Effects of selenium supplementation on olive under salt stress conditions

This study was conducted in order to determine the effects of exogenous selenium (Se) supply (10 and 30 mg L−1 Na2SeO4) on the resistance to salt stress (NaCl 200 mM) of olive (Olea europaea L.) cv. Arbequina grown in hydroponic culture. Vegetative indices were monitored: plant growth, photosynthesis, leaf gas exchange and relative water and chlorophyll content. The bio-molecular parameters relative to proline, total Se in the leaves, and the quantity of proline, SeO42- and Ca2+ released by the roots were also monitored. The present study describes for the first time the monitoring of proline, Se and Ca2+ released from the roots and their content in leaves after treatment with selenate in olive trees grown in hydroponic culture and subjected or not to salt stress. The results showed that NaCl partially reduced the absorption of selenate in the Arbequina cultivar. Despite this, treatment with Na-selenate in salt stressed plants stabilized the levels of proline in the leaves and reduced the loss of this osmolyte from the roots. Selenate also promoted the release of Ca2+ from the roots, thus contributing to the restoration of ionic homeostasis. The positive effects of Se on the monitored bio-molecules were also confirmed by the improvement of vegetative indices dramatically altered bystrong salt stress. Indeed, treatment with selenate helped to reduce the amount of toxic effects on leaf gas exchange, improving photosynthesis, and mitigated the reduction of leaf dry weight and relative water content of the leaves.