Unlike microspectrophotometry and image cytometry,
flow cytometry analyses microscopic particles in suspension,
which are constrained to flow in single file within a
fluid stream through the focus of intense light. Pulses of
scattered light and fluorescence are collected and converted
to electric current pulses by optical sensors and classified.
Because the particles are analysed individually and at high
speed, large populations can be measured in a short time and
the presence of subpopulations may be detected (Shapiro,
2003). Since there is no need to employ tissues with dividing
cells, the ease of sample preparation, and the ability to
measure DNA quickly in large populations of cells, made
flow cytometry an attractive alternative to microspectrophotometry.
Indeed, there has been a shift towards flow
cytometry during the last decade (Bennett and Leitch,
1995; Bennett et al., 2000a). This review focuses on the
use of flow cytometry for estimation of nuclear DNA content
(DNA flow cytometry) in plants with a special emphasis
on the estimation of DNA in absolute units (genome size).