A study of methods of incorporation and source of14C on distribution of radioactivity in potato plants

Russet Burbank potato plants grown in the greenhouse were given¹⁴C as¹⁴CO₂ and as uniformly labelled sucrose. Labelled sucrose was applied; (1) by injection into the main stem, (2) injection with a hypodermic needle into the debladed petiole and (3) uptake of labelled sucrose kept in a vial fastened to the main stem using thread as a wick. Plants harvested 6 hours later were analyzed for radioactivity in the foliage, roots, and tubers. The greatest proportion of radioactivity was found in the foliage. Tubers were analyzed for radioactivity in the basic (amino acids), acidic (organic acids and sugar phosphates), neutral (sugars) and alcohol insoluble solid (starch) fractions. Most of the radioactivity was found in the sugar component of the chemical fraction. Plants treated with¹⁴⁷CO₂ had a higher percentage of radioactivity in the acidic and starch fractions than plants treated with sucrose. Sucrose applied by petiole injection not only showed higher total incorporation but also exhibited more translocation of labelled material into the tubers than the other methods.