Fertilization involves interaction between two gametes and exchange of
genetic information. In addition, information is transferred which re
sults in triggering of the particular cellular and developmental respo
nses of the organism. This review considers the cellular signals invol
ved during different stages of gamete interactions in plants, includin
g gamete attraction, recognition, fusion, zygotic activation and devel
opment. A wide range of signalling mechanisms can be seen to operate d
uring fertilization, reflecting both the diversity of systems bringing
gametes together and the different cellular responses to fertilizatio
n throughout the plant kingdom. Moreover, signals involved in triggeri
ng early development following gamete fusion appear to differ signific
antly even between species showing at least superficially similar cell
ular responses. Much of our current understanding comes from studies o
f a few easily accessible systems though recent developments in gamete
isolation, in vitro fertilization and embryo culture should increase
the scope for studies of signalling mechanisms in vascular plants.