Backyard Aquaponics
A place to discuss aquaponics

Hi all,

I'm new - stumbled across aquaponics and am immediately hooked. The only reason I haven't started a veggie patch or hydroponic system is because I wanted something more complete and with less environmental impact. Bingo.

Anyway, I have a question regarding plants.

It's mainly to do with what plants do at night. I'm confused about a couple of things.

1. Is root respiration different to respiration as the opposite of photosynthesis?

2. Do roots ever know that it's night? (sounds dumb - it's always dark underground) If so, what do they do different?

3. I assume nutrients aren't used at night because there's no light to start photosynthesis... if that's the case then am I right in assuming root systems play no part in the respiration phase (dark cycle) of the plant?

4. During the day the plant needs carbon dioxide and the roots need oxygen. At night the plant uses oxygen and releases carbon dioxide... do the roots also reverse and look for carbon dioxide under the ground?

Sorry for the crazy questions. I'm not even sure what relevence the questions have!

Hi Phil and welcome to the forum, there will be some intelligent beings coming on line shortly and will be able to answer

welcome to the addiction phil. You've already taken the first step in admitting you have a problem

Here are my views on your questions;

1) i think its quite different, not sure of the mechanics, but it has been demonstrated many times that a high O2 content in the root zone promotes quicker growth, see DWC or even aeroponics

2) I don't think so, their alarm clock is broken. no, seriously i'm not sure but i may have read that they grow more at night? not sure though.

3) I would agree with not taking part in photosynthesis, but who knows if they transport nutes at night as well into a store for the daytime?? dunno

4) I don't think so.

Welcome!

Hi Philbert, welcome to the forum....

To put it simply.... plants respire "all the time" - day and night.....

They only "photosynthesis during daylight....

Quick comaprison...

http://extension.oregonstate.edu/mg/botany/respire.html

Do they take up nutrients during the night..... hummmm.... good question.

I would think minimally if at all....

Do the roots respire.... yes.

"Transpiration" is different ....

http://extension.oregonstate.edu/mg/bot ... nspir.html

that covers it beautifully rope!

SO i would be correct in paraphrasing that NPK is NOT a plants food (energy source) but is used during photosynthesis along with co2 to produce the energy that plants will use for growth day and night?

Day time respiration ("photorespiration") is the primary means by which plants take up the nitrates from an AP system...

Although this apparantly takes nearly 25% of the energy photosynthesised and effectively reversed....



This was taken from a UC Davis study which was looking at the idea that...



They found that in fact ...



VERY interesting ... given the use of CO2 injection into hydroponic greenhouses

Taken from here ...

http://www.scienceblog.com/cms/node/3367

great links rope. this one here http://extension.oregonstate.edu/mg/botany/growth.html

highlights that the roots always uptake O2 and release CO2, not reversibly............see picture

hey, that's all really helpful! Thanks. And so fast... I love an active forum.

I guess what started my questions were the aeroponic theories and also the use of CO2 injections into the greenhouses. Very interesting to read that elevating levels of CO2 actually reduces growth.

I don't see any harm in providing as much oxygen to root systems as possible.

I guess that also gives us reason to not run pumps all night, as the plant theoretically shouldn't be using anything from NPK intake???

within a certain range elevated CO2 increases growth, above that it drops off again

Possibly true enough Philbert.... but the other aspects of the cycle and fish respiration, ammonia conversion etc tend to deplete the available oxygen in the water....

Think the jury might still be out regarding running pumps over night....

but having read the above maybe there isn't a need to do so as long as a means of oxygenation is supplied.... i.e a separate air pump runing over night....

Course that might be somewhat location specific as well.... i.e if the temperature is really high then there's a possible risk to growbed media, bacteria and plants literally dehydrating....

i used to turn my pump off at night, running an airstone in the tank. temps didn't fluctuate as much then