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Black or green shade net?
I read in the book, Orchids Of Asia by Teoh Eng Soon that green ranges and green PVC as cover for orchids represses plant growth. Does this cover green shade cloth rather than a black net? I'm using green shade net. What's the difference between the two colors?
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On Wed, 5 Oct 2005 12:52:05 +0000 in blass wrote:
I read in the book, Orchids Of Asia by Teoh Eng Soon that green ranges and green PVC as cover for orchids represses plant growth. Does this cover green shade cloth rather than a black net? I'm using green shade net. What's the difference between the two colors? Remember plant foliage tends towards green because they are pulling the energy out of the red and blue ends of the spectrum. I suspect, and will defer to the knowledge of those with greenhouses and shadehouses, that use of green shade netting will lead to higher measured light levels, but less light that is useful to the plants. And on that thought, are there places that sell red/blue shade netting? :-). -- Chris Dukes Suspicion breeds confidence -- Brazil |
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 |
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" wrote in message ... 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? The color we perceive is due to the difference between the light reflected (or that passes through translucent material) and the light absorbed. If you shine white light on a green material, we seen green because most other frequencies in the visible spectrum are absorbed and it is primarily green light that is reflected. In the context of a greenhouse, then, you will have light of various frequencies bouncing around, reflected by different surfaces. An opaque green cloth will absorb the frequencies most useful to plants and reflect those frequencies that are least useful to plants. This is why, for example, leaves appear green; they absorb red and blue and reflect green. I could go on, but I am sure those interested can find a text on plant physiology or biochemistry. It may help to think about the ultimate fate of the light that enters through the openings in the shade cloth. While sunlight is nowhere near white, lets assume that the light entering the greenhouse through the pores in the shadecloth is white. What happens to it once inside. It bounces around, reflected by one surface or another until it either escapes through another pore or is absorbed. Since the plants will be absorbing red and blue frquencies and reflecting green, the spectrum will increasingly include primarily green colors. Similarly, if the shade cloth is green, any red or blue light hitting it will be absorbed (and probably reradiated as infrared), while the light reflected will be green. Does any of this make a significant difference? I don't know since I have not looked at, or conducted, any experiments that would tell us. I would expect that there may be some effect on rates of primary production, and thermal effects, but only a series of controlled experiments will tell us for sure. I am not sure this is even important, except for those who design and test shade cloth, since for ordinary growers and breeders, the recommendations of how to use shade cloth will probably largely be based on experience of how well different plants perform with different amounts of shade cloth in different regions. I don't know if this is helpful, but it is fun to think about. 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 |
I had considered the fact that there might be edge effects - some slight
diffraction around the edges of the openings, but I doubt it's significant. My mind still wants to go back, though - if I have a white board and a green board creating shadows, aren't the shadows the same? Likewise, I suppose it's possible that some light is transmitted through the mesh material, in which case the color might be important, but again I doubt it's significant. -- Ray Barkalow - First Rays Orchids - www.firstrays.com Plants, Supplies, Artwork, Books and Lots of Free Info! "Ted Byers" wrote in message ... "Ray" wrote in message ... 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? The color we perceive is due to the difference between the light reflected (or that passes through translucent material) and the light absorbed. If you shine white light on a green material, we seen green because most other frequencies in the visible spectrum are absorbed and it is primarily green light that is reflected. In the context of a greenhouse, then, you will have light of various frequencies bouncing around, reflected by different surfaces. An opaque green cloth will absorb the frequencies most useful to plants and reflect those frequencies that are least useful to plants. This is why, for example, leaves appear green; they absorb red and blue and reflect green. I could go on, but I am sure those interested can find a text on plant physiology or biochemistry. It may help to think about the ultimate fate of the light that enters through the openings in the shade cloth. While sunlight is nowhere near white, lets assume that the light entering the greenhouse through the pores in the shadecloth is white. What happens to it once inside. It bounces around, reflected by one surface or another until it either escapes through another pore or is absorbed. Since the plants will be absorbing red and blue frquencies and reflecting green, the spectrum will increasingly include primarily green colors. Similarly, if the shade cloth is green, any red or blue light hitting it will be absorbed (and probably reradiated as infrared), while the light reflected will be green. Does any of this make a significant difference? I don't know since I have not looked at, or conducted, any experiments that would tell us. I would expect that there may be some effect on rates of primary production, and thermal effects, but only a series of controlled experiments will tell us for sure. I am not sure this is even important, except for those who design and test shade cloth, since for ordinary growers and breeders, the recommendations of how to use shade cloth will probably largely be based on experience of how well different plants perform with different amounts of shade cloth in different regions. I don't know if this is helpful, but it is fun to think about. 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 |
Thanks you guys and to Ted for that lengthy insightful piece. To quote from the book, Orchids Of Asia by Teoh Eng Soon, top orchid grower of Singapore, (Chapter 6 on Light)......
"The type of light is also important for the proper growth of orchid. Light in the ultra-violet, near ultra-violet and green ranges represses plant growth, and green PVC sheets are TOTALLY UNSUITED for roofing of orchid houses. When too much green algae collect on top of the plastic roofing, it similarly represses plant growth. The algae must be scrubbed off or the roofing replaced. The simplest approach is to employ shading which will not interfere with the normal spectrum of sunlight, such as with lath houses, white paint over glass, or black saran cloth." Now comes the subject of the color black in shade net trapping heat efficiently more than the green one. Any takers? |
"Ray" wrote in message ... I had considered the fact that there might be edge effects - some slight diffraction around the edges of the openings, but I doubt it's significant. My mind still wants to go back, though - if I have a white board and a green board creating shadows, aren't the shadows the same? Yes, the shadows would be the same. However, don't forget that in the case of the shade cloth, you have the pores that let some of the light through. What happens to that light? It isn't all absorbed by the plants and fixtures in the greenhouse. Much of it is reflected, and much of what is reflected will hit the inside surface of the shade cloth. So the shade cloth is hit by light on both of its sides. To see what I mean, you could try some ray tracing. Draw a cross section of your greenhouse, with a solid floor and walls and roof that have gaps in the line syou've used to represent them. Then, draw a series of parallel lines hitting the greenhouse, representing incident light. Some of those will hit the lines used to represent one of the walls or the roof. Those will either end there or be reflected away from the greenhouse. Those that hit the simulated pores will enter. Then continue those lines until they hit a surface, and start drawing the path that would be taken by the reflected light. Some of these will escape the greenhouse through the pores in the shade cloth. Many, though, will hit the walls (shade cloth) and be reflected back into the greenhouse. These paths will continue inside the greenhouse until they happen to hit a pore, or until the light is absorbed by something. Energy is conserved. Light doesn't just enter the greenhouse and disappear. Whatever isn't absorbed is reflected, and that reflected light must go somewhere. The ray tracing exercise described allows one to see this, in simplified form. A complicating factor is that any light absorbed is either used by the plants in photosynthesis (converting electromagnetic energy into chemical energy) or reradiated at a lower frequency (usually in the infrared range), and this is reradiated in all directions. So, on average, half of the light absorbed by the shade cloth will be radiated into the greenhouse in the infrared, and half will be radiated out of the greenhouse. Cheers, Ted |
I found a site (http://www.diatex.fr/uk/produits/agri/ombrage.htm) 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. |
Now comes the subject of the color black in shade net trapping heat efficiently more than the green one. Any takers? If attention is focussed solely on thermodynamics, the answer is obvious. Instead of answering directly, I'll put the question back to you in slightly different terms. NB.: A flat black surface is absorbing light energy in all frequencies in the visible spectrum. NB.: A green surface is absorbing all frequencies in the visible spectrum EXCEPT for green. Green is reflected which is why it appears green. Which do you suppose is absorbing more energy, assuming both are subject to the same intensity of white light? Which will reradiate more energy out of the greenhouse as infrared radiation? Which will reradiate more energy into the greenhouse as infrared radiation? 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 |
"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.* This seems generally OK, with a couple points that don't quite make sense. What is said about green shade nets is obviously true. What is said about black shade nets seems only partially true. While it is true that a black material will reduce the quantity of light, I don't see how it can reduce the quality of light (with respect to photosynthetically active radiation or PAR) and appear black. I can see how a black net can result in less PAR than a white one, due to more of the light that is reflected inside the greenhouse being absorbed by the interior surface of the net. But I'd hazard a guess that the effect of a choice between white and black shade nets on photosynthesis would involve a tradeoff between a little more PAR vs a little more heat. 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 |
Ah HAH! I had forgotten about the reflected light. Do you think it's
that significant? -- Ray Barkalow - First Rays Orchids - www.firstrays.com Plants, Supplies, Artwork, Books and Lots of Free Info! "Ted Byers" wrote in message .. . "Ray" wrote in message ... I had considered the fact that there might be edge effects - some slight diffraction around the edges of the openings, but I doubt it's significant. My mind still wants to go back, though - if I have a white board and a green board creating shadows, aren't the shadows the same? Yes, the shadows would be the same. However, don't forget that in the case of the shade cloth, you have the pores that let some of the light through. What happens to that light? It isn't all absorbed by the plants and fixtures in the greenhouse. Much of it is reflected, and much of what is reflected will hit the inside surface of the shade cloth. So the shade cloth is hit by light on both of its sides. To see what I mean, you could try some ray tracing. Draw a cross section of your greenhouse, with a solid floor and walls and roof that have gaps in the line syou've used to represent them. Then, draw a series of parallel lines hitting the greenhouse, representing incident light. Some of those will hit the lines used to represent one of the walls or the roof. Those will either end there or be reflected away from the greenhouse. Those that hit the simulated pores will enter. Then continue those lines until they hit a surface, and start drawing the path that would be taken by the reflected light. Some of these will escape the greenhouse through the pores in the shade cloth. Many, though, will hit the walls (shade cloth) and be reflected back into the greenhouse. These paths will continue inside the greenhouse until they happen to hit a pore, or until the light is absorbed by something. Energy is conserved. Light doesn't just enter the greenhouse and disappear. Whatever isn't absorbed is reflected, and that reflected light must go somewhere. The ray tracing exercise described allows one to see this, in simplified form. A complicating factor is that any light absorbed is either used by the plants in photosynthesis (converting electromagnetic energy into chemical energy) or reradiated at a lower frequency (usually in the infrared range), and this is reradiated in all directions. So, on average, half of the light absorbed by the shade cloth will be radiated into the greenhouse in the infrared, and half will be radiated out of the greenhouse. Cheers, Ted |
"Ray" wrote in message ... Ah HAH! I had forgotten about the reflected light. Do you think it's that significant? -- I'll give a definitive "It depends!" ;-) It all depends on the details of the geometry of the structure. If the geometry of the greehouse, and the properties of the shade cloth, are such that a large proportion of the light entering the greenhouse is ultimately absorbed inside the greenhouse (meaning used by plants to produce new tissue, or ultimately converted into heat), then this effect may well overwhelm the contribution to plant production from light that has entered the greenhouse and not yet been reflected. On the other hand, if the combination of the geometry of the greenhouse and the properties of the shade cloth are such that most of the reflected light exits the greenhouse, then the effect is likely negligible. The only way to know for sure if the effect is likely to be significant is to construct a computer simulation; a numerical experiment if you will. The physics, and the computational requirements for ray tracing, is simple enough. The data management, though, would be challenging, since you'd have to run a reasonably large number of rays, simulating a constant input of new rays, and keep track of rays that have left the structure or been absorbed, until the system approaches equilibrium (probably reached almost instantly in the real world, but likely to take some time in the simulation). You can then estimate the proportion of rays striking a given surface that have been bouncing around the greenhouse before striking the surface in question (and do this for a number of different frequencies, simultaneously, to get a sense of the impact of this effect on the spectral quality of the light. Of course, once such a simulation model has been constructed, it is easily modified to examine the consequences of using black shade cloth rather than white shade cloth (or any other color for that matter), both for the quality of light reaching a given surface and for thermodynamic effects. While I am a specialist in environmental modeling, I am not sure I want to spend the months needed to produce an application to do this to the standards I maintain for my own work; especially when I am working hard on getting a new business established. If I was working at some university, though, I'd certainly assign it to graduate students to give them a sense of the application of science in the real world. 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 |
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. -- Ray Barkalow - First Rays Orchids - www.firstrays.com Plants, Supplies, Artwork, Books and Lots of Free Info! "Ted Byers" wrote in message .. . "Ray" wrote in message ... Ah HAH! I had forgotten about the reflected light. Do you think it's that significant? -- I'll give a definitive "It depends!" ;-) It all depends on the details of the geometry of the structure. If the geometry of the greehouse, and the properties of the shade cloth, are such that a large proportion of the light entering the greenhouse is ultimately absorbed inside the greenhouse (meaning used by plants to produce new tissue, or ultimately converted into heat), then this effect may well overwhelm the contribution to plant production from light that has entered the greenhouse and not yet been reflected. On the other hand, if the combination of the geometry of the greenhouse and the properties of the shade cloth are such that most of the reflected light exits the greenhouse, then the effect is likely negligible. The only way to know for sure if the effect is likely to be significant is to construct a computer simulation; a numerical experiment if you will. The physics, and the computational requirements for ray tracing, is simple enough. The data management, though, would be challenging, since you'd have to run a reasonably large number of rays, simulating a constant input of new rays, and keep track of rays that have left the structure or been absorbed, until the system approaches equilibrium (probably reached almost instantly in the real world, but likely to take some time in the simulation). You can then estimate the proportion of rays striking a given surface that have been bouncing around the greenhouse before striking the surface in question (and do this for a number of different frequencies, simultaneously, to get a sense of the impact of this effect on the spectral quality of the light. Of course, once such a simulation model has been constructed, it is easily modified to examine the consequences of using black shade cloth rather than white shade cloth (or any other color for that matter), both for the quality of light reaching a given surface and for thermodynamic effects. While I am a specialist in environmental modeling, I am not sure I want to spend the months needed to produce an application to do this to the standards I maintain for my own work; especially when I am working hard on getting a new business established. If I was working at some university, though, I'd certainly assign it to graduate students to give them a sense of the application of science in the real world. 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 |
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 |
"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 |
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 |
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. |
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 |
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 |
"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 |
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. |
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 |
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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