Quantitative Study of Nucleic Acids and Proteins in the Shoot Apex of Sinapis Alba During Transition From the Vegetative to the Reproductive Condition

Quantitative changes in DNA, histone, RNA, and total protein have been measured in meristematic cells during floral evocation. 2 A single 22‐hr, long‐day exposure induced two‐month‐old vegetative plants of Sinapis alba to flower. Periodic collections of shoot apices were made and stained with Schiff's reagent (DNA), azur B (RNA), alkaline fast green (histone), and naphthol yellow S (total protein). The two‐wavelength method was used for DNA and histone measurements and the one‐wavelength, two‐area procedure was chosen for RNA and total protein determinations. The DNA and histone amounts per cell decreased to a minimum value 34 hr after treatment, and most of the nuclei shifted from 4C to 2C values. DNA and histone quantities paralleled each other from 34–46 hr, after which time the histone values continued to increase and the DNA values decreased. The RNA values increased rapidly after treatment as did the total protein quantities, after a slight decrease at 34 hr concurrent with the 4C to 2C cell population shift. The significance of these events is discussed in relation to the changes which were previously described in the shoot apex of Sinapis in transition to flowering.