Physiological, biochemical, and ultrastructural characterization of selenium toxicity in cowpea plants

Selenium (Se) is considered a beneficial element for plants; however, in high concentrations, it causes negative effects on plant physiology and development. This study reports the first physiological, nutritional, and ultrastructural description of Se toxicity in cowpea growing under field conditions. Selenium was supplied as a foliar application of sodium selenite at varying concentrations (0, 50, 100, 200, 400, 800, 1200, and 1600 g ha−1). An increased yield was observed with the application of 50 g ha−1 Se. Application of concentrations higher than 50 g ha−1 caused leaf toxicity. Increased lipid peroxidation and hydrogen peroxide concentration and reduced total sugars, sucrose, and carotenoid concentration were observed at highest doses tested (1200 and 1600 g ha−1). Applications of more than 50 g ha−1 Se reduced the phloem diameter, caused chlorosis of the leaf blade with a coalescence of lesions, and caused pink salt deposits to appear. Lesions were observed mainly near the trichomes on the adaxial surface of the leaf blade. An analysis of the element distribution with microprobe X-ray fluorescence spectrometry (μ-XRF) revealed accumulation of Se, calcium (Ca), potassium (K), copper (Cu), and manganese (Mn) near the primary vein and in the necrotic brown areas of the leaf lesions. In contrast, Na was homogeneously distributed in the leaf tissue

Análise comparativa da construção de estufas ecológicas de baixo custo e convencional: uma alternativa econômica para a agricultura familiar

The main crops in Tupã Region are peanuts and horticulture products such as lettuce, tomate and cucumber. The available low cost technology and alternative projects are needed to facilitate family farming routine and also to expand the productions of horticulture products. However, the low incomes for investments on new project alternatives like construction of low cost greenhouses are needed to generate economically viable solutions for family farming. This study aimed to build an ecological, sustainable and cheap greenhouse using treated eucalyptus wood to cultivate different types of horticultural crops in rural zones. We conclude the ecological greenhouses using treated eucalyptus wood are a good strategy and economically feasible for build low cost greenhouses to attend family farming needs.Na região de Tupã, as principais hortícolas produzidas por agricultores familiares são alface, tomate e pepino. Na região há carência de tecnologia acessível e a necessidade de projetos alternativos que facilitassem a rotina do produtor rural, e que o impulsionasse a melhorar e expandir suas produções e técnicas agrícolas. Entretanto, à baixa renda das famílias para investir em novas propostas mostra que essa necessidade precisa ser suprida a partir de soluções economicamente viáveis e por meios que facilitem o planejamento e o desenvolvimento do projeto. Esse estudo objetivou a análise comparativa da construção de estufa ecológica de baixo custo e convencional. Esse trabalho propõe a utilização de toras de eucaliptos tratado para a construção de estufas em substituição aos materiais de cimento. Conclui-se que a construção de estufas ecológicas utilizando toras de eucaliptos tratados é uma boa alternativa, é economicamente viável e de fácil acesso e manejo para o pequeno produtor rural