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

研究了酸雨、土壤水分状况、菌根共生体等环境因子与松材线虫病发生的复合系统。日本赤松暴露于模拟酸雨在pH值为3年以上，既没有枯萎症状，也没有显着减少树脂分泌。pH 2的模拟酸雨对接种病原线虫的6月龄松树幼苗均有毒害作用，而pH 3的模拟酸雨对松树枯萎病的发生既有促进作用，又有抑制作用。松材线虫（Bursaphelenchusxylophilus）接种松材线虫后，木质部薄壁细胞中渗出一种未知的亲脂性物质，覆盖在木质部的纹孔膜上，破坏纹孔膜的阀门功能，从而阻碍水分的传导。水分胁迫和/或干旱促进了松材线虫病的症状发展。如果菌根发育良好，这些共生体可以通过它们的细菌丝体延伸到周围的土壤中来提供水和矿物质。酸雨对松树幼苗地上部和地下部的作用会破坏松树的菌根系统，从而破坏菌根共生体对水分和养分的供应。

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.