The embryology and relationships of Gyrostemonaceae*

Abstract

On the basis of studies of Codonocalpus and Gyrostemon, this is the first report on the embryology of the Gyrostemonaceae, one of 15 glucosinolate-producing families. The embryology of Gyrostemonaceae was studied in an effort to clarify the phylogenetic relationships of those families that have been the subject of some dispute. Embryologically, Gyrostemonaceae possess distinctive features in integuments, seeds and seed coats. These include: the outer integument (or testa), non-multiplicative (i.e. two-cell-layered) and non-vascularised; seeds reniform and albuminous; the seed coat 'exotegmic', with exotegmic cells fibrous and all other tegmic cells crushed. Nearly all of these features are common to Capparaceae and Resedaceae (glucosinolate-producing families of Capparales), but are not found in Sapindaceae (a non-glucosinolateproducing family of Sapindales), both of which have recently been considered to be close allies of Gyrostemonaceae. Shared embryological features suggest strongly that Gyrostemonaceae are closely related to Capparaceae and Resedaceae and should be placed near them within Capparales. Available embryological evidence neither supports close relationships between Gyrostemonaceae and Bataceae nor one linking Gyrosternonaceae with Sapindaceae.

* Dedicated to Professor G. B. Marini Bettolo, on the occasion of his 75th birthday in 1990, and his retirement from the Università Degli Studi di Roma.