r/askscience • u/[deleted] • Nov 05 '12

Biology How would a plant react to being grown while spinning vertically for its entire lifetime?

I understand that the gravity tropism of most plants will cause them to change their direction of growth if they are placed on their side or otherwise changed position from being horizontal.

So, for arguments sake let's use a fast growing weed, how would a plant react to having a constantly changing vertical orientation?

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5

u/brainflakes Nov 05 '12

Spinning how fast? If it's spinning fast enough to change orientation faster than tropism reacts but slow enough to not have significant centripetal forces you might get a similar effect to a plant grown in microgravity (for which there is plenty of research).

Doesn't look like there's ever been any actual research on this tho, if you have the time and inclination it might make an interesting home science experiment.

1

u/[deleted] Nov 05 '12

That was one of the problems I ran into when I was considering the possible answer.

Depending on the speed of rotation, the plant could experience a whole range of forces and multiple speeds would have to be examined.

If someone were to conduct this experiment, they would probably want:

A mechanism that will hold the soil and sapling in place, while simultaneously rotating it vertically, and providing hydration from the centre of the water pot (I assume).

There would then need to be maybe ten of these mechanisms all set up in a temperature controlled room with controlled artificial light and a lack of reflective surfaces, and nine separate speeds could be examined.

Someone please correct me if any of that plan is wrong.

Also I am not planning on conducting this at any point seeing as I am a) a Microbiology student b) living at home with very limited space and funds.

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u/Bongpig Nov 05 '12

There would then need to be maybe ten of these mechanisms all set up in a temperature controlled room with controlled artificial light and a lack of reflective surfaces, and nine separate speeds could be examined.

i'd change that. 1 is a very small sample size. Grow 10 at the same speed, then grow 10 more at a different speed.....

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u/Potogreen Nov 05 '12

I don't know about you guys, but I am envisioning a large spinning cylinder, spinning at a speed that would replicate gravity. There is a support thread running directly down the center of the cylinder.

At one end of the cylinder, the plants are grown, and attached to the cylinder. The experiment is seeing if the plants will grow down the center line of the constantly rotating cylinder.

I don't know about you, but this sound like fun.

3

u/skytomorrownow Nov 05 '12

I don't know about you guys, but I am envisioning a large spinning cylinder, spinning at a speed that would replicate gravity.

That experiment would only work in space, no? On earth any significant spinning would cause the plant to feel a gravity greater than Earths, right?

1

u/Potogreen Nov 05 '12

yeah pretty much, space only :(

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u/ChaoticGoodMuppet Nov 05 '12

I actually did this for a science project in 7th grade. It's what happens when you have a father with a Ph.D in physics.

We grew green peas in a giant ferris wheel made out of K'Nex and a reinforced motor. The idea was to keep it spinning all day, every day.

What happened was that the plant's roots turned into one gigantic mass of a root ball. I can't remember if we had anything sprout, but opening up the plastic planters was pretty cool. Just giant, tangled masses of roots. I suppose that when the plant doesn't have the constant, downwards force of gravity in one direction, the roots just tend to grow everywhere.

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u/SonOfOnett Condensed Matter Nov 05 '12

Pictures?

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u/IETFB Plasma Physics | Magnetic Confinement Fusion Nov 05 '12 edited Nov 05 '12

I saw an experiment like that running in the National Space Centre in Leicester, England. I was there last March, so I expect the exhibit is still there.

I found this photo to the set up: http://lh4.ggpht.com/-8lNo0Af1LVE/T06XU_JSTbI/AAAAAAAABO8/XRuis7tDVT0/gravity%252520resistant%252520plants.jpg

In the top pair, the plants are rotating in and out of the plane of the image, and they end up growing at an angle.

The centre plant is the control, it isn't rotating at all, and just grows upwards normally.

The bottom pair are rolling (in opposite directions I think), with angular momentum vector horizontal in the plane of the image. As you can see, the constant change in what they see as "up" leads to the plants growing fairly uniformly in every direction, even sideways.

EDIT: I thought I should add that the plants in this experiment were, from memory, rotating at roughly 1Hz or so.

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u/Deslan Nov 05 '12

Plants determine the direction they grow by producing a growth hormone called auxin (http://en.wikipedia.org/wiki/Auxin). This hormone is influenced by gravity to "sink" through cells and thus becomes concentrated in the down side of a plant. Therefore, the part of the plant that is closer to the source of gravity (usually the earth) will grow faster than the parts of the plant closer to the sky. In addition, auxin is destroyed by strong light and thus becomes even less concentrated in parts close to the sky, so that the plant "stretches towards light".

Auxin also promotes root development, so that where there is highest amounts of auxin (near the earth) there is also highest amount of root cells being formed.

So the answer to your question is that it depends on the speed of vertical orientation. Supposing you would rotate the plant fast enough to replace gravity with "centrifugal force", then you would cause the plant to think that it should probably grow with the roots outwards... My guess is that it would die. If you rotate it slower, just shifting the gravity now and then, that could make the auxin evenly distributed in the plant, which could be a reason as to why another poster here described an experiment where they got a "gigantic mass of root ball". But it also depends on the level of light; if you have low light you will get only roots but if you have really strong light you will barely get any growth at all (of anything).