Soil Anti-Scouribility Enhanced by Plant Roots

The magnitude of soil anti-scouribility depends on the physical condition of the soil. Plant roots can greatly enhance soil stability and anti-erodibility. A scouring experiment of undisturbed soil was conducted to investigate the effects of roots on soil anti-scouribility and its distribution in the soil profile. At the end of each erosion test, plant roots were collected from soil samples and root surface area was calculated by means of a computer image analysis system (CIAS). Root surface area density (RSAD), the surface area of the roots per unit of soil volume, was related to soil anti-scouribility. More than 83% of root surface area was concentrated in the 0 - 30 cm soil layer. Soil anti-scouribility increased with an increase in RSAD and the value of intensified soil anti-scouribility (ΔAS) can be expressed by exponential equations, depending on the plant species. These equations were ΔAS =9.578 6 RSAD0.8321 (R2= 0.951) for afforested Pinus tabulaeformis Carr, ΔAS = 7.808 7 RSAD0.7894 (R2= 0.974) for afforested Robinia pseudoacacia L., and ΔAS= 9.256 6RSAD0.8707 (R2= 0.899) for Bothriochloa ischemum L.

Intercropping of Sonchus asper and Vicia faba affects plant cadmium accumulation and root responses

The cadmium(Cd)pollution of farmland soil is serious in the world.The present study investigated the effects of intercropping Vicia faba and the hyperaccumulator Sonchus asper on the Cd accumulation and root responses(morphology and secreted organic acids)of plants grown on soil from a mining area in Yunnan Province,China,under different Cd stress levels(0,50,100,and 200 mg kg-1).Intercropping increased the biomass of both S.asper and V.faba,as well as the Cd accumulation and Cd transfer coefficient from roots to shoots of S.asper,but decreased those of V.faba in the 200 mg kg-1Cd treatment.The Cd concentrations in roots,shoots,and grains from intercropped V.faba plants were positively correlated(P<0.05)with the N,N-diethyl phenylacetamide-extractable Cd content in soil.In the 50 mg kg-1Cd treatment,intercropping decreased citric and malic acids in root secretions of S.asper.Intercropped V.faba secreted more citric,oxalic,acetic,and malic acid compared with S.asper.Intercropping also increased root length and root surface area of both S.asper and V.faba.At 50 mg kg-1Cd,root length for S.asper was higher than that at 0 mg kg-1Cd,whereas V.faba roots had significantly decreased length and mean diameter.Intercropping of S.asper and V.faba is suggested as an in situ phytoremediation strategy of Cd-contaminated soils and may improve the food quality of V.faba.

Modelling sulphate-enhanced cadmium uptake by Zea mays from nutrient solution under conditions of constant free Cd^(2+) ion activity

A controlled hydroponic experiment was undertaken to investigate Cd uptake in relation to the activity of Cd species in solution other than the free ion （Cd^2＋） by maintaining a constant Cd^2＋ activity under variable SO4^2- and Cl^- concentrations exposed to maize （Zea mays vat. Cameron） plants. The objectives of these experiments were： （1） to distinguish and quantify the different uptake rates of free and inorganic-complexed Cd from nutrient solution, and （2） to model the uptake of Cd by maize with a Biotic Ligand Model （BLM） in a system which facilitates the close examination of root characteristics. Results of the current experiments suggest that, in addition to the free ion, CdSO4^0 complexes are important factors in determining Cd uptake in nutrient solution by maize plants. Higher nominal SO4^2- concentrations in solution generally resulted in a greater Cd accumulation by maize plants than predicted by the Cd^2＋ activity. A better integration of the complete dataset for the 3 harvest times （6, 9 and 11 days after treatment） was achieved by including consideration of both the duration of Cd exposure and especially the root surface area to express Cd uptake. Similarly, the fit of the BLM was also improved when taking into account exposure time and expressing uptake in terms of root morphological parameters.