Lloyd AD, Mellerowicz EJ, Chow CH, Riding RT, Little CHA
Fluctuations in Ribosomal-Rna Gene Content and Nucleolar Activity in the Cambial Region of Abies-Balsamea (Pinaceae) Shoots During Reactivation
American Journal of Botany: 1994 81:1384-1389
Tissue was collected from the vascular cambial region of 1-year-old balsam fir shoots over an Ii-week period during which cambial reactivation occurred. The amount of rDNA (ribosomal RNA genes) relative to total genomic DNA was determined by quantitative slot blots for three trees, one of which showed a 3-week delay in reactivation. In addition, nucleolar activity was estimated by measuring nucleolar volume, number, and staining intensity. Relative rRNA gene content increased transiently prior to the onset of cambial cell periclinal division. Nucleolar volume also increased transiently, but 1-2 weeks prior to the maximal relative rDNA value. The increases in relative rDNA and nucleolar activity were delayed in the tree in which reactivation was late. We interpret these changes as reflecting the amplification and loss of genes encoding rRNA to facilitate cambial cell reactivation.
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