Agronomic Regulations Of Cadmium Low Accumulation In Pak Choi(brassica Rapa Ssp.Chinensis L.)for Food Safety And The Mechanisms

Food chain contamination by cadmium(Cd)is a serious health problem throughout the world.Crops grown on Cd contaminated soils have the potential to uptake of Cd,thus posing threat to human health through food chain by consuming these crops.pak choi(Brassica rapa ssp.chinensis L.)grown in Cd contaminated soil has higher capacity to accumulate Cd in its edible parts and poses potential health risks.Therefore,minimum Cd accumulation in edible parts of pak choi plants through soil amendments is a better approach that can directly affects its mobilization to avoid the human health risks attributed to Cd.In this study,Cd low and high accumulator cultivars of pak choi were selected and used from previously identified screening experiments.Different Chinese agricultural soils were used for this study on the basis of their pH and characteristics including Mollisol,Alfisol,Inceptisol and Ultisol soils.The objectives of this study were:1)to identify suitable low metal accumulator cultivars of Brassica rapa ssp.chinensis L.also known as Chinese cabbage with high yield and better quality,2)effect of different Cd concentrations on Cd low and high accumulator cultivars of pak choi and its bioaccessibility to human from ingestion of these vegetables,3)apply soil amendments to ensure food safety by immobilization and reduce Cd uptake in pak choi.1.In vitro oral bioaccessibility of Cd in Cd low Xianggangsijizhongjiaoheiyebaicai(XGSJ)and high;Changgengbaicai(CGBC)accumulation cultivars Cd accumulating affinity cultivars of Brassica rapa ssp.chinensis L.(pak choi)grown on Cd contaminated Alfisol soil was assessed.In this study,physiologically based extraction test(PBET)was chosen to assess the bioaccessibility for Cd by stimulating human digestion of plant material.The pak choi cultivars were grown on Cd contaminated soil with six different Cd concentrations(0,0.5,1.0,1.5,2.0,2.5,and 3.0 mg kg-1).It was found that Cd concentration was linearly correlated with Cd concentration in soil and its accumulation in pak choi shoots but it was assessed that the XGSJ has relatively low Cd accumulation in its edible parts and bioaccessibility to gastrointestinal tract.It was observed that Cd absorbed more in gastric phase than intestinal phase.Furthermore,the availability of Cd in the Phase II(intestinal phase)was largely determined by the mobility of Cd in the Phase I(gastric phase).2.Cadmium(Cd)is one of the inauspicious abiotic stress that not only affects the crop productivity and its growth parameters,but also have adverse affects on human health by consuming these effected crops.In the present study,to reveal growth parameters,amino acid composition and ultrastructural localization of Cd differences in response to Cd accumulation between two low and high Cd accumulating pak choi(Brassica rapa ssp.chinensis L.)cultivars,differing in Cd accumulation ability were compared.Results showed that the elevated Cd concentrations significantly reduced the plant growth rate,biomass,leaf gas exchange parameters and concentrations of amino acids as compared to respective controls of both cultivars.The electron microscopy showed that the effect of high Cd concentration on ultrastructure of leaf cells were related to damages the cell functionality,i.e.irregular cell wall,withdrawal of the cell membrane and the chloroplast structure which negatively affected the photosynthetic performance,thus leading to a significant plants growth inhibition.The energy dispersive micro X-ray spectroscopy of both cultivars leaf exposed that the cellular structure exhibited an exudates of Cd-dense material.These results suggested that both pak choi cultivars responded positively towards Cd stress whereas;the findings will be useful in uncovering the mechanisms of differential Cd-tolerance in pak choi cultivars and the way the species exposed to biotic and abiotic stresses.3.Cd contamination in soil and its movement into food chain through vegetable dietary poses a risk to human health.A pot experiment was conducted to investigate the effect of humic acid(HA)and two cultivars of Brassica rapa ssp.chinensis L.(pak choi)with differing Cd accumulation abilities on Cd accumulation in different Cd contaminated soils.The results showed that HA significantly increased soil pH and cation exchange capacity in Ultisol(acidic)and Mollisol(neutral)soils.HA was more effective in Ultisol and Mollisol soil in reducing bioavailable Cd and its accumulation in both cultivars.Low and high Cd accumulating cultivars combined with HA effectively reduced shoot Cd concentration by 7-34%and 19-35%in Mollisol soil whereas,22-34%and 11-26%in Ultisol soil,respectively.However,no such reduction was observed for Cd accumulation and bioavailability in Cd contaminated Inceptisol(alkaline)soil.Application of HA enhanced shoot dry biomass in both pak choi cultivars grown in Mollisol and Ultisol soils.Therefore,the HA amendment combination with low Cd accumulating cultivars of pak choi could be an effective method for phytostabilization and reduce health risks associated with consuming this vegetable grown in Cd contaminated acidic and neutral pH soils.4.Biochar has become eco-friendly material which is preferably using for phytoavoidation with low Cd accumulating cultivars of crops to ensure food safety in Cd contaminated soils.In this study,five biochar with different waste feedstock material were attributed for their effectiveness on essential trace metals mobility,Cd bioavailability and its accumulation in two contrasting Cd accumulating cultivars of pak choi grown in Cd contaminated Mollisol soil.The application of all biochar significantly increased plant shoot dry weight but CM and TGM biochar were more effectively increased the dry weight of both cultivars which may be due to exhibiting liming effects and the increased supply of soil nutrients.The application of TGW and CM derived biochar was more effectively decreased Cd in shoots of both cultivars as compared to other biochar.5.The organic amendment is a promising in situ phytostabilization approach for heavy metal contaminated soils to alleviate the phytotoxic effects.The aim of this study was to evaluate the effect of cow manure(CM)and its derived biochar(CMB)as a soil amendment on the Cd availability and accumulation in contrasting to Cd low accumulator(Aijiaoheiye 333)and high accumulator(Zhouyeheiyoudonger)cultivars of Brassica rapa ssp.chinensis L.(pakchoi)grown in an acidic red soil.The application of CM and CMB to Cd contaminated red soil increased the soil pH and reduced the phytoavailability of Cd.With increasing application rates of CMB,Cd accumulation in both Aijiaoheiye 333 and Zhouyeheiyoudonger cultivars of pak choi was significantly reduced.