Exploring the role of auxin in the androgynophore movement in Passiflora.

The flowers of the species belonging to the genus Passiflorashow a range of features that are thought to have arisen as adaptations to different pollinators. Some Passiflora species belonging to the subgenus Decaloba sect. Xerogona, show touch-sensitive motile androgynophores. We tested the role of auxin polar transport in the modulation of the androgynophore movement by applying auxin (IAA) or an inhibitor of auxin polar transport (NPA) in the flowers. We recorded the movement of the androgynophore during mechano-stimulation and analyzed the duration, speed, and the angle formed by the androgynophore before and after the movement, and found that both IAA and NPA increase the amplitude of the movement in P. sanguinolenta. We hypothesize that auxin might have a role in modulating the fitness of these Decaloba species to different pollination syndromes and demonstrate that an interspecific hybrid between insect- and hummingbird-pollinated Xerogona species present a heterosis effect on the speed of the androgynophore movement.

Rapid touch-stimulated movement in the androgynophore of Passiflora flowers (subgen. Decaloba; Sect. Xerogona): an adaptation to enhance cross-pollination?

Plant touch-sensitive organs have been described since Darwin's observations and are related to a quick response to environment stimuli. Sensitive flower organs have been associated to an increase in the chances of cross pollination but there are few studies regarding this topic. Here we describe for the first time the kinetic of the androgynophore movement of 4 Passiflora species (P. sanguinolenta, P. citrina, P. capsularis, and P. rubra). For that, we collected flowers and recorded the movement after mechano-stimulating the androgynophore. From the recordings, we described the movement regarding its response and sensibility to mechanical stimulus and calculated the duration, speed, and the angle formed by the androgynophore before and after the movement. From our data we were able to propose a link to the pollination habit of these species. The movement of the androgynophore in these Passiflora is a noteworthy floral feature that might lead us to another astonishing example of a mechanism that evolved among angiosperms to assure sexual reproduction.