. 2017 Apr 13;174(2):487–519. doi: 10.1104/pp.16.01949

Table IV. Predominant ion channels in the plasma membrane of guard cells and their functional characteristics.

Genetic codes relate to Arabidopsis, functional data relate to V. faba under typical guard cell ionic contents (see Table II) and external solutions of 10 mm KCl, 1 mm CaCl₂, pH 6.1, unless noted otherwise; channel currents are typical values at −200 mV (I_Cl S-type, I_K,in, I_Ca), −50 mV (I_Anion R-type), and +50 mV (I_K,out). Shorthand identifiers in parentheses cross-reference to Box 1. n.d., not determined. References are as follows: A (Schroeder et al., 1987; Blatt, 1990, 1992; Fairley and Assmann, 1991; Thiel et al., 1992, 1993; Luan et al., 1993; Obermeyer et al., 1994; Müller-Röber et al., 1995; Grabov and Blatt, 1997; Roelfsema and Prins, 1997; Forestier et al., 1998; Blatt et al., 1999; Sokolovski et al., 2008; Dreyer and Uozumi, 2011; Eisenach et al., 2012); B (Schroeder et al., 1987; Blatt, 1988b, 1999; Hosoi et al., 1988; Thiel and Blatt, 1991, 1994; Fairley-Grenot and Assmann, 1992; Thiel et al., 1992; Armstrong et al., 1995; Lemtiri-Chlieh, 1996; Roelfsema and Prins, 1997; Forestier et al., 1998; Miedema et al., 2000; Sokolovski et al., 2008); C (Keller et al., 1989; Hedrich et al., 1990; Linder and Raschke, 1992; Marten et al., 1992, 1993; Schroeder and Keller, 1992; Schmidt and Schroeder, 1994; Schmidt et al., 1995; Schwartz et al., 1995; Brearley et al., 1997; Grabov and Blatt, 1997; Pei et al., 1997; Dietrich and Hedrich, 1998; Forestier et al., 1998; Raschke et al., 2003; Negi et al., 2008; Vahisalu et al., 2008; Chen et al., 2010; Diatloff et al., 2010; Meyer et al., 2010; Sasaki et al., 2010; Geiger et al., 2011; Wang and Blatt, 2011; Mumm et al., 2013); D (Hamilton et al., 2000, 2001; White, 2000; Köhler and Blatt, 2002); E (Uehlein et al., 2003; Grondin et al., 2015; Byrt et al., 2016; Wang et al., 2016; Zhao et al., 2016).

Type	Name	Locus	Function	No.	γ	G_max	I_V	E_rev	δ	v_1/2	Activation voltage	Activation Time	Deactivation Time	Ion Selectivity	References
				cell⁻¹^*	pS	mS cm⁻²	µA cm⁻²	mV		mV	mV	t_1/2 in s	t_1/2 in ms
I_K,in (KAT)	KAT1	AT5G46240	K⁺ uptake	900	4–9	0.3–0.4¹	−50 to 120^f	−70	1.5–1.9^f	−176 to −224	<−100	0.3–0.5	50–100	K⁺>Rb⁺>NH₄⁺	A
	KAT2	AT4G18290		−2,000	4^b	0.3–0.5^d	−400 to −480^a			−155 to −180^d				>>Cs⁺>Na⁺
	KC1	AT4G32650				0.7–1.1^a				−186 ± 2^a
	AKT2	AT4G22200
I_K,out (GORK)	GORK	AT5G37500	K⁺ release	200	20–30	0.5–0.6^a^,^d^,^e	100–300^a^,^d	−70	1.8–2.1	0	>E_K	0.1–0.6	<30	K⁺>Rb⁺>Na⁺	B
				−800										>Li⁺>>Cs⁺

I_Anion, R-type (ALMT)	ALMT12/QUAC1	AT4G17970	Anion release, membrane depolarization	40	38–40	0.01–0.04²	−1 to 2^f	+20	−2.0–2.2^f	−58 to −45	>−100	1–2	20–50	NO₃⁻∼SO₄²⁻	C
				−200	9^a					−116^a		3.7–20^a	8.4^a	>I⁻>Br⁻
					36^c									>Cl⁻∼Mal
I_Cl, S-type (SLAC)	SLAC1	AT1G12480	Cl⁻ release	40	34–36	0.01–0.02³	−5 to 10^f	+10	<1^f	>−200	>−200	10–20	200–500	NO₃⁻>Br⁻>F⁻	C
	SLAH2	AT4G27970	NO₃⁻ release	−200										>Cl⁻>I⁻
	SLAH3	AT5G24030												>>Mal (SLAH3)
														Cl⁻>NO₃⁻ (SLAC1)
I_Ca (Ca_V)			Ca²⁺ entry	50	12^f	0.2–0.4⁴	−0.05 to 2	>+30	−0.9 to 1.2	−100 to −140	<−100	<0.05	<50	Ca²⁺∼Ba²⁺	D
				−300				+17 (CNGCs)	−1.0 to 1.2^a	−80 to −140^a				>>K⁺>Cl⁻
										−110 ± 5^d				Mg²⁺∼Ba²⁺>Ca²⁺
														(CNGCs)
Aquaporins	PIP2;1	AT3G53420	H₂O transport	n.d.										can transport Na⁺	E
	PIP1;2		H₂O₂ transport
			CO₂ transport

Arabidopsis.

Zea mays.

Xanthium strumarium.

Nicotiana tabacum.

Vicia faba.

Equivalent characteristics available in the literature for Nicotiana tabacum, Arabidopsis, and Zea mays.

pH_o 5.5 to 6.1, [Ca²⁺]_i < 200 nm.

pH_i 7.6 to 7.8, [Ca²⁺]_i < 200 nm.

⁴

[Ca²⁺]_i < 200 nm.

Calculated from whole-cell and single-channel currents recorded under equivalent conditions.