Why do plants grow the opposite of the force of gravity?
Plants grow in all directions. The green part needs air and light to function and that, as a general rule, is in the “up” direction from the ground.
Light is the main reason for growing towards the sky but the thing holding them up is their cell walls. The cell wall is made of chitin which is very sturdy, preventing collapse of the plant or tree.
If at first you don’t succeed, skydiving is not for you.
Turgor from the water in the cells also contributes to their rigidity. When plants wilt it is water that’s been lost, not cellulose (which is what I think you meant to say instead of chitin – chitin is what insect exoskeletons are made of.)
Plants have hormone-like compounds that guide their growth. I think the generic term for them is auxins, although that might be a particular one. Some do things like help them grow toward light, some that help the roots grow downward and the stems grow upward.
If all you have is a hammer, everything looks like a nail.
Plants have these types of indiffereitiated types of cells called meristematic cells, which are ‘growth’ cells. The meristematic cells in the roots of plants are called root meristem, and the cells at the other end are called the shoot meristem.
Shoot meristematic cells are small, thin-walled, and uniform in size and shape. They also have a dense cytoplasm and contain many small vacuoles. (The above was paraphrased from “A laboratory Guide to Plants.” Dorothea V. Dicecco. University of Connecticut, 1993. Page 20.)
The only relative part of the above, actually is the blurb about the many vacuoles that are in these apical, or shoot meristematic cells. If you are unfamiliar, vacuoles in cells are spaces that the cell uses to store things in…various gasses, liquids, wastes, etc. While these things are never actually empty, sometimes they only contain the cell’s own cytoplasm while they are waiting to be used for other purposes.
It is ‘theorized’ that some of these many vacuoles contain some sort of granular nutrient or crystalized molecules of somesort that are affected by gravity. Once these crystals have fallen to the bottom of this vacuole, they react chemically with the membrane of the vacuole, and in effect what ever other chemical receptors there are in the cell’s cytoplasm. Once this certain reaction is detected by the cell, it then somehow ‘knows’ not to focus it’s cell building activities in the region of the reaction. Instead, it focuses its energy on the opposite end, as far from the reaction detection as possible.
Now, if this all sounds far fetched, I’m sorry. However, it may sooth readers to know that a system similar to this is also used in our own inner ears for us to be able to detect which way is down, up, etc.
“If we submit everything to reason, our religion will have no mysterious or supernatural element. If we offend the principles of reason, our religion will be absurd and ridiculous.” Blaise Pascal
Oh, and FWIW, I’m pretty sure that light isn’t responsible for the plant’s growing up. Otherwise, it wouldn’t grow anywhere while it is still trying to push its way out of the ground shortly after germination. And, since the light source moves across the sky every day, with varying times of duration, this seems like an unlikely cause.
Zen why do we grow opposite of gravity?
Meant to add in brief: From a thermo view, cells are doing work (energy) against gravity to build upwards.