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[APD] Re: Night Growth?

Since no one else answered I'll give you a brief answer (just look in a textbook or online for detailed descriptions of photosynthesis and respiration).

Yes, plants do grow at night.  Keep in mind that CO2 is used in photosynthesis.  Photosynthesis is the plants method of creating food (i.e. sugars) which is then stored for use during growth (by the way fertilizers are not food, they are nutrients).  Oxygen is a byproduct of the reaction.

Here is the basic photosynthesis reaction:

6CO2+ 12H2O +light energy--> C6H1206+ 6O2+ 6H2O

C6H12O6 is glucose and is stored until needed for respiration. Photosynthesis only takes place during the day, but photosynthesis is NOT responsible for growth in a plant, respiration is (well, actually it provides the energy directly used for growth, but I don't want this to be too confusing).  Respiration USES glucose and O2 and PRODUCES CO2.  Here's the respiration reaction:

C6H12O6+ 6O2 --> 6CO2+ 6H2O + Energy (ATP)

Respiration goes on 24hrs a day basically.  So plant growth does too.  But plants use much less energy than they store in sugars from photosynthesis.  So when photosynthesis is going on you get a net production of oxygen.  But at night only respiration is going on so only O2 is needed and used.  This is why many people do not use CO2 at night.  Since the rate of respiration is much less than that of photosynthesis you shouldn't have to worry about the 02 levels dropping too low at night and harming your fish.  As for fertilizer, I would think the uptake would be similar at all times but I can't say for sure.  I don't see any reason to adjust your fertilizing schedule.

Hope that helps!

-Kyle Williams



Message: 7
Date: Mon, 1 Nov 2004 13:08:09 -0600
From: "Tom Wood" 
Subject: [APD] Night Growth?

Am I just imagining things, caught in a parallel universe, or living on top 
of a burial mound, when noticing that the plants seem to do a lot of growing 
when the lights are out? Which would raise questions about whether CO2 
should be off at night, and whether it's better to dose ferts then.



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