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Old 14-04-2008, 04:01 AM posted to rec.gardens.orchids
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I go back and forth as to whether its duration or intensity of light tat
makes our plants bloom.. I think the answer is qualified 'yes' but if
one was to err I think it would be on intensity rather than duration..
I think plants need a minimum of light but it has to be of a certain
intensity. 8 hours of non sufficient light isn't equal to 8 hours of
intense light.

Or am I nuts,?

Has anyone any input on intensity vs duration?\

K Barrett

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Old 14-04-2008, 11:33 AM posted to rec.gardens.orchids
Xi Xi is offline
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Probably a combination of both. For example, P. gigantea needs higher
light levels, and it just won't bloom otherwise, no matter the
duration. But getting 3 hours a day of extra strength daylight
probably won't give you very happy plants either.... And every
species will be different as well.

Cheers,
Xi

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Old 14-04-2008, 02:12 PM posted to rec.gardens.orchids
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The quality of flowering is related to the overall health of the plant, but
narrowing the discussion as we have done, I suspect that it's a combination
of intensity, duration, and temperature that are key.

Photosynthesis is "just" a photochemical reaction, and as such, requires a
certain amount of light and a certain temperature to occur optimally. The
consumption of the photosynthetically-generated chemical energy (and its
storage) are also chemical reactions that are certainly affected by
temperature.

Respiration - the consumption reaction - goes on pretty much all the time,
but increases with increasing temperature.

Photosynthesis obviously occurs faster with more light, but I believe there
is a "temperature inhibition" thrown in there somewhere. Add to that the
fact that a plant used to being grown very bright will have less chlorophyll
per unit of surface area. All else being adequate, we are balancing a mass
of stores creation and utilization - both rate x duration dependent.

So.... longer duration of light at lower levels means a slower generation
of energy, and slower respiration and growth. Raise the temperature, and
the respiration and growth can outstrip the "building" process of
photosynthesis. (There is another reaction that leads to "legginess" in
warm, low-light conditions, but let's ignore that one.)

High light level increases the rate of generation, but also warms the plant,
increasing the respiration rate. Again, maybe to the point of negative
returns, especially if the warming impedes the photosynthesis. The shorter
duration means less total mass is created.

However, if we can keep the plant cool while increasing the light intensity
without shortening its duration, you "push" the energy creation and storage
more than the consumption, so a "stronger" plant should result.

A caveat to that, however, is that some plants don't do well a high light
levels. I think I must grow my phals too bright, for example. The best
phal blooming I have ever seen was a guy in NJ whose greenhouse was so
totally enveloped in algae that you had to wait a minute for your eyes to
adjust to the low light levels when coming in from outside.

--

Ray Barkalow - First Rays Orchids - www.firstrays.com
Plants, Supplies. Books, Artwork, and lots of Free Info!


"K Barrett" wrote in message
. ..
I go back and forth as to whether its duration or intensity of light tat
makes our plants bloom.. I think the answer is qualified 'yes' but if one
was to err I think it would be on intensity rather than duration.. I think
plants need a minimum of light but it has to be of a certain intensity. 8
hours of non sufficient light isn't equal to 8 hours of intense light.

Or am I nuts,?

Has anyone any input on intensity vs duration?\

K Barrett



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Old 14-04-2008, 04:24 PM posted to rec.gardens.orchids
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I keep going back to the examples set by the Phal houses in Taiwan, who grow
their plants at high light, high nutrition, and high temps, forcing them,
then drop light and temps and the plants flower fantasticly. Or dope
growers who keep the growlights on 24/7 never pausing for the so called
'dark reaction' and still their plants bud fantastically.

Windowsill growers with a south facing window that gets decent light 6-7-8
hours in a day may or may not get their plants to bloom (let's not talk
about lo-e coatings for now.) Sure, like Xi says, its species specific.
Some require more light (or as Ray says more food production, utilization
and storage) to grow & bloom and some don't. So the windowsill grower
selects for plants that grow in his/her conditions. GH growers get a wider
range of plant choices, but still, siting can be less than optimal, trees
grow, and shady spots occur. Again leading me to wonder is it duration or
intensity? If I put a GH on the eastern side of my house where it'll get
shaded from about 2PM onwards (nevermind what may occur in winter time when
the sun is lower in the sky) would I have better success if I supplement
light from 2PM onwards? Or shade less? Or depend on light bounce?

To say nothing about the idea that many orchids are from the tropics where
the day length is 12 hrs give or take, and there's a surplus of incoming
solar radiation. So the person growing in a windowsill in higher latitudes
with only 6-7-8 hours of less intense sun... or me thinking about adding a
second GH to my property in a less than optimal setting....

Ack! It is a marvel that we can get these things to bloom at all. I'm over
thinking.

K Barrett


"Ray B" wrote in message
news:[email protected]
The quality of flowering is related to the overall health of the plant,
but narrowing the discussion as we have done, I suspect that it's a
combination of intensity, duration, and temperature that are key.

Photosynthesis is "just" a photochemical reaction, and as such, requires a
certain amount of light and a certain temperature to occur optimally. The
consumption of the photosynthetically-generated chemical energy (and its
storage) are also chemical reactions that are certainly affected by
temperature.

Respiration - the consumption reaction - goes on pretty much all the time,
but increases with increasing temperature.

Photosynthesis obviously occurs faster with more light, but I believe
there is a "temperature inhibition" thrown in there somewhere. Add to
that the fact that a plant used to being grown very bright will have less
chlorophyll per unit of surface area. All else being adequate, we are
balancing a mass of stores creation and utilization - both rate x duration
dependent.

So.... longer duration of light at lower levels means a slower
generation of energy, and slower respiration and growth. Raise the
temperature, and the respiration and growth can outstrip the "building"
process of photosynthesis. (There is another reaction that leads to
"legginess" in warm, low-light conditions, but let's ignore that one.)

High light level increases the rate of generation, but also warms the
plant, increasing the respiration rate. Again, maybe to the point of
negative returns, especially if the warming impedes the photosynthesis.
The shorter duration means less total mass is created.

However, if we can keep the plant cool while increasing the light
intensity without shortening its duration, you "push" the energy creation
and storage more than the consumption, so a "stronger" plant should
result.

A caveat to that, however, is that some plants don't do well a high light
levels. I think I must grow my phals too bright, for example. The best
phal blooming I have ever seen was a guy in NJ whose greenhouse was so
totally enveloped in algae that you had to wait a minute for your eyes to
adjust to the low light levels when coming in from outside.

--

Ray Barkalow - First Rays Orchids - www.firstrays.com
Plants, Supplies. Books, Artwork, and lots of Free Info!


"K Barrett" wrote in message
. ..
I go back and forth as to whether its duration or intensity of light tat
makes our plants bloom.. I think the answer is qualified 'yes' but if one
was to err I think it would be on intensity rather than duration.. I think
plants need a minimum of light but it has to be of a certain intensity. 8
hours of non sufficient light isn't equal to 8 hours of intense light.

Or am I nuts,?

Has anyone any input on intensity vs duration?\

K Barrett





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Old 20-04-2008, 02:02 AM posted to rec.gardens.orchids
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Default light

I don't think there is a simple answer to your question since orchids
are so different in their natural lighting environments and probably
adapt over time to changes in the environment. If we could only see
them in their natural habitat that would give us some clues as to what
ideal conditions are.

On Apr 13, 11:01*pm, K Barrett wrote:
I go back and forth as to whether its duration or intensity of light tat
makes our plants bloom.. I think the answer is *qualified 'yes' but if
one was to err I think it would be on intensity rather than duration..
I think plants need a minimum of light but it has to be of a certain
intensity. *8 hours of non sufficient light isn't equal to 8 hours of
intense light.

Or am I nuts,?

Has anyone any input on intensity vs duration?\

K Barrett




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