Scent glands in legume flowers

Abstract

Scent glands, or osmophores, are predominantly floral secretory structures that secrete volatile substances during anthesis, and therefore act in interactions with pollinators. The Leguminosae family, despite being the third largest angiosperm family, with a wide geographical distribution and diversity of habits, morphology and pollinators, has been ignored with respect to these glands. Thus, we localised and characterised the sites of fragrance production and release in flowers of legumes, in which scent plays an important role in pollination, and also tested whether there are relationships between the structure of the scent gland and the pollinator habit: diurnal or nocturnal. Flowers in pre-anthesis and anthesis of 12 legume species were collected and analysed using immersion in neutral red, olfactory tests and anatomical studies (light and scanning electron microscopy). The main production site of floral scent is the perianth, especially the petals. The scent glands are distributed in a restricted way in Caesalpinia pulcherrima, Anadenanthera peregrina, Inga edulis and Parkia pendula, constituting mesophilic osmophores, and in a diffuse way in Bauhinia rufa, Hymenaea courbaril, Erythrostemon gilliesii, Poincianella pluviosa, Pterodon pubescens, Platycyamus regnellii, Mucuna urens and Tipuana tipu. The glands are comprised of cells of the epidermis and mesophyll that secrete mainly terpenes, nitrogen compounds and phenols. Relationships between the presence of osmophores and type of anthesis (diurnal and nocturnal) and the pollinator were not found. Our data on scent glands in Leguminosae are original and detail the type of diffuse release, which has been very poorly studied.

Trichomes that secrete substances of a mixed nature in the vegetative and reproductive organs of some species of Moraceae

“…Secretory trichomes present in floral organs can produce nectar, volatile and non-volatile oil or sticky substances (Vogel & Machado 1991;Lopes et al 2002;Moyano et al 2003;Marinho et al 2014), contributing to the pollination of the species and its reproductive success. This does not seem to be the case for the floral trichomes of S. bonplandii since their morphology and secretory content are similar to those of the secretory trichomes of leaves.…”

Grain Legumes

“…The blends of the BVOCs are usually produced in petal conical cells (Whitney et al 2011) and in scent glands or osmophores during anthesis (Farré-Armengol et al 2013). Marinho et al (2014) localized the sites of fragrance production and release in legume flowers in the perianth and particularly the petals, in which scent plays an important role in pollination. An analysis of cut flower scent in Lathyrus odoratus showed that the aroma was almost exclusively produced by the standard and the wings while the keel petals and other floral parts emitted very little (Sexton et al 2005).…”

The uncommon cavitated secretory trichomes inBauhinia s.s.(Fabaceae): the same roles in different organs

“…(Orchidaceae), the trichomes on petals produce non‐volatile oils (Vogel & Machado, ; Blanco et al ., ); and in Anadenanthera peregrina (L.) Speg. (Fabaceae), the petal secretory trichomes produce volatiles (Marinho et al ., ).…”