HOW DO SALINITY AND WATER DEFICIT INFLUENCE THE INITIAL DEVELOPMENT OF CAATINGA SEEDLINGS?

Abstract

The Caatinga presents high climatic variability, marked by long periods of drought, irregular rainfall, and high evapotranspiration rates, factors that shape vegetation dynamics. The intensification of anthropogenic activities, especially deforestation and irrigated agriculture with inadequate management, has expanded processes of salinization and environmental degradation, compromising the establishment and regeneration of native vegetation. In this context, understanding the effects of salinity and water scarcity on the early stages of plant development is essential to support conservation and ecological restoration strategies. Salinization, whether of natural or anthropogenic origin, reduces the soil’s osmotic potential, hinders water and nutrient uptake, and causes ionic toxicity, affecting germination, growth, and physiology. In Caatinga species, these effects include decreased germination speed and percentage, accumulation of reactive oxygen species, plasmolysis, nutritional disorders, and severe reductions in early growth, with losses exceeding 90% in some sensitive species. At the same time, recurrent water deficit intensifies developmental limitations by promoting stomatal closure, reducing CO₂ assimilation and compromising gas exchange, biomass accumulation, and leaf expansion. Evidence shows wide interspecific variation in responses to these stresses, involving osmotic adjustments, morphological changes, antioxidant mechanisms, and biomass allocation strategies. This functional diversity highlights both the vulnerability and the adaptive potential of Caatinga species in the face of environmental changes. The evidence found showed that salinity and water deficit act as the main limiting factors for the establishment of Caatinga species, directly affecting germination processes, initial growth, and physiological functioning. Although many species exhibit adaptive mechanisms capable of mitigating part of these effects, the intensity and combination of stresses often result in significant reductions in plant performance.