Figure 11.

Schematic Model of Observed Cytosolic ABA, Ca²⁺, H⁺, Cl^–, and Redox Changes in Arabidopsis Roots.

ABA treatment and uptake did not induce rapid cytosolic Ca²⁺ or H⁺ concentration changes. By contrast, IAA, glutamate (Glu), ATP, PEP1, and GSSG triggered cytosolic Ca²⁺, H⁺, and Cl^– concentration changes with high spatiotemporal overlap. For comparison of the obtained data see also Supplemental Figure 8 and Supplemental Movies 4, 5, 14, and 16. Compared to 20 µM H₂O₂ and 1 mM GSSG, redox changes in response to Glu, ATP, and PEP1 were very low and below the threshold required to trigger ROS-induced Ca²⁺ signaling. Regions with highest response are color coded according to the adjacent response curves that were taken from the corresponding main figures (ABA, H₂O₂, and E_GSH, black; Ca²⁺, magenta; H⁺, yellow; Cl^–, cyan). For a better illustration of cytosolic H⁺ and Cl^– concentration increases, the PA-17 and E²GFP response curves were inverted. Horizontal arrows indicate cytosolic concentration increase or decrease and vertical arrows the direction of the response. EZ, elongation zone; MEZ, meristematic zone; MZ, maturation zone; RC, root cap.