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为了尽快繁殖推广白榆优良单株、优良类型,对优树早期预测就显得特别重要。二年来,我们在加速繁殖白榆优良单株的实践中发现,虽采用同一株优良母树上的种子进行育苗,但幼苗个体却差别很大。通过大量的比较鉴定,发现白榆的生长快慢和叶片厚度成正相关,即叶厚是白榆优良单株的显著标志。一九七八年十一月一日,我们在一年生苗圃的五千株苗木中,选出九株厚叶单株与临近九株一般苗木进行实测,厚叶苗木平均高103厘米,对照的仅75厘
In order to breed and popularize the excellent single plant and excellent type of elm as soon as possible, it is particularly important to predict the elite early stage. In the past two years, we found that in the practice of accelerating the propagation of fine elm plants, we found that although seedlings are raised with seeds from the same good parent tree, the seedlings vary greatly. Through a large number of comparative identification, it was found that the growth speed of Ulmus pumila was positively correlated with the leaf thickness, that is, the leaf thickness was the significant mark of excellent individuals of Ulmus pumila. On November 1, 1978, out of 5,000 seedlings of one-year-old nurseries, nine thick-leafed and nearly nine common seedlings were selected for measurement. The average thickness of thick-leafed seedlings was 103 cm. Only the control 75%