In view of the ecological, social, and economic importance of Myracrodruon urundeuva Allemão, the objective of this study was to investigate the strategies of this species under drought during its initial phase of development. Two-monthold plants were cultivated under continuous irrigation or no irrigation for 20 d. After this period, the water-stressed plants were rehydrated for 20 d. Physiological, biochemical, and anatomical variables were evaluated on 20 th and 40 th day. Water deficit (25 and 85 % leaf relative content) caused senescence followed by leaf abscission. Growth in height was negatively affected by water deficit (37 % reduction). A decrease in the thickness of the mesophyll was accompanied by a decrease of the total chlorophyll content. Water deficit affected saccharide metabolism and altered cellular component dynamics. Enzyme activities were higher during the rehydration period than during the water stress. There was no increase in lipid peroxidation in plants subjected to water deficit. A reduction in the stomatal opening during water stress was a strategy of reducing water loss through transpiration.

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Objetivou-se, com o estudo, avaliar a adição do estéril resultante da extração da gipsita, como condicionante do solo, sobre a disponibilidade de água em um Neossolo Quartzarênico coletado no Município de Petrolina, PE. A capacidade de campo (CC) foi obtida pela saturação e subseqüente drenagem de um perfil simulado de solo em uma coluna de cilindros de PVC com 100 cm de altura, nas proporções de 0, 20, 40, 60 e 80 g kg-1 do estéril, incorporadas nos 40 cm superiores. O ponto de murcha permanente (PMP) foi determinado pelo método fisiológico; adicionalmente, a CC e o PMP o foram pela metodologia usual utilizando-se o extrator de Richards com uma pressão de 10 e 1500 kPa, respectivamente. A incorporação de doses crescentes do estéril aumentou a água disponível do solo, de 4,8 para 8,67%, quando determinado pelo método tradicional, nas doses 0 e 80 g kg-1, respectivamente, e de 14,76 para 15,08%, nas mesmas doses, quando a água disponível foi determinada a partir da CC e o PMP obtidas pelo método da coluna de drenagem e método fisiológico, respectivamente. Inserindo-se a umidade gravimétrica da capacidade de campo obtida pelo método da coluna de solo na curva de retenção de umidade, vê-se que este parâmetro foi melhor representado por um potencial matricial próximo -6 kPa.

The present study is to assess the morphophysiological development in vitro of Lippia grata Schauer, an endemic ''Caatinga'' species that shows pharmacological properties. Young cuttings containing nodal segments were divided into three explant types, namely E1 (apical bud), E2 (nodal segment below the apical bud) and E3 (nodal segment below E2); the explants were inoculated in MS medium supplemented with antioxidant compound (polyvinylpyrrolidone) or adsorbing agent (activated charcoal). The survival index, the occurrence of oxidation, contamination and the number of leaves and sprouts were assessed. The explants were cultivated in MS medium supplemented with polyethylene glycol 6000 (0, 0.5 and 1 g L-1) and closed with aluminum foil (total sealing) or with aluminum foil containing one hole (partial sealing), in the multiplication stage, due to hyperhydricity in vitro. Histological and biometric analyses were performed at the 45th cultivation day, as well as the analyses of antioxidative enzyme, and hydrogen peroxide and malondialdehyde levels. Normal leaves have presented greater organization and cellular development than hyperhydric leaves. The use of antioxidants was not efficient to control the oxidation of inoculated apical buds (E1), only. The lowest hyperhydricity rates in the multiplication stage were found in the partial sealing treatments; however, the total sealing of tubes, in combination with the PEG addition, has led to increased lipid peroxidation. In view of the results, it is concluded that the explant types, as well as the suitability of a functional gas exchange system in vitro, have favored the growth and development of cells and tissues, thus attenuating the hyperhydricity symptoms. In addition, this study demonstrates the suitability of the culture system through the facilitation of gas exchange allows the use of the protocol for in vitro propagation without compromising the leaf morphoanatomy.

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