Moderate Doses of Selenium Alleviate the Effects of Salt Stress on the Growth of Eucalyptus Seedlings

ABSTRACT Although selenium (Se) is not essential for plant metabolism, low Se concentrations can enhance tolerance to abiotic stress. This study evaluated the effects of exogenous Se (1, 5, and 25 μM) on two eucalyptus genotypes (VCC 865 and AEC 0144) under saline stress (100 mM NaCl). Growth, biomass, gas exchange, ion accumulation (K+, Na+, Ca2+), and pigment content were analyzed. Salinity significantly impaired physiological performance, reducing height, stem diameter, net photosynthesis (PN), transpiration (Tr), and stomatal conductance (gs), while increasing Na+ in roots and leaves. Se at 1 and 5 μM mitigated these effects, particularly by reducing Na+ accumulation. VCC 865 showed increased K+ in roots and decreased Na+ in shoots with 1 μM Se, while AEC 0144 displayed improved ionic balance in roots and leaves. The chlorophyll pigment content remained unchanged between the treatments. However, 25 μM Se intensified salinity damage, indicating the importance of dose optimization. Photosynthetic parameters were sensitive indicators of Se-mediated responses. Therefore, the targeted use of selenium represents a promising strategy to improve seedling establishment in environments affected by salinity, contributing to the development of more resilient forest systems and the expansion of areas suitable for production.