The histochemical localization of dehydrogenases in the cotyledons of Pisum sativum L. during germination

Succinate dehydrogenase activity, NAD-linked malate, isocitrate and alcohol dehydrogenase activity and NADH :nitro-blue tetrazolium reductase activity were demonstrated in sections of fresh or frozen pea cotyledons, using nitro-blue tetrazolium as indicator. The localization of the various enzymes shows much resemblance. Initially, high enzyme activity is present in the cells of the epidermis and hypodermis. This activity decreases during germination. In the storage parenchyma, the enzyme activity in almost all cells increases during the first three days of the germination, and decreases subsequently, especially in the cells of the outer abaxial zone. The tracheary elements do not show any dehydrogenase activity. They appear during germination. The activity of the other cells of the vascular system increases during the first three days of germination but hardly changes in the subsequent seven days.