Growth Traits of Pinus yunnanensis Franch.Seedlings with Straight and Twisted Stems
The seeds of 25 lines with straight stems and 25 lines with twisted stems of Pinus yunnanensis Franch.were collected from Xinping in Yunnan.The seeds were sown,and the heights and ground diameters of one-year-old seedlings were measured,on the basis of which the growth traits of P.yunnanensis Franch.with two different stem types were analyzed.The results showed that the heights and ground diameters of the seedlings with straight and twisted stems presented the S-shaped trend of slow growth-fast growth-slow growth.The rapid growth stage of seedling height lasted longer while that of ground diameter was shorter.The net increments of both seedling height and ground diameter at the rapid growth stage contributed most to the growth.Seedling height and ground diameter demonstrated allometry.Regarding the seedling height,the seedlings with straight stems showcased better growth performance than those with twisted stems,with shorter linear growth stage and greater growth parameters than the seedlings with twisted stems.In terms of the ground diameter,the seedlings with twisted stems presented better growth performance than those with straight stems,showing slight difference in the linear growth stage and larger growth parameters than the seedlings with straight stems.In general,the one-year-old seedlings with straight stems demonstrated better growth performance than those with twisted stems.It is therefore suggested that the lines with straight stems should be selected for the plantation of P.yunnanensis Franch.and to serve as elite lines for national afforestation and reserve forest construction.
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