PHILANTHROPY AND PHILODENDRONS
Asclepiad Pollination
I recently decided I wanted to start pollinating some of the Asclepiads at the conservatory, so I took six plants, two plants of each species I could find in flower, on a cart upstairs to where the microscopes are kept. You could call it Noah's Ark for Asclepiads.
I started first with the Huernia because their flowers are bigger than the Pseudolithos but the plants themselves are smaller than the Stapelia so they fit more comfortably underneath the microscope.
I used the species Huerna schneideriana, but I forgot to take photos of the plant itself so Figure 1 is of my personal H. schneideriana from when I was in high school.
Figure 1: My Huernia schneideriana from high school that I bought at a nursery in rural Wisconsin.
Corpusculum
Guide Rails/
Staminal Lock
One Pollinium
Corpusculum
Pollinia
Pollinarium
Figures 2 + 3: H. schneideriana flower under a dissecting microscope.
Figure 4: H. schneideriana pollinarium through a dissecting microscope lens.
Once I got the flower situated underneath the dissecting microscope as shown in Figure 3, I used a 0.3mm beading needle to carefully remove one of the pollinaria from where it sits directly atop the guide rails/staminal lock.
To do so, I used the needle to hook the corpusculum and slide the pollinium out. The pollinarium is shown separately in Figure 4. Each of its pollinium contains about 40-60 pollen grains, which aren't inside of a sac but rather stuck together by the pellicle, which is a lipid-rich substance excreted by specialized cells called tapetum (Wyatt 2000; Demarco 2017).
I also want to clarify ahead of time that pollinaria is plural for pollinarium and pollinia is plural for pollinium. When researching this topic, my eyes did not immediately catch the difference between all four of these words and then when they did I was very confused for a moment.
However, it turns out removing the pollinarium was the easy part. After removing it from the first flower, I set the needle it was stuck to aside and replaced the H. schneideriana plant under the microscope with the other one.
For reference, I temporarily moved the pollinarium to a tweezers and placed it under the microscope as shown in Figure 5. This photo is meant to show just how difficult the pollinarium is to see without the microscope.
Picking the needle back up, I tried to insert one of the pollinia inside the staminal lock. However, it turned out that the 0.3 mm needle was not quite thin enough. I did not end up taking photos of this part of the process because as much as a tried, I was unsuccessful. Also, I learned just how much nectar these flowers produce--if I accidentally poked the flower with the needle while looking under the microscope, I could see a large amount of fluid start to come out of the pore I had poked, flooding that area of fused corolla.
As a result, I ordered 0.15mm acupuncture needles and they are supposed to arrive tomorrow. Hopefully they will come midday and I will have the time to head over and try them
Pollinarium
Figure 5: H. schneideriana pollinarium under a dissecting microscope.
out. Nonetheless, I still wanted to try pollinating the Stapelia and Pseudolithos flowers to see if they were at similar levels of difficulty and what other challenges I might face while pollinating them. I started first with the
Stapelia hirsuta, which I had to keep in place with my wallet as seen in Figure 6.
Figure 6: Stapelia hirsuta situated under a dissecting microscope.
Once I had it situated under the microscope, I removed the pollinarium and swapped the plant out for the other of its species. Figure 7 shows the needle with the pollinarium on it hovering over the flower I wanted to pollinate.
Pollinarium
Pollinarium
At the time, the staminal lock/guard rails looked more prominent than it is in Figure 7.
However, once again, I was unable to fit the pollinarium inside the staminal lock, which I believe is due to the needle being too large in diameter.
Staminal Lock/
Guard Rails
Figure 7: Stapelia hirsuta flower with the pollinarium of another flower on a needle.
Corpusculum
Caudicle Wings
Caudicle
Pollinium
Pollinium Key
Figure 8 shows the pollinarium of the Stapelia hirsuta, which is a much clearer photo than the one I took for the Huernia pollinarium. Because of that, I labeled the anatomy more thoroughly.
It should be noted that, like the caudicle wings, there are two caudicles, pollinia, and pollinium keys. I chose not to label both of each of these parts because I didn't want to add too many arrows to the picture and make things more confusing.
All labelling sourced from: (Barad 1990; Mulej + Strlič 2002)
Figures 8 + 9: Pseudolithos migiurtinus at the UC Davis Botanical Conservatory.
The last species I attempted to pollinate was our Pseudolithos migiurtinus, which has the smallest flowers but also the smallest plant, meaning that the flowers are probably the most difficult to pollinate but the plant itself fits underneath the microscope most comfortably.
Figure 10: P. migiurtinus pollinarium.
Figure 12: P. migiurtinus flower through a microscope lens.
Figures 10, 11, and 12 are the remaining photos of I took of the P. migiurtinus while trying to pollinate it. I wish Figure 12 was a little clearer, but after looking at the previous photos of Huernia and Stapelia it should be relatively easy to see which parts are which. I will make sure to update with more photos once I get a chance to try pollination with the 0.15 mm needles!
Figure 11: P. migiurtinus flowers through a microscope lens.
Works Cited:
Barad Gerald S. 1990. Pollination of Stapeliads. Cactus and Succulent Journal. 62: 130-140. https://barad.asclepiad-international.com/pollin.html.
Demarco Diego. 2017. Floral glands in asclepiads: structure, diversity and evolution. Acta. Bot. Bras. 31(3). https://doi.org/10.1590/0102-33062016abb0432.
Mulej Iztok, Strlič Matija. 2002. Stapeliads, morphology and pollination. Welwitschia. 5: 6-13. https://www.huernia.com/Morphology.pdf
Wyatt Robert, Broyles Steven B., Lipow Sara R. 2000. Pollen-Ovule Ratios in Milkweeds (Asclepiadaceae): An Exception That Probes the Rule. Systematic Botany. 25(2): 171–80. https://doi.org/10.2307/2666636.