Nucleic acid, protein, and protein-bound lysine and arginine patterns in epidermal nuclei of the mature and senescing onion bulb.
Eight macromolecular indices were determined for nuclei of outer epidermal cells in the equatorial plane from young through old leaf bases (sequential leaf senescence) and for nuclei in basal, equatorial and three apical locations within one leaf base (apical cell senescence). The eight nuclear indices were total nucleic acid. DNA, RNA, histone, non-histone, total protein, and protein-bound lysine and arginine. Cell senescence and death were accompanied by startling decreases in these eight indices. In sequential leaf senescence, nuclei in the second innermost turgid leaf base contained about four to five times the amount of nucleic acids and nuclear proteins in the youngest leaf base. The nuclei in the outermost leaf base contained about 20% less of the nucleic acids and proteins measured than the second outermost leaf base. We infer that this represents a decline in nuclear constituents due to senescence, since less than 30% of the cells in the innermost paperlike leaf base contained nuclei and those present were almost devoid of the nuclear constituents measured. Cell senescence in the apical section of a turgid leaf base showed sequential declines in all nuclear indices studied from areas composed of living cells to areas at the apex composed of dead cells. Possible changes in histone content due to physiological ages were detected in the equatorial but not in the vertical study; the protein-bound lysine to arginine ratios increased from younger to older leaf bases.
D001120:Arginine / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D010944:Plants / Q000378:metabolism*; D012313:RNA / Q000378:metabolism; D013997:Time Factors
D010940:Plant Proteins; D012313:RNA; D004247:DNA; D001120:Arginine; D008239:Lysine