The study was performed in the greenhouse of the Federal University of Grande Dourados (UFGD), from April to May, 2015. The aim of this study was to assess the effect of abscisic acid (ABA) different concentrations on Hymenaea courbaril L. seedlings water stress response and recovery after the rehydration. The following six treatments were evaluated: 1) Irrigation 0 µM ABA; 2) Irrigation + 10 µM ABA; 3) Irrigation + 100 µM ABA; 4) Irrigation without 0 µM ABA; 5) Irrigation without + 10 µM ABA and 6) Irrigation without + 100 µM ABA. The irrigation without treatment was performed by withouting water until the photosynthetic rate was close to zero, after which the plants were rehydrated. The plants were then irrigated daily to maintain 70% of the water holding capacity of the soil for a 12-day recovery period. The ABA doses applied exogenously during the irrigation without period neither prevented the reduction of photosynthetic activity nor optimized the recovery of the gas exchanges and the carboxylation efficiency of Rubisco after water and seedling quality restoration. The 100 µM ABA concentration promoted the degradation of chlorophylls independent of irrigation, showing that high concentrations of ABA may cause a residual effect on this species. The seedlings exhibited normal metabolic recovery after about 12 days of re-irrigation of the soil, which we attribute to species characteristics and not the tested treatments. Key words: Ecophysiology, restoration, water condition ResumoInfluência da aplicação exógena do ácido abscísico nas trocas gasosas de plântulas de Hymenaea courbaril L. (Fabaceae) submetidas ao déficit hídrico. O estudo foi realizado na casa de vegetação da Universidade Federal da Grande Dourados -UFGD, Dourados -MS, de abril a maio de 2015. O objetivo desse trabalho foi avaliar o efeito de diferentes concentrações de ácido abscísico (ABA) nas respostas ao estresse hídrico e na recuperação das mudas de Hymenaea courbaril L. após o reiirigação. Foram avaliados seis tratamentos sendo eles: 1) Irrigado sem ABA; 2) Irrigado + ABA 10 µM; 3) Irrigado + ABA 100 µM; 4) Sem irrigação e sem ABA; 5) Sem irrigação + ABA 10 µM; 6) Sem irrigação + ABA 100 µM. O tratamento sem irrigação consistiu na suspensão da irrigação até que a taxa fotossintética apresentasse níveis próximos de zero, quando as plantas foram reidratadas novamente com subsequente irrigação diária mantendo 70% da capacidade de retenção de água no solo, representando o período de restabelecimento, o qual durou 12 dias. As concentrações de ABA aplicadas exógenamente na época da suspensão da irrigação não evitaram a redução da atividade fotossintética e nem tão pouco otimizaram a recuperação das trocas gasosas e a eficiência de carboxilação da Rubisco após o restabelecimento normal de água e de qualidade das mudas. A concentração de 100 µM de ABA promoveu degradação das clorofilas independente da condição hídrica, evidenciando que altas concentrações de ABA podem provocar efeito residual nesta espécie. As mudas apresentaram restabeleci...

The restoration of altered and degraded ecosystems will only be successful if research studies generate biological, ecological and physiological knowledge about the species of different Brazilian ecosystems. In order to produce quality seedlings, ecophysiological knowledge of the initial phase of the species is essential, since artificial shading can interfere with the growth rate and quality of the seedling. The aim of this study was to assess the effect of different levels of shading on the emergence, initial growth and photosynthetic metabolism of Ormosia arborea. The experiment was carried out with 30% and 70% shade and in full sun. At 60 days after sowing, non-destructive (gas exchange and chlorophyll fluorescence) and destructive (growth measures) analyzes were performed. 70% shade provides greater emergence, initial growth, gas exchange and photosynthetic efficiency of PS II. Cultivation at 0% shade (full sun) is not suitable for this species.

In this research, we hypothesized that Ormosia arborea (Vell.) Harms seedlings should grow better and achieve greater levels of gas exchange when grown in soils with higher water availability. Thus, this study was developed to assess the metabolic responses of the seedlings to different levels water availability. Irrigation was performed on alternate days, at water holding capacities (WHC) of 25%, 50%, 75%, and 100%. The metabolic responses were analyzed at 15, 50, 85, and 120 days after starting treatments. The O. arborea plants grown in conditions of higher water availability (75% and 100% WHC) had higher leaf water potential and chlorophyll content, in addition to higher values for chlorophyll a fluorescence and gas exchange, than those grown in other conditions.  Water deficit caused by low levels of water availability (25% or 50% WHC) reduces leaf water potential, chlorophyll a fluorescence, and gas exchange. As a strategy to tolerate stress, seedlings tend to invest in their antioxidant system, as shown by the high levels of activity of the enzymes Superoxide dismutase (SOD), Peroxidase (POD), and Catalase (CAT). Although the seedlings may be tolerant to cultivation under 50% WHC, the best functioning of the photosynthetic apparatus occurred under WHC of 75%.