if you pump in o2 it will just bubble out of the resevoir into the atmosphere, thus hindering photosynthesis. but yes more oxygen to roots=better plants. when you pump in air you are helping "gas off" carbon dioxide

Oh, I believe you kinggraham69! Not to believe this would almost amount to heresy.

I have read a few articles on aerobic and anaerobic respiration of the root system, and I have found that some plants can survive without oxygen, in which case it is assumed that the oxygen is supplied by the leaves of the plant and transported to the roots.
What I know is that the root cells expend energy to transport nutrients, and for that they (probably) need oxygen. But I wouldn't mind learning how exactly that oxygen is being used. Something must be oxidised to release the energy. Probably sugar.
Not so?
The expending of energy in human muscle produces lactic acid as a byproduct. Anything similar in roots?

What you are making is a big, overly complicated, DWC system, not a 'hybrid'. I do not see what purpose is served by adding a water pump and seperate resivior?

Example- take a 30G rubbermaid tub and add an air pump and bubble wand. now plant 11 plants in net cups in the top of it. this is how most of us do it. building the same system but only adding 2 plants so they have more nutrient solution per plant would acomplish the same thing you are trying to achieve but without all the extra cost and added failure points. in engineering- usually the simplest solution is the best.

Also...

Bartender, I'd like to have one of whatever greystoke is drinking.

I have found that some plants can survive without oxygen

no you haven't

some plants may obtain oxygen differently than others but ALL terrestrial plants require oxygen for the chemical equasion they use to make energy we lovingly refer to as photosynthesis.

Sorry bru. Private bottle.

You were quoting me out of context. I meant " . . .without oxygen around the roots". This refers to an article I read about young plants placed in agar with all oxygen removed. The plant then transports oxygen from the leaves to the roots.
And . .
Photosynthesis is the process whereby carbon dioxide is converted into sugars under the influence of sunlight while producing oxygen as a by-product.

you win on a technicality. :)

I stand by my stating that terrestrial plant roots need oxygen though. the equation i was thinking of was cellular respiration, not photosynthesis. In cellular respiration, which occurs in plant roots, six molecules of glucose (C6H12O6) react with six molecules of oxygen to form six molecules of carbon dioxide, six molecules of water, and 36 molecules of ATP. This can be represented by the following chemical equation: 6C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 36 ATP

Look into float valves as they might help you out when tanks start to get low. I only mention this since you say that you find maintinance a pain with the DWC. Other things I found to help include rigging yourself a way to access the tank for measurments and topping up without having to lift plants up. The main trouble I see with really large DWC systems is that it is difficult to find appropriate containers for such things so most people wind up with multiple bins that become a pain to deal with.

I still have lettuce indoors in DWC but for outdoors I've switched to media filled troughs that get a continous drip or flow. So far this has been the simplest as I can hook everything up to one big resivuar and water top up happens with a float valve so I just need to check nutrient strength and pH regularly. I do have one pump for getting the nutrient up to the troughs and one air bubbler to help with airation for that system.

That's big of you.

Your equation gave me the idea to google for: "roots + ATP", and bingo I got the articles I've been looking for.
One is particular pertinent to the subject: The Impact of Flooding Stress on Plants and Crops It confirms your equation.
It also confirms that there IS an anaerobic respiration, but that it will eventually lead to death by "self poisoning". Interesting!

Thanks for the exchange!

I'm working on a simple design for building an automated float valve system to replenish hydro-nutrient tanks. I'm still in the design/build/test phase, but if/when it works, I'll post details like a parts list and instructions. I know you can buy commercial units, but i think many home hydro growers enjoy designing and building stuff as much as they enjoy the growing its self.

greystoke

lol. I think sarcasm is often lost in text based communications. I knew what you were talking about, i was just messing with you. If there is a local college near you, and you can access their library, you can learn more than you ever wanted to know about how and why roots work. I think we spent 4-5 weeks on nothing but roots when i was working on my horticulture degree. I would not recomend these college level reference books to the casual gardener becasue they are very dry, scientific data that has not been dumbed-down for the masses the way the books @ the book store have. you seem like you have a deeper interest in really understanding things so you might enjoy scientific type books though.

darthhelmut
I realized my previous post sounds really mean. i did not intend to make fun of your design, i just don't understand the function of the seperate resivior if the regular resivoir never drains? If/when you get it built we want pictures!

You reckon I hadn't noticed?

I have built some solar powered bubblers though.