Flow-cytometric cell counting and DNA estimation for the study of plant cell population dynamics

A one-step procedure is presented for simultaneous measurement of cell number and DNA content in cultured plant cells by flow cytometry. In order to obtain nuclei representative of the growth stadium of the culture and of all phases of the cell cycle, cells were carefully sampled and immediately fixed. Next, nuclei were isolated by enzymatic and mechanical maceration, and stained with a DNA-specific fluorescent dye. In the resultant preparation, cells can be counted at relative ease by means of a fluorescence microscope. However, flow-cytometric counting appeared to be superior to manual counting since the time needed for flow-cytometric counting was one-fourth that for manual counting and the variance between counts of the samples was significantly less. In addition, from the same routine, accurate DNA distributions were obtained as a second important parameter of the population dynamics.