Mecanismos de tolerância à seca em quatro espécies arbóreas ocorrentes no semi-árido brasileiro

Abstract

The savanna biome is the only exclusively Brazilian, which means that most of its biological heritage can not be found anywhere else on the planet. Watersheds where existing vegetation component have little known and present in an advanced state of degradation especially in marginal areas of the watercourses. In these areas, it is believed that the species, after transplanting, are subject to dry cycles and must have the characteristics necessary for adjusting and setting survival highly specific under the circumstances. Within this context we studied the mechanisms of drought tolerance in four tree species in semi-arid [Caesalpinia ferrea (pau-ferro), Tabebuia aurea (craibeira), Aspidosperma pyrifolium (pereiro) and Bauhinia forficata (mororó)]. An experiment was set for submission of plants to water deficit in greenhouse installed in two stages, both arranged in completely randomized design with factorial arrangement 2 (species) x 3 (water conditions), with five replicates each. Thus, we studied the quantum efficiency of photosystem II, the accumulation of organic solutes and chlorophyll in the leaves, growth, accumulation and distribution of biomass and leaf water potential in the pre-dawn at the end of the experiment. In craibeira out yet studied the gas exchange of leaves facing the stress cited. The data were submitted to ANOVA and means compared by Tukey test at 5% probability. In general water stress reduced the stem diameter, plant height, leaf number, dry masses of roots, shoots, and total leaf area in addition to increasing the root / shoot of the species. The stomatal conductance, transpiration and photosynthesis were negatively influenced by water deficit. The contents of proline and N-α-aminossolúvel increased with the increase of stress cited in craibeira, ironwood and mororó. Regarding the contents of chlorophyll a species ironwood and pereiro showed reductions while craibeira mororó and remained stable. However these species tended to recover all the variables, indicating that these species have mechanisms to tolerate a lower water availability.