| The soil heavy metal Cd pollution problem is becoming more and more serious,and phytoremediation is widely studied as a new green remediation technology,and the selection of ultra-enriched plants is the key to the implementation of phytoremediation.Celosia cristata L.,an annual herb of the genus Amaranthaceae,is named after the corolla shaped like a cockscomb.It is planted and cultivated throughout the country and is a common horticultural flower.Most plants in the family Amaranthaceae have a strong ability to accumulate Cd.Celosia cristata L.is specially selected as the test material,and the physiological response and enrichment characteristics of Celosia cristata L.to heavy metal Cd have not been reported.Therefore,this experiment conducted a preliminary study on the Cd tolerance characteristics of Celosia cristata L.at different growth stages,and discussed the ability of Celosia cristata L.to tolerate Cd stress and its physiological response,and provided basic data for plant detoxification mechanisms and phytoremediation research.Hydroponics and pot culture were used to treat seeds of Celosia cristata L.and Celosia cristata L.at different growth stages with different concentrations of Cd stress,and the tolerance of seeds to Cd during germination and the physiological response characteristics of Celosia cristata L.at different stages to Cd stress were analyzed;using inductance the coupled plasma mass spectrometer measured the content of mineral elements and Cd in different parts of Celosia cristata L.under Cd stress,and preliminary explored the interaction between Cd and mineral elements(Fe,Cu,Zn,Mg,P,S,K).The influence of its absorption and migration;The effect of changes in the DNA methylation level of Celosia cristata L.on the mechanism of cadmium stress tolerance under Cd stress was analyzed by MSAP technology.The main findings are as follows:1.Different concentration of Cd stress(5?100mg/L)treatment of Celosia cristata L.seeds,found that low concentration of Cd stress treatment will increase the germination potential,germination rate,germination index of seeds,and show the phenomenon of "low promotion and high suppression".But under Cd stress,the root growth of Celosia cristata L.seedlings was significantly inhibited,the root length was lower than the seedling length,and the root system was severely damaged,which led to the obstruction of nutrient absorption and the gradual decrease in biomass.2.When different concentrations of Cd(50?200mg/kg)are stressed for 30 days,the content of Chla is 0.398?0.926mg/g,the content of Chlb is 0.183?0.518mg/g,and the content of Car is0.057?0.185mg/g,photosynthetic with the prolongation of Cd stress time,the pigment content showed a significant decrease;the osmotic regulator(soluble protein,PRO content)showed a significant increase in different ranges.When Cd stress 30 d,the overall soluble protein content reached the highest 1.678?3.329mg/g.For different periods of stress(10d,20 d,30d),the PRO content was all at a Cd concentration of 200mg/kg,and the highest content was 35.514?g/g,59.642?g/g,45.542?g/g;when Cd stress was 30 d,the activity of SOD was significantly reduced,and its activity was as high as 75.201U/g.When the concentration of Cd was 50 mg/kg,the activity of POD was as high as 2391.333U/g.The activity of POD was significantly increased.The activity of CAT is 18.080?543.520nmol/min/g under different periods of stress(10d,20 d,30d),and APX activity is 95.253?291.713nmol/min/g,CAT and APX activity first increased and then decreased significantly;GR activity was significant decrease,the activity is 26.8?123.3nmol/min/g under different periods of stress(10d,20 d,30d),resulting in the continuous increase of GSSG content,the highest content is 20.168nmol/g,and it promotes the increase of GSH,Cys and NPT content.Increase,GSH content is 0.347?1.282?mol/g,Cys content is 13.484?70.372?mol/g,NPT content is0.142?2.277?mol/g,which improves the chelating ability of cadmium ions and reduces the toxicity to cells.3.Cd stress inhibited the absorption of Cu,Zn and P in the roots of Celosia cristata L.,and promoted the accumulation of Fe,Mg,S and K in the roots of Celosia cristata L.It shows that Cd stress inhibits or promotes the absorption of Cu,Zn,Fe,Mg,S,K,and P to varying degrees.Among them,the size of the biological absorption coefficient is S>K>Mg>P>Fe>Zn>Cu,and the sulfur absorption content is relatively high,which may be related to the synthesis of sulfhydryl compounds.4.Under different concentrations(50?200mg/kg)of Cd stress,the DNA methylation level of Celosia cristata L.changes as the total methylation rate(MSAP),which increases by 59.7%,84.2%,132.0%,and 181.4%,respectively,compared with the control,when the Cd concentration is50?200mg/kg,the re-methylation rates are 12.72%,15.54%,18.60%,20.63%,and the demethylation rates are 8.38%,6.78%,5.39%,4.18%,respectively,indicating that Cd stress caused an overall increase in its methylation level,and the main re-methylation pattern changes.5.With the increase of the Cd stress concentration,the Cd enrichment in the roots of Celosia cristata L.was the most,while the above-ground parts(stems,leaves,flowers)were less in content,but the Cd content in different parts showed a significant increase.Among them,the enrichment coefficient reaches a maximum of 1.47 when the Cd concentration is 100mg/kg,and the transfer coefficient reaches a maximum of 1.79 when the Cd concentration is 50mg/kg,and the enrichment coefficient under high concentration(200mg/kg)Cd stress and the transfer coefficient is greater than1,indicating that Celosia cristata L.is a potential Cd-rich plant and can be used as a test material for soil Cd pollution remediation. |
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