HISTOCHEMICAL STUDIES OF ENZYME DISTRIBUTION IN SHOOT TIPS OF WHITE SPRUCE (PICEA GLAUCA (MOENCH) VOSS)

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Abstract
The relationship between morphological and metabolic or enzymic differentiation in shoot tips of white spruce has been investigated by histochemical methods revealing the distribution of several enzymes and other cellular constituents in tissues of the shoot tip at different times during the growing season. Most of the enzymes studied showed well-defined distribution patterns which varied with the stage of development of the shoot tip. Less seasonal variation was observed in the distribution of the other substances included.Activity of cytochrome oxidase and succinic dehydrogenase was high in the shoot apex during the flush of growth in the spring, indicating a high level of respiratory activity in that region, consistent with the rapid growth of the shoot. Peroxidase activity was associated particularly with meristematic or potentially meristematic tissue regions. The evidence substantiates the view that mitotic activity is greatest on the flanks of the apex and supports the existence of a quiescent center with relatively low activity in the apical mother cell zone, classically the origin of the primary stem tissues. High phosphatase activity was observed in the crown region and at the bases of needle and cone scale primordia.Young cones in fall or spring exhibited enzyme distribution patterns distinctly different from those in vegetative shoot tips. No evidence was obtained to indicate what enzyme or enzymes might be particularly involved in the differentiation of reproductive buds, but the results provide a basis for a further critical investigation of this differentiation by histochemical means.