Effects Of Lead And Cadmium Stress On Germination And Seeding Morphology Of Wheat And Identification Of The Tolerance (Resistance) For American Wheat Germplasm

In order to study the tolerance of different wheat germplasm resources to different heavy metals,to screen out the wheat germplasm with strong tolerance,further to explore its physicochemical properties and lay the foundation for selecting heavy metal resistant varieties,we analysed the(resistance)tolerance of 15 wheat varieties,and then,the result was used to classify the 103 American wheat germplasm resources based on their resistance.From the influence of heavy metal lead and cadmium stress on wheat germination and seedling growth,we knew that the responses of the 15 wheat cultivars to each tolerance index were different under different concentrations of heavy metal stress.Through the data analysis of the germination potential of the third day,the germination rate of the seventh day and the root and shoot length of the seedlings for different varieties,we can concluded that :(1)In the germination stage,the effects of Pb and Cd were not significant,There was no significant difference between germination potential and germination rate in the third day and the seventh day,but the germination rate was slightly higher than that of germination potential in the third day.(2)For the treatments with different concentrations of lead,when the lead concentration was 500mg/L,the difference of the germination rate among the cultivars was the most significant.With lead concentration increasing,seedling growth was inhibited,and the stress of root growth was significantly stronger than that of the shoot in the seedling stage.When the lead concentration was 300mg/L,the difference in root length between wheat varieties was the most significant.The difference in seedling shoot between varieties was the most significant in the minister in the 500mg/L lead solution,but not as good as 300mg/L root significantly.When the concentration of lead reached 500mg/L,the difference of the shoot length was the most significant among different varieties,but the difference was not so significant as the root length in 300mg/L.(3)Cadmium is more toxic than lead.The germination potential and germination rate under the Cadmium stress were similar to those of lead stress,and the germination potential was slightly higher than the germination rate.When the cadmium concentration was 160mg/L,the difference in the germination rate between varieties was the most significant.Cadmium toxicity significantly strengthened with the germination going.The root length had significantly decreased when using 20mg/L cadmium,and the absolute value of the stress index of M5 had reached by 51%.The root growth was completely inhibited in 160mg/L.By contrast,the root stress was more serious than the shoot.When the cadmium concentration was 80mg/L,the shoot had the most obvious difference among the different varieties.But at 20mg/L,the most significant difference was occurred in root,while it was not so significant as that at 80mg/L.However,the difference in the upper root can be reflected in the differences between the wheat varieties at the time of cadmium concentration was 80mg/L.When screening of 103 American wheat varieties for resistance to heavy metals,the followings should be paid attention: Firstly,we should calculate the membership function values of the germination rate of each variety in lead 500mg/L and the root length of seedling at 300mg/L.we should also calculate the subordinate function on the germination rate in the concentration of cadmium 160mg/L and the upper root of each species in 80mg/L at the same time.And then the average value of the two membership functions value was used for the comprehensive evaluation of the test materials.Finally,it was concluded that M87,M73,M1,M55,M7,M42,M15 had stronger tolerance to lead;M91,M7,M15,M73,M55 M42 had stronger tolerance to cadmium.That is to say,TRP11L-8、IDRD09-4、Dup09L-plot406、NIN09L-18、Dup09L-plot468、Dup09L-plot697 and Dup09L-plot494 had stronger tolerance to lead;TRP15L-24、Dup09L-plot468、Dup09L-plot494、IDRD09-4、NIN09L-18、Dup09L-plot697 had stronger tolerance to cadmium.