Physiological and Biochemical Responses of Perennial Ryegrass Mixed Planting with Legumes under Heavy Metal Pollution

In artificially controlled pot experiments,perennial ryegrass was mixed with other leguminous plants(white clo-ver and alfalfa)and treated with lead,zinc and cadmium(337 mg·kg^(-1),648 mg·kg^(-1),and 9 mg·kg^(-1),respectively)to simulate compound pollution conditions.The results showed that the concentrations of heavy metals,trans-port factors,and bioconcentration factors in mixed planting of ryegrass decreased compared with those in mono-culture.Regardless of whether heavy metal pollution was introduced,mixed planting increased the aboveground and underground biomasses of ryegrass.The different mixed planting treatments had no significant impact on the chlorophyll concentration of ryegrass.The mowing time,mixed planting treatment,and heavy metal treatment had impacts on antioxidant and osmotic adjustment substances,and there were some interactions.The mixed planting treatment did not significantly affect glutathione concentration,cysteine concentration,or nonprotein thiol.Mixed planting generally increased the nitrogen and phosphorus concentrations of ryegrass while reducing the stoichiometric ratio of carbon,nitrogen,and phosphorus.These results suggest that the mixed planting of ryegrass with legumes promotes the growth of ryegrass in the presence of high concentrations of heavy metal pollution.However,it does not enhance the ability of ryegrass to remediate heavy metal pollution in the soil.

Arbuscular mycorrhizal fungi inoculation and exogenous indole-3-acetic acid application induce antioxidant defense response to alleviate cadmium toxicity in Broussonetia papyrifera

Cadmium(Cd)contamination in soil poses a huge threat to plants even at low concentrations;Broussonetia papyrifera has great potential in remediation of soil heavy metal contamination.However,whether exogenous indole-3-acetic acid(IAA)application and arbuscular mycorrhizal fungi(AMF)have synergistic effects on Cd tolerance of B.papyrifera remains unclear.To investigate the effects of AMF inoculation and IAA application on the tolerance of B.papyrifera to Cd stress,two experiments were conducted:the first to investigate the effect of AMF(Rhizophagus irregularis)inoculation on the tolerance of B.papyrifera to Cd stress and the second to investigate the combined effects of AMF inoculation and IAA application on the tolerance of B.papyrifera to Cd stress.Parameters including endogenous hormone concentration,antioxidant defense response,malondialdehyde(MDA)content,and gene expression related to antioxidant enzyme system and hormone were measured.The results indicated that AMF alleviated Cd toxicity of B.papyrifera by reducing MDA content and improving antioxidant enzyme activities and Cd absorption capacity.Furthermore,the combination of AMF inoculation and IAA application had a synergetic effect on the tolerance of B.papyrifera to Cd stress through upregulating BpAUX1 and BpAUX2,which might contribute to root growth and root xylem synthesis,and by upregulating BpSOD2 and BpPOD34 to enhance the antioxidant enzyme system.This work provides a new insight into the application of IAA in the remediation of soil Cd pollution by mycorrhizal plants.

Research Progressing of Present Contamination of Cd in Soil and Restoration Method

Cadmium is one of the important contaminative heavy metals. Due to continuous increase of discharge of Cadmium in industrial and agriculture production, cadmium contamination of soil is more and more serious day by day, which seriously threatens ecological environment and human health. Treatment of cadmium becomes an urgent issue and research hot point. At present, remedy for cadmium pollution upon soil mainly are physical restoration, chemical restoration and biological restoration, also there are measurements by means of adding external source matter and selecting low-Cd-accumulation varieties so as to reduce cadmium harm upon agricultural products. This article introduces in detail the resource of cadmium in soil and the present condition of cadmium pollution in farmland and processing of domestic cadmium pollution research, processing stage of domestic and foreign research of restoration of cadmium polluted soil as well as various peculiarities of repair methods. Finally, the expectation of research is discussed.

Spatio-temporal variation prediction on Cd content in the rice grains from Northern Zhejiang Plain during 2014–2019 based on high-precision soil geochemical data

In recent years,Cadmium(Cd)pollution has been found in many soil geochemical surveys in Northern Zhejiang Plain,a crucial rice production area in East China,located in the lower Yangtze River.To more scientifically predict the effect of soil Cd on rice safety,data including 348 local rhizosphere soil-rice samples obtained in 2014 were used in this study.Meanwhile,we extracted 90% of random samples as variables based on soil Cd content(Cd_(soil)),soil organic matter(SOM),pH,and other indicators.In addition,a multivariate linear model for rice Cd content(Cd_(rice))prediction based on the indicators including the soil Cd content(Cd_(soil)),the soil organic matter(SOM),and the pH value.The remaining 10%of random samples were used for the significance test.Based on the 2014 soil Cd content(Cd_(soil14))and the 2019 soil Cd content(Cd_(soil19)),this study predicted Cd content in 2019 rice grains(Cd_(p-rice19)).The spatio-temporal variation of Cdrice was contrasted in the five years from 2014 to 2019,and the risk areas of rice safety production were analyzed using the Geographical Information System(GIS).The results indicated that compared with the actual Cd content in 2014 rice grains(Cdrice14),the proportion of Cd_(p-rice19),which exceeded the standard food level in China(GB2762-2017),increased dramatically.Moreover,the high-value areas of Cdrice distributed greatly coincidentally in these two years.By contrast,both Cdrice and Cdsoil show very different spatial scales.The dominant reason is the distribution of the local canal systems,indicating that economic activities and agricultural irrigation may aggravate the risk of soil Cd pollution,thus threatening safe rice production.