Botany word of the week.

Pappose

A plant that bears a pappus (or more likely, pappi) is said to be pappose. With purpose.  And no porpoises.  (Please stop me before I go any further).

What’s a pappus, you say?

See this dandelion flower (actually a cluster of florets) that has gone to seed?  If you’ve ever held one in your hand and pulled a single seed away from the head, and then eyeballed it really closely…you’ll see that the fine, fuzzy white stuff on top (actually a modified calyx) sits above the thin brown seed like a skeletonized parachute.  The parachute calyx is a pappus, and although you can’t see all of them really well without a microscope, if you could count, you’d find that there are around 100 bristle-like filaments comprising each one. As dandelion seed is dispersed via wind, this pappus structure proves very useful, able to carry the seeds up to 100 kilometres (62 miles).

SONY DSC

Dandelions aren’t the only plants that are pappose – you’ll find that most members of the daisy (Asteraceae) family are as well – but I’ve got one more fascinating dandelion pappus story to share before I sign off on this post. Get this: In 2018, researchers at the University of Edinburgh (using some cool gadgets such as a wind tunnel, lasers, high speed cameras, and x-ray microtomography) discovered the precise number of and the specific way the filaments in each pappus are arrayed makes even more of a difference to the efficiency of wind dispersal of the seeds than previously thought. It was an accepted theory that the resistance (drag) of individual filaments to wind makes dandelion seed so good at flying. It turns out that the way that moving air flows around each individual filament – and the filaments around it – creates a sort of stabilized vortex ring, allowing the seeds to stay buoyant for an impressive time and over long distances. You can read all about the physics of this amazing adaptation here.

Sources:
Martina Ribar Hestericova. “Dandelion seeds create vortexes to remain aloft.” Physics World. October 22, 2018. https://physicsworld.com/a/dandelion-seeds-create-vortexes-to-remain-aloft/.
Nature. “Revealed: The extraordinary flight of the dandelion.” October 17, 2018. https://www.nature.com/articles/d41586-018-07032-6.

20 thoughts on “Botany word of the week.

  1. And milkweeds! We played with milkweed pappi as much as those of the dandelions when we were kids. This was a good word choice. I was especially surprised to read that the pappus is a modified calyx. I’m still not sure I understand that, since I’m so used to thinking of the calyx as the sepals.

  2. I wrote about horticultural slang that my colleague down south and I invented over the decades to compensate for lack of some technical lingo. With all the proper horticultural terminology, you would think that everything is covered.

      1. Thank you, Sheryl. We are all doing well and sheltering in place. I’m home with my husband and eldest son. My younger son is sheltering in place and take all classes on line at university. I miss him. How are you?

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