Table 2.

Metal ligand concentrations (malate and citrate in mM and the rest in μM) in xylem sap, leaf apoplastic fluid and phloem sap.

Species	Stress	Malate	Citrate	NA	DMA	His	PCs	References
XYLEM SAP
A. lesbiacumH	Ni					40–500S		Kerkeb and Krämer, 2003
A. serpyllifoliumH	Ni	2S	0.5S			nd		Alves et al., 2011
A. deliciosa	Fe	0.2–0.4S						Rombolà et al., 2002
A. halleriH	Cd	0.02S	0.3S			12S		Ueno et al., 2008
A. thaliana			0.06G–0.09					Durrett et al., 2007
			0.2–0.9G					Schuler et al., 2012
B. vulgaris	Fe	2–30S	0.2–5S			nd–4S		López-Millán et al., 2000
	Fe	2–14S	1–3S					Larbi et al., 2010
	Zn	0.5C–2S	0.06–0.3S					Sagardoy et al., 2011
B. carinata	Cu			64–271S		17–140S		Irtelli et al., 2009
B. junceaH	Ni					40S–50		Kerkeb and Krämer, 2003
	Cd	0.02–0.23S	0.01S–0.7					Wei et al., 2007a
B. napus	Cd	0.7–0.9S	0.5–0.6S			66S–76		Nakamura et al., 2008
H. vulgare	Fe	0.01–0.03S	<0.01–0.02S		30–450S			Alam et al., 2001
	Fe				90S			Kawai et al., 2001
	Fe	0.8–5S	0.3–1.3S					López-Millán et al., 2012
G. max	Zn	0.04S–0.9	0.08S–1.5S			26S–62S		White et al., 1981
N. glauca						10		Hocking, 1980
O. sativa		0.15–0.18G	0.05G–0.1					Yokosho et al., 2009
	Fe	0.3S–0.4GS	0.1GS–0.2S					Yokosho et al., 2009
	Fe			10–18S	10–48S			Kakei et al., 2009
	Cu		0.08	28	34			Ando et al., 2013
P. communis	Fe	0.1–3	0.03–0.5S					Larbi et al., 2003
P. persica	Fe	0.7–2S	0.05–0.8S					Larbi et al., 2003
Q. suber	Cd	1–2S	0.5–1.2S					Gogorcena et al., 2011
S. lycopersicum	Fe	0.6–4S	0.04–0.6S					López-Millán et al., 2009
	Fe		0.01–0.17S					Rellán-Álvarez et al., 2010
	Cu			ndGS–20S				Pich and Scholz, 1996
	Zn	0.06S–0.8S	<0.04S–0.3S			6S–18		White et al., 1981
	Cd	0.1–0.3S	0.01S–0.03–0.06S					Sagardoy, 2012
T. arvense	Zn	0.1–0.3S	nd			110–140S		Lasat et al., 1998
	Ni					ndS–57		Persans et al., 1999
T. caerulenseH	Zn	0.1–0.2S	nd		nd			Lasat et al., 1998
T. goesingenseH	Ni					8–18S		Persans et al., 1999
LEAF APOPLASTIC FLUID
B. vulgaris	Fe	0.7–2S	0.7–4S			<1–4S		López-Millán et al., 2000
	Fe		0.2–4S					Larbi et al., 2010
P. communis	Fe	1.6S–2	0.8–1.8S					López-Millán et al., 2001
PHLOEM SAP
C. maxima		1.6	2.1					Fiehn, 2003
L. texensis		5.5	1.1					Lattanzio et al., 2013
N. glauca						370		Hocking, 1980
O. sativa	Cu		>0.08	66	152			Ando et al., 2013
	Cd		>0.001–>0.002S	66–83S	152–176S		nd–63S	Kato et al., 2010

^SHigh or low metal supply;

^GMutant or transgenic genotypes; and

^HHyper-accumulator plant species.

Nd, not detected; NA, nicotianamine; DMA, 2'-deoxymugineic acid; His, histidine; PCs, phytochelatins.