Homesteading Forum banner
1 - 19 of 19 Posts

·
Don't let "good enough" be the enemy of perfect.
Joined
·
3,471 Posts
Discussion Starter · #1 ·
I'm an engineer---not a biologist. But I was looking at a forest of tall pine trees and got to wondering why, exactly, do trees grow upwards?

Is it because they are the attracted to the sun?
Or repulsed by gravity?
How do they even know which way "up" is?
Would a tree growing on a spaceship (absent gravity) under artificial light grow towards the light?
And what, internally, makes them grow towards the sun, if that is the driving factor?
 
  • Like
Reactions: doc-

·
Registered
Joined
·
4,747 Posts
If they were repulsed by gravity we would have figured out how that works and have made antigravity machines. Also there would be trees in low earth orbit.

Trees grow up because they need sunlight to prosper and evolution selected for tall trees so they would compete with other trees.
 

·
Premium Member
Joined
·
7,098 Posts
Because if they grow down they die?

Mon
 
  • Like
Reactions: wdcutrsdaughter

·
Registered
Joined
·
22,057 Posts
To get sunlight. Look at a woods sometime along the edge. Trees do not always grow up. Sometimes they grow up a couple feet and then turn sharply toward the light. I cut a 60 foot cottonwood tree in my woods about a month ago that was growing out over our yard about 6 feet off the ground and the stump was 42 feet back in the woods. I was very careful with that one. All that weight hanging at about a 30 degree angle makes them prone to snapping off or barber chairing when you start cutting. Good way to get killed.
 
  • Like
Reactions: NRA_guy

·
Registered
Joined
·
4,667 Posts
I'm an engineer---not a biologist. But I was looking at a forest of tall pine trees and got to wondering why, exactly, do trees grow upwards?

Is it because they are the attracted to the sun?
Or repulsed by gravity?
How do they even know which way "up" is?
Would a tree growing on a spaceship (absent gravity) under artificial light grow towards the light?
And what, internally, makes them grow towards the sun, if that is the driving factor?
In a nutshell, trees, like all plants, grow upward reaching for the light of the sun because they're hungry. They all collect sun energy, CO2 and moisture to combine and convert into glucose to provide themselves with the food energy they need to store to stay alive. It's called photosynthesis.

The first link posted here explains how that works.

The second link is about the zero gravity experiments that have been done with growing plants on the space station using artificial lights. If a space station was a lot bigger than the existing space station the same thing could be done with trees.

What Provides Electrons For the Light Reactions?

The sun is the main source of energy for almost every living thing on Earth. It gives a plant the light energy it needs to photosynthesize, which converts that light energy into a storable form (glucose) and keeps plants alive. A by-product of photosynthesis is the oxygen all animals need to survive.


.
 

·
Registered
Joined
·
9,355 Posts
I'm an engineer---not a biologist. But I was looking at a forest of tall pine trees and got to wondering why, exactly, do trees grow upwards?

Is it because they are the attracted to the sun?
Or repulsed by gravity?
How do they even know which way "up" is?
Would a tree growing on a spaceship (absent gravity) under artificial light grow towards the light?
And what, internally, makes them grow towards the sun, if that is the driving factor?
Engineers make trees grow down all the time, and have been for thousands of years. They call it kengai.
 
  • Like
Reactions: Paumon

·
Registered
Joined
·
9,355 Posts
Yes! Kengai is an excellent example of engineering trees to grow downwards. But the leaves still all point towards the light so they can use their solar collectors.

Pictures of kengai:


.
I'm working with an olive tree. It hasn't told me yet if it wants to be Kengai, Han-kengai or Fukinagashi. I'm hoping the latter, but there is still much time.
 
  • Like
Reactions: Paumon

·
Registered
Joined
·
4,487 Posts
I'm an engineer---not a biologist. But I was looking at a forest of tall pine trees and got to wondering why, exactly, do trees grow upwards?

Is it because they are the attracted to the sun?
Or repulsed by gravity?
How do they even know which way "up" is?
Would a tree growing on a spaceship (absent gravity) under artificial light grow towards the light?
And what, internally, makes them grow towards the sun, if that is the driving factor?
Excellent questions...The trivial answer to why plants seem to seek the sun is because "That's what works.."

A more mechanistic answer ---

It's easy to see that as photosynthesis procedes after germination, new cellulose & lignin is produced and laid diown in a genetically determined manner producng elongation of the new shoot....Then the shoot bends towards the light due to the forces of the differential cell turgor (intracellular hydrostatic pressure) between the side towards the light vs the side away from the light. That difference in pressure is caused by more water loss from the cells on the warm side....Once a direction of growth is established, it will become permanent as the shoot becomes more lignified (harder).....The oriental horticultural techniques, or Indians bending "Trail trees" in the forest provides an unnatural force to get the directional growth.

Nature seems to always follow The Minimum Principle-- no excess effort expended in accomplishing a goal. The professor in my Bio 101 course in college was an old-time British naturalist (He had idscovered a couple new species of hydra in his early research. One is named after him.) He always said about evolution--"How long is a giraffe's neck?...Long enough."...

.In keeping with the concept that an apple doesnt fall far from the tree-- If you notice how an outcrop of trees or flowering plants grow, you'll see that the tallest are in the middle of the group and they are progressivley shorter away from the center-- each grows just fast enough to get the optimum amount of light.
 

·
Don't let "good enough" be the enemy of perfect.
Joined
·
3,471 Posts
Discussion Starter · #12 ·
Thanks @doc-

Great details. Exactly answers my questions.

I love
Nature seems to always follow The Minimum Principle-- no excess effort expended in accomplishing a goal.
Humans (as part of nature) follow that principle. It's why humans vote for politicians who promise them the easiest life, the most welfare, and increased benefits.

About 50 years ago, I went out on the Mississippi River to watch a large floating Corps of Engineers mat sinking operation. I asked the Chief how they ever figured out how to do the difficult, complex job of starting the process up on the shore and continuing it out to the middle of the river.

He said, "Whenever you have a difficult operation, just tell the men to do it. Don't tell them HOW to do it. Then watch. Not only will they figure out how to do it---they will figure out the way to do it with the least effort."

PS: I wrote the specifications for much of the equipment you can see (and much you cannot see) in that video.
 
  • Like
Reactions: doc-

·
Registered
Joined
·
7,753 Posts
Actually they grow up and down. The part we can see grows up, and what we can't see are the roots. I have seen tree roots two hundred feet down in mine shafts.
 

·
Don't let "good enough" be the enemy of perfect.
Joined
·
3,471 Posts
Discussion Starter · #14 ·
Actually they grow up and down. The part we can see grows up, and what we can't see are the roots. I have seen tree roots two hundred feet down in mine shafts.
Hmmm. So they grow up to get to the sun and down to get away from it. Sounds like some people I know. ;)
 

·
Don't let "good enough" be the enemy of perfect.
Joined
·
3,471 Posts
Discussion Starter · #18 ·
heliotropism
Yep. Thanks. I see that's what the directional growth is called. My curiosity was what exactly (inside the plants) causes them to behave like they do.
---------------------------
he·li·ot·ro·pism
noun
the directional growth of a plant in response to sunlight.
-------------------------
 

·
Don't let "good enough" be the enemy of perfect.
Joined
·
3,471 Posts
Discussion Starter · #19 ·
Now that I think about it, I remember that some folks grow tomato plants upside down (but it looks like the plants want to turn around and grow upright):
Plant Window Fixture Rectangle Door


Plant Natural environment Land lot Grass Groundcover
 
1 - 19 of 19 Posts
Top