GERRATH, JEAN M. Department of Biology, University of Northern Iowa, Cedar Falls, IA 50614-0421. - Tendril development in Antigonon leptopus Hook. & Arn. (Polygonaceae).
Tendrils are cylindrical coiling organs used as a climbing and support
mechanism by a number of vines. The morphological origin of tendrils
varies, and may be the leaf, shoot, or inflorescence rachis, depending
on the species. Thus tendrils are a good example of convergent
evolution. Coral vine (Antigonon leptopus), a native of Mexico
and Central America, possesses tendrils on the axillary
inflorescences. Typically, bract-subtended flowers develop on the
basal portion of the inflorescence. A transition zone consisting of
one or two nodes with tendril-subtended flowers occurs in the middle
portion of the inflorescence, and the inflorescence is terminated by
three "empty" tendrils. Tendrils are initiated in the same
manner as a leaf or a bract, but they remain cylindrical except for
what appears to be a rudimentary blade at the tip. Developmental and
histological evidence indicates that the tendril in this species is a
leaf homologue. The initial thigmotropic response and coiling take
place in the tendrils, but subsequently, coiling also occurs in the
inflorescence rachis which becomes sclerified and forms the permanent
support structure for the vine. Thus, this species uses both stem and
leaf homologues for support.
Key words: anatomy, Antigonon leptopus, development, Polygonaceae, tendril