| Cadmium(Cd)as the most highly toxic,great harm organism,one of the most polluting elements,not only affect the normal growth and development of the plant,falling crop yields and quality,but also easy to migrate through the soil plant system and enter the food chain,a serious threat to human health.As one of the best plants in urban landscaping,ground-cover chrysanthemum has the characteristics of large biomass,long flowering period,strong adaptability and extensive management.But at present,the research on the resistance of chrysanthemum is mainly concentrated on the drought resistance,salt resistance and light shading treatment,and there is little research on its resistance to cadmium.Therefore,it is of great significance to select cadmium resistant varieties from ground-cover chrysanthemum and apply them to urban landscaping.The seedlings of 14 species of chrysanthemum were used as the materials to study the growth of the seedlings under the cadmium concentration of 20 mg/L,the cadmium content in the aboveground and underground parts,and the transfer and enrichment factor of cadmium,and to screen the variety of ground covered chrysanthemum with less cadmium or less cadmium absorption.The C,F,G and I varieties were subjected to 0?10?20?50?10Omg/L cadmium concentrations stress,the cadmium resistance,accumulation and transport characteristics,physiological resistance and ultrastructure were studied,which provided a theoretical basis for the study of the mechanism of Cd toxicity against chrysanthemum.The mainly research results are as follows:1 Different ground-cover chrysanthemum has a certain tolerance to cadmium stress.The cadmium content in roots and aboveground increased with the increase of the treatment concentration.Cd absorbed mainly in roots,and only a small amount of cadmium could migrate to the ground.The tolerance of different varieties of ground-cover chrysanthemum to cadmium is significantly different,in which C(Donglin Rui Xue),F(battlefield yellow flower),G(Pocket red)and I(nu 9714)have a stronger cadmium tolerance,transfer and accumulation ability.2 The aboveground dry weight of four species of ground-cover chrysanthemum was not obvious at low concentration(10,20mg/L)Cd stress(P>0.05),and decreased significantly at high concentration(P<0.05).With the increasing of cadmium concentration,the roots and aboveground cadmium content of the four species were increasing.The threshold of 10Omg/LCd was achieved,the cadmium content of the four ground-cover chrysanthemum is higher than that of 10Omg/kg,and the bioaccumulation factors is far more than 1,which has a certain characteristic of hyperaccumulator.With the increase of Cd concentration,the bioaccumulation factors of Cd of four ground-cover chrysanthemum gradually decreased,and the translocation factors of F,G and I also showed a decreasing trend,while C was on the contrary.3 The net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr)of the four species decreased significantly with the increased concentration,they all reached the threshold at 10Omg/L,while Ci increased,this indicated that the limitation of Cd treatment on the photosynthesis of ground-cover chrysanthemum might be influenced by the non-stomatal factors.The structure and function of stomata in leaves were not changed.The content of chlorophyll and chlorophyll a?b decreased significantly with the increase of cadmium concentration.Under the high concentration of cadmium stress,the largest decrease in chlorophyll content was F,followed with G,I and C varieties.I varieties had the largest reduction in chlorophyll a/b compared with C,F and G varieties.4 Cadmium stress induced the membrane lipid peroxidation in the leaves of 4 species of ground-cover chrysanthemum.With the increase of cadmium concentration,there was a positive correlation between the MDA content of leaves and the concentration of Cd stress.At low concentration(l0mg/L),the change of cadmium stress was not significant.With the increase of cadmium concentration,the content of malondialdehyde(MDA)in various varieties increased significantly.When the concentration of Cd2+is 100mg/L,it reaches the threshold,the changes of MDA were 155.56%for C,325.27%for F,173.91%for G,322,18%for I.The relative electrical conductivity of the four species was increased by Cd stress.At low concentration,the relative electrical conductivity was not significant compared with the control.With the increase of cadmium concentration,the relative conductivity of various varieties increased significantly.When Cd2+ stress concentration was 1OOmg/L,the relative electrical conductivity of C,F,G and I was 146.48%,223.66%,165.96%and 154.92%respectively.5 The activity of antioxidant enzymes in the leaves of 4 species of ground covered chrysanthemum was changed by cadmium stress.The activity of SOD,POD and CAT enzyme increased at a low concentration of cadmium,but with the increase of cadmium concentration,the change of antioxidant enzyme activity was not consistent.The POD activity of C cultivar increased first and then was lower.The threshold was reached when cadmium stress was 20 mg/L.The activity of SOD and CAT reached the threshold value at 1OOmg/L;the SOD,POD and CAT activity of F varieties reached the threshold when 50mg/L cadmium stress.After decreasing,they all reached the threshold value at 50mg/L,and POD activity reached the threshold value at 10Omg/L Cd stress.6 Changes in ultrastructure of chrysanthemum leaf cells were observed under Cadmium Stress.With the increase of cadmium concentration,the cell nucleus,chloroplast,mitochondria and cell wall were gradually increased.With the increase of cadmium concentration,the damage degree of the three major organelles of nuclei,chloroplasts,mitochondria and cell wall in the leaf cells were gradually increased.There were differences among different varieties,and the damage of organelles in F varieties was more serious.Different species were damaged in different degrees in the cell wall,cell membrane,chloroplast,mitochondria and nucleus,and the overall performance was the most severe.The overall expression of the most serious damage was mitochondria. |
PDF Full Text Request