Recent Advances in Clearing Techniques for Study of Ovule and Female Gametophyte Development

Abstract

In the past twenty years, several clearing techniques have been developed to replace or supplement traditional section methods for the study of ovule and female gametophyte development in angiosperms. A common feature of these new approaches is the use of specific chemical treatments to make the tissue of the ovules translucent with minimal extraction of protoplasmic content. At the level of transmission light microscopy, the ovular tissues are structurally unaltered by the process. Although the operative mechanism is not fully understood, apparently cellular organelles which ordinarily differ in their refractive properties become more closely uniform in this respect. The effect is a very low contrast among cellular components of cleared tissue examined with bright-field optics. Phase contrast and Nomarski interference optics, however, intensify the small refractive differences among organelles and so reveal features of cellular structure.