Study On The Acute Injury Reaction Of Garden Trees To SO₂ And The Protective Effect Of Exogenous Chemicals

In order to select garden trees resistant to SO₂ and to provide information concerning acute injury symptom types, fumigation experiments were carried out with 42 species in the stable fumigated chamber designed personally. The acute injury symptoms were observed, described and taken pictures. And superoxide anion radical(O₂^-), cell membrane relative permeability, malondialdehyde(MDA), superoxide dismutase(SOD), peroxidase(POD), catalase(CAT), chlorophyll content and soluble protein content of resistant plant Euonymus japonicus and susceptible plant Chaenomeles speciosa were measured. And the relations among these physiological and biochemical changes and plant resistance were analyzed. Meanwhile, the protective effects of the four chemical compounds sodium benzoate, calcium chloride antydrous, phosphate buffer and 8-hydroxyquinoline were studied. The results were listed as following:1. Treated with five different concentration of sulfur dioxide, the results showed that two types of symptom, which are chlorosis and necrosis, were established according to the characteristic of leaf acute injury symptoms. Based on the established threshold value of leaf injury and critical concentration, the relative resistance to SO₂ of the tested trees can be grouped into 5 categories, which are very sensitive, intermediate sensitive, sensitive, resistant and more resistant. And there were 15 very sensitive plants, 5 intermediate sensitive plants, 5 sensitive plants, 5 resistant plants and 7 more resistant plants.2. The physiological and biochemical changes of the both plants under SO₂ stress was: (1)The O₂^- velocity, MDA content, cell membrane permeability and soluble protein content were increased in the Chaenomeles speciosa and Euonymus japonicus treated with 0.1mg/L, 0.5mg/L and 1.0mg/L SO₂, but the increased ratio of the former is larger than the latter. And these four indexs were increased with the increase of sulfur dioxide concentration.(2)The SOD and POD activity were increased in the both plants treated with sulfur dioxide, but the increased ratio of the susceptible plant is greater than the resistant one. And the increased ratio was increased with the increased concentration sulfur dioxide After fumigation, the POD activity had a stimulated ascent then descend, but the stimulated course is earlier in the Euonymus japonicus than in the Chaenomeles speciosa. The CAT activity was decreased in the both plants and the descend ratio was increased with the increase of sulfur dioxide concentration. ?The content of chlorophyll a and b in the both plants are descended after fumigated with sulfur dioxide, and there is not linearity relation between the descended ratio and the concentration of sulfur dioxide.3. The results of study on resistance to sulfur dioxide of exogenous chemicals showed that sodium benzoate, calcium chloride antydrous, phosphate buffer and 8-hydroxyquinoline had some defensive and protective effect on the Euonymus japonicus under sulfur dioxide stress. And combined the physiological and biochemical results with the apparent injury reaction, the calcium chloride antydrous was affirmed the best chemical of resistant to SO₂. Treated with different concentration CaCl₂, the result showed that Ca²+ had positive effect on the protective enzyme activity in the leaf of Euonymus japonicus under SO₂ stress and it descended the degree of membrane lipid peroxidation. But Ca²+ had appropriate concentration and high concentration had a negative effect.