| Langfang Poplars were also called Jilang Poplars. Langfang Poplar No. 1,2,3 were selected from 382 hybrid compounds,28143 clones,with 16 years studied by Langfang acdaemy of agricultural and forestry sciences.The paper studied the different adaptability on external shape,growth,the abilities of cold and salt resistance with the nursery stock of Langfang Poplars and their parent species Shan Haiguan poplar.The results are summarized as below.(l)Langfang Poplars had the character of Fast-growing and high yield in compared with their parent species Shan Haiguan Poplar.Their survival rate was high if the materials of cuttage had suitable length and width.The film for covering earth had promotive effect.(2) The abilities of cold resistance on four clones were tested with the ralative leakage of electrolytes,ralative leakage of K+,protective enzyme activity,content of MDA and soluble protein ,chlorophyll fluorescence induction kinetics parameters such as qn, qp, Fv/Fo and Fm/Fo.By fuzzy subordinate index method,all of indexes were evaluated comprehensively.It was concluded that Langfang Poplars had higher abilities of cold resistence than Shan Haiguan Poplar and Langfang Poplar No.3 had the highest abilities of cold resistance in Langfang Poplar clones.(3)The ability of salt resistance on four colnes were tested with items of growth,physiology and bio-chemistry to salt stress.The clones" growth including leaf growth, height and dry matter accumulation was intensely influenced by salt stress. The growth factors decreased rapidly with salt consistence increasing,but it was defferent in extent.The leaf area and height were the most sensitive to salt stress,especially under higher salt stress,which led to above ground of plant more sensitive to salt stress than below ground.The ratio of root/stem+leaf went up with the salt consistence increasing and this was benefited to enhancing the clones" salt resistance.The plant photosynthesis parameters such as pn,Tr,Rs,Ci and chlorophyll content such as chlorophyll a,chlorophyll b,chlorophyll a+b and a/b were measured.It was found that the chlorophyll a,chlorophyll b,chlorophyll a+b of Langfang Poplars clones increased at first and then declined with the salt consistence increasing,however chlorophyll a,chlorophyll b,chlorophyll a+b of Shan Haiguan Poplars declined with the salt consistence increasing; chlorophyll a/b of four clones declined with the salt consistence increasing.The four clones' pn Tr Rs Ci had significant diurnal change law,and pn and Tr diurnal change basically presented double peak curve.the changelaw of Rs and Ci presented negative interrelation. With the salt consistence increasing, pn and Tr declined and Rs and Ci increased,but change extent of clones was defferent. Langfang Poplar No.3 had the highest resistence to salt stress,secondary Langfang Poplar No.2, then Langfang Poplar No. 1 and Shan Haiguan Poplar was the lowest.The enzyme activity,membrane permeability and the content of free proline were studied under salt stress.The results indicated that SOD and POD activiy increased under low salt stress ,but decreased under high salt stress. With the salt consistence increasing, membrane permeability of root,stem and leaf were increased,but the change extent was defferent,among organs, root's was the largest and leafs was the less. With the salt consistence increasing, contents of free proline of root ,stem and leaf were increased,but stem's was the highest,root"s was the less.Under the salt stress, the ion content of clones and the characteristics of transportation and distribution of K+, Na+, Ca2+, Mg2+were analyzed and the differences among clones were compared.The result showed that the Na+ content in the plant increased as the solution concentration increased, but the increasing range was different in different tissues, the Na+ content in root was the highest and the content in stem was higher than that in leaf .As the salt stress increased, the K+ content decreased in the root and stem. The change of the K+ content in lea...
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