Raindrop-powered Lousewort Launchers

by Dana Atkinson | Apr 1, 2024 | 0 comments

blooming lousewort, wood betony
Blooming louseworts or wood betony. Photo © Dana Atkinson.

Have you ever launched something through the air from the bowl of a plastic spoon? I sure have. Similarly, louseworts catapult their seeds to new areas using raindrop power. Those raindrop-powered seed launchers were the main reason that louseworts were on my bucket list of things to see.

One day in late April, I was driving down a dirt road when I spotted a lousewort patch. The thought of seeing the lousewort catapult its seeds stopped me in my tracks. Since seed pods come after the flower blossoms, I would have to wait awhile to see raindrops launching seeds. But that’s ok, because there’s more to the lousewort’s story, and I soon discovered that as I crawled through the warty lice—I mean louseworts—chasing their bumblebees with my camera.

Lousewort (also called wood betony) flowers are really good at attracting bumblebees to do their pollinating. Their flowers are specially created with a hook-shaped hood, or beak, that has the stigma protruding from the tip. This allows the stigma to contact pollen that is in hard-to-reach places on the bumblebee. One of the areas that is hard for the bumblebee to reach when it is grooming (gathering the pollen to fill its pollen baskets) is the area between the bumblebee’s head and its thorax. In this close-up photo, take notice that this is where the stigma is contacting the bumblebee.

Bumblebee feeding on lousewort. Photo © Dana Atkinson.

Something else of note that you can’t really see happening in that photo is this: as the bumblebee is getting nectar from the flower, it gets a shower of pollen from the stamens hidden in that hook-shaped hood. This pollen can now get a ride to another flower. There, the pollen in hard-to-reach places has a good chance of connecting with the stigma. This process is a nifty design that ensures cross-pollination of the louseworts.

While I was in the lousewort patch, I was thinking about the strangest thing…and had to dig up a lousewort’s roots to see it for myself. Why? Lousewort steals from nearby plants. In other words, lousewort is a parasitic plant. Technically it’s called a “hemiparasite” because it’s not totally dependent on parasitizing others but can do some photosynthesis on its own.

Here’s a photo of what I dug up. The whitish root (from the lousewort) looks to me like a snake that has bitten, and is hanging onto, a blackish brown one (root of a neighboring plant). The “head,” or that kinda bell-shaped, suction-cup-looking thing, is called a “haustorium.” Haustoria are what louseworts form to attach themselves to their neighbors’ roots.

haustorium on lousewort root
Haustorium on lousewort root. Photo © Dana Atkinson.

Here’s how this works. When a lousewort’s root encounters a root from a nearby plant, it forms a haustorium to graft itself onto the root, penetrate the root, and connect to the transport system (xylem and phloem) of the host’s root. It does this to steal water and nutrients from the parasitized host.

That’s not as easy as it sounds, because first, the lousewort has to avoid or, in some cases, overcome the host plant’s immune response. In other words, there’s a chemical skirmish. Secondly, once the lousewort wins and successfully connects to the piping system, it has to actively take from the host by establishing flow/exchange from the host to itself by the use of gradients, osmotic pressure, etc. It’s quite an elaborate and complicated theft system.

If you happen to get the opportunity to get out in a lousewort patch to see the lousewort’s pollination system or its seed dispersal mechanism, take a moment to ponder this. Why might the Creator have made such an amazing plant like lousewort with its raindrop-powered seed-launchers and its nifty pollination system, but then, for some reason, have given it the ability to steal from other plants?

Well, these parasitic plants may actually be beneficial. Not to the parasitized plants, of course, but by keeping certain plants from dominating the area and, in turn, allowing a more diverse community. So it is possible lousewort’s parasitic activity is engineering more species richness in its local ecosystem.

Anyway, I got to see all those fun things and more as I kept my eye on the lousewort patch while awaiting the right time to see the seed-launching process. This turned out to be mid-June in our area of north-central Pennsylvania. After the seed pods turned brown and opened up into cups, they looked ready to disperse their seeds.

lousewort seeds
Lousewort seeds. Photo © Dana Atkinson.

I went out in the rain to see the catapults in action. Of course, the chances of seeing a direct hit were rather slim, but I did see some action out of the corner of my eye. I was dreaming up ways to drip drops of water into the seed cups to predictably send the seeds flying, but settled on using my finger to trigger the catapult.

I turned my camera on slo-mo video recording and swung my finger down, like I was going to launch something from a plastic spoon, just catching the tip of the seed pod’s cup. It worked! In the slo-mo playback, the seed dispersal process is visible. As my finger brushed the end of the seed cup, it tipped down, and a seed was dispensed toward the tip of the cup. On the cup’s rebound, the seed was catapulted into the air. The seed was launched very rapidly at about a sixty-degree angle. If flew so fast that is was just a barely-visible blur in the video while all the other action seemed to take a long time. I wonder how far the seed flew.

Wouldn’t it be fun to set up a dropper system to predictably trigger the catapults so you could see the raindrop-powered lousewort launchers in action? Then, while you’re at it, spread a sheet nearby to see how far the seeds are thrown?

I’m sure you’ve figured out there’s even more to the lousewort’s story. Like, how did it get a name like warty lice? And, who are its enemies, besides the plants it steals from? Or, who are its friends, beside the bumblebees? Yes, there’s always more to explore when it comes to God’s fascinating creations.

lousewort seed heads
Lousewort seed heads. Photo © Dana Atkinson.

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