Environmental vulnerability index in Dipteryx alata: influence of abiotic stresses on central processes of plant physiology and metabolism

Abstract

Dipteryx alata is an important plant species in the Brazilian Cerrado. In this work, we evaluated biochemical and physiological changes in plants exposed to the following treatments for 15 days: control (plants grown in ideal conditions, without stress), drought, flooding, and salinity. Each treatment had six replicates of one plant per pot, evaluated concerning their water relations (water potential, osmotic potential, and daily transpiration), physiological processes (chlorophyll a fluorescence, gas exchange, respiration, and photorespiration), and biochemical parameters (sugars, proline, hydrogen peroxide, malondialdehyde, and antioxidant enzymes). Drought and salinity decreased the leaf water potential and the osmotic potential, indicating osmotic adjustment, but sugars and proline did not contribute to this process. All three stresses decreased the photosynthetic rate by inducing stomatal closure. Salt stress and hypoxia, however, also altered pigment concentration and electron transport, and promoted limitations to photosynthesis. Only plants subjected to drought stress showed increased photorespiration, which although is a source of H₂O₂, may have helped to protect photosystems. The balance in antioxidant enzyme activities varied significantly among treatments, but membrane damage was observed only in plants grown at high salt concentrations. Although drought is commonly considered the main abiotic stress responsible for tree mortality, the vulnerability index and the hierarchical grouping of plants indicated that D. alata seedlings showed greater sensitivity to flooding and salinity stress. These results are consistent with the evolutionary history of this species and highlight the detrimental effects of land misuse on species conservation in the Cerrado Domain.