ABSTRACT Toxic levels of aluminum (Al) in the soil can reduce the growth of different grain crops. To understand the effects of Al in soybean (Glycine max L.) seedlings Al accumulation and its effect on anatomy, morphology, and metabolism in roots of two soybean genotypes were evaluated: Suprema and A7002. For this, soybean plants were grown in nutrient Clark solution, pH 4.0, without Al (control) and with 100 µM of Al for 72 hours. Both genotypes accumulated Al in the roots, however, Suprema showed a higher Al accumulation than A7002. The latter genotype showed Al accumulated only in the cell walls of the epidermis and root cap, which did not affect root growth. On the other hand, in Suprema, Al accumulated in the cells of the root cap, epidermis, and the nucleus of the ground meristem cells, which resulted in inhibited root growth and structural damage in the root epidermis cells. Al modulated the primary metabolism with increases in the levels of glucose, fructose, sucrose, and malate in the roots of the genotype A7002 and reduced the starch levels in the Suprema genotype. The findings of this study suggest the A7002 genotype seems to be more resistant to Al than Suprema, mainly by the use of two important mechanisms: an increase in malate content and Al immobilization in the external cells of the root.

Resumo: O objetivo deste trabalho foi avaliar os efeitos do estresse hídrico no estádio reprodutivo (R3) sobre os parâmetros fisiológicos e o rendimento de grãos de duas linhagens de soja (Glycine max). As linhagens de soja Vx-08-10819 e Vx-08-11614 foram cultivadas em casa de vegetação, onde foram irrigadas até atingirem o estágio de desenvolvimento R3. Durante três dias, o peso dos vasos foi monitorado diariamente para manter 100, 60 e 40% da capacidade de campo (controle e estresses moderado e severo, respectivamente). Foram determinados os parâmetros trocas gasosas e fluorescência da clorofila a, além dos pigmentos cloroplastídicos, solutos osmorregulatórios e enzimas antioxidantes. Após o estresse, as plantas foram reidratadas até o final do estádio reprodutivo (R8) para avaliar o rendimento de grãos. Vx-08-10819 apresentou características que contribuíram para a tolerância à seca, como melhor eficiência no uso da água, modulação da área foliar e atividade enzimática, bem como aparato fotossintético mais eficiente e menor peroxidação lipídica que Vx-08-11614. Além disso, Vx-08-10819 manteve sua produtividade mesmo após deficiência hídrica severa. Em contraste, as limitações hídricas afetaram negativamente a produtividade de Vx-08-11614. A linhagem de soja Vx-08-10819 pode suportar eficientemente períodos de seca durante o estádio reprodutivo, sem que haja interferência no rendimento final de grãos.

Abstract: The objective of this work was to evaluate the effects of drought stress in the reproductive stage (R3) on the physiological parameters and grain yield of two soybean (Glycine max) lines. The Vx-08-10819 and Vx-08-11614 soybean lines were grown in a greenhouse, where they were irrigated until they reached the R3 development stage. During three days, the weight of the pots was monitored daily in order to maintain 100, 60, and 40% field capacity (control and moderate and severe stress, respectively). The parameters gas exchange and chlorophyll a fluorescence, as well as chloroplast pigments, osmoregulatory solutes and antioxidant enzymes, were determined. After stress, the plants were rehydrated until the end of the reproductive stage (R8), to evaluate grain yield. Vx-08-10819 showed traits that contributed to drought tolerance, such as better water-use efficiency, modulation of leaf area, and enzymatic activity, as well as a more efficient photosynthetic apparatus and a lower lipid peroxidation rate than Vx-08-11614. In addition, Vx-08-10819 maintained its productivity even after the severe water deficit. By contrast, water limitations affected negatively the productivity of Vx-08-11614. The Vx-08-10819 soybean line can efficiently withstand drought periods during the reproductive stage, without any interferences on final grain yield.

Abstract The presence of stachyose and raffinose is considered an antinutritional factor for humans and monogastric animals, leading to limitations on soybean consumption as a protein source. In the present study, the effect of a mutation in the raffinose synthase 2 gene was measured on soybean quality traits. We used an F2 population with 168 soybean individuals developed by crossing four soybean lines and evaluated oil, protein, sucrose, raffinose, stachyose and fatty acid contents and their relationships. The mutation explained 69.61%, 51.81% and 31.96% of stachyose, raffinose and sucrose variation, respectively, and we were able to produce soybean with average stachyose of 0.18%. The low coefficients of determination for protein and oil indicate that the mutation can be used to increase sucrose and reduce raffinose and stachyose content without major changes in oil and protein.