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How do plants grow?

andymcstab
Posts: 308
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5/28/2014 11:40:26 AM
Posted: 2 years ago
I always thought that matter is never destroyed or created, so, how do plants grow?
From where does the matter that subsists the plant come from?
Yes, i understand that plants have to be fed nutrients, but if you dry the plant when it is grown, you have far more matter than the sum of the total matter it absorbed to grow. It is not as though the plant eats the soil...
..... the plant eats the sun, but light.. has no matter, does it? If it does, surely its not enough to build a plant.

This question has been bugging me for a whole 25 minutes so i thought i would just throw it open for someone to explain to me.

Thanks.
edomuc
Posts: 29
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5/28/2014 11:59:13 AM
Posted: 2 years ago
At 5/28/2014 11:40:26 AM, andymcstab wrote:
I always thought that matter is never destroyed or created, so, how do plants grow?
From where does the matter that subsists the plant come from?
Yes, i understand that plants have to be fed nutrients, but if you dry the plant when it is grown, you have far more matter than the sum of the total matter it absorbed to grow. It is not as though the plant eats the soil...
..... the plant eats the sun, but light.. has no matter, does it? If it does, surely its not enough to build a plant.

This question has been bugging me for a whole 25 minutes so i thought i would just throw it open for someone to explain to me.

Thanks.

Plants use carbon taken from CO2 that is in the air, the process is roughly 6(CO2)+6(H2O)=C6H12O6+6(O2) AKA the photosynthesis.

http://en.wikipedia.org...
PeacefulChaos
Posts: 2,610
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5/28/2014 5:23:39 PM
Posted: 2 years ago
At 5/28/2014 11:40:26 AM, andymcstab wrote:

..... the plant eats the sun, but light.. has no matter, does it? If it does, surely its not enough to build a plant.

No, plants do not eat the sun. If they did, that would be rather bad.

More seriously, light is but another form of energy. It is captured by the chlorophyll in the chloroplasts of the cell (these are the "organs" of a plant cell, commonly known as organelles). I don't remember the specifics, but ultimately what happens is that the light can excite electrons. When electrons are excited, they jump to higher energy levels, giving off more energy.

This energy is used in what is essentially a reverse process of cellular respiration to make sugars (glucose being an example).

Of course, the plant doesn't need just sunlight. It also needs water, hydrogens, and oxygens (well, those last two can be found in water, so it was redundant to mention them). It obtains water by essentially "sucking" it in through the roots. In many plants this is known as "capillary action," which is caused by the cohesive and adhesive properties of water. Just put a straw in a glass of water, and you'll see that the water level in the straw is higher than the actual water level in the glass. This is an example of capillary action. Another factor allowing water to travel through roots is transpiration, where water vapor is given off at the top near the leaves of the tree. Water will thus travel upwards, as water will travel from higher to lower density (something known as osmosis).

Through the roots, it will also obtain minerals that water will carry. I don't know the specific chemical reactions the minerals play in the plant, though.
Mhykiel
Posts: 5,987
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5/28/2014 10:15:45 PM
Posted: 2 years ago
At 5/28/2014 11:40:26 AM, andymcstab wrote:
I always thought that matter is never destroyed or created, so, how do plants grow?
From where does the matter that subsists the plant come from?
Yes, i understand that plants have to be fed nutrients, but if you dry the plant when it is grown, you have far more matter than the sum of the total matter it absorbed to grow. It is not as though the plant eats the soil...
..... the plant eats the sun, but light.. has no matter, does it? If it does, surely its not enough to build a plant.

This question has been bugging me for a whole 25 minutes so i thought i would just throw it open for someone to explain to me.

Thanks.

Photosynthesis is how the plant makes energy it is not how the plant grows.

Can you provide me with evidence that when you dry a plant out it weighs more than the nutrients it takes in. Because I think that is false.

Plants take water, nutrients in the soil, and energy from photosynthesis to construct more cells to grow.
Juan_Pablo
Posts: 2,052
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5/28/2014 10:49:52 PM
Posted: 2 years ago
Plants grow because of cell division and cell growth..

Plants take in water and nutrients through their roots (which includes nitrogen-carrying molecules) and they breathe in carbon dioxide through their leaves to create sugar (via photosynthesis). However, the sugar can also be broken down to provide the plant with energy and the remaining products, which consist of carbon, can be used to facilitate cell division and cell growth, which causes the plant to grow.

That's right! Plants take carbon dioxide from the air and transform the gas into a solid a solid constituent of sugar; when the sugar is used for energy, the carbon and other elements the plant has absorbed go onto to facilitate cell division and cell growth in the plant!

That's the quick version of how plants grow!
Juan_Pablo
Posts: 2,052
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5/28/2014 10:53:23 PM
Posted: 2 years ago
Correction:

"That's right! Plants take carbon dioxide from the air and transform the gas into a solid constituent of sugar; when the sugar is used for energy, the carbon and other elements the plant has absorbed go onto facilitate cell division and cell growth in the plant!

That's the quick version of how plants grow!
GarretKadeDupre
Posts: 2,023
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5/30/2014 12:06:45 AM
Posted: 2 years ago
At 5/28/2014 11:40:26 AM, andymcstab wrote:
I always thought that matter is never destroyed or created, so, how do plants grow?
From where does the matter that subsists the plant come from?
Yes, i understand that plants have to be fed nutrients, but if you dry the plant when it is grown, you have far more matter than the sum of the total matter it absorbed to grow. It is not as though the plant eats the soil...
..... the plant eats the sun, but light.. has no matter, does it? If it does, surely its not enough to build a plant.

This question has been bugging me for a whole 25 minutes so i thought i would just throw it open for someone to explain to me.

Thanks.

I had this same question about a decade ago (when I was about 10) and like you, it bugged me immensly.

The answer: the plant eats soil + air + water!
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