Effects of using just RED or BLUE lighting for plant growth.

[Box of Demons]

Does anybody have any information on this? Local aquarium plant supplier said to only use RED led lights for growth. And use white light just for viewing on a night time, any thoughts on this?

 

[Colin_T]

Red light causes plants to grow upwards.
Blue light causes plants to grow outwards.
White light increases brightness and helps plants photosynthesise better.

Get globes with a 6500K rating and look for equal wave lengths in red and blue light with a bit of green.

 

[Byron]

I concur with Colin. As for the claim the plant supplier made, that is incorrect if you want good overall plant growth. I have never tried growing plants under just red light, but I cannot image they would look like much.

I did delve into aquatic plant light extensively a few years ago. Red and blue are essential for photosynthesis. But when green is added to the mix, plants do respond better. This is probably because the green light is being reflected (which is why the leaves appear green to us) and this allows the red and blue to be more fully used, the result being overall stronger light. Which is not surprising, since mid-day sun under which plants have evolved is near identical to 6000K-6500K light (high in red, blue and green wavelengths).

 

[StevenF]

Plants are absorbed light and make food most efficiently in the red and blue ends of the spectrum. However plants will also all other colors of visible light including green, yellow, and orange. Plants are less efficient at these colors but they can still grow. Even if no red and blue light is available. Some plants willl actually do better under white light then they would under a light that just produces blue and red light. Some plants grow taller under blue light while others grow bushy and some have the opposite behavior. Also some plants will due better under low kelvin lights like 2700K while others will like 6000K lights.

There is little detailed information on this so my advice is to use a lithe that is most pleasing to your eyes.

 

[utahfish]

In aquaponics red light is used for flowering while blue light is used for foilage. If one is attempting to get ones above water aquarium plants to flower then a red light will In theory help them flower.im guessing you arent trying to get your aquarium plants to flower though so stick with full spectrum lighting between 350-700 nanometers and 5000 K- to 6500 k rating. Warmer lights like 5000k will have more red light and cooler lights like 6500 k will have more blue. Above 6500k you lose reds and get more whites and blues below 5000k you lose blue and get more red and yellows. Plants utiilize blue and red with some green best which just plain red does not offer. Stick with full spectrum.