Photosynthesis -The importance of Illumination/Light

Why do Plants need Photosynthesis?

All living things need energy to grow and reproduce. As for plants, they use cellular respiration to produce Adenosine Triphosphate (ATP). ATP is the energy-carrying molecule found in the cells of all living things. This respiration process needs glucose thus photosynthesis. Just like humans eat food to survive, plants make their own “food” through photosynthesis. Moreover, carbohydrates are also needed by the plant to build plant cell structures, like the cellulose cell wall.

How does photosynthesis work?

In the simplest explanation, it is a process where plants use light, water, and carbon dioxide to make glucose to survive.

The complex explanation is that plants take in and use carbon dioxide through tiny holes in a plant’s leaves, flowers, branches, stems, and roots. Water is then absorbed by the roots to make the plant’s food with the presence of lights. You might be wondering by now; How does a plant take carbon dioxide and water to generate food? This is when the light comes in. The energy from light causes a chemical reaction that breaks down carbon dioxide and water to make sugar (glucose) and oxygen. The sugar is then broken down into energy that can be used for the plant’s growth. The oxygen that is produced will be released to the atmosphere.

For our nerd friends, the formula is;

6CO2 + 6H2O + Light energy → C6H12O6 (sugar) + 6O

Illustration showing the process of photosynthesis. < Created by Brgfx – Freepik.com>

Why are lights important?

Lights are one of the 3 core components (the others are carbon dioxide and water) that keep a plant alive through the process we discuss earlier known as “photosynthesis”. Plants are known to seek out light as you probably have observed a plant leaning toward a window or light source. In science, they call it “phototropism” where the hormones in the plant’s stem force the plant towards the light.

What are the light spectrums used in Photosynthesis?

Sunlight is the best source of lights for plants. I believe this is un-debatable. However, for many of us, sunlight is a luxury that we do not have in an indoor urban environment. Thus we need to rely on artificial lights to emulate sunlight.

As much as technology is improving by leaps and bounds, artificial lights are still not able to 100% replicate sunlight. Thus we need to dig a bit deeper when we are using artificial lights to emulate sunlight for our indoor plants. Which spectrum(s) in the light wavelength is the most critical for the health of our plant from growth and repair to flowering and bearing fruits?

Plants Photosynthesis Wavelenght

Plants Photosynthesis Wavelength

Different plants do have a different preference for light spectrums. In most cases, we can identify certain light spectrums contributing to the plant performance for specific tasks as presented in the diagram above.

Blue Light Spectrum

Blue light is in the 400-500 nm (wavelength) range. Plants use this spectrum to promotes root growth and intense photosynthesis. It is found that blue light reduced the dry weight, height, and leaf area in the plants compared to other light spectrums.

In simple terms, blue light is crucial for the young plant to maintain healthy growth. It promotes strong roots and leaf growth which means bigger biomass.

Red Light Spectrum

Red light is in the 640-720 nm range which stimulates and stem growth, flowering, and chlorophyll production. Studies have been made and found that plants grown under red lights alone has developed less vegetative growth, grew longer stems and leaves, and yielded fewer seeds.

As such, if you have a matured fruiting plant, you might want to ensure it has its fair share of red lights bear your desired fruits.

Other Spectrum (green, infrared, white)

This is an area that many kinds of research are still on-going. The general consensus is that Plants do use these other spectrums. For example, Green Spectrum has an average relative quantum efficiency higher than Blue spectrum and are strongly absorbed by chloroplasts in the upper part of the leaf as Greenlight penetrates deeper into the leaf. Texas A&M University also found that infrared light plays a part in the blooming of flowering plants.

It is also widely believed (not sure if there is any scientific proof) that with RGB (Red, Blue Green) lights, 90% of the plant’s lifecycles requirements are been taken care of. This is also probably why more and more commercial farms are moving indoors using artificial lightings as the advantages of indoor farming overly out-weight open space farming.

What it means to us, the indoor urban farmers

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