Extrafloral Nectaries in Leguminosae: Review and Original Observations in Erythrina and Mucuna (Papilionoideae; Phaseoleae)

Abstract

LERSTEN, N. R. AND C. L. BRUBAKER (Dept. Bot., Iowa State Univ., Ames, IA 5001 1). Extrafloral nectaries in Leguminosae: Review and original observations in Erythrina and Mucuna (Papilionoideae; Phaseoleae). Bull. Torrey Bot. Club 114:437-447. 1987.-A comprehensive review revealed references that mention or describe extrafloral nectaries (EFN's) in 42 genera of Leguminosae (13 Caesalpinioideae, 19 Mimosoideae, 10 Papilionoideae). EFN's of the two former subfamilies, with rare exceptions, have a compact, palisade epidermis and are not on stipules or stipels. Papilionoideae EFN's are known almost exclusively from tribes Vicieae and Phaseoleae; all unambiguous reports indicate that these EFN's consist of an aggregation of clavate nectariferous trichomes on either stipules or stipels. We found that Mucuna pruriens (L.) DC has filiform stipels with nectariferous trichomes scattered from base to tip. Stipels of four species of Erythrina (E. berteroana Urban, E. greenwayi Verdcourt, E. herbacea L., E. variegata L.) examined are thick and variously shaped but all have abaxial depressions, ranging from a shallow depression to a cryptic cavity, lined by clavate nectariferous trichomes. EFN's of Mucuna and Erythrina resemble those of other Phaseoleae by having a loose aggregation of trichomes, but their modified stipels are different. The literature and our observations lead us to conclude that EFN's of Papilionoideae have evolved independently, and in a simpler manner, than EFN's of Caesalpinioideae and Mimosoideae.