| Polycyclic aromatic hydrocarbons(PAHs)have strong teratogenicity,carcinogenicity and mutagenicity.PAHs in the environment can be transmitted into human body through food chain and cause harm to human health.Therefore,the migration process of PAHs in soilplant has attracted great attention of many researchers,and its pollution to crops has also aroused people’s interest in research.However,there are few reports on the short-distance transport characteristics and mechanisms of PAHs in crop roots.In this paper,wheat,corn,soybean and castor are taken as the research objects,and the relationship between the apoplastic characteristics of wheat,corn and soybean roots and the transportation of phenanthrene in roots is studied through hydroponic experiments.Time dynamics and concentration effects and their kinetic and thermodynamic processes of the absorption of phenanthrene in apoplast and symplast of maize and soybean root;Phenanthrene concentration and pH value in xylem sap of maize,soybean and castor treated with different phenanthrene concentrations;Influencing factors of phenanthrene concentration in corn and castor xylem sap.The purpose of this paper is to reveal the short-distance transport characteristics and mechanism of PAHs in crop roots and provide scientific theoretical guidance for ensuring the safe production of agricultural products and phytoremediation of contaminated soil.The main research results of this paper are as follows:(1)The phenanthrene absorption in wheat,maize and soybean roots is related to the characteristics of the apoplast of each crop.For crops of different seedling ages,the cation exchange capacity(CEC)of the apoplast of roots will change.With the increase of CEC exchange capacity of the apoplast of roots,the phenanthrene absorption of each crop apoplast and symplast will increase.As a complex dynamic structure,the cell wall of plant roots changes the content of each component as the plant grows and develops.The absorption of phenanthrene in the root apoplast of three crops decreases with the increase of pectin and lignin content,and increases with the increase of cellulose and hemicellulose content.(2)Under three different temperatures(15℃,25℃ and 35℃),the absorption of phenanthrene in maize and soybean root apoplast and symplast increased with the increase of treatment time.The absorption rate reached the fastest in 0-8 h,and decline in 8-36 h.The absorption gradually reached a flat level.Under the same temperature condition,the absorption of phenanthrene by maize and soybean root apoplast was different from that by symplast,and the absorption of phenanthrene by symplast was greater than that by apoplast.Under different temperature conditions,the absorption of phenanthrene by the same crop reached the maximum at 35℃ and the minimum at 15℃.The time dynamics of the absorption amount of the two crops root apoplast and symplast phenanthrene conform to Elovich equation.The activation energy for the absorption of phenanthrene was positive and it was an endothermic process.The activation energy of the symplast is smaller.Under different phenanthrene concentrations,the absorption of phenanthrene by maize and soybean root apoplast and symplast increased with the increase of phenanthrene concentration,and the absorption rate was faster when phenanthrene concentration was lower in the medium..The response to temperature of two crops was 15℃<25℃<35℃.(3)Active transportation participates in xylem loading of phenanthrene The phenanthrene concentration in corn,soybean and castor xylem sap increased with the increase of phenanthrene concentration in the medium,and the pH showed a slowly decreasing trend,and the pH under each concentration treatment was lower than that of the blank control group.The loading mechanism of PAHs in plant xylem is affected by metabolic inhibitors,low temperature and dissolved oxygen.They are have inhibitory effects on phenanthrene concentration in xylem sap.Under different phenanthrene concentrations,the inhibitory rate of sodium vanadate on xylem sap is between 19.80%and 25.82%.However,the inhibitory effect of low temperature on phenanthrene concentration in xylem sap showed different inhibitory rates under different crops and different phenanthrene concentrations.Under hypoxia,the inhibition rate is about 20%.In summary,the short-distance transportation of PAHs in crop roots is affected by many factors,including crop species,temperature,time,PAHs concentration,inhibitor,dissolved oxygen,etc. |
PDF Full Text Request