Effects of Selenium-Methionine against Heat Stress in Ca 2+ -Cytosolic and Germination of Olive Pollen Performance

Climate change (CC), which causes temperatures to rise steadily, is causing global warming. Rising temperatures can reduce plant yield and affect pollen characteristics. In particular, heat stress strongly influences pollen viability for its sensitivity to this extreme environmental condition. This work evaluated the effect of heat stress on olive pollen after in vitro incubation at different temperatures (20, 30, and 40 °C). Furthermore, the potential of selenium-methionine (Se-met) in mitigating the detrimental effects of heat stress on olive pollen was investigated. In particular, how thermal stress can affect pollen was evaluated by testing the effect of temperature on pollen germinability and morphology and cytosolic Ca 2+ content. The results suggest that the heat stress at 40 °C caused a marked reduction in the germination rate, changes in the morphology of the external pollen wall, and a decreased response to Ca 2+ -agonist agents. On the contrary, in vitro treatment of pollen with Se-met improved the germination rate and Ca 2+ -cytosolic homeostasis under heat stress conditions and confirmed the protective role of this compound in containing the hydrogen peroxide (H 2 O 2 ) toxicity. Therefore, this study revealed that organic selenium could play a crucial role in promoting heat tolerance in olive tree pollen.