Changes in Nuclear Protein Contents of Root Cells during Germination

Abstract

Total protein content and area of nuclei were determined for cells of the primary root of Vicia faba during the first 144 hours following the onset of imbibition. We wished to determine what change, if any, occurs in protein contents of nuclei as meristematic cells move from a dormant into a proliferative condition. Nuclear proteins were stained with dinitrofluorobenzene and protein content, in arbitrary units, was determined by microspectrophotometry. In the first 50 hours mean protein content of nuclei increase; this, as we have shown, is the period in which cells and nuclei increase in size as they complete their first cell cycle. During subsequent cell cycles, cell area decreases markedly, nuclear area decreases to a lesser extent; accompanying these decreases, the mean and the range of protein contents of nuclei decreased significantly. Thus, as the proliferating population of cells of a root meristem becomes steady-state, there is an absolute decrease in the concentration of total proteins within the nucleus. This was revealed particularly clearly by comparing unclei of identical areas from roots of different ages. Increases in nuclear size were induced by treatment with 5-aminouracil for upto 24 hours: this did not result in a significant increase in protein content of nuclei. These results agree with those from untreated roots that area and protein content of nuclei can, to a considerable extent, vary independently of one another.