Éditeur(s) : HAL CCSD Wiley
Résumé :  
Pollination ecology and reproductive success of Jack-in-the-pulpit (Arisaema triphyllum) were studied in two natural populations in Québec, Canada. Individual A. triphyllum plants can be of three types: male, female or bisexual. In both populations studied, the presence of bisexual inflorescences was not negligible (13%), where 'female' and 'male' bisexual plants were categorised according to the relative number of stamens and ovaries. 'Male bisexual' plants produce only pollen and 'female bisexual' plants produce only fruit. Hence, A. triphyllum is a true dioecious plant, as each plant only reproduces through either the male or the female function. 'Female bisexual' plants were equivalent to female plants in terms of visitation rate by insects, fructification rate and production of berries and seeds. Neither agamospermy in female plants nor self-pollination in 'female bisexual' plants was found, thus A. triphyllum relies on insects for cross-pollination. Despite the long flowering cycle, a low visitation rate was documented: only 20-40% of inflorescences were visited, according to gender, by a mean of 1.5 insects. In this study, Mycetophilidae represented the most generically diversified and abundant family, as well as the most efficient insect pollinator, especially the genera Docosia and Mycetophila.
ISSN: 1435-8603

hal-01032127
https://hal.archives-ouvertes.fr/hal-01032127
DOI : 10.1111/j.1438-8677.2009.00192.x

Éditeur(s) : HAL CCSD National Research Council Canada
Résumé : International audience
The spadix of Arum italicum Miller consists of two main parts: a clavate sterile portion (appendix) and a cylindroid fertile portion. In the fertile portion with both male and female zones, there are two zones of sterile flowers (bristles). The basal portion of bristles is surrounded by a verrucose structure consisting of a mass of tissular excrescences. During early stages of development, there is no free space between the different zones of the inflorescence. The elongation of the inflorescence axis is what eventually separates the different zones from each other. There are no atypical flowers that are morphologically intermediate between male and female flowers as is the case in other genera of Aroideae (e.g., Cercestis, Philodendron, Schismatoglottis). The structure of the bristles in the inflorescences of Arum does not correspond to any type of atypical flower (unisexual or bisexual) that has been analysed previously in the Araceae. From a developmental point of view, it is not possible to determine if the bristles correspond to aborted or modified female or male flowers. In the early stages of development, the stamens, staminodes, and appendix are covered by globular masses of extracellular calcium oxalate crystals.
Le spadice de l’Arum italicum comporte deux parties principales : une portion claviforme stérile (appendice) et une portion cylindroïde fertile. Dans la portion fertile avec zones mâles et femelles, il y a deux zones de fleurs stériles (soies). La portion basales des soies est entourée par une structure verruqueuse, constituée d’une masse d’excroissances tissulaires. Aux premiers stades du développement, il n’y a pas d’espace libre entre les différentes zones de l’inflorescence. L’élongation de l’axe de l’inflorescence est ce qui sépare éventuellement les différentes zones l’une de l’autre. Il n’y pas de fleurs atypiques intermédiaires entre des fleurs mâles et des fleurs femelles, comme c’est le cas dans d’autres genres d’Aroideae (p. ex. Cercestis, Philodendron, Schismataglottis). La structure des soies chez les inflorescences de l’Arum ne correspond à aucune des fleurs atypiques (unisexuées ou bisexuées) qui ont précédemment été analysées chez les Araceae. Considérant le développement, il n’est pas possible de déterminer si les soies correspondent à des modifications de fleurs femelles ou mâles avortées. Aux premiers stades du développement, les étamines, les staminodes et les appendices sont couverts de masses globuleuses constituées de cristaux extracellulaires d’oxalate de calcium.
ISSN: 0008-4026

hal-01206194
https://hal.archives-ouvertes.fr/hal-01206194