Development of shoot inHydrangea macrophylla II. sequence and timing |
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Authors: | Tian Su Zhou Noboru Hara |
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Institution: | (1) Department of Biology, College of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, 153 Tokyo |
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Abstract: | The development of axillary buds, terminal buds, and the shoots extended from them was studied inHydrangea macrophylla. The upper and lower parts in a nonflower-bearing shoot are discernible; the preformed part of a shoot develops into the
lower part and the neoformed part into the upper part (Zhou and Hare, 1988). These two part are formed by the different degrees
of internode elongation at early and late phases during a growth season, respectively. Leaf pairs in the neoformed part of
the shoot are initiated successively with a plastochron of 5–20 days after the bud burst in spring. The upper axillary buds
are initiated at approximately the same intervals as those of leaf pairs, but 10–30 days later than their subtending leaves.
Changes in numbers of leaf pairs and in lengths of successive axillary buds show a pattern similar to the changes in internode
lengths of the shoot at the mature stage. The uppermost axillary buds of the flower-bearing shoot often begin extending into
new lateral shoots when the flowering phase has ended. The secondary buds in terminal and lower axillary buds are initiated
and developed in succession during the late phase of the growth season. Internode elongation seems to be important in determining
the degrees of development of the axillary buds. Pattern of shoot elongation is suggested to be relatively primitive. Significances
of apical dominance and environmental conditions to shoot development are discussed. |
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Keywords: | Hydrangea Plastochron Shoot development Shoot elongation |
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