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  #16   Report Post  
Old 07-10-2005, 01:19 PM
Steve
 
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Reka wrote:
................
...............................
Okay, I know a little about orchids, but more about orchards, a subject
that I have grown up with. (Shades of those poor newbies who think this
is "rec.gardens.orchards"!) Over here, we have problems with hail damage
on apple crops from summer to early fall. Thus, hail netting is
stretched over the trees during that time period. Very dark green,
black, or white nets have been used. It has been proven that the red
apples under white netting color up much better than those under the
other two dark colors. Now, how this can be correlated to orchids, I
don't know, but perhaps it is worth the time I took to write it. And I
am a slow typer. :-) I am assuming it could be the extra heat generated
under the darker colors that prevent better color. Red apples need
temperature swings from cool nights to warmer days without rain in order
to color up well.



Hi Reka.
We haven't had one of those orchard/orchid confused people in a while now.
About the red apples under white netting... You are obviously right
about better color with cooler temperatures. That's why they grow a lot
of Macintosh apples in Vermont and here in northern New York but not
much farther south. I bet heat isn't the factor with the netting though.
I'm not sure a dark netting would cause more heat around the trees.
(Also not 100% sure it wouldn't.) I bet it's just more light getting
through. You KNOW the apples color up better on the sunny side of the tree.
My first thought was that maybe this does translate into better orchids
and the better light that colors up apples would probably help orchid
blooming. On second thought, if it's just the quantity of light, then
for orchids that need the shade, they need the right amount of shade and
it probably doesn't matter if that amount is created by black or white
cloth.

Steve



  #17   Report Post  
Old 07-10-2005, 04:04 PM
Ted Byers
 
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"Ray" wrote in message
...
Well Ted, I guess we can ignore light reflected from the plants, since
it's the wavelength they don't use. Then we have to speculate on the
reflectivity of the benches, floor, media, algae, moss, etc.

No, we can't ignore light reflected from the plants. The light reflected
from a plant appears green because there is more green light than anything
else, but that does not imply that there is no blue or red. Blue and red
light may well be present in the reflected light, but in equal values of the
plant looks green, or a bit more red if there is a reddish hue to the
leaves. From a scientific perspective, we can not say that all green light
is reflected by leaves, nor that all red and blue light is absorbed. All we
can say is that more green light is reflected by the leaves and more blue
and red light is absorbed. And of the light that enters the leaves, more of
the green light will pass right through while less blue or red light will
pass through. Most leaves are translucent; not opaque!

While I didn't mention it before, there is the question of light that passes
through the leaves. In most species, if you hold a leaf up to the light,
you can see light coming through the leaf, and this light is normally green,
and this happens even though you can not normally see anything on the other
side of the leaf. This will be greater or less depending on the species,
but the important point to remember is that there is no such thing as an
energy conversion process that is 100% efficiency. It is unusual to get
better than 5 to 10 % efficiency, although I suppose that with some
creativity, some engineer might come up with something better. In the
biological world, the vast majority of energy of light of any frequency is
either reflected or absorbed and converted to heat.

And you're right. If we are to be thorough, we'd have to consider
everything in the greenhouse. Consideration of allgae and live moss,
though, could be lumped together with the other plants in the greenhouse as
they'd have similar properties. As they'd all be using the same process of
photosynthesis, they'd all have very similar optical properties. Alas,
things get much more complicated as we consider them in more detail.

Here is a question that might help understand the implications of this. You
have two surfaces, both subject to the same white light. One surface
appears to be dark green and the other appears to be light green. Since
both are subject to the same white light, they both get the same amount of
green light. How, then does one appear lighter than the other?

Here is a tip, to help answer the above question: In computer graphics, one
can lighten the color green obtained from the brightest green setting for a
set of pixels by adding equal amounts of blue and red. You can break the
light coming from a pixel, in this context, into two components: one made of
pure green light and another made of white light. I use this routinely in
any computer graphics I add to my applications.

My guess is that it's insignificant compared to the incoming light.

--


I am not so sure. I will not say anything definitive, since I have not seen
reports of experiments designed to test it, nor have I done any myself.
However, theory suggests it could be significant and Reka has provided some
evidence that plants are affected by the color of netting used, in her case
for protection from hail, but the purpose of the netting is immaterial here.

Cheers,

Ted

--
R.E. (Ted) Byers, Ph.D., Ed.D.
R & D Decision Support Solutions
http://www.randddecisionsupportsolutions.com/
Healthy Living Through Informed Decision Making


  #18   Report Post  
Old 07-10-2005, 04:18 PM
Reka
 
Posts: n/a
Default

In article , =20
says...
Reka wrote:
................
...............................
Okay, I know a little about orchids, but more about orchards, a subject=

=20
that I have grown up with. (Shades of those poor newbies who think this=

=20
is "rec.gardens.orchards"!) Over here, we have problems with hail damag=

e=20
on apple crops from summer to early fall. Thus, hail netting is=20
stretched over the trees during that time period. Very dark green,=20
black, or white nets have been used. It has been proven that the red=20
apples under white netting color up much better than those under the=20
other two dark colors. Now, how this can be correlated to orchids, I=20
don't know, but perhaps it is worth the time I took to write it. And I=

=20
am a slow typer. :-) I am assuming it could be the extra heat generated=

=20
under the darker colors that prevent better color. Red apples need=20
temperature swings from cool nights to warmer days without rain in orde=

r=20
to color up well.

=20
=20
Hi Reka.
We haven't had one of those orchard/orchid confused people in a while now=

..
About the red apples under white netting... You are obviously right=20
about better color with cooler temperatures. That's why they grow a lot=

=20
of Macintosh apples in Vermont and here in northern New York but not=20
much farther south. I bet heat isn't the factor with the netting though.=

=20
I'm not sure a dark netting would cause more heat around the trees.=20
(Also not 100% sure it wouldn't.) I bet it's just more light getting=20
through. You KNOW the apples color up better on the sunny side of the tre=

e.
My first thought was that maybe this does translate into better orchids=

=20
and the better light that colors up apples would probably help orchid=20
blooming. On second thought, if it's just the quantity of light, then=20
for orchids that need the shade, they need the right amount of shade and=

=20
it probably doesn't matter if that amount is created by black or white=20
cloth.
=20
Steve
=20
=20
=20

I *do* know that the orchardists have to wear sunglasses under the white=20
netting because of the glare. I wonder if the quality of the light is=20
different, though.

From an abstract:
"The effect of hail netting on light penetration and fruit quality was=20
evaluated in commercial apple orchards in Eastern Switzerland. Black=20
nets reduced light levels (PAR) by 18 to 25 %, white netting by 8 to 12=20
% and grey nets (black and white fibres) by 15 to 17 %. No definite=20
influence of black hail nets on maturity and fruit quality has been=20
observed under good conditions (weather, site, small trees with loose=20
canopies, optimal fruit load, etc.) and with varieties for which fruit=20
colour is mainly genetically determined. For ?Jonagold? the light=20
intensity is decisive for development of fruit colour. Reduced colour=20
development under black nets may be observed on this variety. The=20
harvest time can be delayed by 8 to 10 days. Flesh firmness, soluble=20
solids content and acidity were not affected. In general the external=20
and internal fruit quality depends on many other factors which are more=20
important than the effect of hail netting."=20
http://www.actahort.org/members/show...rarnr=3D557_56
So it's a light/shade factor rather than a heat factar, though most=20
farmers here will swear that it is hotter under the darker nets.
--=20
--=20
Reka=20

This is LIFE! It's not a rehearsal. Don't miss it!=20
http://www.rolbox.it/hukari/index.html
  #19   Report Post  
Old 07-10-2005, 04:18 PM
Nancy G.
 
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Ray wrote:
Well Ted, I guess we can ignore light reflected from the plants, since it's
the wavelength they don't use. Then we have to speculate on the
reflectivity of the benches, floor, media, algae, moss, etc.

My guess is that it's insignificant compared to the incoming light.


Not contributing much to the discussion, but I did research some
interesting articles regarding light used, benefits of reflection for
increased light, even an old comparison of light bulbs.

http://64.233.161.104/search?q=cache...ed+light&hl=en

http://plasticulture.cas.psu.edu/DSuccess-mulch.htm

http://www.pubmedcentral.nih.gov/art...?artid=1062077

http://www.ccpo.odu.edu/SEES/veget/class/Chap_3/3_1.htm

http://www.thekrib.com/Lights/intensity.html

My sun room uses transluscent insulation under a clear roof, unshaded
windows. I've considered adding mirrors or foil against the back wall
to try to limit the shadowed places and balance the development of
plants. The plants are outside during the summer and get good light
coverage from most directions, but the blooms concentrate on the the
sunny side of the plant during the winter. In the southeast area of
the room the blooms on the cattleyas develop in all directions around
the plant.

Someone that uses supplemental light may try using bulbs with enhanced
spectrum designs or colored reflectors and filters to increase
different light bands in the spectrum.

Orchids take such a long time, even a single bloom season. There may
be more in the color of the floor and encouraged reflection of the
walls than most people have given credit in their pursuit of light.

  #20   Report Post  
Old 08-10-2005, 03:57 AM
Don
 
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Red mulch under tomato plants will increase yield, could colour of
benches, shade cloth and walls help our orchids? I have painted
surfaces white for total light intensity but could there be a colour
that would be an improvement?
Don
S.W. Ontario


  #21   Report Post  
Old 08-10-2005, 03:22 PM
Ray
 
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Doesn't that raise the question about what the red pigmentation does
(assuming all other mulch properties are identical)? Is it the reflected
red light back to the plant that makes a difference or is it a change in the
ground temperature under it?

--

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


"Don" wrote in message
...
Red mulch under tomato plants will increase yield, could colour of
benches, shade cloth and walls help our orchids? I have painted surfaces
white for total light intensity but could there be a colour that would be
an improvement?
Don
S.W. Ontario



  #22   Report Post  
Old 08-10-2005, 05:14 PM
Ted Byers
 
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"Ray" wrote in message
...
Doesn't that raise the question about what the red pigmentation does
(assuming all other mulch properties are identical)? Is it the reflected
red light back to the plant that makes a difference or is it a change in
the ground temperature under it?

Yes. ;-)

Both are likely to be happening. Any red light reflected onto a leaf will
likely contribute to photosynthesis, and possibly other processes. It is
certain that any light absorbed by the ground will be converted into heat,
producing nonlinear changes in soil temperature with depth. Now
understanding that process is considerably more complicated, involving
conduction and transport of heat, but the salient point is that light
hitting the soil will raise the temperature of the top layers of the soil,
and that will have the usual effect on reaction rates in the plant's roots.

How significant each process is is a different matter that can really only
be determined experimentally. I know the agriculturalists I know talkof the
importance of soil temperature, but I personally have not heard them discuss
the colour of the ground.

Cheers,

Ted


  #23   Report Post  
Old 08-10-2005, 05:57 PM
Don
 
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Ted Byers wrote:
"Ray" wrote in message
...

Doesn't that raise the question about what the red pigmentation does
(assuming all other mulch properties are identical)? Is it the reflected
red light back to the plant that makes a difference or is it a change in
the ground temperature under it?


Yes. ;-)

Both are likely to be happening. Any red light reflected onto a leaf will
likely contribute to photosynthesis, and possibly other processes. It is
certain that any light absorbed by the ground will be converted into heat,
producing nonlinear changes in soil temperature with depth. Now
understanding that process is considerably more complicated, involving
conduction and transport of heat, but the salient point is that light
hitting the soil will raise the temperature of the top layers of the soil,
and that will have the usual effect on reaction rates in the plant's roots.

How significant each process is is a different matter that can really only
be determined experimentally. I know the agriculturalists I know talkof the
importance of soil temperature, but I personally have not heard them discuss
the colour of the ground.

Cheers,

Ted


The following is copied and pasted here from the Lee Valley site -
www.leevalley.com . Do orchids have this phytochrome, the colour
sensitive protein the stimulates rapid growth?
Don

Super Red Mulch
Super Red Mulch - Gardening
From time to time research comes up with some astounding results. This
is one of them.

When this red plastic mulch is put on the soil under tomatoes, it will
increase yields by up to 20% over black mulch, and makes the fruit set
earlier. It works by reflecting a certain spectrum of light back to the
plants, which in turn triggers the release of phytochrome, a
color-sensitive protein that stimulates rapid growth and development.

The research was done by a number of universities and our own tests
proved it accurate.
  #24   Report Post  
Old 09-10-2005, 08:33 PM
Kenni Judd
 
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Black shadecloth definitely blocks more light than does white. There may be
some "quality" reduction on a 1-1 basis, but it would take at least 2 [and
I'm afraid maybe more] similarly-rated layers of white to provide the shade
of 73% black [what we started with, for phals, and had to add more shade to,
here in So. Fla.]

Second-hand: Aluminet has a number of customers buying its red and gray
products, or so they told me when they were here trying to sell me ... Not
so much orchid growers, mostly growers of flowering terrestrials. According
to Aluminet, these big growers move blocks of plants under different colors
of shade to time their flowering. FWIW. Kenni

"blass" wrote in message
...

I found a site (http://tinyurl.com/8znl8) selling shade nets. And this
is what they have to say or warn (darn, why now?) before buying their
shade nets:


*-Caution-

Green and black shade nets behave like filters. Essential radiation for
photosynthesis is reduced.
Thus, the growth is reduced. A green and black shade net decreases the
light's quantity and spectrum quality.

White shade nets :
They decrease only light's quantity, without altering luminous'
spectrum quality. As a consequence, the plant's growth is faster with a
white shade net.*


--
blass



  #25   Report Post  
Old 30-04-2017, 08:58 AM posted to rec.gardens.orchids
external usenet poster
 
First recorded activity by GardenBanter: Apr 2017
Posts: 1
Default Black or green shade net?

On Wednesday, October 5, 2005 at 2:37:15 PM UTC-7, Ray wrote:
OK, I give up.

In shade cloth, the solid material blocks the light, and the openings let it
pass, right? As an opening is an opening is an opening, what difference
does it make what color the light-blocking part is?

--

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


"Kenni Judd" wrote in message
...
Aluminet comes in a variety of colors. I know they have red, not sure
about blue.
--
Kenni Judd
Juno Beach Orchids
http://www.jborchids.com

And on that thought, are there places that sell red/blue shade netting?
:-).




--
Chris Dukes
Suspicion breeds confidence -- Brazil




Ray..you know about Rays much


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