| Iris ensata is a kind of perennial herb with strong cold tolerance and high ornamental value.It is widely used in northeastern landscaping.In recent years,with the accelerating urban construction,copper(Cu)and cadmium(Cd)pollution has become more and more serious,which has also caused certain impacts on related garden plants.Therefore,strengthening the research of Iris ensata under copper and cadmium pollution can provide scientific basis for greening of mining areas and polluted waterfront In this study,we used the Iris ensata as the experimental materiall.The Iris ensata was treated with different concentrations of copper,cadmium and their combined stress,and the seed germination,seedling growth and physiological characteristics were measured to comprehensively analyze its ability to resist copper and cadmium.The results are as follows:1.Effects of different treatments on seed germination of Iris ensata:When the single copper concentration was lower than 50mg/L and the cadmium concentration was lower than 5mg/L,it would promote the germination of the seeds or have no significant effect on the germination of the seeds,while the copper concentration was higher than 50mg/L or the cadmium concentration was higher than 5mg/L,it would inhibit the germination of the seeds.Copper and cadmium had strong inhibitory effect on the growth of primary roots of Iris ensata,and there was almost no root growth when the single treatment concentration of copper was 400mg/L.The treated leaves turned yellow,indicating that poisoning has appeared in the Iris ensata.When cadmium was treated at a concentration of 200 mg/L,its growth was also affected,and some of the seedling roots turned red.Under the combined stress of copper and cadmium,the low concentration of 5-lmg/L(copper-cadmium concentration)combined treatment promoted the germination of the seeds of Iris ensata,and its germination were severely inhibited with increasing concentration.It was stronger than single stress inhibitions.2.Effects of different treatments on the growth Indexes of Iris ensata seedlings:When the treatment of copper less than 50mg/kg,the seedlings showed normal growth state,the leaf length and leaf width were basically larger than the control group in the 50d,and with the treatment concentration increased,part of the leaf tip turned yellow and the leaves had red spots.When the single treatment concentration of cadmium was 0.3mg/kg,the leaf length were longer than those in the control group and Iris ensata growed normally.When the combined stress concentration was 50-0.3mg/kg(copper-cadmium concentration),the leaf length and leaf width were lower than the control group.It was inhibited by certain treatments.Each treatment had an inhibitory effect on the root length of Iris ensata,and the roots grew slowly.In severe cases,the roots became red and soft,but no plant death occurred at the end of the experiment.Therefore,Cu50 and Cd0.3 had a certain degree of promoting effect on Iris ensata,and other groups had certain damage,and the degree of damage to the root was higher than that of the leaf,The degree of damage caused by compound stress was higher than that of single stress.3.Effects of different treatments on physiological indexes of Iris ensata seedlings:With the increase of treatment time and concentration,the relative conductivity,malondialdehyde(MDA),soluble sugar and free proline content of leaves increased gradually.When the concentration was 50,100mg/kg and the concentration of cadmium was 0.3 and 1mg/kg,the activity of SOD,POD and CAT in leaves of Iris ensata increased with the prolongation of treatment time,but decreased when the concentration of copper higher than 400mg/kg or the cadmium concentration higher than 30mg/kg after 30 days,and the difference was significant(P<0.05).the chlorophyll,Pn,Gs and Tr content decreased with the increase of treatment concentration,and Ci increased.Looking at the growth morphology and physiological indicators of the Iris ensata,the growth was best at a concentration of 50mg/kg copper.In general,it is recommended that Iris ensata can be planted in a heavy metal environment(Soil 5.5?pH?6.5)with a copper concentration of less than 50mg/kg,a cadmium concentration of less than 0.3mg/kg,and a compound concentration of less than 50-0.3(Cu-Cd mixed concentration)mg/kg. |
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