Protocol describes a useful way to observe the development of embryos, as well as meristems & young primordia developing at the shoot apex by confocal microscopy after staining the nuclei with propidium iodide. The number of cells can be exactly quantified in a meristem or in young primordia. Because embryonic & meristematic cells are largely filled out by their nuclei, it is easier to image only the nuclei. This method allows analysis of whole-mount material, which is more easily reconstructed.
