Re: HYB: indoor versus outdoor growth

Steve,

I read two things just this morning that may or may not be relevant.

One, apparently when it comes to triggering growth/bloom it is the duration of the darkness that is most significant, not the duration of the light.  The hypothesis I read was that there is some unknown hormone that is manufactured in darkness.  When the darkness is too short (in some plant species) or too long (in other plant species) the plant cannot build up enough of this hormone to stimulate (or inhibit) the affected growth processes.

The other thing I read was about two types of light, red light and dark red light.  Apparently, red light stimulates certain growth processes including bloom and germination and dark red light inhibits these processes.  They function like a light switch, whichever one was left on last is the one that has the influence.  So if the plant is exposed to constant dark red light it will be vegetative and never bloom.  If the last exposure was to red light then germination and bloom sequences will be activated.

Actually, I was thinking that this red/dark-red sequence might explain certain phenomena that some of us have observed in our burritoed seeds, like how they seem to germinate in flushes, and how germination seems to "shut off" while seeds still appear viable.  Previously we have hypothesized that these patterns were due to the short exposures to warm air while we process our burritoed seeds, but it seems likely that our seeds may be exposed to red/dark-red lights at these same intervals.

Christian




________________________________
From: mahlberg s <s_j_mahlberg@yahoo.com>
To: iris@hort.net
Sent: Saturday, July 4, 2009 9:05:59 PM
Subject: [iris] HYB: indoor versus outdoor growth

Hello,
I have a question concerning iris growth indoor versus outdoors.
I have raised several various iris seedlings over winter.
I have noticed decent growth, but the growth seems to improve after I move the
plants outside.
Even if I leave them in pots, they grow better outside, regardless of the
outside temperature.
I'd better understand improvements or quicker growth rates in warmer temps,
but it doesn't seem to matter.
Is this simply a matter of artificial light versus sunlight?
I've tried experimenting with12 hour on/off light and 24 hr light on with
various spectrum flourescent lighting.
Granted my basement is consistant in cooler temps over the winter, but at the
beginning of my outside growing season,
when I place potted irises outside, the temps are about the same or cooler
than my basement during the daylight hours and
most certainly cooler at night.
I still see improved growth outside.
I am pretty sure my artificial lighting source is good enough to grow in but
not good enough to flourish.
Is ther an ideal spectrum flourescent lighting source?
thanks for any insight as to what I might be missing or overlooking.

Steve zone 4b Minnesota

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