Hydroponics

[YT2095]

here`s a question I`ve never managed to work out nor experiment with yet in its truest form.

 

I`de like to know how hydroponics actualy works without killing the plant, when it`s quite clear that overwatering a plant will eventualy kill it?

[Sayonara]

I would have thought the idea is to keep the osmotic pressure "balanced". Can't say I've ever looked into it though.

[wolfson]

Hydroponics is the cultivation of plants without soil, research has shown that plant life organisms can survive and "freely" grow without the soil, as the nutrients gained are in the water.

[Sayonara]

That's not what he's asking.

[wolfson]

Try a hand watered bucket of sand with a single plant and an o2 pump, the plant should grow.

[Glider]

Hydroponics doesn't necessarily mean the roots of the plant are constantly immersed in water. Usually, there is an inert medium like expanded fired clay granules that the plants root into. Water and nutrients are pumped through this medium at regular intervals.

[Sayonara]

If the roots are not immersed in a liquid medium, how do you get around the problem of transpiration-led flow in the xylem?

[Skye]

Transpiration occurs regardless of water supply to the roots. The inside of the plant has a higher concentration of water than the surrounding air, so it will automatically evaporate from the plant into the air.

[YT2095]

what stops the roots from rotting like they do in an ordinary plantpot with soil that`s overwatered though? would it perhaps NOT rot if it were fed nutrients? also I`ve found that it`s possible to OVERFEED a plant and that`s equaly fatal

 

I have done something similar in a pure sand and pearlite mix, and fed it dillute food solutions and grew a rather handsome looking beasty tho. so maybe it`s something in regular compost that`s the problem?

[Glider]

...and be taken up from wherever it can be found in the ground.

 

The vast majority of plants (excluding aquatic and bog plants) don't like having their roots immersed. The microscopic root hairs responsible for taking up water and nutrients develop and function best in the humid spaces between the granules of whatever medium they're in. The high humidity of these air spaces, and moisture on the surface of granules of the inorganic components of the medium are sufficient.

 

In most cases, these root hairs work in conjunction with either an exomycorrhyzal or endomycorrhyzal fungus (depending on the species of plant), which lives in symbiotic partnership with the plant either in the cells of the root tip, or surrounding it. This fungus sends out microscopic hyphae and brings moisture and nutrients (particularly nitrogen) to the root from places the root itself can't reach. These fungi also enter the tissues of rotting organic matter and help fix the nitrogen resulting from their decomposition. In return, the fungus receives sugers produced at the root tip of the plant (the exception are the legumes, which fix nitrogen from the air and store it in nodes in their roots). In any event, the fungus can't live in saturated soils, and nor can the plants which depend on them.

 

There are exceptions, for example rhododendra and azalea, which prefer wetter soils. The roots of these plants don't have the symbiotic relationship with fungus (too wet). But then (and partially as a result), the roots of these plants are very inneficient and can't easily take up certain elements (iron in particular). As a result, these plants have to live in acidic soils (pH <6) as alkeline soils lock up iron, whereas acidic soils leave iron in a form easily available to these plants.

[YT2095]

wow! thnx

 

interesting what you mentioned about legumes, I wasn`t aware the took in nitrogen from the air instead!

perhaps a few bottles of ammonia onder my runner bean frame might be an idea?

any thoughts?

[Sayonara]

Skye said in post #8 :

Transpiration occurs regardless of water supply to the roots. The inside of the plant has a higher concentration of water than the surrounding air, so it will automatically evaporate from the plant into the air.

I understand that. My question was intended to ask how you prevent stresses on the plant due to constant transpiration when there is frequently no water supply to the roots. Is it just a matter of timing?

[apollo2011]

I don't know much about Hydroponics but let me give it a shot:

 

Hydroponics is the growth of plants in water containing the nutrients needed by the plant rather than in soil. Thus, When you overwater a plant, you flood it with water. Or, the water washes a way needed minerals. But, if the water contains the nutrients the plant needs, than it can't flood the plant nor wash away the nutrients. Just my thoughts.

[Glider]

Sayonara³ said in post #12 :

I understand that. My question was intended to ask how you prevent stresses on the plant due to constant transpiration when there is frequently no water supply to the roots. Is it just a matter of timing?

 

Yes, it's timing. The surface of a root cannot be allowed to dry out completely (this results in die-back of the root hairs), but the roots of most plants thrive best in air of (extremely) high humidity, such as that found in spaces between soil particles. The roots of plants grown hydroponically thrive in the humid (saturated) air spaces between the inert granules of whatever medium is being used. Water is pumped through either at regular intervals, or is trickled through constantly to ensure the granules stay moist. Roots have to breathe though. There are not many (land) plants that can survive for very long with their roots completely and constantly immersed.