Studies of Growth and Flowering in Picea sitchensis (Bong.) Carr. 2. Initiation and Development of Male, Female and Vegetative Buds

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Abstract
Vegetative shoots from the base of the crown, and from parts of the tree likely to form male or female buds, were collected from 40–years–old trees of Picea sitchensis (Bong.) Carr. throughout the 1973–4 annual growth cycle. The morphology and growth rates of the terminal buds on these shoots were assessed. Bud scale primordia were formed most quickly in the female position, at an intermediate rate in the male position and most slowly in the basal vegetative position during April, May and June. In July and early August the apical meristems swelled to form domes and continued to grow at the same relative rates in the male, female and basal vegetative positions. Reproductive buds were first morphologically distinct in late August and sporangia appeared in October. Dormancy, defined by the pause in apical volume increase, extended from mid-October to mid–March. Young strobili grew much faster than basal vegetative shoots of the same age between mid–March and bud burst in late April. Throughout the growth cycle, external changes in bud size reflected changes in size of the apical meristem, young strobihis or young vegetative shoot inside the bud. It is proposed that the rate of growth of an apical meristem may be causally related to the type of bud which subsequently develops from it.