Wait, what's PAR?

[gradolabs]

The part you put in B, or bold, the par lumen... thats cool. But what it boils down to is par density per cm^3/sec*nm... Hard to read I know, but its just the density of photons of a certain wavelength at a certain length from the light source.

Another way to put it is: 59 blue photons in this box thats shaped like a leaf at 12 inches from the light and a little off center. And on the red side of things we have 125 red photons hitting a box shaped like a leaf every second... blah blah blah. But we need to identify key reactions and which wavelengths at blank intensity this far from the light and prove thats all the plant needs cause I'm pretty sure you can't grow plants with gamma rays. That kills them. Most things actually, but we're getting off topic.

Photosynthetically active radiation is the narrow (relatively) band of usable light that plants need to grow.

 

[SCARHOLE]

p.s. green light is great for secondary photosynthetic pigments like carontenoids. You're alright with some green, but blue then red should dominate your spectral output.

Maybe the green light is usable?
This is hard to read but its amazing!


Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong White Light: Revisiting the Enigmatic Question of Why Leaves are Green

http://m.pcp.oxfordjournals.org/content/50/4/684.full

 

[SCARHOLE]

The Emerson effect is also not taken into consideration when measuring PAR.

The Emerson effect.

When Emerson, a scientist, exposed green plants to differing wavelengths of light, he noticed that at wavelengths of greater than 680 nm the efficiency of photosynthesis decreased abruptly despite the fact that this is a region of the spectrum where chlorophyll still absorbs light (chlorophyll is the green pigment in plants - it absorbs mainly the red and blue wavelengths from light, leaving the green light to bounce back and hit our eyes). When the plants were exposed to short-wavelength light, (less than 660nm), the efficiency also decreased. Emerson then exposed the plants to both short and long wavelengths at the same time, causing the efficiency to increase greatly. He concluded that there must be two different photosystems involved in photosynthesis, one driven by short-wavelength light and one driven by long-wavelength (PS1 and PS2). They work together to enhance efficiency and convert the light energy to forms that can be absorbed by the plant.[1]


The light excites the chlorophyll molecules at the reaction centre and causes an increase in energy. As the molecule becomes less excited, its energy is transported through a chain of electron carriers to the next photosystem which does much the same thing and produces energy-carrying organic molecules.

(enhancement effect) The observation (made by Robert Emerson in 1957) that photosynthesis, which proceeds very slowly using light of 700 nm wavelength, can be greatly increased when chloroplasts are also illuminated with light of shorter wavelength (650 nm). This was a surprising observation as it was then thought that light absorbed by the chlorophylls and other pigments was all passed on to a small percentage of chlorophyll a molecules (the energy trap) absorbing at 700 nm. This and later work indicated a second energy trap absorbing at 680 nm. See Photosystems I and II.[\quote]

 

[gradolabs]

I just hadn't wrapped my head around the emerson effect... thats why I didn't include and literature about it. But I guess it means photosynthesis is hampered by near infrared unless you also have 680 amd 650nm red to back it up... I'll look into it and see if thats what it is... thanks for bringing it up scarhole... on one hand now I have to study more.. on the other we'll gain a better understanding.