Use of pectinase to dissociate plant nuclei for squash preparations: effect of hydration procedures

Scale tissues taken from cones of pendent Douglas-fir Pseudotsuga menziesii (Mirb.) Franco were treated with pectinase to dissociate nuclei for Feulgen staining. Hydration of fixed tissues with water or a graded series of ethyl alcohol before pectinase treatment resulted in distention and faint staining of nuclei and inadequate disintegration of cell walls. These problems were overcome by adopting citrate buffer hydration. Analysis of digitized scans of nuclei provided information about the distribution of the stained material in density classes and nuclear size which is usually unavailable through the conventional double wavelength DNA measuring method.