Silicon (Si) is an element that can improve the growth and development of rice plants in water-deficient environments because it is an enzymatic stimulant, signaling for production of antioxidant compounds. Therefore, the aim of this study was to examine the relationship between water deficiency and the effect of Si on two rice cultivars whose seeds were treated with dietholate. The experimental design was fully randomized with three replicates, and treatments were organized in a 3x2x2x4 factorial arrangement: three water soil conditions (50% and 100% of soil water retention capacity (WRC) and complete submergence in a water blade of 5.0 cm); two cultivars (IRGA 424 RI and Guri INTA CL); two sources of Si (sodium metasilicate and potassium metasilicate); and four rates of Si (0; 4.0; 8.0 and 16 g L-1). Chlorophyll a and b, leaf area and shoot and root dry weight increased at higher rates of Si under the three soil water regimes. There was an increase in superoxide dismutase and guaiacol peroxidase enzyme activity in the cultivars at higher rates of Si, reducing lipid peroxidation caused by water deficiency. Therefore, Si did indeed attenuate water deficiency stress in rice plants emerging from seeds treated with dietholate.

A ocorrência de biótipos de Cyperus difformis L. com característica de resistência à aplicação de herbicidas no setor da orizicultura é uma preocupação mundial. Nesse sentido, objetivou-se avaliar a eficiência do controle de C. difformis por herbicidas inibidores da acetolactato sintase (ALS) e mimetizador de auxina. O delineamento experimental foi inteiramente casualizado, com quatro repetições, totalizando 252 unidades experimentais compostas por vasos com 12 quilogramas de solo e os tratamentos arranjados em esquema fatorial 3x7x2x2: três herbicidas (dois inibidores da ALS pirazossulfurom-etílico e bispiribaque-sódico e um mimetizador de auxina triclopir-butotílico); sete doses dos herbicidas (0.0x, 0.5x, 1x, 2x, 4x, 8x e 16x a dose de registro); dois biótipos de C. difformis (Santa Rosa do Sul e Meleiro, Santa Catarina (SC)); e duas umidades de solo (100% saturado e lâmina d’água de 5,0 cm). O biótipo C. difformis de Meleiro-SC é 8x (320 g. i.a. ha-1) mais resistente a dose de registro do bispiribaque-sódico, já o biótipo de Santa Rosa do Sul-SC é mais sucetivel, reduzindo 50% da massa seca da parte aérea com 0.5x da dose de registro (20 g i.a. ha-1). O pirazossulfurom-etílico demostrou-se ineficiente na redução da massa seca da parte aérea em ambos os biótipos. Os biótipo C. difformis de Santa Rosa do Sul-SC e Meleiro-SC, nas duas condições de umidade do solo são suscetíveis ao triclopir-butotílico, reduzindo 50% da massa seca da parte aérea com 0.5x (166 g. i.a. ha-1) a dose de registro.

No abstract

Silicon (Si) is an enzyme stimulator that can promote signaling for the production of antioxidant compounds, important in cellular detoxification of excess ROS accumulated during stress. The aim of the study was to evaluate the effects of Si on post-germination rice seeds in the mitigation of cold stress combined with stress induced by seed treatment with the dietholate protector. The experimental design was fully randomized with three replicates and a 3x2x2x4x2 factorial arrangement: three temperatures (5, 10 and 20 °C), two cultivars (IRGA 424 RI and Guri INTA CL), two seed pretreatments (with and without dietholate), four rates of Si (0; 4.0; 8.0 and 16 mg.L-1) and two sources of Si (sodium and potassium metasilicate). Seed pretreatment with dietholate reduced shoot and radicle length, especially at the lower temperatures of 5 and 10 °C. Sodium metasilicate as the source of Si was more efficient in boosting shoot and radicle length, both with and without pretreatment, regardless of temperature. Si was found to attenuate low-temperature stress and the impairment of shoot and radicle growth in rice seedlings grown from seeds pretreated with dietholate.

Urochloa plantaginea and Urochloa platyphylla are common weeds in the highland area. However, in recent years, they have been found in wetlands and poorly drained soils, but the biology and behavior of the species in these conditions are not known. Thus, the objective was to assess anatomical changes in plants of Urochloa plantaginea and Urochloa platyphylla grown under different soil moisture conditions, as well as the adaptive structures generated as a result of each environment. A completely randomized experimental design in the form of a 2x2 factorial design was used, with factor A being two species of Urochloa (U. plantaginea and U. platyphylla), and species B being three soil moisture conditions (50 and 100% FC and 5 cm water depth), with four repetitions. The assessments were performed by means of anatomical cuts, observing the number and diameter (micrometers - μm) of aerenchymas in stems, roots and leaves; total diameter and the central root cylinder (μm); diameter of the fistula medulla and cortex (μm) in stems; mesophyll thickness and leaf midrib (μm). It was found that, for the two species of Urochloa, the water depth condition induced an increase in the number and diameter of aerenchymas in roots and leaves and provided a larger diameter of the fistulous pith in stems. The diameter of the central cylinder and the thickness of the leaf mesophyll midrib were more compact at 50% FC, also, for both species. Therefore, the adaptive structures generated vary as a result of the field capacity of the soil.