Studies On The Ecological Adaptability And Overwintering Technique Of Magnolia Wufengensis Seedlings In Beijing

Magnolia wufengensis is a rare plant species discovered in Wufeng, Hubei province of China in early 20th century. Magnolia wufengensis has huge scientific, greening and economic values, and is the only Magnolia species with pure red flowers. However, the Magnolia wufengensis seedlings introduced to Beijing always suffer severe overwintering injury.Magnolia wufengensis does not suffer overwintering injury in its origin region, and the native Magnolia species of Beijing rarely suffer it as well. Thus, the overwintering injury of Magnolia wufengensis in Beijing should be related to poor adaptability to the local environments. Firstly, this study analyzed the differences in the climatic environments between the origin region Wufeng and the introducing region Beijing, and the differences in the adaptability of the native species Magnolia denudate and Magnolia wufengensis to oversummering and overwintering environments of Beijing. Secondly, to determine the overwintering protection technology, this study analyzed the effects of winter protection methods on the cultivation environments and overwintering ability of Magnolia wufengensis. Finally, to determine the overwintering regulation technology, this study analyzed the effects of several oversummering and overwintering regulation methods on the overwintering ability of Magnolia wufengensis. The main conclusions are as follow:(1) There are significant differences in the climatic environments between Wufeng and Beijing. Compared with Wufeng, Beijing has hotter summers, colder winters, and less precipitation and more strong light in the whole year.(2) Both oversummering and overwintering adaptability of Magnolia wufengensis are poorer than those of Magnolia denudate. Compared with Magnolia denudate, Magnolia wufengensis has more significant overgrowth characteristics, poorer photosynthetic ability, slower cold acclimation and weaker cold hardiness. For both Magnolia species, chlorophyll content, soluble protein content, proline content, SOD activity and POD activity in leaves are the main biochemical factors affecting leaf photosynthetic rate; relative water content, proline content, soluble protein content, soluble sugar content, glucose content and fructose content in shoots are the main biochemical factors affecting shoot cold hardiness.(3) Winter protection can improve the temperature and moisture environments and overwintering ability of Magnolia wufengensis. By contract, open-type brooder is the optimal overwintering protection technology, by which all the seedlings pass winter without any injury; the second choice is closed-type brooder, by which more than 95% seedlings pass winter without any injury; the third choice is synthetical treatment of ground coverage and seedling package, by which more than 30% seedlings pass winter without any injury, and no seedling suffers severe injury; the fourth choice is ground coverage, by which less than 12% seedlings suffer severe injury; seedling package is much less efficient.(4) Among shading treatments,70% sunlight is the optimal treatment for improving oversummering adaptability.70% sunlight improves seedling growth characteristics and leaf morphological, photosynthetic, biochemical characteristics, by which and winter ground coverage 31.67% seedlings pass winter without any injury, and no seedling suffers severe injury.(5) Among farm manure treatments,75 g.N-1 is the optimal treatment for improving oversummering adaptability.75 g.N-1 improves seedling growth characteristics and leaf morphological, photosynthetic, biochemical characteristics, by which and winter ground coverage 20.00% seedlings pass winter without any injury, and only 1.67% seedlings suffer severe injury.(6) Synthetical treatment of 70% sunlight and 75 g.N-1 is more efficient in improving oversummering adaptability than each individual treatment. The synthetical treatment improves seedling growth characteristics and leaf morphological, photosynthetic, biochemical characteristics at higher degree, by which and winter ground coverage 58.33% seedlings pass winter without any injury, and no seedling suffers severe injury.(7) Among foliar ABA application,600 mg.L-1 is the optimal treatment for improving overwintering adaptability.600 mg.L-1 treatment promotes growth cessation, leaf senescence, bud dormany, cold hardiness, dehydration and compound accumulation during cold acclimation, by which and winter ground coverage 33.33% seedlings pass winter without any injury, and no seedling suffers severe injury.(8) Root ABA application is more efficient in improving overwintering adaptability than foliar treatment. Root ABA application not only promotes bud dormancy, cold hardiness, dehydration and compound accumulation during cold acclimation, but restrains the corresponding inverse processes during deacclimation, by which and winter ground coverage 65.00% seedlings pass winter without any injury, and no seedling suffers severe injury.(9) Only ABA application without winter protection is much less efficient for improving overwintering ability. Under natural overwintering conditions, about 90% seedlings suffer severe overwintering injury.(10) Synthetical treatment of 70% sunlight,75 g.N-1 farm manure, root ABA application of 600 mg.L-1, and winter ground coverage is the optimal overwintering regulation technology, by which 98.33% seedlings pass winter without any injury.