Though Selenium (Se) is a nonessential micronutrient to plants, its presence under appropriate concentrations helps in the plant antioxidant system, thus benefiting crop growth and productivity. Considering the need for acclimatization of crops due to climate changes and the need for diversification of the energy matrix, this study aimed to assess the different concentrations and forms of application of selenium (sodium selenite and sodium selenate) suitable for the cultivation of sunflower plants through growth analysis (height, diameter and number of leaves) and relative chlorophyll contents. The experimental design was completely randomized, and consisted of 18 treatments with 5 replications each, with applications of selenium in the substrate or by leaf spraying. All 18 treatments were independently assessed. Analysis of variance was performed and means were independently compared using the Tukey test (P ≤ 0.05) in the AgroEstat program. Sunflower plants supplemented with 0.8 mg L-1 of sodium selenite in the substrate presented values higher than those of the other treatments for plant height variable. For relative contents of chlorophyll, concentrations of 0.8 mg L-1 and 1.7 mg L-1 of selenate in the substrate and 3.3 mg L-1 of selenite in the substrate stood out. For the other variables, treatments containing selenium were equivalent to the control. It was concluded that the treatments whose application was directly made on the substrate showed higher values than those that received foliar application.

The use of soil additives such as selenium can positively influence the antioxidative system of plants, making them more tolerant to abiotic stresses. The aim of this work was to evaluate the concentration of sodium selenite or sodium selenate applied to the substrate that causes improve in plant growth and antioxidative enzyme activities in sunflower plants. The treatments were divided in: control (absence of selenium); 0.2 mg L-1 of sodium selenate; 0.4 mg L-1 of sodium selenate; 0.8 mg L-1 of sodium selenate; 0.2 mg L-1 of sodium selenite; 0.4 mg L-1 of sodium selenite and 0.8 mg L-1 of sodium selenite. The analysis of Shoot Dry Mass (SDM) production and activities of the antioxidantive enzymes: Ascorbate Peroxidase (APX), Guaiacol Peroxidase (GPX) and Catalase (CAT) was performed. For SDM and APX the concentration of 0.8 mg L-1 of sodium selenite caused higher values. CAT showed greater activity in treatments that received 0.4 and 0.8 mg L-1 of sodium selenate and 0.4 and 0.8 mg L-1 of sodium selenite than the control treatment. GPX showed superior activity in the treatments 0.8 mg L-1 of sodium selenate, 0.2 mg L-1 of sodium selenite and 0.8 mg L-1 of sodium selenite than the control treatment. It was concluded that selenium promoted improvements in the antioxidant activity and in the production of shoot dry mass of sunflower plants.

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A reutilização de resíduos industriais de diferentes processos, como fertilizante ou suplemento mineral constituem alternativas de destinação sustentável. Assim sendo, o presente estudo objetivou avaliar os efeitos da utilização de Resíduo de Suplemento Animal (RSA) em diferentes granulometrias como componente do substrato de plântulas de girassol submetidas à condições de estresse hídrico. Para se obter diferentes granulometrias, utilizaram-se quatro peneiras com malhas em inox: 1 mm; 0,500 mm; 0,250 mm e 0,105 mm. O delineamento experimental foi inteiramente casualizado disposto em arranjo fatorial 2x6, sendo dois tratamentos hídricos (com irrigação e sem irrigação por 3 dias) e seis tipos de substratos: (1: 100% em volume de areia; 2: Areia + húmus comercial a 100% da recomendação de 80 kg de N ha-1; 3: Areia + RSA 1 mm; 4: Areia + RSA 0,500 mm; 5: Areia + RSA 0,250 mm e 6: Areia + RSA 0,105 mm). Avaliando as variáveis de crescimento (massa seca da parte aérea, da raiz e total), bem como, mensurando as atividades das enzimas antioxidativas [Catalase (CAT), Peroxidase do Ascorbato (APX), Peroxidase do Guaiacol (GPX) e Superóxido Dismutase (SOD)]. O aproveitamento do resíduo de suplemento animal (RSA), com granulometria de 0,500 mm na fertilização do solo, promove a minimização dos impactos ambientais gerados pela destinação inadequada e ocasiona redução de custos com a adubação tradicional.