Ecophysiological and biochemical responses of two tree species from a tropical dry forest to drought stress and recovery

Abstract

Droughts are predicted to increase in frequency and severity, thus affecting the functioning of forest ecosystems. However, it is not clear how the recovery dynamics of Erythrina velutina and Poincianella pyramidalis work following these events. Thus, we investigated the ecophysiological and biochemical responses of these tree species to drought stress and recovery. The study was conducted under greenhouse conditions, where the effects of two water regimes (1 – control and 2 – drought stress followed by recovery) were evaluated over time. Gas exchange parameters, leaf water potentials and biochemical attributes were measured. Under drought, E. velutina rapidly downregulated photosynthesis, reducing leaf gas exchange and improving water use efficiency to compensate for the temporary loss of xylem water transport, and recovered slowly after having a high consumption of non-structural carbohydrates. In contrast, the photosynthetic activity of P. pyramidalis was gradually reduced with increasing drought, but quickly recovered when rewatered, and the leaf water potential was effectively reduced through the accumulation of proline. Although showing different mechanisms behind their drought tolerance, in both species, the full recovery of photosynthesis upon rewatering was possibly related to enhanced photoprotection by carotenoids, which can contribute to the resilience of these trees in the face of recurring droughts.