tannerm wrote:No one said they can't use it. Plants respond best to red (bloom) and blue (foliage) growth LEDs & the good ones combine white LEDs as well. Show me the evidence to back up your insane claims that they're "based on the (false and widely circulated) idea [...]" - numerous scientific studies have been done.... also I will add that UV can be harmful to plants, especially sensitive highlanders.
Maybe I shouldn't say it's false, but most people misinterpret the commonly-available information so I will attempt to explain here. I should note that I'm not trying to say that red/blue LED lights are bad - they work just fine. I just don't want people to believe they HAVE to buy those to get the best plant growth or that they're inherently more efficient than white lights as the marketing frequently claims.
We're all familiar with the common chlorophyll absorption chart:
https://en.wikipedia.org/wiki/Photosynt ... tra-en.svg This chart is created by measuring the light absorption of pure chlorophyll extracted from plants in a laboratory but is widely believed to represent the light absorption capabilities of plant leaves. Not only does it leave out accessory pigments like anthocyanin (here's a graph with a common anthocyanin overlaid on it:
https://en.wikipedia.org/wiki/Anthocyan ... in_(1).PNG,) but it doesn't take into account any part of the leaf structure of the plant. It's really only applicable to organisms like cyanobacteria and algae because of this.
This chart is one of the primary reasons for the design of these red/blue LED lights with the other being the "bloom" and "veg" spectra that you mentioned. These terms were coined by marijuana growers who want their plants to grow in a very specific way. The thing is, the only part of the plant that matters to them is the flower buds as the leaves do not contain any THC. The "veg" spectrum is very heavy on blue light which acts as a growth regulator in plants - low blue light causes etiolation, while high blue light causes very compact growth and extra branching (important so there are more growth points to produce flowers.) Once the plants begin to flower they switch to the "bloom" spectrum which is very heavy on red light, since red is more photosynthetically-efficient than blue so the plant has more energy to put into the flowers.
Now about why the chart is misunderstood and misleading: If you read the Wikipedia article about PAR (photosynthetically-active radiation)
https://en.wikipedia.org/wiki/Photosynt ... _radiation you can see the absorption spectrum of an individual chloroplast (plant organ that performs photosynthesis) at the top just under the chlorophyll graph and further down the page the PAR conversion graph which measures how much photosynthesis is performed for a given wavelength of light (the energy-weighted line is the important one.) You can see that the efficiency of GREEN light is actually higher than blue. Even this chart isn't 100% accurate, as the efficiency of green light in comparison to the other colors increases with light intensity and actually beats out red when the chloroplasts are fully-saturated.
For why this is the case, this paper has in-depth information
http://onlinelibrary.wiley.com/doi/10.1 ... 0563.x/pdf but the tl;dr of it is that because individual chloroplasts absorb a low amount of green light, it can penetrate deeper in the leaf and reach more of those chloroplasts while red and blue are absorbed closer to the surface. Once the surface chloroplasts are saturated, the plant can only use the green light that penetrates deeper. So basically - the stronger the light, the more photosynthetically-efficient green wavelengths are compared to others.
About UV, while I do not have a source for this I've been told by someone who knows a lot more about photosynthesis than I do that plants that grow at high elevations commonly can utilize some UV radiation. There are no studies that have been done specifically on Nepenthes in this regard that I'm aware of and it's certainly not necessary to grow the plants. UV supplementation certainly can be helpful when starting seeds indoors for plants that will be moved outside in the future, to reduce the necessary acclimation period.
Benurmanii wrote:http://msue.anr.msu.edu/news/green_ligh ... ant_growth
Keep in mind with studies like these that light intensity will alter the efficacy of green light compared to the other wavelengths and that some plants will respond VERY poorly to single wavelength light sources like that, especially the overabundance or lack of blue light. This particular plant does seem to closely match the PAR yield curve in this particular experiment though.
