Lignina é um bom preditor da resistência de espécies ao estresse hídrico?

Abstract

Tropical plant species resist seasonal drought by avoidance or tolerance, keeping or losing leaves, respectively. Since drought resistance is influenced by wood attributes and lignin is a major component of wood, we investigated whether lignin is related to foliar retention time (LR). We selected 22 species, determined the stem lignin content by thioglycolic acid and quantified guaiacyl (G) and syringyl (S) monomers by thioacidolysis and GC-MS analysis. Among these species, we selected 15 species to measure vulnerability to embolism by pneumatic method. In our analyses, were considered measures of wood density, stem water saturation and stem water potential in the dry season, published by other authors. Our analyses showed that there are two ways of surviving drought. A small group of species, for which the lignin does not seem to matter, stores water in the stem and loses leaves right at the end of the rainy season. A large group of species, from early deciduous to evergreens, retains leaves in the dry season for increasingly longer periods the higher the S/G ratio is. Higher values of the S/G ratio allow greater LR by reducing vulnerability to embolism.