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Discussion Starter · #1 ·
Dear APC

I hope you are all well and your tanks are bursting over with green stuff :)
I had a very interesting discussion with one of the guys on a plant tissue culture list I'm subscribed to. It relates to the myth about giving your plants afternoon siestas. I would appreciate any feedback from you more experienced plant enthusiasts as I do believe that this could open up a whole new can of worms.

The thread was about growth room lights and light cycles etc (just to give you a better picture of where this is coming from). OK Here goes:

Comment made by Neha:

> Dear Alan,
>
> In Plant tissue culture,
> Are plants required continuous light for 12 - 16 hrs?
> Or Can we split it up?

Answer from Mike:

>Dear Neha

>The simple answer is yes, you can split up the light period. In fact, the
>more you split it up the more efficient photosynthesis will be.
>Basically,
>most plants add up the dark periods to determine the season.

>Mike

Question by myself:

Dear Mike

As an avid aquatic gardener I have always believed (from the literature and
other hobbyists) that giving your plants afternoon 'siestas' is an absolute
no no. Whats the point? In my opinion this is only going to hinder the
photosynthesising process. No light = no food, is that right?
Give your plants the usual 12 hours on and 12 hours off with no break in
light cycles inbetween. Please correct me if I'm wrong but you say that the
more you split up the light cycle the more efficient the plant will be at
making food. How does this work? Please enlighten this amateur plant
enthusiast.

Answer from Mike:

Dear Cameron

When light first hits a leaf, photosynthesis quickly reaches maximum levels
however, the metabolism of the products of photosynthesis lags a little
behind production so that in a short time the backup of photosynthetic
products slows up the whole process. During the dark period, the
metabolising of the photosynthetic products continues, using up the backlog
allowing photosynthesis to resume at full capacity when the light returns.

This is why the newer types of shadecloth were developed with strips of
aluminium rather than the even shade of the standard cloth. Basically a 50%
strip shade cloth allows full sun for half the time and full shadow
intermittently on the leaf as the sun passes overhead.

This process happens very quickly, and many experiments have shown that even strobe lighting is more efficient than steady light.

I hope my explanation is clear. Perhaps someone on the list might know what
are the most efficient photoperiods. I must add that I know nothing about
how photoperiods affect fish.

regards

Mike.
*End of thread*

So the thought of putting a strobe light under the hood gave me an incredibly good laugh (I'm an artist so I have vivid visualisations). So I suppose possibly the best way to simulate this would be with light timers right? Or possibly some aquatic company can manufacture some sort of device that imitates the shade cloth scenario stated in the thread.
I found this very interesting and seeing that these guys are tissue culture guru's I thought that it would be great food for thought for all of us too. What do you guys think of all this?

Kindest Regards
Cameron James
 

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There seems to be a large number of false premises behind the info you are getting about the value of interrupting light periods. I guess the biggest one is the assumption that you would normally be working with a light level so intense that the plant would be making food faster than it can use it and, therefore, the photosynthetic rate would be limited, not by light level, but by rate of food translocation and use, and, therefore, there would be a benefit from interrupting the light. What would the benefit be? Lowering your electric bill? Is lowering your bill the problem? If that is not the problem, what is the problem? Are you dissatisfied with the growth rate you get with continuous light? If so, do you have the level of continuous light so high that photosynthesis is limited by the plant's ability to translocate and use the sugars produced in photosynthesis? Somehow, I doubt it. Is it your goal to have to prune your plants back every day instead of just on weekends???
 

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Discussion Starter · #3 ·
HeyPK said:
Somehow, I doubt it. Is it your goal to have to prune your plants back every day instead of just on weekends???
Hi Paul and thanks for the response. I just thought the above info was worth sharing as I found it interesting! Sorry if this is all old hat to you but I'm fairly new to this game and all these little bits I learn about plants may be of interest to other likeminded hobbyists so i thought I would post it here too. Do with it what you will.

Kind regards
Cameron
 

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Hi, Cameron,

I am not mad at you or anything. It is just that there were so many annoying false premises in the explanations by Mike, and they all would lead one to think that one should be turning the light on and off to get some imagined growth benefit even at the usual lighting levels we use. I guess I came across as too annoyed, but perhaps that was because I heard a speech last night that put me in a bad mood. It also had a lot of false assumptions in it. :rolleyes:
 

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I do believe this thread is gonna open up a big ole can of worms :)

I think the variable that is missing here is that Mike is talking about terrestrial plants being grown in controlled conditions...not aquatic plants grown by hobbiests in aquariums with a much more limited light source.

I have seen this on-off-on again type of lighting routine praised by some to limit algae growth but have never seen it proven to actually limit the growth of algae.

I don't think I would want faster growth from my aquatic plants as that would just require more maintenance. However, it would be nice to get HC to grow a bit faster
 

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Discussion Starter · #6 ·
HeyPK said:
Hi, Cameron,

I guess I came across as too annoyed, but perhaps that was because I heard a speech last night that put me in a bad mood. It also had a lot of false assumptions in it. :rolleyes:
Its no Bother Paul, no offense taken. We all have our bad days!
 
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