FIGURE 7.1 - Nuclei prepared using OPTION X (see CHAPTER 7) from (a) Sorghum bicolor (grain sorghum) and (b) Solanum lycopersicum (tomato). The preparations have been stained with methylene blue and photographed using bright-field microscopy. The nuclei stain dark blue and are variable in shape (though most are roughly spherical). Within a picture, much of the observed variation in nucleus size and shape is attributable to the fact that not all of the nuclei lie in the same focal plane. Nuclei within the focal plane (e.g., red arrows) exhibit greater definition than nuclei above or below the focal plane (e.g., yellow arrows). Starch grains (e.g., purple arrows) often pellet with nuclei. However, unlike nuclei, starch grains stain only lightly (if at all) with methylene blue, and tend to have a refractile appearance (especially when viewed by phase-contrast microscopy). Much of the starch can be eliminated from nuclear preps by performing successive low-speed centrifugations as described in the METHODS. In most species we examined, some of the debris that pellets with nuclei stains lightly with methylene blue (light purple regions, e.g., green arrows). Magnification = roughly 1000x.