Arbuscular mycorrhizal fungus (Glomus aggregatum) influences biotransformation of arsenic in the rhizosphere of sunflower (Helianthus annuus L.)

Figures & data

Table 1 Chemical properties of the soil collected from Shimane Prefecture, Japan, as affected by sterilization

Parameter		Non-sterile	Sterile
pH (1:5, water)		5.69	5.82
Electrical conductivity (1:5)	dS cm^−1	4.11	4.13
Total carbon	g kg^−1	5.36	5.22
Total nitrogen	g kg^−1	0.483	0.457
Available P (Bray 1)	mg kg^−1	6.03	8.09
Water soluble P (1:100)	mg kg^−1	14.3	18.2
Total As	mg kg^−1	620	619
1.0 mol L^−1 HCl-extractable As	mg kg^−1	6.50	8.30
Water Soluble (WS) As
Total WS-As	mg kg^−1	0.190	0.260
WS-As^III	mg kg^−1	0.114	0.137
WS-As^V	mg kg^−1	0.076	0.123
MMAA	mg kg^−1	nd	nd
DMAA	mg kg^−1	nd	nd
TMAO	mg kg^−1	nd	nd
“Free” Fe-oxide	g kg^−1	2.30	2.26
nd, not detected.

Figure 1  Design of the rhizobag system.

Table 2 Normalized As toxicity scores, AM root length colonized, dry matter yield, and the As and P concentrations in shoots and roots of sunflower grown in As contaminated soil†

Treatment	Normalized toxicity scores	Root length colonized (%)	Dry matter		As concentration		P concentration
			Shoots (g plant^−1)	Roots (g plant^−1)	Shoots (mg kg^−1)	Roots (mg kg^−1)	Shoots (mg kg^−1)	Roots (mg kg^−1)
+AM/NS	1.06 b	35 b	1.86 b	0.39 a	1.56 c	85.6 a	2210 a	1150 a
–AM/NS	1.53 a	7 c	1.46 b	0.20 b	2.16 a	67.7 ab	1330 b	814 b
+AM/S	0.66 b	42 a	2.74 a	0.55 a	1.36 c	78.6 ab	2210 a	1210 a
–AM/S	1.38 a	0 d	2.04 b	0.42 a	1.87 b	61.7 b	1420 b	856 b
^†Means within the same column followed by the same letter(s) are not significantly different from each other based on Tukey's test at P < 0.05.

Table 3 Contents of As and P, ratios of shoot content to root content, and ratios of P content to As content in the shoots and roots of sunflower plants grown on As-contaminated soil†

Treatment	As			P			P/As		Shoot uptake^‡
	Shoots (µg plant^−1)	Roots (µg plant^−1)	Shoots/ roots	Shoots (µg plant^−1)	Roots (µg plant^−1)	Shoots/ roots	Shoots	Roots	As (µg g^−1rdw)	P (mg g^−1rdw)
+AM/NS	2.90 a	33.5 a	0.09 b	4.10 b	0.45 b	9.35 a	1420 a	14 a	7.40 b	12.0 a
–AM/NS	3.16 a	13.5 b	0.24 a	1.95 c	0.16 c	12.20 a	624 b	12 a	15.90 a	10.7 a
+AM/S	3.72 a	43.0 a	0.09 b	6.06 a	0.66 a	9.24 a	1640 a	16 a	6.80 b	12.3 a
–AM/S	3.83 a	26.1 ab	0.15 ab	2.89 bc	0.36 b	8.54 a	753 b	14 a	9.07 ab	8.1 a
^†Means within the same column followed by the same letter(s) are not significantly different from each other based on Tukey's test at P < 0.05.
^‡Calculated as shoot uptake divided by root dry weight (rdw).

Figure 2  Amounts of water soluble P (WS-P) in the soil collected from the rhizosphere and bulk compartments of the rhizobag system. Data are mean ± standard deviation for three replications. Bars on the top right indicate the least significant differences (LSD) for comparison between treatments (left), between compartments (middle) and between any pair of data (right) at P < 0.05. +AM, plus arbuscular mycorrhizal fungus inoculation; –AM, without arbuscular mycorrhizal fungus inoculation.

Figure 3  Amounts of (A) water soluble (WS)-AsIII and (B) WS-AsV in the soil collected from different compartments of the rhizobag. Bars on the top right indicate the least significant differences (LSD) for comparison between treatments (left), between compartments (middle) and between any pair of data (right) at P < 0.05. +AM, plus arbuscular mycorrhizal fungus inoculation; –AM, without arbuscular mycorrhizal fungus inoculation.

Figure 4  Amounts of (A) water soluble dimethylarsinic acid (WS-DMAA) and (B) water soluble trimethylarsine oxide (WS-TMAO) in the soil collected from different compartments of the rhizobag. Bars on the top right indicate the least significant differences (LSD) for comparison between treatments (left), between compartments (middle) and between any pair of data (right) at P < 0.05. +AM, plus arbuscular mycorrhizal fungus inoculation; –AM, without arbuscular mycorrhizal fungus inoculation.

Figure 5  (A) Acid phosphatase and (B) dehydrogenase activity in the soil collected from different compartments of the rhizobag planted with sunflower. Bars on the top right indicate the least significant differences (LSD) for comparison between treatments (left), between compartments (middle) and between any pair of data (right) at P < 0.05. +AM, plus arbuscular mycorrhizal fungus inoculation; –AM, without arbuscular mycorrhizal fungus inoculation; INF, iodonitrotetrazolium formazan.