Date: Fri, 7 Aug 1998 15:37:21 -0500 From: "Benjamin F. Lasseter" <benjamin@twister.tamu.edu> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg2622$foo@default> Subject: Re: Photoperiods and the Dark Cycle.
>I have been growing CPs under various combinations of discharge lamps (total
>replacement lighting) for a number of years now and have found, over time,
>with day lengths in excess of 14 hours that some plants exhibit this
>photoinhibition that you mention. At least, I think you are referring to a
>problem I have! I would describe it as a foreshortening or rosetting affect
>which gets worse over time irrespective of light level.
>
>As you obviously know what you are talking about, I was wondering if you can
>tell me if you think it is a phytochrome (R/FR ) reaction which, as far as I
>am aware, is affected by day length, or more accurately night length?
>
>Steve Gordon
Dear Steve,
It could be photoinhibition, but I (in my semi-uninformed opinion)
think that it is not. I perceive three possibilities, and can suggest what
to do in case of each.
(1) It is photoinhibition.
Admittedly, such things have been observed before, especially the
foreshortening effect. However, I gather from your message that you have
varied the amount of light the plants receive. If you see no change over
time with different amounts of light, then it is not photoinhibition.
(2) Hormonal problems.
Yes, indeed, plants have trouble with hormones, too. If it should
be a deficiency in hormonal levels at the leaf tips, you would observe the
effects you mention. You might also see a loss of apical dominance in
special cases. Generally, hormonal problems are genetic, and there is
nothing you can do about them. In other cases, the addition of a product
like "Miracle Gro" or similar products will clear everything up. (If, by
chance, one of your plants is overexpressing ENOD-40, could I get a tissue
sample...?)
(3) Nutritional problems.
By far, I consider this the most likely cause of your problems.
This one breaks down into a couple of different classes:
(a) metal deficiency:
All plants do require a constant low level intake of
certain metals, of which Manganese, Iron, Zinc, Magnesium, and Copper rank
very high. The deficiency in any of these metals results in the symptoms
you mention as well as the formation of yellowing patches. (Do you observe
a general yellowing?) Too much Calcium also will cause foreshortening and
rosetting, so you might have a problem with Calcium levels. Low metal
concentrations can become a real problem with deionized water. If you have
too low a metal concentration, at the risk of heresy, I would say use TAP
WATER for a while, until the problem goes away. If you are using tap water
already and have too much calcium, I would say stop using that type of
water and start using deionized water. I hope that no one minds me giving
out contradictory advice.
(b) organics deficiency:
Many of the organic compounds a plant needs come straight
from the soil. More precisely, they come from bacteria living ubiquitously
in soil. These organics that I refer to are vitamins. Vitamin
deficiencies an cause the effects you mention. If you have a vitamin
deficiency problem, there are various products that can be sold. I don't
know the brand names in the UK.
I personally doubt that it is a vitamin problem. Not with
CPs. If they are eating heathily, then would they ever suffer from a lack
of vitamins? Maybe our more experienced members can say.
If there is anything that I have said that seems incorrect to
anyone, please do not hesitate to correct me. I take correction fairly
well. I do hope, though, that what I have said is of some value. Good
luck, Steve.
Benjamin F. Lasseter
Texas A&M University
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