Date: Mon, 03 Aug 1998 17:05:36 PDT From: "Chris Teichreb" <cteichreb@hotmail.com> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg2581$foo@default> Subject: Re: Photoperiods & the dark cycle
Trevor,
>I
>am only writing this because I have been growing concerned with the
>growers whom I have seen set timers for 18-20 hour photo periods, or
>abandon the timer all together and just leave the lights on 24 hours a
>day.
If it works for them, why be concerned?
> There are events which show that night-like darkness isn't essential
>for decent plant growth. Take Alaska for example. During a part of the
>year where Alaska is under a tremendously long day, the crops grown
>there, like cabbage, experience explosive growth (I know this, I have a
>relative in Fairbanks). I don't really feel like going in-depth about
>such a topic, because that leads to too-many contradictions and such.
>I'm not saying that no night-like darkness is bad for your plants, but
I
>believe it to be so. Do what you wish, really. But I do recommend you
set
>some limitation to the photo period, give the dark cycle time to work
>it's magic, then go back to catering to the light cycle.
>Trevor
I'm not quite sure why this topic was even brought up, however...
You state that you do not wish to discuss this in depth due to
contradictions which may arise. However, your above statements have a
number of contradictions. You say that plants north of 66.5 degrees
latitude have tremendous growth rates in the summer under 24 hour
sunlight (which they do, I'm currently in Inuvik, Northwest
Territories!), and then in the following sentence say that you believe
no night time darkness to be bad for the plants.
The fact is, if you want good plant growth and are cultivating
species which are not sensitive to light periodicity for flowering (ie:
short versus long versus neutral daylight plants), then there is no
reason why you cannot leave lights on for 24 hours a day. Under proper
light conditions, plants both photosynthesize and respire. Under dark
conditions, they respire any of the created glucose. As you can see,
respiration which contributes to the plants growth, is not a dark
requiring process, it is only a non-light requiring process (this is a
common mistake made amongst people). While it is true that extremely
high light levels will lead to photoinhibition, the moderate light
levels which we often provide our plants with are rarely approaching
those levels.
I would suggest consulting an introductory text on plant physiology
for further details. Please do not critisize those growers who choose
to supplement their plants with long durations of light. If the plant
doesn't like it, it'll let the grower know. Otherwise, use whatever
works for you. If these plants were as easy to grow as throwing 12 hour
light and a bit of water on all of them, that would take away from the
challenge and fun of maintaining them.
My 2 cents worth!
Regards,
Chris
*************************************
* Chris Teichreb *
* Department of Biological Science *
* Simon Fraser University *
* Burnaby, BC *
* *
* cteichreb@hotmail.com *
*************************************
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