Histochemical Studies of Sclereid Induction in the Shoot ofRauwolfia Species

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Abstract
Results of histochemical tests for cytochrome oxidase activity in four species of Rauwolfia have been reported. The cells beneath the terminal shoot meristem constitute the pith. Histochemical tests showed intensified enzymatic activity in those cells of the pith which would differentiate as sclereid initials. Similar cytochrome oxidase activity also occurred in the sclereid initials and the developing sclereids. The cytochrome oxidase activity was associated with two types of particulate formation, the granular and rod-shaped. The ground parenchymatous cells of the pith and the leaf-base showed very little enzymatic activity of cytochrome oxidase. The characteristic indophenol blue coloration due to cytochrome oxidase activity did not appear in control sections. Physiological changes correlated with morphogenetic expression of some pith cells demonstrate that the physiological changes occur before the initiation of sclereids in the morphologically homogeneous parenchymatous cells of the pith. Intensified cytochrome oxidase activity was also recorded in the meristematic tissues of shoot apex, procambium, axillary buds and the laticiferous cells of Rauwolfia.