RESUMO O feijão comum (Phaseolus vulgaris L.) é uma leguminosa importante por ser fonte de proteína, carboidratos e rico em vários minerais. Em situação de alagamento, a disponibilidade de oxigênio pode proporcionar uma condição de anoxia ou hipóxia. O presente trabalho teve como objetivo avaliar o comportamento da cultivar BRSMG-Uai submetida a hipóxia em diferentes fases fenológicas, analisando as respostas em relação ao crescimento e produção, metabolismo de carboidratos e assimilação de nitrato. Desta maneira, sementes de feijão comum foram semeadas e ao atingirem o estádio de desenvolvimento V1 foram transferidas para recipientes contendo 40L de solução nutritiva e aeração constante. As plantas foram expostas a condição de falta de aeração por 9 dias, em três diferentes fases fenológicas. Foram consideradas as fases fenológicas V3/V4, R6 e R7. Após as coletas foram realizadas análises bioquímicas e de crescimento, com delineamento inteiramente casualizado (n=6). Plantas submetidas a baixa disponibilidade de oxigênio apresentaram redução no número de grãos, sendo em V3/V4 a maior perda em produção conferindo maior sensibilidade a hipóxia nesta fase. Em contrapartida, ocorreu aumento na concentração de açucares nas folhas. Foi possível observar nas folhas e raízes, aumento no conteúdo de peróxido de hidrogênio, redução da atividade da enzima dismutase do superóxido nas fases fenológicas V3/V4, R6 e R7, aumento da atividade da enzima peroxidase do ascorbato nas raízes em R6 e da atividade da enzima redutase do nitrato. Conclui-se que a cultivar BRSMG-Uai apresentou sensibilidade a baixa disponibilidade de oxigênio, e que a fase fenológica V3/V4 é a mais crítica.

ABSTRACT Common bean (Phaseolus vulgaris L.) is an important source of protein and carbohydrates, besides being rich in several mineral nutrients. In a flooding situation, the low availability of oxygen may result in hypoxia or anoxia condition. Therefore, this study aimed to evaluate the responses of the common bean cultivar BRSMG-Uai subjected to hypoxia in different phenological phases, analyzing its responses in terms of growth, productivity, carbon and nitrogen metabolism. Thus, seeds of common beans were germinated and when the seedling reached growth stage V1, they were transferred to plastic boxes containing 40L of nutritive solution with steady aeration. Distinct series of plants were exposed to air-restriction on their roots for nine days, in three different phenological phases V3/V4, R6 and R7. Samples were collected for biochemical and growth analyses in a completely random design (n=6). The plants subjected to low availability of oxygen presented a reduction in bean number, displaying the greatest loss in productivity in V3/V4, conferring the highest sensitivity to hypoxia in this phase. On the other hand, there was an increase in sugar concentration in leaves, and it was also possible to observe an increase in hydrogen peroxide in leaves and roots, concomitant with a decrease in superoxide dismutase activity in all phenological phases. There was also an increase in ascorbate peroxidase activity in roots in R6, as well as in nitrate reductase activity. We conclude that the cultivar BRSMG-Uai presents sensitivity to low oxygen availability, and the phenological phaseV3/V4 is the most critical for it.

ABSTRACT In order to investigate the existence of a possible abscission zone in the binding region between the peduncle and the coffee fruit, as well as the biochemical events involved in fruit ripening, we studied peduncles and fruits of Coffea arabica L. cv. “Icatu amarelo”. Coffee fruits were harvested at different maturation stages by using specific intervals of detachment force. It was observed a breakdown in the cells of the connecting region between peduncles and fruits throughout the maturation process. This disruption is probably caused by increased activity of the cell wall-loosening enzymes (polygalacturonase and cellulase) as well as by higher levels of lipid peroxidation in the final maturation stages. In general, physiological differences between maturation stages were observed and can largely explain the different detachment forces required at different stages. In conclusion, there is no clear abscission zone between the peduncle and the coffee fruit cv. “Icatu amarelo”. Nevertheless, the decrease in the detachment force throughout the maturation process can occur due to the activity of cell wall-degrading enzymes together with increased oxidative stress during the fruit ripening.