Studies on the complexed system of environmental factors influencing on the Pine Wilt

点击翻译按钮获取中文摘要

The complexed system of some environmental factors such as acid rain, water status in soil, mycorrhizal symbiont and so on were studied in relation to development of pine wilt disease. Japanese red pine trees exposed to simulated acid rain at pH 3 for more than 3 years have shown neither wilt symptom nor significant reduction in resin exudation. Simulated acid rain at pH 2 always showed deteriorative effect on 6 month-old pine seedlings which had then inoculated with pathogenic nemtodes, while pH 3 acid rain had both promotive and supressive effects on development of Pine Wilt disease.Histochemical survey was also conducted for the shoot segments of Japanese black pine saplings. When inoculated with pathogenic nematode, Bursaphelenchus xylophilus some unknown lipophilic substance(s) leaked out of xylem parenchimatous cells, and covered the pit membrane of xylem, thus the valve function of the pit membrane must be damaged, thereby water conduction must be hindered.Pine wilt disease is promoted its symptom development by water stress and/or drought.If mycorrhizae are well-developed, these symbionts may supply water arid minerals via their fine mycellium extending into surrounding soil. Acid precipitation applied for either terrestrial or under ground parts of pine seedlings make damage on mycorrhizal system of the pine trees, thereby damaged water and nutrient supply via mycorrhizal symbionts.