How do planted seeds know which was is up?
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Short answer – seeds can feel gravity and they grow opposite to gravity. This is something we’re researching with our space stations and missions but the belief is that the force of gravity forces certain parts of the seeds’ cells to sink lower than other parts. This gives plants a sense of “down” and they orient their roots “down” and their stalks “up” as a reaction to this.
Seeds use gravity to figure out which way is up and which way is down. The seed shoots roots in the direction of gravity and shoots stems and leaves in the opposite direction. We actually don’t know how the seed figures this out exactly, but something inside the cell can figure out where gravity is pulling and then the seed responds accordingly. Incidentally, most seeds have a spot where the first root (called the radicle) will emerge, so you can face the seed in that direction to make things easier, although it will figure it out on its own if you orient the seed the wrong way.
There are multiple techniques, each plant tend to use more then one of them and it varies between plants which is doing it. Most plants have hormones with different density. The lighter hormones will end up in the top of the plant because the plants do not have a heart to circulate and mix all tho bodily liquids. The heavier hormones end up at the bottom. So by looking at the ratio between these hormones the cells in the plant can tell if they are towards the top or towards the bottom and then change their behavior accordingly.
Another technique we see is to sense the water that is found deeper in the ground. The wetter the soil the deeper it is. This allows roots to grow deeper into the ground even on a slope. The plants also react to the light, the more light the higher it is. This allows it to grow towards the light even on a slope or when partially obscured by other plants. Water and light can also make existing limbs change behavior so a branch might turn into a root and a root can turn into a branch. So it does not matter which direction a seed will grow as the limbs will become correct either way.
This is an area of biology which is actively being researched. We are doing things like planting various plants upside down and see how they react. There is also a planter in space aboard the ISS where all the effects of gravity can be eliminated which allow us to introduce one element at a time to observe how different plants behave. The result of this can help us build more efficient greenhouses, genetically engineer plants to grow in a more favorable way, or to better understand things like soil compaction to better manage the soil on our fields to suit the plants optimal growing environment.
There are different parts of the seed. They grow up to be different parts of the plant. The part of the seed that will grow up to be the stem, leaves, flowers will naturally take the harder direction to grow. The gravity that keeps the dirt down is always pulling things down. So it’s harder to grow up than to give into gravity and grow down. The stem,leaves, flowers part of the seed know this and grow up in the harder direction.
Remember the parts of the seed turning into parts of the plant? The part that grows up to be roots decided that it’s easier to grow down than up against gravity. So the roots grow down into the dirt towards the earth. They also know the nutrients they need are in that direction and will grow toward them as well.
Also fun fact, actually, I’m not totally sure this is true but I think it is. The reason why plants grow towards the light is because the part of the plant that isn’t receiving light doesn’t have anything else to do but grow. (The side with the light is doing all that photosynthesis stuff). So the backside without light is just growing more.
Plants are made of cells. A plant cell is like a cardboard box with water-filled bag in it. Floating in the water is a chemical plant that pumps out chemicals. Some of the chemicals leak into nearby cells. Some sink in water, and some float. The sinkers fall to the bottom and the floaters to the top. The sinkers are a chemical message that says: “become roots!” and the floaters “become a stalk and leaves!”.
Was up with you man?
So many wrong answers about “seeds sensing gravity”
Its the heat they are attracted to. The top of the soil is warmer than the bottom, so the seeds go towards this. Anyone that’s tried to grow multiple weed plants with one grow light can tell you the plants furthest from the light will start leaning towards the light because it’s warmer.
Heat is the transfer of energy from one object to another, so of course when that little tip of green comes out of the seed, its going to follow where the most energy(heat) is.
Plants have a built-in sense of which way is up, and they use it to direct their roots downward and their shoots upward. This ability, called geotropism, comes from the uneven distribution of a plant hormone called auxin. Auxin is produced in the tips of growing plants, where it helps to regulate cell growth. It also plays a role in phototropism, or a plant’s response to light. When auxin accumulates on one side of a plant Shoot tip ,it causes that side of the plant to grow more quickly than the other side. As a result, the shoot bends away from the source of light
How did your growing body know which way is up? 🤷🏽♀️😂
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