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Does the colour of light affect growth of plants?


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It depends which phase of the life cycle the plant is in which colour bands it prefers to to utilise. In the vegetative phase where there is active growth of leaves and stems, yes, it tends to favour the blue end but in the reproductive phase it will bias towards the red end.



Blue Light

The shorter wavelengths of blue light, also known as cool light, trigger chlorophyll production, which ends plant dormancy and starts the development process. Plants initially grown under blue light will have compact growth with thick leaves and strong stems. Outdoors, this light is strongest in spring and summer. Inside, home gardeners often use the blue light spectrum in the form of fluorescent lights to start seedlings.

Red Light

Combining the longer wavelengths of the red light spectrum with the shorter blue light spectrum wavelengths will begin the next phase of plant growth. This phase encompasses germination; development of the plant's underground network of roots, tubers or bulbs; and finally blooming and the development of fruit. Red or warm light is more prevalent as days shorten in the fall and winter. Eventually, this will cause the onset of dormancy in some plants.

Green and Yellow Light

Plants reflect green and yellow light, which are in the middle of the color spectrum. Thus, these two wavelengths have little effect on plant growth.



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To my meager knowledge, plants have converters for red and for long blue light.

Removing the infrared from the Solar spectrum may avoid excessive heat.

Adding short blue or violet would bring only trouble if the last converter is for long blue.


More: it's possible that both the red and long blue receiver must operate to sustain the plant's metabolism, in which case the red light can't be removed.


It would be a surprise if plants, who have been there for long and evolve quickly, were not optimum for Sunlight as it is.


Let's see what more knowdegeable people mean. Some plants grow industrially under artificial light, so the answer must be known.

Edited by Enthalpy
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  • 7 months later...

My knowledge of this topic stems from experimentation with hydroponics, or at least a version of hydroponics.
I successfully grew some plants in pots with soil as the growing medium, so for that part, the experiments were not 100% hydroponic as I used soil and watered them with water each morning and evening and weekly I feed them with a soluble fertilizer.

For light, the 1st 2 times I did this over three months, I several everyday fluorescent light bulbs One along the top, over the three plant and one each side of each plant, 7 bulbs all up. I never let the plants sleep for 2 weeks after the first 'real' leaves appeared, in other words, I left the lights on for 24hrs a day. After 2 weeks, I alternated the lights on a 12/12 hr cycle, 12 on and 12 off. This caused the plants to flower. I let the flowering plants grow under 12/12 light conditions for 3 months and the result was good. In another experiment, I came into possession of a proper grow light. This light bulb was much brighter, 400w, and was as close to the suns normal ray as could be manufactured. Growth under this light bulb was amazingly fast. Unfortunately, I do not have the exact specs of that bulb but it 'outshun' the ordinary bulbs tenfold as far as growth goes.

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Ordinary fluorescent light bulb have a spectrum composed of few rays, as they convert by a few phosphors the UV produced by gas discharge in mercury. This may match more or less our three types of receptors in the retina but must be suboptimum for the plants. Different phosphors would match the plant's needs better.

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