| As a precious timber species,Erythrophleum fordii has been subjected to deforestation and environmental stress in recent decades,resulting in a sharp decline in the number of wild Erythrophleum fordii populations.It has been listed as a rare and endangered plant in China.In this study,the most common and harmful heavy metal cadmium(Cd)in the environment was selected as the test factor.The 1-year-old seedlings were used as test materials to determine and analyze the growth,physiology and nutrients of cadmium against grids.The effects of absorption,clarify the damage mechanism of heavy metal cadmium on the growth and development of Erythrophleum fordii and the tolerance mechanism of Erythrophleum fordii to heavy metal cadmium stress,in order to provide a certain theoretical basis for the cultivation and promotion of Erythrophleum fordii.The results of the study are summarized as follows:(1)The growth of seedling height,the growth of ground diameter and the accumulation of biomass in the seedlings treated with different concentrations of cadmium were consistent,showing a growing trend.During the whole experimental period,the growth of seedling height,the growth of ground diameter and the accumulation of biomass reached the maximum under the treatment of 50 mg·kg-1 cadmium,and the growth and biomass of seedling height and ground diameter of the seedlings treated with 150 mg·kg-1 cadmium concentration.The accumulation was significantly lower than the other three treatments.(2)Under the treatment of different concentrations of cadmium,the content of N in the roots,stems and leaves of the seedlings showed:leaf>root>stem,and the content of N decreased with the increase of cadmium concentration;The content of the content showed:stem>leaf>root,P content increased first and then decreased with the increase of cadmium concentration;Cu content showed trend:leaf>stem>root,Cu content in stem and leaf with cadmium concentration The increase of Mn content was:root>leaf>stem,Mn content at low concentration was significantly higher than Mn content at high concentration,and cadmium concentration in Fe,stalk and leaf of sapwood was increased.The content of Fe in different parts showed the same trend.The Mg content in the roots and stems decreased with the increase of cadmium concentration,while the Mg content in the leaves decreased first and then increased slowly with the increase of cadmium concentration.(3)Chlorophyll a,chlorophyll b,total chlorophyll content,Pn,Tr,Gs,Pmax,LCP and LSP all increased first and then decreased with the increase of Cd concentration,and reached the maximum value when Cd concentration was 50 mg·kg-1.The light compensation point increases with the increase of Cd concentration.(4)At the physiological level,in terms of the overall trend,the physiological indicators of the plant’s protective enzyme system(SOD,POD,CAT)and osmotic adjustment substances(soluble sugar and soluble protein)generally rise first with the increase of Cd concentration.The trend of the decrease was the lowest in the cadmium-free stress(control group),and reached the maximum when the Cd concentration was 100 mg kg-1.The content of MDA decreased first and then increased with the increase of Cd concentration.(5)Correlation analysis showed that there was no significant correlation between height growth and N,P contents in roots and leaves,but positive correlation between root biomass,stem biomass and leaf biomass and Cu,Mn,Fe,Mg and P contents in roots and stems.Under cadmium treatment,the growth of seedling height,ground diameter and biomass accumulation in different parts were not related to the contents of Cu,Mn and Fe in roots and stems.(6)Principal Component Analysis(PCA)showed that the eigenvalue of F1 principal component was greater than 1,and the cumulative contribution rate reached 97.35%.There was a close positive correlation between SOD activity and soluble sugar content,and the correlation coefficients were 1.13 and 1.16,respectively.It was indicated that the index SOD activity and soluble sugar content were the main physiological indicators that determine the Cd stress. |
