An ultrastructural and Nomarski-interference study of the sperms of barley

Abstract

Male gametes of barley are small cells with conspicuous nuclei and compact cytoplasm. The cytoplasm is limited by a unit membrane. Between sperm and vegetative cell unit membranes is a thin, relatively homogeneous region which failed to stain with common cell wall specific reagents at the light microscope level. Cytoplasmic contents include mitochondria, ribosomes, dictyosomes, endoplasmic reticulum, and microtubules. Microtubules occur nearly around the entire periphery of a transected sperm, sometimes occurring in clusters of up to 16 tubules. Their chief orientation is longitudinal. No plastids or plastid-like organelles were observed. Chromatin in the nucleus is condensed; when present, there are two nucleoli. Living sperms observed with Nomarski-interference optics exhibited marked cytoplasmic activity, but no directional motility. Observed transitions from spindle-shaped to more spherical sperms could be facilitated by changes in disposition of sperm microtubules.