The Growth And Physiological Characteristics Of Populus Tomentosa Hybrid Clones Seedlings

In this paper, eight Populus tomentosa hybrid clones whose type was 1(2)—0 were selected for the materials,clones seedling growth and physiological characteristics between different clones were studied, including the height, diameter, specific leaf weight, biomass, leaf anatomical features, water consumption features,leaf water physiological characteristics,stomatal exchange properties,carbon isotopic composition, the activity of antioxidant enzymes and the content of malondialdehyde and so all, it will provide a theoretical basis for the Populus tomentosa seedlings practice. Main conclusions are as follows:(1)The growth law of Populus tomentosa clones seedlings typed 1(2)—0 was that from June to August was a fast growing period, and they entered the late growth stage in August mid-late, high growth and diameter growth pattern were similar, specific leaf weight was gradually increased with the growth trend, May and June were the promotion of seedling growth and the critical period developing high-quality seedlings.so well watering, fertilization and pest control measures shoud be taken on the seedlings during this period.Clones BL5, S86 growed faster, its height respectively 149.30,161.50cm, diameter respectively 1.24,1.12cm,10 months, specific leaf weight respectively 99.44,95.80g-m-2, biomass, respectively 62.96g,59.739g, they were larger than other clones.(2) The moisture content of clones 42,50 leaves in three periods were large, clones BT17,BL5 were relatively small. The leaf water lossing rates of clones S86,83,42 were smaller than other clones. The water lossing rate when the leaves departed from the body 8 to 12 hours was the best identification for leaf water holding capacity. Populus tomentosa hybrid clone seedlings on water consumption and water consumption rate curve showed a "single peak" type, the peak occurred at 12:00-14:00, clone S86, 83,42 water consumption rate was lower during the day; studying on eight clones seedlings had shown that the maximum day water consumption rate was 1.62 to 1.78 times than the average water consumption rate. With the increased of drought stress, the difference of different clones water consumption rate was less and less, eight clones water consumption rate was very close in severe drought stress. Under drought stress, drought resistance of clone 83 was stronger than the others.(3)Theδ13C values of leaves, branches clones 83,1316 were higher, and they had the higher water use efficiency. Different periods of clonesδ13C values and instantaneous leaf water use efficiency were significantly positive correlation, the coefficient reached 0.766 in July,0.872 in August,0.675 in September, indicating that 513C values was a certainly feasible index to judge water use efficiency of Populus tomentosa, and in the seedling vigorous growth period August,it can get more reliable results for the breeding. (4)Tested eight clones of the light saturation point (LSP) were above1200μmol·s-1,the light of the potential contracts of clones 83,42 leaves were larger; net photosynthetic rates of clones S86,50 were higher, the transpiration rates of clones 1316, BT17 were smaller. Under drought stress, clones 26, S86 had smaller decrease in net photosynthetic rate, transpiration rates of clones 42, S86 decreased greatly.(5)With the decline of leaf water potential, drought stress increased, leaf MDA content of eight clones increased. peroxidase, superoxide dismutase, catalase three kinds of protective enzymes activities are higher than normal water conditions.The changes of 3 protective enzyme activity in different periods of drought stress were different; three kinds of protective enzymes were in synergy.