Leaf blast, caused by the hemibiotrophic fungus Pyricularia oryzae, is the most important disease affecting rice production worldwide. The present study investigated the potential of using glutamate (Glu) to increase rice resistance to leaf blast. Rice plants (cultivar Metica-1) were non-supplied (−Glu) or supplied (10 mM) (+Glu) with Glu and non-inoculated or inoculated with P. oryzae. Leaf blast severity and the number of lesions per cm 2 of leaf were significantly lower by 55 and 50%, respectively, for +Glu plants in comparison to -Glu plants at 96 h after inoculation (hai). The area under the leaf blast progress curve was significantly lower by 70% for +Glu plants in comparison to -Glu plants. For inoculated +Glu plants, the activities of chitinase, β-1-3-glucanase, phenylalanine ammonia-lyase, and polyphenoloxidases as well as the concentrations of total soluble phenolics and lignin-thioglycolic acid derivatives were significantly higher for inoculated +Glu plants in comparison to inoculated -Glu ones. The use of glutamate may become an alternative to be used in the management of rice blast in the context of a sustainable agriculture.
RESUMO:A importância do milho (Zea mays) não está apenas na produção de uma cultura anual, mas em todo o relacionamento que essa cultura tem na produção agropecuária brasileira, tanto no que diz respeito a fatores econômicos quanto a fatores sociais. Todos os aspectos de crescimento e desenvolvimento das plantas podem ser afetados pela deficiência hídrica e saturação de água nos tecidos, causada pela excessiva demanda evaporativa e/ou limitado suprimento de água. O objetivo desse trabalho foi avaliar os efeitos do alagamento sob conteúdo relativo de água, nº de folhas, massa seca do colmo, massa seca da raiz e massa seca das folhas em plantas de milho submetidas ao alagamento. O experimento foi conduzido em casa de vegetação da Universidade Federal Rural da Amazônia (UFRA -Capitão -Poço), utilizando-se plantas de milho variedade BR 5102, o delineamento experimental foi inteiramente casualizado (DIC) com fatorial 2 x 4, com duas condições hídricas: controle, déficit hídrico e quatro ciclos de estresse com 5 cinco repetições. Obtiveram-se resultados significativos em todos os parâmetros avaliados, concluindo que o alagamento influenciou negativamente na biometria das plantas. PALAVRAS-CHAVE:anoxia, produtividade, raiz. BIOMETRICS IN CORN SUBJECT TO FLOODINGABSTRACT: The importance of maize (Zea mays) is not only in the production of an annual crop, but in any relationship that culture has on Brazilian agricultural production, both with regard to economic factors as social factors. All aspects of growth and development of plants can be affected by water stress and water saturation in the tissues caused by excessive evaporative demand and / or limited water supply. The aim of this study was to evaluate the effects of flooding on relative water content, number of leaves, dry weight of stem, root dry mass and leaf dry weight in maize plants subjected to flooding. The experiment was conducted in a greenhouse at the Federal Rural University of Amazonia (UFRA -Capitão -Poço), using corn plant variety BR 5102, the experimental design was completely randomized design (CRD) with 2 x 4 factorial, with two conditions water: control, drought and four cycles of stress with 5 repetitions. Achieved significant results in all parameters evaluated, concluding that the flooding negatively in biometrics plants.
Com o objetivo de obter equações que, por meio de parâmetros lineares dimensionais das folhas, permita a estimativa da área foliar de Limoeiro-Cravo (Citrus limonia (L.) Osbeck), foi conduzido um experimento em uma propriedade rural no município de Capitão Poço -PA. A área foliar foi determinada pelo método dos discos. Ajustaram-se modelos lineares, lineares sem intercepto, quadráticos, cúbicos, logarítmicos, exponenciais e potenciais entre área foliar e o comprimento, a largura, a soma (comprimento + largura) e seus produtos (comprimento x largura), sendo eliminados os que apresentaram coeficiente de determinação menor do que 0,80. A estatística utilizada para avaliar o desempenho dos modelos foi o coeficiente de correlação de Pearson (r), o de determinação (R²), a raiz do quadrado médio do erro, o erro absoluto médio, o índice d de Willmott e o índice CS. Os modelos que melhor se ajustaram aos dados foram: o linear, o linear sem intercepto, o potencial e o quadrático, considerando a relação (comprimento x largura) como variável independente. Palavras-chave: Coeficiente de determinação. Citrus limonia (L.) Osbeck.. Dimensões do limbo foliar.
Considering the potential of white mold, caused by the fungus Sclerotinia sclerotiorum, to reduce tomato production, this study aimed to determinate the effect of manganese (Mn) phosphite on the resistance of tomato plants to this disease by assessing the photosynthetic performance (gas exchange and chlorophyll a fluorescence), the activities of defence enzymes and those related to the antioxidant metabolism as well as the concentrations of photosynthetic pigments, malondialdehyde (MDA), hydrogen peroxide (H2O2) and superoxide anion (O2−). The in vitro assays showed that S. sclerotiorum mycelial growth was inhibited by Mn phosphite in a dose‐response manner. The spray of Mn phosphite reduced white mold severity on the leaves of tomato plants. Additionally, there was a higher foliar Mn concentration for plants sprayed with Mn phosphite. The negative effects of S. sclerotiorum infection in the photosynthetic process were mitigated by Mn phosphite application as noticed by the net carbon assimilation rate, stomatal conductance to water vapour, transpiration rate, maximal photosystem II quantum yield values and concentration of photosynthetic pigments. The concentrations of MDA, H2O2 and O2‐ on inoculated leaves were lower upon Mn phosphite spray. In general, the activities of defence enzymes and those related to the antioxidant metabolism were higher for water‐sprayed plants inoculated with S. sclerotiorum in comparison to those inoculated and sprayed with Mn phosphite. Based on the present study results, the application of Mn phosphite may represent a feasible alternative for white mold management in tomato plants.
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