Crescimento, metabolismo fotossintético e enzimático em mudas de Copaifera langsdorffii Desf. sob condições de estresse hídrico e luminoso

Abstract

Copaifera langsdorffii Desf., popularly known as copaíba, is a tree with wide distribution in the Brazilian territory, originating from the Amazon to the Midwest and Southeast regions, which makes it occurs in the most diverse environments such as forests, wetlands, flooded river banks and the cerrado forests of central Brazil, suggesting that the species has a broad adaptation and survival capacity under stress conditions. Therefore, the objective of this work was to evaluate the gas exchange, the efficiency of the photosynthetic apparatus and activity of antioxidante enzymes of C. langsdorffii seedlings submitted to different conditions of water stress and light availability. For this, two experiments were carried out. In the first one, gas exchanges, efficiency of the photosynthetic apparatus and activity of antioxidante enzymes of seedlings submitted to intermittent water deficit with application of 0, 10 and 100 μM of ABA were evaluated, besides the potential of recovery of the physiological status after the suspension of the condition stressful. At the end of the experimental period, low performance was observed in all physiological aspects of seedlings during the periods of suspension of irrigation, with worse values found in the non-irrigated seedlings that did not receive ABA application. The application of ABA proved to be efficient for obtaining better values of gas exchange, the efficiency of photosystem II and the activity of antioxidant enzymes. The seedlings presented survival capacity in all the treatments to which they were submitted. In the second experiment were evaluated initial growth, gas exchanges, photosynthetic efficiency and activity of antioxidante enzymes of 0, 45 and 90 days of flooded plants under 30%, 70% and 100% of luminosity and the potential of recovery after the suspension of flooding. At the end of the experiment it was observed that during the periods that were conducted under flooding, the seedlings showed lower growth, gas exchange, efficiency of photosystem II and greater activity of antioxidant enzymes in all the light availability to which they were submitted. C. langsdorffii does not recover most of the characteristics evaluated after the flooding suspension, however, the absence of mortality indicates recovery potential, making necessary to evaluate the recovery of the plants for a longer period. The survival capacity of C. langsdorffii in all the stressful conditions to which it was submitted indicates tolerance to periods of drought, periods of flooding and different light availability, which justifies the occurrence of the species in heterogeneous environments.