A few harmless questions

pup

Trees are like me lazy, the shortest root!!! to the top and back again is a straight line. so that is why the grow that way!!!!.

__________________
PUP
Advanced begginner


Heatzone USA9/10
Aus 3/4

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lehket

Actually, you can't separate the environmental forces that affected the plant's evolution from the general form the plant currently has. It's all well and good to say that a plant kept in darkness will still grow upward, but the reason it does so it that its genotype (genetic material) provides the basis upon which the phenotype (the actual appearance of the plant) is built, and that genotype evolved in an environment filled with light, air of a particular mix, soil of a particular composition, and in the gravitational field of the Earth. The phenotype arises from the expression of the genotype through biochemical processes and can be greatly affected by prevailing environmental factors.

If you took a particular species, put it into a radically different environment than is natural for it (say, perpetual darkness) and tried to grow it over many generations, one of two things would happen. (A) It would go extinct, in which case you'd no longer be asking why it grew upright. (B) The members of the species that survived would gradually become better adapted to the new environment. It's entirely possible that after a long enough time under such unusual conditions, the form(s) that evolved would not be upright, or not entirely upright.

So the real answer to why plants generally grow upright has to be found not in a single factor but in a combination of all factors: what they can get from soil, air, and sun and how the gravitational field helps or constrains them in acquiring those things.

As an aside, centrifugal force is a pseudoforce, as someone else indicated. It's what you think you feel when you are, for example, in a car making a sharp turn. You feel like you're being thrown against the side of the car, but you're not. In reality, that's just inertia: your body "wants" to continue moving in a straight line at a constant speed. The real force arises from the fact that the car is not moving in a straight line. It's turning, so it's pushing you into the turn. This real force is called centripetal ("center-directed") force.

Objects on the Earth's surface feel a centripetal force due to gravity. They are attracted towards the center of the Earth. They "think" they experience a centrifugal force (which is, remember, not a real force) tangent to the Earth's surface in the direction of the Earth's rotation. But this effect is so small compared to the strength of the Earth's gravity that we don't notice it.

It's not an issue for trees, either.

__________________
--Dale
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Co-author of Spiritual Telemetry,
Host of Planet Baha'i and the Planet Baha'i Forum

kingkong

Very good Dale! Time for a little break.

photo by Fred Jacobs Western Juniper #2

Attached Images

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jondenver

Geotropism

MattO

Exactly.. and Kong knows this already...

kingkong

Iraq and Idaho....what beautiful countries.

MattO

Now don't go trying to rile me up, and get me inta this scrap!

And we don't claim that desert down south, it might as well just be part of Nevada...

malhaku

Oh fun! A bonsai thread with discussions of real vs. psuedo forces in a rotating reference frame!

I feel compelled to provide this link - http://www.xkcd.com/123/

BonsaiManNJ

An overview and list of tropisms:


http://en.wikipedia.org/wiki/Tropism
In complete lack of light, a newly sprouted seed follows geo/gravi tropisms until it exhausts its reserve then dies.