Abstract
The vast majority of highly valuable species of the Leguminosae in temperate latitudes belong to the Inverted Repeat-Lacking Clade (IRLC). Despite having a generally conserved monosymmetric floral morphology, members of this group are remarkable with a pronounced diversity of floral sizes, modes of staminal fusion, and pollination strategies. This paper examined androecia and floral nectaries (FNs) in selected genera of the IRLC. External morphology was investigated using stereomicroscopy and scanning electron microscopy. In some cases, the pattern of staminal fusion was additionally examined in transverse sections using light microscopy. Androecia of all selected genera fell into one of four types, viz., monadelphous, pseudomonadelphous, diadelphous or diadelphous reduced (with inner stamens converted into sterile staminodes). However, there was significant variation in the stamens’ mode of contact, as well as the shape and size of the fenestrae providing access to FNs. Some types seemed to arise independently in different genera, thus providing a high level of homoplasy. FNs were more conserved and comprised areas of secretory stomata in the abaxial part of the receptacle and/or hypanthium. Nectariferous stomata could be found in very miniaturized flowers (Medicago lupulina) and could even accompany monadelphy (Galega). This indicates that preferential self-pollination may nevertheless require visitation by insects.
Highlights
The pronounced evolutionary success of angiosperms is connected with the outstanding variety in their reproductive strategies, mostly conditioned by the structural and functional diversity of their flowers
In A. cicer, Ca. arborescens, and O. kamtschatica, wide gaps remain on either side of the vexillary stamen, whereas in Co. arborescens two large fenestrae are formed at the base of this stamen
All these events suggest that different androecial morphologies are of little taxonomic importance due to a high level of homoplasy, they are undoubtedly intriguing for studies of adaptations towards different pollination strategies
Summary
The pronounced evolutionary success of angiosperms is connected with the outstanding variety in their reproductive strategies, mostly conditioned by the structural and functional diversity of their flowers These display a broad range of adaptations towards different modes of pollination, using either their own (autogamy) or other plants’ (allogamy) pollen. Numerous leguminous species from temperate latitudes, such as pea (Pisum sativum L.), faba bean (Vicia faba L.) and other cultivated vetches, grass pea (Lathyrus sativus L.) and other valuable species of the same genus, lentil (Lens culinaris Medik.), chickpea (Cicer arietinum L.), and many others, belong to the Inverted Repeat-Lacking Clade (IRLC) of the subfamily Papilionoideae [2] This group includes genera of high ornamental, forage, melliferous or medicinal value, such as Trifolium, Melilotus, Medicago, Glycyrrhiza, Wisteria, etc
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