Aristolchia labiata Research Text

Plant. Aristolchia labiata

Name: Aristolchia labiata (Pelican Pipevine)

Family: Aristolochiaceae

Date & Location: Lausanne Botanical Garden, Switzerland, January 2025

magicflute002. "Aristolochia labiata / Mottled Dutchman's pipe / Rooster Flower,".11 November 2019. iStock

Figure 1 displays the flower's utricle (blue arrow), tube (yellow arrow), and the bilabiate, highlighting the two-lips: the upper lip (red arrow) and lower lip (red arrow).

Why I chose this plant: From observing a few dead and unusual flowers on a staircase leading to another level of the greenhouse and a strong stench prompted numerous questions. What species of flower is this, and what are the functions of its design? How have ecological and evolutionary factors shaped them?

Scientific question: How does this unique flower structure of Aristolochia labiata evolved to optimize pollination in attracting flies for pollination? 

As one of the earliest lineages of angiosperms to evolve trap flowers (Oelschlagel et al. 2009), the Aristolchia ringens Vahl is a perennial twining plant native to South America that grows in tropical regions. The flower features a lid, tube, and the utricle (Figure 1). The flowering plant has evolved unique mechanisms to maximize pollination efficiency—attraction of pollinators, nectar feeding, and pollination—to attract various fly species, including the bluebottle fly, flesh flies, and common housefly.

The two-day protogynous flowering/pollination process for Aristolochia begins with the maturity of the female reproductive organs, the pistil, releasing an odor resembling decay, which is highly concentrated in the tube. As a result, the flies are lured into the tube lined with hairs facing downwards, trichomes, which produce nectar from its glands. Now, the fly is enticed by the nectar and moves further down the tube and is prevented from exiting because the trichomes allow for easy entry but a complicated exit, ensuring they spend more time in contact with the flower. They force the fly to continue further down the tube and then into the utricle. The fly is trapped in the belly, where the gynostemium, a fused male and female reproductive organ uniquely found in a few angiosperms, is open and ready to be pollinated. This is where the fly will remain there, fed by the nectar producing glands from the utricle wall until the next day when the flower switches to the maturity of the stamen.

While the flies are held captive, because more than one fly can be helped in the utricle, the flies are drawn to a small area resembling a window with the open gynostemium at the center at the bottom of the utricle, manipulating a false exit. Incentivizing the transfer of pollen from other plants to the stigmatic lobes while the flower's pollen sacs remain closed[, which hold the male pollen] (Bhaskar, S., Paul .M, & Stephen A. 2023). The Aristolochiaceae developed another unique trait: the anthers' ability to burst explosively, covering the entire utricle with [male] pollen grains during the stamen phase (Oelschlagle et al. 2009). Additionally, the male flowering phase changes its inner surface to enable the flies to exit. "The stigmatic lobes wilt and fold together [gynostemium stigmatic’s surface closes]".

Reference List:

Bhaskar, S., Paul .M, & Stephen A. (2023, January). Insights on the flower behaviour and trap mechanisms of Aristolochia ringens, gaping Dutchman’s pipe [report]. ResearchGate, https://archive.org/details/httpsdiscoveryjournals.orgspeciescurrent_issue2023v24n73e37s1516.pdf_202311/page/n1/mode/2up. 

Datiles. M.J (2015, October 8). Aristolochia ringens (Dutchman’s pipe) [report]. CABI Digital Library. Aristolochia ringens (Dutchman’s pipe) | CABI Compendium

Oelschlagle . B, Gorb. S, Wanke. S, & Neinhus. C. (2009, July 14). Structure and biomechanics of trapping flower trichomesand their role in the pollination biology of Aristolochiaplants (Aristolochiaceae) [report]. New Phytologist. Structure and biomechanics of trapping flower trichomes and their role in the pollination biology of Aristolochia plants (Aristolochiaceae). 

Stashenko, E. E., Andrés Ordóñez, S., Marín, N. A., & Martínez, J. R. (2009). Determination of the volatile and semi-volatile secondary metabolites, and aristolochic acids in Aristolochia ringens Vahl [report]. Journal of chromatographic science, https://doi.org/10.1093/chromsci/47.9.817.