Table VII. Activators and inhibitors of the predominant plasma membrane transporters and ion channels in stomatal guard cells (data relate to V. faba or Arabidopsis unless noted otherwise).
References are as follows: A (Blatt, 1988a; Blatt and Clint, 1989; Clint and Blatt, 1989; Lohse and Hedrich, 1992; Goh et al., 1995, 1996; Kinoshita et al., 1995; Baunsgaard et al., 1998; Kinoshita and Shimazaki, 1999; Taylor and Assmann, 2001); B (Palmgren and Harper, 1999; Geisler et al., 2000; Sze et al., 2000); C (Blatt et al., 1990b; Blatt, 1992; Fairley-Grenot and Assmann, 1992; Lemtiri-Chlieh and MacRobbie, 1994; Kelly et al., 1995; Ilan et al., 1996; Grabov and Blatt, 1997, 1999; Romano et al., 2000; Garcia-Mata et al., 2003; Dreyer and Uozumi, 2011); D (Blatt and Armstrong, 1993; Ilan et al., 1994; Lemtiri-Chlieh and MacRobbie, 1994; Miedema and Assmann, 1996; Blatt and Gradmann, 1997; Grabov and Blatt, 1997; Garcia-Mata et al., 2003; Hosy et al., 2003; Eisenach et al., 2012); E (Dietrich and Hedrich, 1998; Garcia-Mata et al., 2003; Chen et al., 2010; Diatloff et al., 2010; Meyer et al., 2010; Wang and Blatt, 2011; Xue et al., 2011; Tian et al., 2015; Wang et al., 2016); F (Hamilton et al., 2000; Pei et al., 2000; Sokolovski et al., 2008); G (Maurel et al., 2008; Verdoucq et al., 2008; Grondin et al., 2015; Byrt et al., 2016).
| Transporter/Channel Type | Activators | Inhibitors | References |
|---|---|---|---|
| H+-ATPase | Fusicoccin (K1/2 = 10 µm) | [Ca2+]i (Ki = 300 nm) | A |
| Blue light (20–100 µmol m−2 s−1 via photophosphorylation) | |||
| Auxin | |||
| Ca2+-ATPase | [Ca2+]i (K1/2 = 0.5–1 µm) | B | |
| Calmodulin (approximate molar ratio) | |||
| IK,in | [H+]o shifts v1/2 positive (+15–24 mV per pH unit) and enhances Gmax (pKa = 6.7; nh = 1) | [Ca2+]i (Ki = 330 nm; nh = 3.8–4.1) shifts v1/2 negative and suppresses Gmax | C |
| Increasing [H+]i enhances Gmax | [Al3+] (Ki = 15 µm) | ||
| [Cs+] (Ki = 0.1 mm) | |||
| IK,out | Decreasing [H+]i | Increasing [H+]i (pKa = 7.4–7.5; nh = 2–2.4) | D |
| Increasing [Ca2+]i | |||
| ABA | |||
| IAnion (R-type) | [ABA]i (K1/2 = 2.6 µm) | [H+]o slows kinetics without affecting steady-state ICl | E |
| [ATP] (K1/2 = 0.4 mm) | |||
| [Ca2+]i enhances Gmax (500–700 nm, nh = 3–4) | |||
| [H+]i enhances Gmax (pKa = 6.9, nh = 1) | |||
| ABA (Ca2+ independent) | |||
| ICl (S-type) | [ABA]cyt (K1/2 = 2.6 µm; Ca2+ dependent or independent) | Insensitive for [H+]o | E |
| [Ca2+]i enhances Gmax (K1/2 = 500–700 nm, nh = 3–4) | |||
| High [HCO3−]i increases [Ca2+]i sensitivity | |||
| High [HCO3−]i (Ca2+ independent) | |||
| ICa | ROS (H2O2) | [K+]i < < 1 mm | F |
| ABA shifts voltage sensitivity for Ca2+ gating | [Ca2+]i shifts v1/2 negative (−25–30 mV/[Ca2+]i decade) | ||
| [H+]i shifts v1/2 negative (possible −55 mV per pH unit) | |||
| Aquaporins | ABA | High [Ca2+]i | G |
| [Cd+]i, [Mn2+]i, [Sr2+]i, [Ba2+]i, [Ni2+]i | |||
| High [H+]i |