Tracheoid Variation among Bignoniaceae Seed Wings, with Emphasis on Campsis radicans

Abstract

Seed wings of 20 species of Bignoniaceae, representing five of the eight tribes, were cleared and stained in order to reveal cell wall patterns of the tracheoids. Tracheoids of some species lacked ornamented secondary walls; others had annular, helical, reticulate, or pitted walls. Some species had all one type of tracheoid wall pattern; others exhibited an array of wall patterns. Wall patterns were not correlated with seed or wing size, which was quite variable. Campsis radicans had an almost complete range of wall patterns; therefore, it was studied in detail using clearings, macerations, resin sections, and scanning electron microscopy. This is the first survey to sample most tribes of Bignoniaceae and to report tracheoid wall pattern variations that equal or surpass those of tracheary elements in xylem.