Study Of Six Ornamental Tree Species On Sulfur Dioxide Stress Resistance

Potted two-year-old seedlings of six ornamental tree species(Fraxinus velutina Torr., Liriodendron chinense Sarg., Koelreuteria Paniculata Laxm., Ligustrum lucidum Ait., Ailanthus altissima var.'Hongye', Clerodendrum trichotomum Thunb., Aesculus chinensis Bunge) were fumigated by sulfur dioxide with different concentrations and different time treatment in a special designed fumigation equipment. The injured symptoms, membrane permeability, content of soluble protein and MDA, activities of SOD, POD and CAT, content of chlorophyll and carotenoid, gas exchange character parameters, activity and absorption area of the root system were tested. Responses and resistant mechanisms of the tree seedlings to sulfur dioxide were studied comprehensively on the basis of data analyses by mathematical methods such as correlation analysis, clustering analysis and subordination function method etc. The main results are as the followings.1. Most tree species had the same injured symptom under long-time mild concentration or short-time severe concentration sulfur dioxide stress, which showed that resistance of each tree species to sulfur dioxide has a threshold value.2. Height growth increment of Ailanthus altissima var.'Hongye', Melia azedarach Linn., Koelreuteria Paniculata Laxm. are higher than that of the check, the others are lower than that of the check under 5.4mg·m-3 sulfur dioxide stress condition. Height growth increment was closely related with the injured degree of each tree species.3. Chlorophyll in the leaves of each tree species was destroyed to different extend under the sulfur dioxide stress, and the severer the stress is, the higher degree of the chlorophll is. The content of carotenoid of Liriodendron chinense Sarg. and Fraxinus velutina Torr. appeared an increasing and then a decreasing trend as the increasing of sulfur dioxide concentration; that of Clerodendrum trichotomum Thunb. and Ailanthus altissima var.'Hongye'appeared a steady decreasing trend and that of Koelreuteria Paniculata Laxm.