# rate of photosynthesis across wavelength of light



## Amazonaquascaper (Sep 20, 2015)

Hi everyone
Can't understand this what happen to rate of photosynthesis before the 400 nm wavelenght of line...does it stop drastically or does it slopes gently to 0 nm.

Thanks for answering me...


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## JeffyFunk (Apr 6, 2006)

Light with a wavelength <400 nm is in the deep UV region of the electromagnetic spectrum. Light with that much energy would b damaging to plants (i think) and is most likely filtered out by the atmosphere before it gets to any flora on earth. 

I wouldnt worry about it.


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## TropTrea (Jan 10, 2014)

Yes Jeff is correct that short wave lenght light can be detrimental. However you realy need to look at the total picture to completly understand light effects on plants.

1. There are several chemicals in the plants that are photosensitive and produces energy in the plants to grow. Different Chemicals are activated with light at specific wavelenghts. As an example Chlorophyll A uses light at 430nm most effeciently on the blue end of the spectrum however its use of light at 470 nm is only half as effecient and between 500nm and 650nm is can barely benefit at all from. But different chemical have different most efficient frequencies. 
Chlorophyll A peaks at 430nm and 680 nm
Chlorophyl B peaks at 470nm and 660 nm
Betta Carotene peaks at 420nm and 690nm
This list can go on.

But also keep in mind that all these chemicals are not in every plant especially in the same balance. One could say that green plants have a tendency to use red light better then red plants do. And that very few plants use light between 520nm and 650 nm very efficiently.

If you were lighting a tank strictly for plant growth you would only need light in the 420 to 490nm rang and the 650 to 700nm range. This is a total of roughly 35% of the visual range from 400nm to 720 nm. So without looking at our visual effects we could have a healthy tank with 1/3 to light that would be full spectrum. Without green light though the green plants would appear near black in color.

There is also the UV spectrum that needs to be avoided and the red needs to also be controled. UV light breaks down the walls of living cells. This started at about 380nm and as the wave lenght shortens this effect is magnified. Cyno cells utilize light in the red spectrum and if excess is given you can get an outburst of various algae and especially cyno bacteria.


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## Diana K (Dec 20, 2007)

The drop off is very fast at the blue end. By 400nm higher plant use is approaching zero for most plant pigments. In this link, 2 pigments are shown with some activity beyond about 400nm, these are found in certain algae, not higher plants.

http://www.ledflowergrowlights.eu/illuminate.html


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## Amazonaquascaper (Sep 20, 2015)

Thanks for all your answers it helped me to understand a lot of things


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