FIGURE 9.

Schematic model of ethylene mediated pollen thermotolerance. Developing pollen grains at polarized microspores-to-bicellular pollen stages exhibit active metabolism, including carbohydrate and energy metabolism and active maintenance of protein homeostasis. Upon exposure to heat stress conditions, without any pre-treatment (‘-Ethylene releaser’), key biological processes in pollen development are affected, together with high reduction in pollen quality. Pre-treating developing pollen grains with ethephon (‘+Ethylene releaser’) increases ROS scavengers and causes upregulated expression of proteins involved in protein, carbohydrate and energy homeostasis following exposure to heat stress, together with maintenance of pollen quality.