ABSTRACT
The metabolic fate of the nonspecific precursors not only depends on enzyme activity but primarily on the way they are distributed over the tissue. Most of this experimental design can be applied in tracing steroid synthesis and is outlined in this chapter. Special applications are required in the administration of these labeled substrates. Intercellular translocation of sugars, amino acids, and organic acids occurs in plants and these compounds may be supplied in greater amounts. A variety of water-soluble C-labeled substrates can be fed to various growing seedlings. Species with an easily removable endosperm are appropriate plants with which to trace radioactivity from water-soluble C-labeled substrates under physiological conditions. In most cases plant parts have to be cut to enable a rapid uptake of labeled substrates and growth will cease for a certain period with a concurrent reduction in sterol synthesis.
