The occurrence of vertical resin canals in Keteleeria, with reference to its systematic position in Pinaceae
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文摘
The variation in the number of resin canals in the secondary xylem of Keteleeria fortunei (A. Murray bis) Carrière is determined. At all levels from base to top of a tree, resin canals are absent nearer the pith, but they (sporadically) appear after a certain cambial age. In addition, the occurrence of resin canals in seven named species ofKeteleeria was surveyed. It was confirmed that normal vertical resin canals do occur in the mature parts of secondary xylem, but that they may be absent in the juvenile parts of secondary xylem of stems, as well as in branches and in seedlings or saplings. Earlier investigations reporting the absence of resin canals altogether in this genus may have been misled by the use of younger (immature) specimens instead of mature stems of trees. The distribution pattern of resin canals found inKeteleeria is systematically significant because it supports a new system of classification of Pinaceae, in whichKeteleeria is believed to have a close relationship with Nothotsuga.