Cd Concentration In Plant Tissues Research Articles

Cadmium Accumulation in Sunflower Plants Influenced by Arbuscular Mycorrhiza

In order to investigate the cadmium (Cd) accumulation patterns and possible alleviation of Cd stress by mycorrhization, sunflower plants (Helianthus annuus L.) were grown in the presence or absence of Cd (20 μmol L−1) and inoculated or not inoculated with the arbuscular mycorrhizal fungus (AMF) Glomus intraradices. No visual symptoms of Cd phytotoxicity were observed; nevertheless, in non-mycorrhizal plants the presence of Cd decreased plant growth. The addition of Cd had no significant effect on either mycorrhizal colonization or the amount of extra-radical mycelia that was produced by the AMF. Cd accumulated mainly in roots; only 22% of the total Cd absorbed was translocated to the shoots, where it accumulated to an average of 228 mg Cd kg−1. Although the shoot-to-root ratio of Cd was similar in both the AMF inoculated and non-inoculated plants, the total absorbed Cd was 23% higher in mycorrhizal plants. Cd concentration in AMF extra-radical mycelium was 728 μg g−1 dry weight. Despite the greater absorption of Cd, mycorrhizal plants showed higher photosynthetic pigment concentrations and shoot P contents. Cd also influenced mineral nutrition, leading to decreased Ca and Cu shoot concentrations; N, Fe and Cu shoot contents; and increased S and K shoot concentrations. Cd induced guaiacol peroxidase activity in roots in both mycorrhizal and non-mycorrhizal plants, but this increase was much more accentuated in non-mycorrhizal roots. In conclusion, sunflower plants associated with G. intraradices were less sensitive to Cd stress than non-mycorrhizal plants. Mycorrhizal sunflowers showed enhanced Cd accumulation and some tolerance to excessive Cd concentrations in plant tissues.

Cadmium in soil–rice system and health risk associated with the use of untreated mining wastewater for irrigation in Lechang, China

Using untreated mining wastewater to irrigate paddy field around Lechang lead/zinc mine in the upper Wu Jiang River basin, Guangdong Province, southern China, caused cadmium transport onto paddy soils and crop contamination. This study characterized Cd concentration in soil–rice system irrigated with the wastewater mentioned above and evaluated potential ecotoxicological hazardous risk to humans and animals. All soil and plant samples were analyzed using atomic absorption spectrophotometer (AAS; Model 3030, Perkin-Elmer, USA). The results showed that all soil samples were extremely contaminated by cadmium, soil Cd occurred primarily in the residual fraction. Using synthetic stomach fluid simulating gastrointestinal condition, result showed that 28.4% of the total soil cadmium concentration would be ingested in human/animal gastrointestinal tract. Mean Cd concentrations in plant tissues (DW) ranged from 0.24 (unpolished rice) to 8.21 μg g −1 (root). Dietary intake of cadmium through contaminated rice consumption was calculated to be 2.2 and 1.5 μg kg −1 body weigh per day for a 60-kg adult and 40-kg child, respectively. The values were much higher than the provisional tolerable daily intake (PTDI; 1 μg kg −1 body weight by FAO/WHO in 1989). Present results indicated that the paddy soil–rice system irrigated with untreated mining wastewater in Lechang lead/zinc mine area was heavily contaminated by Cd and would pose a human/animal health risk through Cd mobility in the food chain. Therefore, local mine wastewater should be decontaminated before being irrigated to surrounding farmland.

Production of low-molecular weight thiols as a response to cadmium uptake by tumbleweed ( Salsola kali)

Tumbleweed ( Salsola kali) is a desert plant species that has shown to be a potential Cd hyperaccumulator. In this study, the production of low-molecular weight thiols (LMWT) as a response to cadmium stress was determined in hydroponically grown seedlings exposed to 0, 45, 89, and 178 μM Cd 2+. The treatment of 89 μM Cd 2+ was tested alone and supplemented with an equimolar concentration of ethylenediaminetetraacetic acid (EDTA) to determine the effect of this chelating agent on Cd uptake and thiols production. After 6 days of growth, the Cd concentration in plant tissues was determined by using inductively coupled plasma/optical emission spectroscopy (ICP/OES). Results indicated that Cd uptake by plants was concentration-dependent. Plants treated with 178 μM Cd 2+, had 10 ± 0.62, 9.7 ± 1.4, and 4.3 ± 0.83 mmol Cd kg –1 dry tissue in roots, stems, and leaves, respectively. The production of thiols was dependent on Cd concentration in tissues. According to the stoichiometry performed, plants treated with Cd concentrations up to 178 μM produced 0.131 ± 0.02, and 0.087 ± 0.012 mmol SH per mmol Cd present in roots and stems. In leaves, the production of thiols decreased at the highest Cd concentration tested. Thus, up to 89 μM Cd in the media, 0.528 ± 0.004 mmol SH per mmol Cd in leaf tissues were produced. EDTA equimolar to Cd reduced both Cd uptake and thiols production. Catalase activity (CAT) (EC 1.11.1.6) was significantly depressed at the lowest Cd concentration. None of the conditions tested affected biomass or plant elongation.

Induction of cadmium-binding peptides in sorghum

Hydroponic experiments with sorghum were carried out in nutrient solution medium, under controlled environmental conditions for different periods of time. Cadmium (Cd ) was added at a final concentration of 0.1, 1 and 10 mg dm−3. The effect of time and cadmium concentration on the content of thiolic groups (TSH) in the “cell sap” of sorghum tissues are discussed in relation to plant resistance/tolerance to metal stress. The increase in Cd level in the nutrient solution was associated with a higher total Cd accumulation in the plant (root and shoot), which produced a significant enhancement on the thiolic groups content. Furthermore, higher Cd concentrations in plant tissues induced not only an increase in sulphur-rich compounds but also enhanced the binding capacity of these compounds.

Cadmium uptake by floating macrophytes

Cd uptake capacity of a group of floating macrophytes ( Salvinia herzogii, Pistia stratiotes, Hydromistia stolonifera and Eichhornia crassipes) was determined in outdoors experiments during the lowest temperature period of the year. Although all studied species were highly efficient in the Cd uptake, Pistia stratiotes was selected for further research because of its superior performance and its higher average relative growth rate. Cadmium% removal by Pistia stratiotes was greater in the first 24 h of the experiments (63, 65, 72 and 74% of the added Cd for 1, 2, 4 and 6 mg Cd l −1, respectively). After 31 days of growth, Pistia stratiotes efficiently removed Cd at the studied concentrations. The macrophyte was able to keep its capacity for Cd removal even though some toxicity symptoms appeared at 4 and 6 mg Cd l −1. The greater the initial concentration, the greater Cd bioaccumulation rates. The increase of Cd concentration in plant tissues occurred especially in roots and was linearly related to the quantity of Cd added. Cd sorption by roots is faster than translocation to the plant aerial part and it occurs mainly during the first 24 h.