Caracterização fisiológica de genótipos de soja submetidos ao estresse salino

Salinity, ever present in agricultural soils, affects plant productivity. However, there are species more tolerant than others, and the study of response mechanisms to salinity is necessary in order to elucidate which responses are correlated with tolerance to salinity. Thus, we aimed at physiologically characterizing two Glycine max L. genotypes concerning saline stress, and identify which variables are more correlated with tolerance to salinity. For this, plants of cultivars AS 3730 and M 8372 were submitted to three saline concentrations (0, 50 and 100 mM), having sampled 0, 8 and 16 days. We conducted analysis for growth, enzymatic and non-enzymatic antioxidant metabolism, photosynthesis beyond the content of chlorophyll a and b, carotenoids, total soluble sugars, reducing sugars, proteins and proline. A results, cultivar M 8372 presented better growth, higher antioxidant enzyme activity and higher content of antioxidants such as ascorbate and carotenoids, when compared to cultivar AS 3730. In addition, cultivar M 8372 also presented lower levels of lipid peroxidation. However, cultivar AS 3730 obtained higher contents of proline, an osmoprotector and lower growth compromise when compared to its control. In conclusion, there is a differential response of the cultivars to salinity.

Compartimentos de K, Ca e Mg em solos e sua relação com o crescimento inicial, fisiologia e produtividade do eucalipto

Forestry has grown in a continuous and accelerated manner in Brazil, constituting a strategic activity for the generation of employment, income and tributes, favoring social and economic development of Brazilian agribusiness. The objectives of this study were: (1) evaluate the contents of K, Ca and Mg in the reserve compartments, non-interchangeable, interchangeable, available and the speed of its release, its correlations and its effects over productivity (annual average increment – AAI) of eucalyptus plantations, in forest sites cultivated in soils of the state of Rio Grande do Sul; (2) evaluate the initial growth, nutrition and physiological aspects of eucalyptus plants, cultivated with and without the addition of mineral sources of potassium (K), calcium (Ca) and magnesium (MG), in soils obtained from forest sites in the state of Rio Grande do Sul. In the first study, contents of K, Ca and Mg were evaluated in sulfuric digestion extract, boiling nitric acid, ammonium chloride, Mehlich-1 (only K), potassium chloride (Ca and Mg), as well as the release speed of these nutrients in the soil. In the second study, growth variables, nutritional aspects, photosynthetic rate (A) and transpiration rate of the plants (E) grown in distinct soils were evaluated under controlled conditions. The contents of K, Ca and Mg varied between compartments and depths in the studied soil classes, with the highest proportions found in the reserve compartment, indicating the importance of this compartment for the supplement of these nutrients at average and long terms. The great majority of K, Ca and Mg compartments presented significant correlations between each other, showing the dependence between them and the importance of evaluating the contents of these nutrients in the different compartments to adapt the nutritional management of the plants to each soil class, and to obtain continuous productions, minimizing the negative effects to the environment. Plants cultivated in soils that present larger reserves, availability and K, Ca and Mg release kinetics, presented similar height (H), stem diameter (SD) and shoot dry mass (SDM), with or without fertilization with K, Ca and Mg. The plants presented higher leaf content and accumulation of K in all soils fertilized with K, Ca and Mg.