Leguminous species, Piptadenia moniliformes (Benth.) and Trischidium molle (Benth.) H. E. Ireland, both prevalent in the Caatinga vegetation, were submitted to varying watering regimes under greenhouse conditions. In experiment I, 60-day-old P. moniliformes plants were maintained under suspended irrigation for 12 days. Assessment on day 12 of drought revealed that leaf relative water content decreased to 40% and stomatal conductance and transpiration were also strongly diminished. Apparent electron transport rate (ETR) and photochemical quenching (qP) values were reduced by water deficit treatment compared to controls, while non-photochemical quenching (NPQ) increased; however, the basal values were recovered in moisturized plants when analyzed after 48 h of rewatering. In experiment II, T. molle plants were watered once (1 9), 3 (3 9) or 5 times (5 9) per week, up to day 65 after emergence. Chlorophyll a, chlorophyll b and carotenoid contents were reduced in the 3 9 and 5 9 watering treatments. Photosystem II maximum efficiency (F v 0 /F m 0 ), ETR and qP values strongly decreased when drainage frequency and NPQ values were increased. Observation verified that chlorophyll fluorescence is a suitable tool for evaluating the developmental characteristics of the arboreal leguminous species studied. Analysis of the data obtained suggest that plant tolerance to the dry climate conditions of the Caatinga ecosystem is directly associated with fast physiological adaptation to water deficit, by accumulating biomass in the root system in detriment to the shoots. The data presented contribute to further understanding the developmental and physiological mechanisms that enable plant adaptation to dry climates and, particularly, to the unique dry environmental conditions of the Caatinga region.

-The predawn leaf water potential (Ψ l ), stomatal conductance (g s ), CO 2 assimilation (A), transpiration (E), chlorophyll a fluorescence and leaf metabolite contents (soluble sugars, proteins and free amino acids) of two tropical fruit species grown in a greenhouse were evaluated to determine the effect of induced water stress on young plants. Six month-old jackfruit (Artocarpus heterophyllus Lam.) and sugar apple (Annona squamosa L.) plants were evaluated in 10.0 L pots after eight days of water withholding, imposed by suspension of irrigation. Jackfruit water status was better than sugar apple. Sugar apple plants showed different daily stomatal behavior when well hydrated, compared to jackfruit plants under the same conditions. The gas exchange of both species showed sensibility to high vapor pressure deficit (VPD). However, under water deficit, photochemical efficiency dropped at midday in both treatments (control and water deficit) and both species showed low tolerance to high VPD and light intensity under greenhouse conditions. In contrast, some chlorophyll fluorescence variables showed good photosystem II stability at highest VPD hour (14:00 h). The present results involving carbohydrate metabolic changes revealed an accumulation of soluble sugars; moreover, protein and free amino acid contents in water stressed leaves also increased. These findings suggest an absence of damage to photosynthetic machinery for water deficit period. Jackfruit revealed greater tolerance to water deficit than sugar apple an important feature for commercial crops in northeastern Brazil. Key words -Annona squamosa. Artocarpus heterophyllus. Semi-arid. Tropical fruit. Water relations.Resumo -A condutância estomática (g s ), a assimilação de CO 2 (A), a transpiração (E), a fluorescência da clorofila e o conteúdo foliar de (açúcares solúveis, proteínas e aminoácidos livres) de duas espécies frutíferas tropicais foram avaliados para determinar o efeito do déficit hídrico induzido sobre as plantas da jaqueira (Artocarpus heterophyllus Lam.) e da pinheira (Annona squamosa L.) de seis meses de idade foram cultivadas em potes com capacidade para 10,0 L e foram avaliadas após oito dias de suspensão da irrigação. A jaqueira quando bem hidratada, foi melhor do que a pinheira. Plantas de pinheira apresentaram comportamento diferente quanto à condutância estomática diária quando comparada com as plantas de jaqueira, ambas bem hidratadas. As trocas gasosas de ambas as espécies apresentaram alta sensibilidade ao déficit pressão de vapor (DPV). No entanto, sob déficit hídrico, a eficiência fotoquímica decresceu ao meio-dia em ambos os tratamentos (controle e déficit hídrico) e ambas as espécies apresentaram baixa tolerância ao alto DPV e intensidade da luz em casa de vegetação. Em contrapartida, algumas variáveis de fluorescência de clorofila mostraram boa estabilidade na hora de maior DPV (14:00 h), indicando estabilidade do fotossistema II. Os resultados envolvendo alterações metabólicas revelaram um acúmulo de açúcares solúveis, ...

The Brazilian Atlantic Forest has experienced a reduction in its original area since the discovery of Brazil. Over the last 30 years, studies and techniques for forest recovery have advanced. Establishing a self-sustainable reforested area with adequate biodiversity is the main parameter for any reforestation program. Thus, knowledge of the ecophysiological behavior of the species to be used is crucial. Our hypothesis is that certain tools are efficient in determining the ecophysiological characterization of native species within different functional groups. Filling group plants show fast growth, intense gas exchange, present mechanisms of water deficit tolerance and show high efficiency in radiation capture, so they are first planted in a reforestation area. While plants pertaining to the diversity group do not exhibit these characteristics, thus are plants after the establishment of the first group of species. To test this hypothesis, two experiments were installed using young plants of four species native to the Atlantic Forest, grown in 9-L pots. Leaf water potential, gas exchange, chlorophyll fluorescence and certain biochemical parameters of leaf metabolism were evaluated. In the first experiment, plants were maintained under two forms of light availability for 15 days, full light (control) and shaded (shade). The species Inga sp. and Brosimum guianensis presented the most contrasting responses on day 15, principally in the variables leaf water potential, gas exchange, leaf soluble sugar content, F 0 v =F 0 m and F v /F m . In the second experiment, plants were divided into two groups: a well-hydrated group (control) and one that underwent irrigation suspension for 7 days (drought); measurements were performed on day 8 of drought. Again, Inga sp. and Brosimum guianensis plants showed responses characterizing them as pertaining to distinct functional groups for the experimental parameters previously described. Thus, Inga sp. was classified as pertaining to the filling group and B. guianensis to the diversity group. The performance of the species Cinnamomum zeylancium and Tapirira guianensis under the conditions studied suggests that these are intermediate species with potential for use as filling group species.