Architecture of cauliflory in the genus Cercis (Fabaceae : Caesalpinioideae)

Abstract

Cercis is a genus with a geographically disjunct distribution in North America, southern Europe, and eastern Asia. The architecture of cauliflory (flowering from the lower branch and trunk areas of woody plants) was examined in 10 taxa, including 9 of the 11 recognized species in the genus Cercis. In each taxon, a linear series of first-order buds (distinguished as 1) was formed in the axils of vegetative leaves before shoot elongation ceased. The first-order bud developed into either a vegetative shoot or more frequently into an inflorescence. Inflorescences matured and then abscised. Second-order and higher order buds were produced in the axils of the basal bud scales of abscised inflorescences. In addition, vegetative shoots that were from first- or higher order buds produced first order buds (distinguished as 1′) in their leaf axils. Buds from the axils of the basalmost leaves of these vegetative shoots, together with higher order buds from the parent shoot, perpetuated the cauliflorous condition in all taxa studied. Since cauliflory was present and since the architecture of cauliflory was similar in all taxa studied, regardless of geographic distribution, cauliflory probably arose only once in Cercis, before the genus radiated from its site of origin. Key words: cauliflory, Cercis, serial buds, order of buds, geographic distribution, architecture of cauliflory.