We tested the hypothesis that effective antioxidant and photoprotective mechanisms are able to avoid photodamage induced by prolonged water deficit (WD) followed by high light (HL). We employed cashew plants (Anacardium occidentale L.), a semiarid adapted species, as a model plant. WD-plants exposed to HL did not show alterations in maximum quantum efficiency of photosystem II (Fv/Fm), cellular integrity, H 2 O 2 and thiobarbituric acid reactive species (TBARS) contents, evidencing that they did not suffered photoinhibition and oxidative stress. These responses were associated with increases in ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities, glutathione (GSH) oxidation and ascorbate (ASC) synthesis. This effective oxidative protection occurred in parallel to strong decrease in photosystem II and I (PSII and PSI) activities, increase in heat dissipation (qE), which was related to enhancement in cyclic electron flux. These favorable photoprotective changes were associated with efficient water use in response to HL, all contributing to avoid excess energy in chloroplasts of drought-exposed leaves. These protective features were associated with a tight regulation in D1 protein accumulation during HL, contributing to avoid reactive oxygen species over-accumulation and a subsequent effective PSII recovery during darkness. Our results indicate that cashew plants are able to avoid photoinhibition, tolerating extreme conditions of drought combined with HL. The displayed mechanisms involve essentially integrated responses to balance energy input and output, avoiding oxidative stress.

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The purpose of this study was to characterize the effect of temperature on the distribution of Na + , Cl -and K + in roots, stems and leaves of cowpea pre-treated with NaCl. After the acclimation period, plants were divided into two groups: 0 NaCl and 100 mM NaCl for 2 days. Subsequently, the plants were divided into 4 sub-groups and subjected to increasing temperatures of 27, 32, 37 and 42 °C, separately, for a photoperiod of 12 hours at each temperature. The treatment without NaCl at 27 ºC was used as reference. The concentrations of Na + and Cl -in different organs were increased by pretreatment with NaCl and this accumulation was intensified by exposure to high temperatures. In roots, for example, at temperature of 42 ºC concentrations of Na were four times higher than in leaves. While Cl -accumulated mainly in leaves, with a 20-fold increase in the concentration of this ion in relation to reference plants. Inversely, K + concentrations were reduced in all organs analyzed. Thus, it is conclude that high temperatures affect the distribution of ions in different organs directly affecting ion homeostasis in plants.

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Os usos múltiplos do solo têm efeitos diferentes sobre a qualidade da água, e a magnitude desses efeitos depende da área ocupada, sendo o processo desordenado de urbanização uma das causas mais comuns de impactos nos corpos hídricos nas cidades. Esta pesquisa objetivou realizar um estudo da influência da urbanização na qualidade da água da microbacia hidrografia do rio Ouricuri na cidade de Capanema – PA. Foram analisados quatro parâmetros: temperatura, oxigênio dissolvido, pH e sólidos totais dissolvidos. As amostras foram coletadas tomando três características: (1) amostras do rio Ouricuri, (2) de córregos urbanos e (3) de tributários. Os resultados foram avaliados com base na resolução do CONAMA nº 357 de 2005. Através dos resultados dos testes estatísticos ANOVA e Tukey, identificou-se que o rio Ouricuri e os córregos demonstram evidencias de ações impactantes nas características físico-químicas e a sazonalidade surgiu como fator preponderante de diferenciação em função do pH, assim como OD e STD em relação aos corpos hídricos analisados. O modelo de regressão gerado pelo método stepwise, evidenciou a interação entre OD e STD eficiente em predizer condições de hipóxia ou anoxia em corpos hídricos de áreas urbanas.

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