Vegetative bud development, cone differentiation and development in Picea engelmannii Parry
Date
1982
Authors
Harrison, Derek L. S. (Derek Laurie Shawn)
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Abstract
The microanatomical development of vegetative and reproductive buds in Picea engelmannii Parry (Engelmann spruce) is described. Vegetative buds of Engelmann spruce from the Prince George Forest District (British Columbia) were collected and studied. In mid-April growth was resumed as determined from leaf mitoses two weeks later mitotic activity was observed in the apex. Bud-scale initiation began in terminal buds by the end of May. Bud-scale initiation began in axillary buds two weeks later than terminal buds when terminal bud shoot elongation began. Bud-burst occurred in late June and both shoot elongation and bud-scale initiation were complete by late July. In early August terminal vegetative buds became anatomically differentiated by the initiation of leaves. Axillary bud leaf initiation began one week later.
In terminal and axillary vegetative buds leaf initiation was completed by late September and buds ceased growth by mid-October.
Putative pollen-cones initiated microsporophylls after bud-scale initiation. Two abaxial microsporangia per sporophyll were initiated by late August. Microsporangial enlargement began in mid-September and ceased by mid-October. Pollen mother cells did not undergo meiosis before growth cessation.
Putative seed-cones initiated bracts directly after bud scale initiation. Bract primordia were initiated as a group of darkly staining cells within the peripheral zone. In mid-August, just above these cells another group of darkly staining cells began to develop into the ovuliferous scales. Two developing ovules formed ad axially and on each side of the median longitudinal axis of each ovuliferous scale. These ovules formed one central meg a spore mother cell which enlarged and overwintered in a pre-meiotic stage.