HO, Ca, and K in subsidiary cells of maize leaves are involved in regulatory signaling of stomatal movement.

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