Respostas fotossintéticas e dinâmica de carbono em plantas de dois morfotipos de Paubrasilia echinata sob déficit hídrico seguido de reidratação

Abstract

According to IPCC reports, environmental disturbances resulting from climate change are predicted for the Brazilian region under the Atlantic Rainforest domain. In Brazilian Northeast, warming and prolonged drought are projected. This climate scenario can compromise the plant physiological processes, growth, and survival of native species of the Atlantic Forest, including the country's symbol species, Paubrasilia echinata. Seeking to gather information about the physiological strategies of this species facing drought, we carried out this study in order to characterize the photosynthetic responses and the dynamics of carbon allocation in two morphotypes of the species, one is shadetolerant (small leaf morphotype) and the other sun-tolerant (medium leaf morphotype). In the first stage of the study, the water potential, electrolyte leakage, gas exchange and transient chlorophyll a fluorescence of plants of the two morphotypes of P. echinata were evaluated under water suspension followed by rehydration. In the second step, the dynamics of the allocation of non-structural carbon: sugars and starch, and structural, cell wall polymers: cellulose, hemicelluloses and lignin were analyzed. It was recorded that the sun-tolerant morphotype, well adapted to drier and warmer environments, when subjected to water deficit presents a less pronounced decline in leaf water potential, photosynthesis and fluorescence parameters. Differently, the shade-tolerant morphotype showed less tolerance under the same treatments. The greater resistance of the sun-tolerant morphotype to drought was attributed to its greater capacity to accumulate sugars and lignification of its tissues. Thus, the habits of the morphotypes reflected in their physiological strategies to adjust the allocation of carbohydrates in drought tolerance. Concluding that, if the drought of climate change in the Atlantic Forest domain regions settles in the next decades, possibly the natural population of shade-tolerant morphotype may suffer reduction, due to its lower tolerance to water deficit in relation to the sun-tolerant morphotype.