Study On Seed Germination And Seedling Establishment Of Four Landscape Shrubs In Hohhot

In arid and semi-arid areas,due to the fragile ecological environment caused by rising temperature and water shortage,there are certain restrictions on the types of plants that can be selected in the construction of landscaping,and suitable arid landscape garden plants are yet to be developed.Therefore,by evaluating the ecological adaptability of 13 landscape shrubs,this thesis screened out 4 shrubs with excellent ecological benefits,such as Lonicera maackii,Halimodendron halodendron,Syringa wolfii and Forsythia suspensa,and studied their sexual reproduction characteristics and drought resistance.Based on this,the optimal germination condition screening experiment with different temperature,light and soaking time was designed;and the seed drought resistance was studied by the seed germination and seedling growth under different water potential conditions;the effects of different methods of breaking dormancy on the germination of dormant seeds were discussed;through the stress test in the seedling establishment stage,the drought resistance mechanism in the seedling stage was revealed.The purpose of this thesis is to deeply study and screen the propagation methods of 4 landscape shrubs,and to provide theoretical basis and technical means for their cultivation in arid and semi-arid regions.The main results are as follows:（1）Through the comprehensive evaluation of fourteen shrubs in Hohhot in terms of cold resistance,drought resistance and pest and disease resistance,According to the comprehensive index of adaptability,there were 8 kinds of excellent garden plants with the first grade score was 1.00～1.50.These plants had certain ornamental value and stress resistance,and could be used as the first choice for the construction of dry landscape garden plants.The second grade score was 1.51～2.50,and there were 5 species in this level,these plants also had good growth habit,but some of the stress resistance indicators were not strong.（2）The research on sexual reproduction technology was carried out on the screened four shrub seeds.It was found that Lonicera maackii and Halimodendron halodendron were dormant seeds.The dormancy of Lonicera maackii seeds was relieved after stratification at 4℃for 60 days.The seeds of Halimodendron halodendron have water absorption barrier of the seed coat,and were treated 98%H₂SO₄for 20min could relieve seed dormancy.（3）The optimum condition for germination of Lonicera maackii seeds was constant temperature of 15℃,which belonged to photoneutral seeds.The light or not had no effect on the germination of the Halimodendron halodendron seeds,and the optimum germination temperature was 25℃.The germination effect of Syringa wolfii seeds was good under the dark condition,and the optimum germination condition was soaked the seeds for 6 hours and then germinating at a constant temperature of 20℃.Forsythia suspensa seeds were light-insensitive seeds,and seeds were soaked for 72h and placed at20℃conducive to seed germination.（4）Germination of seeds was inhibited under drought stress.The seeds of Lonicera maackii and Forsythia suspensa could withstand moderate drought,Halimodendron halodendron and Syringa wolfii seeds could withstand low levels of drought.（5）Under drought stress conditions,the growth of four species of shrub seedlings was inhibited to a certain extent,and also showed drought responses.In terms of seedling survival rate and morphological indicators,the growth of seedlings was once favorable under 80%field water capacity,but water deficit was not conducive to its establishment.Each shrub adapted to drought by reducing membrane lipid peroxidation and regulating its own growth status,antioxidant enzyme activity and osmotic regulation substances.The stress resistance of the four shrubs was different.The membership function method was used to comprehensively evaluate the growth morphological and physiological indexes of shrub seedlings for drought resistance.The results showed that:Forsythia suspensa>Halimodendron halodendron>Syringa wolfii>Lonicera maackii.