H2O2, Ca2+, and K+ in subsidiary cells of maize leaves are involved in regulatory signaling of stomatal movement

Abstract

The stomata of maize (Zea mays) contain a pair of guard cells and a pair of subsidiary cells. To determine whether H₂O₂, Ca²⁺, and K⁺ in subsidiary cells were involved in stomatal movement, we treated four-week-old maize (Zhengdan 958) leaves with H₂O₂, diphenylene iodonium (DPI), CaCl₂, and LaCl₃. Changes in content and distribution of H₂O₂, Ca²⁺, and K⁺ during stomatal movement were observed. When exogenous H₂O₂ was applied, Ca²⁺ increased and K⁺ decreased in guard cells, while both ions increased in subsidiary cells, leading to stomatal closure. After DPI treatment, Ca²⁺ decreased and K⁺ increased in guard cells, but both Ca²⁺ and K⁺ decreased in subsidiary cells, resulting in open stomata. Exogenous CaCl₂ increased H₂O₂ and reduced K⁺ in guard cells, while significantly increasing them in subsidiary cells and causing stomatal closure. After LaCl₃ treatment, H₂O₂ decreased and K⁺ increased in guard cells, whereas both decreased in subsidiary cells and stomata became open. Results indicate that H₂O₂ and Ca²⁺ correlate positively with each other and with K⁺ in subsidiary cells during stomatal movement. Both H₂O₂ and Ca²⁺ in subsidiary cells promote an inflow of K⁺, indirectly regulating stomatal closure.

Keywords: Ca(2+); H(2)O(2); Inhibitor; K(+); Signaling substance; Stomatal movement; Subsidiary cells.