Sperm dimorphism in Nicotiana tabacum L.

Abstract 

Sperm cells of tobacco have been intensively studied as examples of isomorphic gametes in which major cellular and organellar parameters remain statistically indistinguishable in the two sperm cells. An examination of sperm cells late in maturation, however, displays that the sperm cell associated with the vegetative nucleus becomes statistically significantly smaller than the other sperm cell in tobacco. If late divergence occurs in the two sperms of other angiosperms, sperm dimorphism may be more prevalent than has previously been assumed and dimorphism may have a major influence on the pattern of double fertilization.