How do seeds know which way is up underground?

Answer 1

It's called gravitropism. Plant cells contain starch granules that fall downwards and that in turn causes the plant to grow upwards.

Answer 2

The shoot from the germinating seed travels in the direction where it encounters the least resistance.

Going deeper underground or to the sides, it finds the soil too tightly packed. Ditto to the sides. But upward - the direction from which it was planted - the soil is looser.

Try this experiment: get a seed and plant it in some earth, up against the side of a transparent container. Use a good-sized amount - enough to *pack* the soil, very deep and very hard, overtop the seed.

Basically, you want to encase that poor seed in what amounts to a brick of soil. Keep the exposed side - the side where the seed is against the glass - away from the light. Best to just drap a towel over the container whenever you're not directly observing it.

Then wait. The seed will probably sprout, but it'll take a long time to breach the surface - if it ever manages.

Answer 3

I'm always amazed at some of the silly answers I see on here. I wonder if people are that dumb or trying to be funny. OK well I majored in Biology and took lots of botany classes. Seeds germinate and grow towards a light source. That's why you see them curve and turn if you leave them in a window where they have to move to get to the light source. They are also able to detect gravity and they use that detection method to direct the roots in the proper direction.

We did an experiment in college where we put seeds on a rotating disk to throw of their gravity detection. The seeds roots were not able to orientate themselves.

Keep in mind that nothing in science is 100%, we only have theories. Since nobody can ask a plant how or why they do something we can only go by our results from experiments. Thus far our experiments show that seeds are able to detect gravity and sunlight to ensure proper orientation.

Answer 4

A germinating seed can be turned upside down several times and the root will still start to bend downwards. This behaviour is an example for a tropism, a movement triggered by a stimulus.

"It is not the soil’s humidity that causes the direction of the root, since the root will grow downwards and the shoot will grow upwards even if the plant is placed in an earth-filled tube where the upper part is moist and the lower is dry. If the plant is put into a water-filled tube the lower part of which is exposed to light while the upper is darkened, the direction of growth will still not change: a proof that it is independent of light." (A. de CANDOLLE, 1834/38)

Rather in 1806 showed the British physiologist A. KNIGHT in a decisive experiment that the direction of root growth is controlled by gravity. Shoot growth thus is mostly negatively geotropic since shoots grow upwards even in complete darkness.

Answer 5

Different plant tissues DIFFERENTIATE in the plant embryo, and each differentiated cell-tissue type is sensitive to different environmental factors at the site of seed's germination, thus different tissues will be able to grow in different directions, above soil or below.

When a seed germinates, the embryo sprouts a pre-root structure called the HYPOCOTYL that goes downwards, away from the air-dirt interface, so it goes deeper, away from sun and warmth and with gravity, down into the soil more deeply to help form earliest rooting structure. A pre-leaf structure called the EPICOTYL also grows from embryo, but it grows UPWARDS towards the warmth and the light of the sun. It might have to push thru some soil before it breaks ground, though.

Answer 6

Seeds cannot KNOW because they have no brain. As for growing up toward the surface of the ground and not the other way is due to factors such as gravity and the need for sunlight. The need to be exposed to carbon dioxide in the open eair, a substance that they cannot obtain if they grow under.

Answer 7

Go towards the light! … ;-)

Hey ROOTS go to where the water is AT.

Water goes and seeps down through the ground (dirt), it’s wetter at the bottom (c0z of gravity the water goes down) so the roots grow towards the water, and the plant grows the other way… and the plant grows to where the light is coming from, and where the soil has more oxigen in it (which would most likely be the top of the soil).

Go to the light (LOL).

P.S.
If you put a plant in space (as in on a space ship, not out in space), and put water beside it, it will grow it's roots towards the water, and I'm pritty sure the plant will grow the other way exspecially if the light source is opposite to the water (of course we could try a space experiment, where both the water and light are comming from the same place, and see what happens LOL, at least we'll most likely figure out the true answer that way eh?)

Answer 8

Gravity. The parts of a seed that germinate the sprout will be lighter than the food, and portions needed to collect fuel from the ground. This creates the "UP/DOWN" orientation.
Every so often a seed WILL actually grow down.

Answer 9

Plants grow upward towards a light source - and upward away from the pull of gravity. You asked how do they know to do this..well their tiny little seed brains tell them too! LOL

Answer 10

Gravity, sound coming from the surface, sun heat and energy and instinct or sense of orientation. Imagine yourself a seed you will know where's up and down.