# Do plants need a break from the light?



## Patriot (Dec 22, 2010)

Plants do need rest, or more accurately a dark period. Plants do not stop functioning in the dark but start a different process altogether. Plants use oxygen and release CO2 in the dark. They also use whatever energy that was created created during the light phase.

Leaving lights on for 24/7 will only leading to algae.


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## Da Plant Man (Apr 7, 2010)

Forgot to mention; this is for my emersed tank. Algae is not an issue whatsoever. 

That makes sense though. I forgot that they comsume O2 at night. Then what is the 'maximum' time the light could be left on? Within reason of course. Not like there is a set time limit.


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## 150EH (Dec 6, 2004)

I think plants absolutely need a rest period but not more than 8 hours, they need time to go through the natural cycles and rest is a definite part of the cycle. The rest may not have to be lights out and you should read about gardening in the Arctic circle, gardeners in Alaska love there fresh salads, so when their 30 day growing window opens they grow, grow, grow and the fact that it never gets absolutely dark helps them to grow large plants quickly, so I think you could get good info from the great white north.


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## Patriot (Dec 22, 2010)

you could try 14 or 16 hours with 8 hours of down time.


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## HypnoticAquatic (Feb 17, 2010)

they do need rest! in other grow areas the longest light cycle is 18 on 6 off but just watch how your plants respond they do speak if they are happy or not so adjust accordingly


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## Patriot (Dec 22, 2010)

You should give CO2 and nutrients in the right ratio to longer lights too for the plants to use to grow faster. Co2 shouldn't be a problem if its an emerged tank.


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## Capsaicin_MFK (Nov 15, 2009)

I always do a 16 hour photoperiod for my emersed stuff. I haven't really noticed a difference in adding a little co2 into the sealed tank.


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## Da Plant Man (Apr 7, 2010)

I shall try to leave them on longer. See what effects it has. Do some testing 

It's also no bid deal if I inject co2 or not. Just using what resources my dad drinks....erm....has...


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## FishFarmer (Feb 8, 2007)

To answer your question, yes and no. You can grow most plants with lights on 24-7--we do that with some plants at my school (with mostly C4 grasses like corn, sudangrass, phrag, etc) . Also, take for example plants growing in far northern regions of the world, such as Alaska. In their summer, they get 24 (or close to 24) hours of daylight per day, and plants grow like crazy (Alaska is famous for produce huge pumpkins). But with other plants it will not work. Take for example, CAM plants, which require darkness to fix carbon.

A day-night cycle is beneficial and necessary to regulate some plant physiological functions, such as flowering. And I'm sure there are also some other functions in plants which are controlled by a dark and light period. So to answer your question, yes, many plants can be grown in 24 hours of light, while some can't, and others (most) will benefit from a day/night cycle. So in general, it is best to grow plants with some sort of dark period. Also, with aquarium plants, leaving the light on for 24 hours is just asking for an algae problem.


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