H 2 O 2 , Ca 2+ , and K +  in subsidiary cells of maize leaves are involved in regulatory signaling of stomatal movement

Background : The stomata of maize ( Zea mays ) contain a pair of guard cells and a pair of subsidiary cells. To determine whether H 2 O 2 , Ca 2+ , and K + in subsidiary cells were involved in stomatal movement, we treated four-week-old maize (Zhengdan 958) leaves with H 2 O 2 , diphenylene iodonium (DPI), CaCl 2 , and LaCl 3 . Changes in content and distribution of H 2 O 2 , Ca 2+ , and K + during stomatal movement were observed. Results : When exogenous H 2 O 2 was applied, Ca 2+ increased and K + decreased in guard cells, while both ions increased in subsidiary cells, leading to stomatal closure. After DPI treatment, Ca 2+ decreased and K + increased in guard cells, but both Ca 2+ and K + decreased in subsidiary cells, resulting in open stomata. Exogenous CaCl 2 increased H 2 O 2 and reduced K + in guard cells, while significantly increasing them in subsidiary cells and causing stomatal closure. After LaCl 3 treatment, decreased and K + increased in guard cells, whereas both H 2 O 2 and K + decreased in subsidiary cells and stomata became open. Conclusions : These results indicated that H 2 O 2 and Ca 2+ were correlated positively with each other and with K + in subsidiary cells during stomatal movement. Both H 2 O 2 and Ca 2+ in subsidiary cells promote an inflow of K + , indirectly regulating stomatal closure.