Effect of Cd²⁺ toxicity on plant growth in plants inoculated with the AM fungus after 80 days (a: 0.5 mg kg⁻¹ Cd treatment; b: 5 mg kg⁻¹ treatment; c: 20 mg kg⁻¹ treatment) and the biomass of alfalfa for untreated plants (No AMF) and treated plants (AMF) after 25–80 days of growth in 0.5, 5 and 20 mg kg⁻¹ Cd soil (d) (0.5-M means 0.5 mg kg⁻¹ Cd treatment without AM fungal inoculation; 0.5+M means 0.5 mg kg⁻¹ Cd treatment with AM fungal inoculation).

<p>Effect of Cd²⁺ toxicity on plant growth in plants inoculated with the AM fungus after 80 days (a: 0.5 mg kg⁻¹ Cd treatment; b: 5 mg kg⁻¹ treatment; c: 20 mg kg⁻¹ treatment) and the biomass of alfalfa for untreated plants (No AMF) and treated plants (AMF) after 25–80 days of growth in 0.5, 5 and 20 mg kg⁻¹ Cd soil (d) (0.5-M means 0.5 mg kg⁻¹ Cd treatment without AM fungal inoculation; 0.5+M means 0.5 mg kg⁻¹ Cd treatment with AM fungal inoculation).</p

Arbuscular Mycorrhizal Colonization Alters Subcellular Distribution and Chemical Forms of Cadmium in <em>Medicago sativa</em> L. and Resists Cadmium Toxicity

<div><p>Some plants can tolerate and even detoxify soils contaminated with heavy metals. This detoxification ability may depend on what chemical forms of metals are taken up by plants and how the plants distribute the toxins in their tissues. This, in turn, may have an important impact on phytoremediation. We investigated the impact of arbuscular mycorrhizal (AM) fungus, <em>Glomus intraradices</em>, on the subcellular distribution and chemical forms of cadmium (Cd) in alfalfa (<em>Medicago sativa</em> L.) that were grown in Cd-added soils. The fungus significantly colonized alfalfa roots by day 25 after planting. Colonization of alfalfa by <em>G. intraradices</em> in soils contaminated with Cd ranged from 17% to 69% after 25–60 days and then decreased to 43%. The biomass of plant shoots with AM fungi showed significant 1.7-fold increases compared to no AM fungi addition under the treatment of 20 mg·kg⁻¹ Cd. Concentrations of Cd in the shoots of alfalfa under 0.5, 5, and 20 mg·kg⁻¹ Cd without AM fungal inoculation are 1.87, 2.92, and 2.38 times higher, respectively, than those of fungi-inoculated plants. Fungal inoculation increased Cd (37.2–80.5%) in the cell walls of roots and shoots and decreased in membranes after 80 days of incubation compared to untreated plants. The proportion of the inactive forms of Cd in roots was higher in fungi-treated plants than in controls. Furthermore, although fungi-treated plants had less overall Cd in subcellular fragments in shoots, they had more inactive Cd in shoots than did control plants. These results provide a basis for further research on plant-microbe symbioses in soils contaminated with heavy metals, which may potentially help us develop management regimes for phytoremediation.</p> </div

Phenanthrene uptake (mg/kg) in tall fescue roots treated by immersion in 100°C water for 5 min, compared to the control.

<p>Plant roots were exposed to phenanthrene at initial concentrations of 0–4 mg/L in aqueous solution and sampled after (a) 12 h, (b) 24 h, and (c) 48 h. Error bars represent standard deviations (SD).</p

Arbuscular mycorrhizal colonization (%) of alfalfa (<i>Medicago sativa</i> L.) exposed to 20 mg kg⁻¹ Cd in soil.

<p>Arbuscular mycorrhizal colonization (%) of alfalfa (<i>Medicago sativa</i> L.) exposed to 20 mg kg⁻¹ Cd in soil.</p

Accumulated Cd in alfalfa inoculated with <i>G. intraradices</i> after 80 days of seedling growth.

<p>Sharing a common lowercase are not significantly different in the Cd concentration in plant shoots and the same capital are not significantly different in the Cd concentration in plant roots (<i>P</i><0.05).</p

Selected physicochemical properties of the PAHs used in this study [33].

a<p>at 25°C.</p

(a) POD and (b) PPO activities in the roots of tall fescue over time.

<p>The uptake time was defined as the time frame from the immersion of plant roots in solution containing phenanthrene to the removal of plant for extraction. Error bars represent standard deviation (SD). The initial phenanthrene concentration was 1.0 mg/L.</p

Inhibition efficiency (E_enzyme, %) of ascorbic acid on (a) POD and (b) PPO activities in plant roots.

<p>E_enzyme was calculated as: E_enzyme  =  (U_c–U_AA)/U_c×100%, where U_AA and U_c represent the enzyme activities in roots grown in the presence and absence of AA, respectively. Error bars represent standard deviations (SD).</p

Inhibition efficiency (E_PHE, %) of ascorbic acid on phenanthrene degradation in plant roots as a function of time.

<p>E_PHE was calculated as: E_PHE (%)  =  (C_PHE-AA–C_PHE-c)/C_PHE-c×100%, where C_PHE-c and C_PHE-AA represent the phenanthrene concentrations in plant roots grown without and with AA, respectively. Error bars represent standard deviations (SD).</p

The proportion of Cd with a subcellular distribution in alfalfa.

<p>The proportion of Cd with a subcellular distribution in alfalfa.</p