Estresse hídrico no crescimento e trocas gasosas em mudas de Copaifera langsdorffii Desf.

Abstract

Copaíba (Copaifera langsdorffii Desf.) is a native tree of the Brazilian Cerrado that has a wide geographic distribution throughout the national territory, in ambience of great edaphoclimatic variation, suggesting that the species is able to withstand water adversities. However, when is aimed the best use of water resources for the production of quality seedlings or the implementation of projects for the recovery of degraded areas and reforestation, there is little information about the capacity of this native plant to withstand water stress. The aim of this work was to evaluate the gas exchange and the growth in C. langsdorffii Desf. submitted to different water stress conditions. For that, three experiments were carried out. In the first one, were evaluated the gaseous exchanges, the efficiency of the photosynthetic apparatus and the antioxidant activity of the seedlings submitted to the water deficit in different light conditions (30%, 70% and 100% light) and the potential for recovery of these characteristics after suspension of the stressful condition. In the second, were evaluated, over the time, the recovery of the efficiency of photosynthetic apparatus and the antioxidant activity of seedlings flooded for different periods. In the third one, were evaluated the gaseous exchanges, the efficiency of photosynthetic apparatus and the antioxidant activity of C. langsdorffii seedlings cultivated under different water retention capacities. At the end of the first experiment, it was observed that the seedlings submitted to the water deficit and exposed to 100% of luminosity showed loss of the capacity for the recovery of the photosynthetic metabolism. As for the second experiment, it was observed that seedlings flooded for prolonged periods showed lower recovery capacity after flooding, with lower indexes for the efficiency of photosynthetic apparatus, gaseous exchanges, photoassimilates production and seedlings quality. In the third experiment it was observed that extreme water availabilities are suggestive of stress for the species under the studied conditions and causes high activity of the antioxidant enzymes (superoxide dismutase, peroxidase and catalase) in the plant.