Chloroplast calcium and ROS signaling networks potentially facilitate the primed state for stomatal closure under multiple stresses

•Stomatal closure requires the primed state of guard cells.•The PQ pool-dependent chloroplastic ROS generation contributes to the primed state.•Stromal calcium signaling potentially contributes to the stress-initiated primed state.•The Ca2+-sensitivity priming of guard cells are regulated by ROS and Ca2+ crosstalk.•The ROS and Ca2+ signaling network is the major step in triggering stomatal closure.