Lights off = more growth

Excellent - I knew there was a logical explanation. Thanks!

As far as biology goes, I can barely remember high school, let alone biology!
No worries, even though I'm 22, well 23 in 26 hrs, high school is nothing but a blur. It's just that I studied biology and decided to head to med school...really loved the college biology though...anytime!
 
The photosynthetic pathway does hold the answer to your question, BK.

The chemical reaction of photosynthesis occurs in two stages. The daytime reaction cleaves water into oxygen, free protons (hydrogen ions), electrons. Oxygen is 'pearled' as a by-product. The dark reaction, for which sunlight is not required, utilizes the protons and electrons generated during the daytime to convert carbon dioxide into carbohydrates. These carbohydrates translate into the observable growth of the plant specimens. By prolonging the period for the dark reaction, the plants have the opportunity to focus on increased tissue construction; it looks you've discovered the optimum balance of your daytime vs. nightime reaction cycles. Incidentally, there is some evidence that fertilization might be more effective when provided proximal to the start of the nightime reaction, when plants are more likely to perform uptake of nutrients from the water column to support active growth.

One of the reasons I want my kids to participate in aquarium keeping is because it provides a fantastic way to apply practical chemistry and biology!
 
The photosynthetic pathway does hold the answer to your question, BK.

The chemical reaction of photosynthesis occurs in two stages. The daytime reaction cleaves water into oxygen, free protons (hydrogen ions), electrons. Oxygen is of course given off as a by-product. The dark reaction, for which sunlight is not required, utilizes the protons and electrons generated during the daytime to convert carbon dioxide into carbohydrates. These carbohydrates translate into the observable growth of the plant specimens. By prolonging the period for the dark reaction, the plants have the opportunity to focus on increased tissue construction; it looks you've discovered the optimum balance of your daytime vs. nightime reaction cycles. Incidentally, there is some evidence that fertilization might be more effective when provided proximal to the start of the nightime reaction, when plants are more likely to perform uptake of nutrients from the water column to support active growth.

And here's the long version of my summary; with all the details lol:grinyes:. Great details DrVader
 
It's a matter of photosynthesis. If you all remember biology, plants in the dark use more CO2 than during day, but some of the energy received during the day is conserved in the plants cells as photons. So when you have a powerful light, this is stored in your plant for quite a few hours, and since its injected CO2 and the plants use more CO2 in the dark it has the perfect conditions to grow. Now, I'm not saying you don't need light or that you must leave 21 hr. periods so your plants grow even more (I cannot assure you that) but I gave you the scientific reason of why this happens. Hope it is clear.

Wasn't aware that plants could "store" sunlight in any way(don't think they can convert heat into something useful for photosynthesis), do you have a reference? Edit; Sorry, I must have mis-read. I thought you meant they could continue the photosynthetic reaction during lights out.

CO2 levels rise in an aquarium at night assuming the supply is left on; This clashes with the idea that plants consume *more* CO2 at night than they do during the day. At night plants transport sugars into the tissues that need energy/food.

When the light is left out it's very, very likely that the plant essentially goes into "panic mode" and starts putting out a lot of growth very quickly. This is both in an attempt to reach light and/or to reach maturity. Fruiting/flowering plants can often be "forced" to flower or fruit by manipulating the photoperiod or environment early. You can do this with a freshly-cloned plant, for example, to force the plant to put out a ton of vertical growth in a very short amount of time and then simply stop and flower. Often this is done on purpose in the case of plants whose flesh you intend to eat.

Depending on how you manipulate the amount of dark the plants recieve, you can get a taller or smaller plant. Rhubarb, I believe, tends to grow much longer with extended dark periods. The plant growth doesn't have to look odd or anything, but it might start to if you do this quite often.
 
The photosynthetic pathway does hold the answer to your question, BK.

The chemical reaction of photosynthesis occurs in two stages. The daytime reaction cleaves water into oxygen, free protons (hydrogen ions), electrons. Oxygen is 'pearled' as a by-product. The dark reaction, for which sunlight is not required, utilizes the protons and electrons generated during the daytime to convert carbon dioxide into carbohydrates. These carbohydrates translate into the observable growth of the plant specimens. By prolonging the period for the dark reaction, the plants have the opportunity to focus on increased tissue construction; it looks you've discovered the optimum balance of your daytime vs. nightime reaction cycles. Incidentally, there is some evidence that fertilization might be more effective when provided proximal to the start of the nightime reaction, when plants are more likely to perform uptake of nutrients from the water column to support active growth.

One of the reasons I want my kids to participate in aquarium keeping is because it provides a fantastic way to apply practical chemistry and biology!

Wow!!
 
I'll add that I would classify what we're seeing differently *IF* the plant only experienced marginally increased growth. We're looking at a dark period extended by maybe 50%, so I doubt you'd see a several-inch growth increase as a normal plant reaction. I could be wrong, but it's not likely we're dealing with plants over 30" tall, which means 3" of growth caused by a 50% extended dark period is more than 10% growth in one night(if the plant is 15" or less, it's more than 20%).
 
Wasn't aware that plants could "store" sunlight in any way(don't think they can convert heat into something useful for photosynthesis), do you have a reference? Edit; Sorry, I must have mis-read. I thought you meant they could continue the photosynthetic reaction during lights out.
No, no this energy just lasts a few hours, eventually they WILL need light or else they will die. Don't worry about the misread part. ;)
 
I think the energy is stored in chemicals like ATP. My guess was essentially what Dr Vader said about focusing on tissue growth and storing energy during the day, light a solar heater with a battery. Just a minor point: you can't "store" photons as they electromagnetic waves.
 
Okay, storing photons is not what it exactly is, it was just a top of the head idea from what I remembered in biology 4 years ago, I did not Wiki search or picked it up from a book either, it was just a brief easy way to explain. Sorry for the "stored" controversy...
 
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