The paramount role of cytokinins (CKs) in initiation, as well as prevention, of senescence is well established. In recent years, experimental methods have become available to raise and lower the CK concentration and experimentally manipulate senescence. Decapitating the apical shoot and adding the
DNA contents and accordingly cell numbers of cotyledons and hypocotyl of the mustard seedling were virtually constant during the experimental period (between 36-60 hours after sowing) in the dark as well as under the influence of P730, the active phytochrome (Table).-Therefore the