包括松类在内的所有林木,都需要同外生性菌根共生。一九七三年Weyerhaeuser公司曾在俄克拉河马州东南部的一个牧区建立苗圃,七四年播种火炬松苗10英亩,播种前未进行土壤熏蒸消毒。在苗木生长季节使用了各种农药防治病虫害和杂草,并施入化肥增加土壤肥力,然而苗木生长却很差,在七月底,所有的700万株松苗中只有不到10％的带有菌根的松苗生长了次生叶,而大部分苗木无菌根,无次生叶,并且生长停滞,开始黄化。至八月中旬,每星期都有上千苗木频于死亡。九月增施杀菌剂和化肥亦未见效果。十一月下旬苗木就提早进入休眠期。到翌年一月起苗时,只有4％的苗木高度超过15cm,地径大于3mm;在苗根上也很少见到外生性菌根。分析原因:松苗之所以生长很 All trees, including pine, need to coexist with ectomycorrhizae. In 1973, Weyerhaeuser Company established a nursery in a pasture area in the southeastern part of the Oklahoma state. In July 1974, 10 acres of flamingo pine seedlings were sown and soil fumigation was not carried out prior to sowing. Various pesticides were used to control pests and weeds during the seedling growing season and fertilizers were added to increase soil fertility. However, seedlings grew poorly. At the end of July, less than 10% of all 7 million seedlings had fungi The root of the pine seedlings grow secondary leaves, and most of the nursery stock mycorrhizal roots, no secondary leaves, and growth stagnation began to yellow. As of mid-August, thousands of seedlings are frequently killed every week. September addition of fungicides and fertilizers also showed no effect. Seedlings early in November to enter the dormant period. By the beginning of January of the following year, only 4% of the seedlings are more than 15 cm in height and have a diameter of more than 3 mm. Ectomycorrhizae rarely occur on the seedlings. Analysis of the reasons: the reason why the growth of pine seedlings