Influência do tipo de solo em respostas ecofisiológicas vinculadas à escassez hídrica e à reidratação em Schinus terebinthifolia Raddi, uma espécie arbórea tropical

Abstract

Schinus terebinthifolia Raddi (Anacardiaceae) is a neotropical tree species recommended for forest restoration that can be found in several coastal locations, mainly in ‘restinga’, semideciduous forest and open tropical forest. The ability to grow in diverse environments may be related to its capacity to adapt to water stress and different soil types, allowing it to colonize degraded environments and even the Brazilian semi-arid (caatinga) region. The objective of this work was therefore to verify the ecophysiological behavior of Schinus terebinthifolia Raddi under dry conditions followed by rehydration in three types of soil, from two different types of Atlantic Forest in northeastern Brazil, more one from the Caatinga. The study was divided into two experiments. In experiment 1, only soil from an area of Atlantic forest forest was used. In experiment 2, two types of soil were used: (i) restinga soil, and; (ii) soil from the semi-arid biome. The experiments were conducted in a greenhouse with completely random distribution in two treatments: (i) control, and; (ii) water stress (‘suspended irrigation’). Irrigation was suspended until average photosynthesis values reached levels near or equal to zero. Plants of this treatment were then rehydrated. All soil types were analyzed for density, screening, flocculation and fertility. Gas exchange, chlorophyll fluorescence and osmoregulatory compounds were quantified on the day of greatest stress and after rehydration. Microclimatic data from the greenhouse were collected throughout the experiment. The first reaction to stress was a decrease in stomatal conductance, which reduced gradually as water deficit settled (independent of soil type) from 0.4 to 0.01 (mmol H2O m-2s-1). Chloroplastíd pigments retained their integrity throughout the treatment, and osmotic potential was regulated mainly through an increase in amino acids and proline. Young S. terebinthifolia were thus resistant to severe drought and had the capacity for rapid recovery in all three soil types. Physiological responses were more severe in the clay soil, probably due to root damage associated with soil compaction during drying.