Answer: What do you call a rotating flower?

This was another hard question, so don't feel bad if you didn't get it instantly.  That's part of the point of this blog--search/research questions often open up into fascinating areas that you might not have expected when you started. 


Here's what I did... 

Started with my first search: 

 [ rotation flower stem ] – and found nothing.  

Then, because I happened to know that plant movements like this are usually called "tropism" (which you could have figured out by using a reverse dictionary), I changed my query to: 

[ rotation plan tropism ] 

And deleted the "flower" term (as I thought it might be overly specialized).  I found a pretty decent Google Books result.  “Plant tropisms and other growth movements”

By skimming through that book, I learned the words “phototropism”  and “heliotropism” (for movement towards light, and more specifically, movement towards the sun).  

So that led me to read the  Wikipedia article on heliotropism , which I got to my doing a serach for:

   [ heliotropism ]

That was a pretty good article, which in turn led to me an article from the journal  Natural History -- where learned that heliotropic plants can be much warmer than surrounding regions, giving insects a warm place to be and that the pulvinus  is a plant organ for sun tracking - not quite what I need, but getting close.  

But in reading this article from Natural History, I got the idea that what I was ACTUALLY looking for was not a tropism (which is a response to external stimuli), but something that's part of the natural growth pattern of the plant.  

So now, I try the query: 

 [ plant stem spiral growth ]  

which led me to an article on Answers.com about yet another word: phyllotaxis.  

After 4 queries and about 10 minutes of reading through articles, I've finally figured out the word that describes the situation at hand... that is, the rotational development of a plant stem as it grows outward.

While this is all great and good, I really really want to confirm that phyllotaxis is causing the mustard stem (and its flowers) to rotate as they grow.  

And this is where I start to get stymied because I haven't yet found a convincing first-hand account of phyllotaxis in mustard plants (or a closely related plant, say another plant in the Brassica family).  

Ideally what I want is a nice time lapse video, so I look for

 [ time lapse phyllotaxis ]

And I find a JSTOR article “The origins of the spiral theory of phyllotaxis”  William Montgomery -- looks interesting, but they want $38 for the article (arrgh!  we call this a paywall, and it's deeply, deeply annoying).  

I kept looking around for another hour or so, and learned that plants have circadian movements (day to night leaf folding) such as this video at Indiana University http://plantsinmotion.bio.indiana.edu/plantmotion/movements/leafmovements/clocks.html

- learned about nutational movements (light seeking… sunflowers waving around looking for light) and I learned about “nastic movements” – e.g., the shoot of a morning glory rotating to find a support (there is remarkable video footage here: http://plantsinmotion.bio.indiana.edu/plantmotion/movements/nastic/nastic.html  - be sure to click on "morning glory twining")

A few images from their movie:

-

SO... in the end, I've figured out what the term and concept describing this behavior is (phyllotaxis), but I have yet to find anything on the web that's specifically about the phyllotaxic movements of common mustard.  

Looks like I'll have to take those pictures myself!  Maybe a weekend project!!!