| With urbanization, industrialization and rapid development of agriculture, soil heavy metal pollution is worsening, has been a threat to human health and quality of life, and heavy metals Cu,Cd is toxic soil several metal contaminants, its governance more difficult than large.In this paper, Hemerocallis hybridus’ Stella de Oro’ and Hemerocallis middendorffii as experimental material, pot simulation methods to study the Cu,Cd single and combined stress on Hemerocallis spp. growth conditions, such as growth and development of the whole process of morphological, and physiological properties of chlorophyll, as well as the impact of antioxidant enzymes such as Cu,Cd difference in two kinds of Hemerocallis spp. in vivo uptake and accumulation patterns and transport characteristics, discusses the heavy metals Cu and Cd stress on Hemerocallis hybridus’ Stella de Oro’ and Hemerocallis middendorffii, with a view to screening Cu,Cd repair plant research foundation soil heavy metal pollution, provide a frame of reference for the selection of areas polluted by green plants. The main findings are as follows:1.Studies have shown that different levels of Cu,Cd stress makes Hemerocallis hybridus’ Stella de Oro’ and Hemerocallis middendorffii are subject to different degrees of impact, at low concentrations Cu,Cd(Cu≤100mg·kg-1, Cd≤1mg·kg-1) stress treatment Hemerocallis hybridus’ Stella de Oro’ and Hemerocallis middendorffii are in good growing state, only a small portion of the blade tip area appears Mortality, chlorosis symptoms; in high concentrations Cu,Cd(Cu400-1200mg·kg-1, Cd20-100mg· kg-1) stress treatment, with the stress concentration and extension of time, most of the leaves appear wilted, yellow, dry spots, leaves, plant height and leaf thinning phenomena such as growth weakens.In a single Cu,Cd stress, compared with the control, the growth index of Hemerocallis hybridus’ Stella de Oro’ and Hemerocallis middendorffii of(height, leaf number, leaf length, leaf width, root length, fresh weight, dry weight, etc.) at low concentrations Cu,Cd(Cu≤ 100mg·kg-1, Cd≤1mg·kg-1) has a corresponding promote stress, as Cu,Cd concentration(Cu400-1200mg· kg-1, Cd20-100mg·kg-1) elevated, and these indicators are showing a declining trend(P <0.05). This is due to the heavy metal element is Cu, although essential for plant growth, but excessive heavy metals Cu,Cd and impedes their growth, and therefore the presence of "low concentration of the stimulating effect and high concentration of the inhibitory effect" phenomenon. Stress in single Cu(Cu1200, Cd100) treatment, at different time(7, 8, 9, 10 month),Hemerocallis hybridus’ Stella de Oro’ and Hemerocallis middendorffii root dry weight to a minimum, Hemerocallis hybridus’ Stella de Oro’ root dry weight decreased as the CK 63.89%, 35.96%, 50.17%, 51.12%, 65.74%, 46.23%, 53.47%, 54.31%; Hemerocallis middendorffii root dry weight decreased to 45.52% of CK, 55.15%, 58.15%, 66.51%, 40.14%, 40.91%, 44.77%, 47.07%. Therefore, from the change of biomass of 2 species of Hemerocallis spp., at high concentration(Cu1200mg·kg-1, Cd100mg·kg-1) treatment inhibited the growth, at the same time, heavy metals Cu, Cd single and combined stress effect on 2 kinds of Hemerocallis spp. roots than shoots.Cu-Cd composite stress, with the increase of compound concentration(100/0.3-1200/100 mg·kg-1), compared with CK, the growth index of Hemerocallis hybridus’ Stella de Oro’(plant height, leaf number, leaf length, Ye Kuan, root length, fresh weight, dry weight) decreased(P<0.05), and the growth indexes of Hemerocallis middendorffii(plant height, leaf number, leaf length, Ye Kuan, root length, fresh weight, dry weight) decreased trend, turning points in the Cu-Cd concentration of 100/0.3 mg·kg-1 composite. The heavy metals of Cu, Cd single and combined stress, the 2 kinds of Hemerocallis spp. can grow, but the growth status of Hemerocallis middendorffii is better than Hemerocallis hybridus’ Stella de Oro’.2.In a single Cu, Cd stress, low concentrations of Cu, Cd(Cu≤100mg·kg-1, Cd≤1mg· kg-1) pollution, pigment content and SOD activity of Hemerocallis hybridus’ Stella de Oro’ and Hemerocallis middendorffii than the control CK slightly increased, but with the Cu,Cd(Cu400-1200mg·kg-1, Cd20-100mg·kg-1) concentration increased, the index also showed a gradual decline trend(P<0.05), the protective enzyme system of Hemerocallis spp. reactive oxygen scavenging capacity was inhibited; while the chlorophyll a/b, the activity of POD with Cu,Cd concentration increased(P<0.05), the effects of Cu,Cd stress on 2 kinds of Hemerocallis spp. chlorophyll b than that of chlorophyll a, POD enzymes play in Hemerocallis spp. the effect is greater than SOD enzyme,in the high concentration of stress, 2 kinds of Hemerocallis spp. showed strong self- adjustment ability. It shows that for low concentration of Cu,Cd promoting effect and high Cu concentration inhibitory effect. 2 species of Hemerocallis spp. photosynthesis is inhibited, the photosynthetic rate(Pn), transpiration rate(Tr), stomatal conductance(Gs) and intercellular CO2 concentration(Ci) of single Cu,Cd increased with the increase of stress concentration showed a declining trend, change trend of similar, presenting a "Shuangfeng" curve morning and afternoon, the 10: 00 and 16: 00 is 2 times the peak time, valley in the afternoon about 14: 00, showed a typical plant "noon break" phenomenon. The intercellular CO2 concentration(Ci) of "W" on the 1 day, showed morning and evening high variation trend and noon rebound, indicated factors restricting 2 species of Hemerocallis spp. photosynthesis is mainly caused by non stomatal. 1 days in different Cu,Cd concentration stress on Hemerocallis hybridus’ Stella de Oro ’ and Hemerocallis middendorffii of photosynthetic rate were: Cu100> CK > Cu400 > Cu800 > Cu1200, Cd1 > Cd0.3 > CK > Cd20. Transpiration rate at Cu concentration of 100 mg·kg-1, Cd concentration of 0.3 kg-1 and 1 mg· kg-1 is slightly higher than that of the control.Cu-Cd composite stress, with the increase of compound concentration(100/0.3-1200/100 mg·kg-1), compared with the control CK, Hemerocallis hybridus’ Stella de Oro’ each physiological photosynthetic indexes(chlorophyll content, SOD activity, net photosynthetic rate(Pn), transpiration rate(Tr), stomatal conductance(Gs) and intercellular CO2 concentration(Ci)) decreased(P<0.05), and Hemerocallis middendorffii physiological indexes(chlorophyll content, SOD activity, net photosynthetic rate(Pn), transpiration rate(Tr), stomatal conductance(Gs) and intercellular CO2 concentration(Ci)) increases firstly and then decreases,turning point in the Cu-Cd composite concentration 100/0.3 mg·kg-1. POD and SOD are 2 kinds of protective enzymes is very important in the antioxidant defense system, an important role for Ros in the clearance of Hemerocallis spp., its activity at low Cu,Cd concentrations increased, while Cu,Cd concentration reaches a certain value, POD activity increased, SOD in the treatment of later showed a declined trend. The heavy metals of Cu, Cd single and combined stress, the physiological indexes of Hemerocallis middendorffii is better than Hemerocallis hybridus’ Stella de Oro ’.3.The results show that, under the stress of single Cu, compared with CK, with the increase of Cu concentration, Cu content in shoots and roots of Hemerocallis hybridus’ Stella de Oro’ and Hemerocallis middendorffii increased significantly(P<0.05), Cu content in roots was greater than that of aboveground. Cu-Cd composite stress, Cu content in shoots and roots of the plants increased with the increase of Cd concentration in soil, and the content of Cu is the same at the site of the Cu-Cd composite stress is higher than that of Cu single stress, in the composite treatment concentration was 1200/100 mg·kg-1, Hemerocallis hybridus’ Stella de Oro’ and Hemerocallis middendorffii aboveground and root Cu content is the single Cu content of 133.83%, 106.82% and 108.65%, 118.30%(P<0.05). Show that exogenous Cd intervention to promote the absorption of Cu by the Hemerocallis, produced a synergistic effect of Cd on Cu absorption.Cd single stress changes of Cu and Cu content under stress of single similar trend(P< 0.05). Compared with the control, Cd content in shoot and root increased with Cd concentration, and root > shoot. The content of Hemerocallis hybridus’ Stella de Oro’ and Hemerocallis middendorffii in single Cd stress absorption of Cd, is much higher than Cu-Cd composite stress, In the composite treatment concentration was 1200/100 mg·kg-1, Cd content in shoot and root accumulation is a single Cd content of 74.59%, 82.98% and 66.66%, 84.83%(P<0.05). Exogenous Cu intervention significantly inhibited the Cd uptake of Hemerocallis middendorffii, which Cu produce the antagonism of the absorption of Cd. Research shows, Hemerocallis hybridus’ Stella de Oro’ and Hemerocallis middendorffii can effectively remove Cu,Cd in soil, heavy metal pollutants, on Cu, Cd single and combined stress showed different tolerance and removal effect, But Hemerocallis middendorffii heavy metal removal effect is better than Hemerocallis hybridus’ Stella de Oro’.Comprehensive analysis shows that, in low concentration Cu,Cd stress Hemerocallis hybridus’ Stella de Oro’ and Hemerocallis middendorffii have a certain ability, that can enhance the ability to adapt to the stress of heavy metals through self adjustment mechanism, and even low concentrations of Cu,Cd can promote the growth of 2 species of Hemerocallis spp.; but at the high concentration of stress, stress intensity is over 2 species of Hemerocallis spp. tolerance, the adjusting ability is limited, the plant begins to suffer damage, but no mortality occurred. This experiment has proved that, Hemerocallis hybridus’ Stella de Oro’ and Hemerocallis middendorffii has the ability of certain anti heavy metal Cu,Cd, and Hemerocallis middendorffii in growth, physiology and enrichment outperformed Hemerocallis hybridus’ Stella de Oro’, therefore, in a land of heavy metal Cu and Cd pollution growth potential of plants were more reasonable choice,and can absorb large quantities of heavy metals enrichment of Cu, shows that it can adapt to the heavy metal pollution to the soil, can provide germplasm resources for Cu,Cd contaminated land greening application in breeding of stress resistant varieties of flowers. |
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