exceptional growth in the dark

[triazole]

for the last three days i've been extremely busy. i didn't have time to do the pwc's over the weekend, or change the diy co2 bottles. so i decided to let the tanks sit in darkness for that period.
today when i turned on the lights, i was amazed with the growth on the plants. all the stem plants (barring a bit of bacopa sp.) have grown a good couple of inches. and the leaves on some kind of sword (un-id-d) have become huge! i was stunned at first, and am looking for explanations.
before this, i had a bit of green algae on the walls. that was completely gone too!

-the plants utilized ambient light better than the algae, and hence the available nutrients.
-more leaves were put out to better utilize the scant light available.

info - 29g planted, ~60W NO lighting, EI method of dosing with dry ferts (not followed strictly, mostly because of forgetfulness), not tested for levels.

any thoughts?

 

[fish_4_all]

Could have been a surge by the plants because they weren't getting nutrient and might have expected a possible dormant period coming on. Would be intersting to know how they respond in the next week or two and theirt growth rates.

 

[An t-iasg]

I have always thought that after a blackout, my plants looked a little taller too. I thought maybe it was because I didn't see the plants for 5 days or so, but every time I ended a blackout I always thought they were bigger. Maybe it wasn't my imagination.

 

[triazole]

hmm. interesting thought. i did put a dose of K just a day or two before shutting the lights. and the tank is heavily populated, so nitrates shouldn't have been short supply.
i'm wondering about the carbon source for such a spurt too. the PH i use to disperse co2 was turned off.
2 of the 5 sp. have hit the water level within this period. so i'll definitely trim them tonight during the pwc's. i have had to trim the plants every other week. so the growth had been good so far. but this was kind of spooky.

An t-iasg, maybe its time to ditch those fancy lights?

 

[Purrbox]

I remember reading someplace, possibly in a thread here, that plants actually do most of their growing at night. They buildup the energy during the day through photosynthesis and then put it to work at night with actual growth.

It would make sense then that healthy plants would be able to perform some exceptional growth during an extended dark period. Eventually they would be likely to use up their stored energy and would start to decline as they suffer from multiple nutrient deficiencies including lack of light.

 

[7Enigma]

I remember reading someplace, possibly in a thread here, that plants actually do most of their growing at night. They buildup the energy during the day through photosynthesis and then put it to work at night with actual growth.

It would make sense then that healthy plants would be able to perform some exceptional growth during an extended dark period. Eventually they would be likely to use up their stored energy and would start to decline as they suffer from multiple nutrient deficiencies including lack of light.

That is correct. I don't know for sure the % of growth that occurs at night (I'm under the impression that growth rate is independent of light level unless its limiting over time), but sugar is created and stored during lighted periods. This can then be used to grow during respiration in the dark when sugars are broken down and used for energy (like we do). Remember sugars are just a long line of carbons in a chain. They can be passively stored as simple sugars or complex starches, but can be broken down and used for tissue building. That's why you see the (sometimes huge) growth during a blackout. All of that stored energy, regardless of CO2 injection, allows for increase in plant biomass. Of course the growth would be greater under perfect conditions, but plants when healthy have a large reserve of a lot of nutrients.

This is also why deficiencies are so difficult to diagnose in plants, since many can store large amounts of particular nutrients, while others might not have the same capacities for those same nutrients. Ideally it would be very interesting to find what plants preferentially store/use different nutrients and have 1 or 2 of each in a tank (preferably fast growers to catch the deficiency early). If you see a deficiency in one but not the others you could say, "Well this is a phosphate weak storer, the rest of the plants are fine, I might have a phosphate deficiency". Obviously not that simple, but you get the drift...

 

[zenkatydid]

so, would it be good for plants' growth to turn the lights off one day a week, say?

 

[Esra]

All plants grow faster over night.
For an experiment put a piece of cardboard over part of your lawn for a day and night and then compare it, you should see the difference.

Problem is this will only last for a couple of days and then the plants will start to suffer from lack of light.

 

[Purrbox]

so, would it be good for plants' growth to turn the lights off one day a week, say?

Not really. Your best bet is to ensure that your plants are getting 12-16hrs with the lights off.

 

[Plantbrain]

Plants are not "growing" in the dark.
What you observe is not a net increase in dry weigh carbon, that is definded as growth or O2 production is another measure of growth in aquatic systerms, plants do not produce O2 at night/in the dark.

Cells can increase in length, but not gain any new biomass.
Plant cells are after all, mostly water.

Regards,
Tom Barr

 

[7Enigma]

Plants are not "growing" in the dark.
What you observe is not a net increase in dry weigh carbon, that is definded as growth or O2 production is another measure of growth in aquatic systerms, plants do not produce O2 at night/in the dark.

Cells can increase in length, but not gain any new biomass.
Plant cells are after all, mostly water.

Regards,
Tom Barr

Correct. When they are using their stored sugars for "growth", since no biophysical conversion is 100% efficient they can only LOSE biomass during non-lighted periods. What appears to be growth is in fact elongation of the plant from a strictly biomass measurement, but I would argue this IS true growth in the sense that a plant with a large storage of sugar is less able to affect its surroundings, than one with low sugar stores but elongation/propogation of new leaves/roots since its photosynthetic capacity is greater than the smaller sugar rich plant.

It's suceptibility towards disease/starvation/parasites, however, would probably also increase (trend) with a decrease in stored sugar.

And no I would agree with Tom et al. that plants should not be manipulated through long periods without light for growth. It is a "defense" mechanism in an attempt to get more light/nutrients and so probably stresses the plant more than a normal lighting period would. The only exception I see to this would be in an instance where a plant is creeping horizontally that you want to grow vertical. An extended dark period will normally result in the plant "growing" quickly toward the surface in an attempt to get light. Most times, however, we never want this, we are normally trying to get the plant to grow horizontally across the substrate.

 

[triazole]

Let me make it clear. I had no intention of achieving elongation or "growth" by means of unnatural conditions. i had presumed that the plants would remain dormant/unaltered during the dark period i was subjecting them too. but that didn't turn out to be the case.

Tom, i guess in layman's terms,growth in defined by the increase in visible surface area of the plant, not the stored carbon content. that's why i misunderstood the phenomenon as growth.
what is puzzling me is the reason behind this cell-elongation and apparent growth. if the plant is not getting light, how does increasing the leaf surface help? there is no driving force to carry out photosynthesis.
is it in just plain anticipation and good faith that i'd turn on the lights some time?

Purrbox, 7Enigma - thank you for your input. please don't be worried. i won't be doing this again (hopefully )

 

[Plantbrain]

Well, to the causual observer you would think plants do "grow in the dark".
But many experiments have been done in the distant past to show this is not the case, stretching towards any source of light is a common trait, makes sense too, if you are in the dark and need light to live, stretching is about all you can do, most plants , unlike critters, cannot get up and move to a better spot.

You can look this phenomenon up on the web Botany sites.


Regards,
Tom Barr

 

[triazole]

well, that makes perfect sense Tom. I'll look up some info on the net. Thanks for the explanation.