Cd and Zn accumulation characteristics and tolerance mechanism of Rosa 'Spectra'
Simulated pot pollution was adopted with Rosa'Spectra'as the research object to further study the enrichment characteristics and tolerance mechanisms of Cd and Zn in Chinese rose.The biomass and physiological indexes,as well as the mechanism of heavy metal accumulation and transport of Rosa'Spectra'were studied under the single stress of Cd content(0,25,50,100 mg·kg-1,and 200 mg·kg-1)and Zn content(0,500,1 000,1 500 mg·kg-1,and 2 000 mg·kg-1).The results showed that:the treatment of low Cd and Zn content promoted the growth of Rosa'Spectra'.With an increase in content,the growth of Rosa'Spectra'was inhibited,but no death was caused.Cd and Zn absorbed by the Rosa'Spectra'were mainly accumulated in the root system,with contents of 68.48 mg·kg-1 and 918.74 mg·kg-1 respectively.Cd predominately existed in NaCl-extracted forms,accounting for 25.19%-60.80%,while Zn primarily existed in HAc-extracted and deionized water forms,accounting for 20.20%-46.65%,12.69%-29.33%respectively.With the increase of treatment gradients,both Cd and Zn treatment groups increased the proportion of extraction states with low toxicity,so as to weaken the toxicity of Cd and Zn in plant roots.Cd and Zn enrichment in the roots were mostly in the cellular debris fraction,accounting for 55.01%-77.38%,52.35%-63.17%respectively,and followed by the metal-rich granule and heat stable protein fractions.With the increase in treatment gradients,Cd and Zn in the root of Rosa'Spectra'showed characteristics of transferring to soluble components.Under Cd and Zn treatment,black particulate matter appeared in root cells of Rosa'Spectra',and the density increased with increasing treatment gradients.The functional groups binding Cd and Zn on the root cell wall are hydroxyl and amino groups.Research shows that root absorption restriction,cell wall fixation,vacuoles segregation,conversion of Cd and Zn into less active forms,and the use of hydroxyl and amino groups on the cell wall to provide binding sites may be significant mechanisms for Rosa'Spectra'to cope with Cd and Zn stress.
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