一、早期封顶当幼苗长出2—4轮针叶时,顶端生出圆形芽苞,初呈绿色,后变褐色而停止生长,形成早期封顶。在这以前,苗梢心叶呈灰蓝色(正常苗为淡绿色),第二轮针叶短而宽,原轮针叶为浓绿色(正常苗为绿色)。这些特征出现在封顶前5天左右。通过现象看本质,苗木这种生态特征的出现,是缺水、肥而造成的。由于气温高,苗木水分蒸腾和土壤的蒸发 First, early capping When the seedlings grow 2-4 rounds of needles, the top gives birth to round buds, initially green, then brown to stop growth, the formation of the early cap. Prior to this, the Miao-min heart leaves are gray-blue (normal seedling is light green), the second conifer is short and wide, and the original coniferous leaves are dark green (normal seedlings are green). These features appear about 5 days before capping. By looking at the nature of the phenomenon, the emergence of such ecological features as seedlings is caused by lack of water and fertilizer. Due to high temperatures, transpiration of seedlings and soil evaporation