Histochemistry of the dormant vascular cambium of Abies balsamea: changes associated with tree age and crown position

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Abstract
On three dates during September-December, the histochemistry and dormancy status of cambial zone cells were investigated in 6- and 19-year-old balsam fir (Abies balsamea) trees at the top of the crown (1-year-old cambium) and near the base of the bole (5- and 13-year-old cambium, respectively). The extent of dormancy on the date of collection and after 4 weeks in controlled-environment conditions favorable for growth indicated that a changeover between the dormancy stages of rest and quiescence occurred in all ages of the cambium during the experimental period. In trees of both ages, cambial dormancy began later, and the number of fusiform cells in the cambial zone was greater at the bottom of the tree than at the top. The staining intensities for total cytoplasmic RNA, protein, and insoluble carbohydrates in the fusiform cambial zone cells increased during the rest-quiescence transition at the top and bottom of the 6-year-old trees and at the top of the 19-year-old trees. However, no significant increase in RNA staining occurred at the bottom of the 19-year-old trees.