The significance of biodegradable methylglycinediacetic acid (MGDA) for iron and arsenic bioavailability and uptake in rice plant

Figures & data

Figure 1. Chemical structure of methylglycinediacetic acid.

Table 1. Composition of modified Murashige and Skoog (MS) pre-experimental* and experimental solutions used in the experiment

Nutrients	Pre-experimental solution (mg L^−1)	Experimental solution (mg L^−1)
Potassium nitrate (KNO3)	1900	1900
Ammonium nitrate (NH4NO3)	1650	1650
Calcium chloride (CaCl2 · 2H2O)	440	440
Magnesium sulfate (MgSO4 · 7H2O)	370	370
Dipotassium phosphate (K2HPO4)	170	170
Ferrous sulfate heptahydrate (FeSO4  · 7H2O)	27.8	50**
Manganese sulfate (MnSO4 · 5H2O)	22.3	22.3
Zinc sulfate (ZnSO4 ·  7H2O)	8.6	8.6
Boric acid (H3BO3)	6.2	6.2
Potassium iodide (KI)	0.83	0.83
Disodium molibdate (Na2MoO4  ·  2H2O)	0.25	0.25
Copper sulfate (CuSO4 · 5H2O)	0.025	0.025
Cobalt chloride (CoCl2  · 6H2O)	0.025	0.025
Arsenic (As)	–	6.0 µM
Methylglycinediacetic acid (MGDA)	–	0.1–5 mM
pH	6.5	8.5
*The pre-experimental solution was used to grow the rice (Oryza sativa L.) seedlings prior to use them in the experiment. Arsenic and MGDA were added only to the experimental solution.
**FeSO4 ·  7H2O was used as iron (Fe) source instead of sodium-iron(III)-ethylenediaminetetraacetic acid (NaFe^3+-EDTA), and its concentration in the experimental solution was 50 mg L^−1.

Figure 2. Biomass of rice (Oryza sativa L.) seedlings at pH between 6 and 11 after growing in Murashige and Skoog (MS) nutrient solution for a total of 3 weeks. Values are mean ± SD (n = 3). Different letters indicate significant differences (p < 0.05) between treatments for roots (lower case) or shoots (upper case).

Figure 3. Shoot biomass of rice (Oryza sativa L.) seedlings grown at different concentrations of methylglycinediacetic acid (MGDA) in nutrient solution. The age of rice seedlings was 3 weeks from germination. Values are mean ± SD (n = 3). Different letters indicate significant differences (p < 0.05) between treatments.

Figure 4. The influence of methylglycinediacetic acid (MGDA) concentrations on iron (Fe) concentrations on root surfaces (a), in roots (b), and in shoots (c) of rice seedlings (Oryza sativa L.). Fe concentrations in roots were measured after removing Fe from root surfaces by citrate–bicarbonate–ehylenediaminetetraacetic acid (CBE) solution. Values are mean ± SD (n = 3). Different letters indicate significant differences (p < 0.05) between treatments.

Figure 5. Arsenic (As) uptake in rice (Oryza sativa L.) seedlings as influenced by methylglycinediacetic acid (MGDA; 0 and 1.0  mM). Arsenic concentrations in roots were measured after removing As from root surfaces by citrate–bicarbonate–ethylenediaminetetraacetic acid (CBE) solution. Values are mean ± SD (n = 3). Different letters indicate significant differences (p < 0.05) between treatments.