Addition of straw from hyperaccumulator plants to cadmium-contaminated soil increases cadmium uptake by loquat seedlings

Soil water stress alters differentially relative metabolic pathways affecting growth performance and metal uptake efficiency in a cadmium hyperaccumulator ecotype of Sedum alfredii

Modeling plants for biomass production and metal uptake from surrounding environment is strongly dependent on the moisture content of soil. Therefore, experiments were conducted to find out how soil moisture affects the phenotypic traits, photosynthetic efficiency, metabolic profile, and metal accumulation in the hyperaccumulating ecotype of Sedum alfredii (S. alfredii). A total of six water potential gradients were set: 0 ~ -15 kPa (T1), -15 ~ -30 kPa (T2), -30 ~ -45 kPa (T3), -45 ~ -60 kPa (T4), -60 ~ -75 kPa (T5), and -75 ~ -90 kPa (T6). Different water potential treatments had a significant effect on plant growth and metal uptake efficiency. Compared to T3, T2 was more effective in promoting plant growth and development, with an increase in biomass of 23% and 17% in both fresh weight (FW) and dry weight (DW), respectively. T2 and T3 had the highest cadmium (Cd) content in the shoot (280.2 mg/kg) and (283.3 mg/kg), respectively, whereas T1 had the lowest values (204.7 mg/kg). Cd availability for plants in the soil was affected by moving soil moisture cycles. Changes in soil moisture that were either too high or too low compared to the ideal soil water content for S. alfredii growth resulted in a significant reduction in Cd accumulation in shoots. Tryptophan, phenylalanine, and other amino acids were accumulated in T5, whereas only tryptophan and phenylalanine slightly increased in T1. Sugars and alcohols such as sucrose, trehalose, mannitol, galactinol, and mannobiose increased in T5, while they decreased significantly in T1. Interestingly, in contrast to T1, the two impaired metabolic pathways in T5 (galactose and starch metabolism) were identified to be glucose metabolic pathways. These findings provide scientific information (based on experiments) to improve biomass production and metal uptake efficiency in hyperaccumulating ecotype of S. alfredii for phytoremediation-contaminated agricultural fields.

Multivariate optimization of ultrasound-assisted liquid-liquid microextraction based on two solvents for cadmium preconcentration prior to determination by flame atomic absorption spectrometry

A method based on ultrasound-assisted emulsification liquid-liquid microextraction (USAEME) for cadmium determination by flame atomic absorption spectrometry (FAAS) was developed in this work. USAEME is based on the use of the mixture of 1,2-dichloroethane and trichloroethylene as an acceptor phase, 2-(2-bromo-5-pyridylazo)-5(diethylamino)phenol (Br-PADAP) as a chelating reagent, and ethanol as a dispersive solvent. The composition of the extraction and dispersive solvents, the volume of the extraction solvent, pH, and the sonication time were optimized using the multivariate strategy. The limits of detection and quantification calculated under optimum conditions were, respectively, 0.39 and 1.33 μg L-1, and the obtained enrichment factor was 21. The accuracy was tested by the analysis of certified reference materials. The method was applied to cadmium determination in bivalve mollusks, water, and urban wastewater from Pontal Bay, Bahia, Brazil. The proposed method is simple, fast, and efficient, and uses small amounts of organic solvents for the determination of cadmium.

Effects of intercropping accumulator plants and applying their straw on the growth and cadmium accumulation of Brassica chinensis L

Two pot experiments were conducted to study the effects of intercropping cadmium (Cd) accumulator plants (Stellaria media (L.) Villars, Cardamine hirsuta, Cerastium glomeratum Thuill, and Galium aparine L.) and applying their straw on the growth and Cd accumulation of Brassica chinensis L. Intercropping with four accumulator plants reduced the biomass, water content, and photosynthetic pigment content of B. chinensis compared with monoculture. Intercropping with accumulator plants increased the Cd content in the roots and shoot of B. chinensis, and the translocation factor (TF), root bioconcentration factor (root BCF), and shoot bioconcentration factor (Shoot BCF) increased. The soil pH decreased and the soil available Cd content increased by intercropping. Thus, intercropping with four accumulator plants can promote the Cd uptake of B. chinensis. The straw of four accumulator plants reduced the biomass, water content, and photosynthetic pigment content of B. chinensis compared with the control. The straw of S. media and C. hirsute increased the Cd content in the roots and shoots of B. chinensis, TF, root BCF, and shoot BCF. The straw of C. glomeratum and G. aparine decreased the Cd content in the roots and shoots of B. chinensis, TF, root BCF, and shoot BCF. The soil pH increased and the soil available Cd content decreased by application of straw. Thus, the straw of C. glomeratum and G. aparine can reduce the Cd uptake of B. chinensis.

Cadmium-accumulator straw application alleviates cadmium stress of lettuce (Lactuca sativa) by promoting photosynthetic activity and antioxidative enzyme activities

The effects of application of straw derived from cadmium (Cd) accumulator plants (Siegesbeckia orientalis, Conyza canadensis, Eclipta prostrata, and Solanum photeinocarpum) on growth and Cd accumulation of lettuce plants grown under Cd exposure were studied. Treatment with straw of the four Cd-accumulator species promoted growth, photosynthesis, and soluble protein contents and enhanced the activities of peroxidase in leaves of lettuce seedlings. The biomass of shoot of lettuce from high to low in turn is the treatment of C. canadensis straw > S. photeinocarpum straw > S. orientalis > E. prostrata > Control. The Cd content in edible parts (shoots) of the lettuce plants was significantly decreased in the presence of straw from the Cd-accumulator species, except the presence of the straw of E. prostrata. And, the greatest reduction in Cd content in shoots was 27.09% in the S. photeinocarpum straw treatment compared with that of the control. Therefore, application of straw of S. orientalis, C. canadensis, and S. photeinocarpum can promote the growth of lettuce seedlings, and decrease their Cd accumulation, when grown in Cd-contaminated soil, which is beneficial for production of lettuce safe for human consumption.