventitious roots at the soil surface, inferring adaptations for survival to anaerobic stress. Negative effects on the transport of electrons and the formation of chlorophyll pigments were observed for both species when submitted to the hypoxic environment and, consequently, there was reduction of dry mass of shoot and roots, as well as reduction in the emission of tiller. It is concluded that the irrigation water management and the water blade in the rice crop are important, together with the control of invasive plants, considering the negative effects caused to the growth and development of these plants

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