Tagged: dichogamy



Accurate position exchange of stamen and stigma resolves the herkogamy dilemma in a protandrous plant, Ajuga decumbens (Labiatae)

Spatial separation of stamen and stigma (herkogamy) is an effective way for angiosperm species to reduce sexual interference and prevent self-pollination. It can however also reduce the possibility of pollinators contacting both sexual organs. For, example, pollen may be deposited on a site of the pollinator’s body that will not come into contact with the stigma. An ideal floral mechanism to resolve this herkogamy dilemma is for male and female functions to separate in time (dichogamy) and moreover, for stamen and stigma to sequentially occupy the same position for pollination at male and female phases. This mechanism of movement herkogamy...

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Herkogamy and dichogamy in style dimorphic flowers of Narcissus broussonetii (Amaryllidaceae)

Across the plant kingdom, there is an extraordinary diversity of flower forms, many of which are related to variation in the morphology and arrangement of reproductive organs. To prevent self-pollination, plants have evolved floral forms where sexual organs are separated spatially (herkogamy) or temporarily (dichogamy) within a single hermaphrodite flower. Both mechanisms are widespread among angiosperms and have been considered to restrict self-fertilization and promote outcrossing. Avoidance of self-interference is proposed to be the driving force for the evolution of these mechanisms, particularly in self-incompatible species. However, species with anthers and stigmas at different levels may increase the rate of...

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Plant biotic interactions and fitness in habitat edges

Habitat variations influence the richness and composition of insect guilds. This affects plant reproduction, which depends upon functional relationships with insects involving both pollination and predation. The impact of changes in insect fauna can be seen in composite landscapes, where forest fragmentation produces transition habitats showing great heterogeneity over small spatial scales. In a recent study published in AoB PLANTS, Gargano et al. investigated herbivory and pollination in an edge-specialist carnation over a forest–open habitat gradient. Visiting insects varied over the gradient, affecting herbivory and pollination rates, and offspring quality and quantity. Their findings emphasize the role of plant–insect interactions...

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Stamen movements and pollination in Ruta

Stamen movements and pollination in Ruta

In Ruta graveolens each stamen elevates to above the flower’s centre for anther dehiscence and then falls back before the next stamen elevates, producing a one-by-one rising and falling pattern of movement. Ren and Tang manipulate individual stamens and find that these movements can enhance pollen removal by presenting pollen in doses to pollinators. If a stamen is prevented from falling back, removal of pollen from the next anther to rise is reduced as pollinators are deterred by the presence of the empty anther and make shorter visits. Some flowers show simultaneous rising of all stamens at the end of...

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Floral traits mediate the pollination role of bees

Floral traits mediate the pollination role of bees

Pollen-collecting bees are the most important pollinators globally, but are also the most common pollen thieves and can significantly reduce plant reproduction. Hargreaves et al. investigate whether floral characteristics mediate the roles played by bees – ranging from avid pollen thieves to the plant’s only pollinators – for ten species of Aloe. Pollen theft is promoted by nectar inaccessibility and strong dichogamy, which discourages visits to female-phase flowers. Furthermore, displays of many flowers facilitate deposition of mostly incompatible self-pollen. Thus species-specific floral and inflorescence characteristics govern the efficiency of pollen-collecting bees as pollinators of aloes.

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