Desiccation sensitivity of fresh and germinating seeds of Tabebuia aurea: physiological and biochemical implications

The mechanisms of tolerance to desiccation are one of the main factors related to the ability to survive the conditions of water deficit imposed by abiotic stress. Understanding the limits of desiccation tolerance in species and environmental factors promotes this capacity, which is of great ecological importance since it can help in the choice of species used for ecological recovery. In this study, we analyze tolerance limits, and physiological and biochemical parameters in desiccation tolerance (DT) of Tabebuia aurea (Silva Manso) Benth. & Hook.f. ex S. Moore (Bignoniaceae) seeds and germinating seeds. First, we analyzed the DT in seeds under different free water contents (0.25, 0.75, 1.5, 2.25, and 3% of free water content) in silica gel at 25 degrees C and forced air circulation oven at 40 degrees C. During development, we evaluated the ability of germinating seeds with different root sizes (0 to 2, 2 to 5, and 5 to 10 mm) to tolerate desiccation. We quantified reducing sugars and total proteins in all evaluated treatments. Seeds and seedlings of T. aurea showed large DT to both types of desiccation. The concentration of reducing sugars increased with decreasing seed-free water contents. The germinating seed also contents of reducing sugars reduced. We conclude that the large DT before and after germination of T. aurea with roots of up to 10 mm is related to changes in biochemical mechanisms that are important to maintaining this tolerance.