How Blue Light Affects Plant Growth

As known, the light spectrum is important in plant growth. Whether growing plants in greenhouses, vertical farms, or grow tents, full spectrum LED grow lights are the common selections for most growers. That is because full-spectrum LED grow lights contain a spectrum in the PAR range, which can improve photosynthesis and balance plant growth. Among the spectrum in the PAR range, blue light and red light are recognized as the most vital light regions for plant development. Research has shown that the absorption of blue and red light by plants could be up to 90%. There is also much research about the effects of blue and red light on plant growth. But how does blue light affect plant growth?

What is blue light

Blue light has a range of wavelength between 400nm and 500nm. Blue light is within the visible spectrum, which means it is visible to human eyes. It is also the waveband in the PAR (Photosynthetic Active Radiation) range. Therefore, blue light is utilized by plants for photosynthesis. Blue light has higher energy than other wavebands in the PAR range. When days start to get longer, more blue light reaches the surface of the earth. And it initiates the vegetative growth for most plants.

Effects of blue light on plant growth

Blue light affects a wide range of plant processes, such as chlorophyll formation and stomata stimulation. It has strong effects on the vegetative stage and suppresses extension growth, thus resulting in compact growth. Blue light can also regulate the flowering of plants.

Chlorophyll formation

It is well known that blue light affects photosynthesis. That is because blue light enables chlorophyll production in plants. Chlorophyll is a green substance that plants use for photosynthesizing nutrients for growth. It is critical for photosynthesis to produce sugar and carbons. Blue light fits with the absorption peak of chlorophyll. This means chlorophyll uses blue light more effectively than red and far-red light. But blue light is less effective in driving photosynthesis than red light. This is because blue light can also be absorbed by carotenoids and anthocyanins. With the lower energy, blue light is not as strong as red light in photosynthesis.

Stimulation of the stomata

Blue light is responsible for stomata opening and closing mechanism. Stomata are tiny pores on leaves that control the exchange of water and gas. Opening and closing stomata allow the intake of carbon dioxide and the discharge of oxygen. These processes are important for photosynthesis. How far plants open and close their stomata is controlled by the quantity of blue light. High levels of blue light make plants open their stomata wider, hence accelerating their metabolism. The increased metabolism will accelerate plant growth and development. Thus, greenhouse lighting and indoor lighting usually include blue light.

Compact growth

Research has shown that plants grown with blue light are normally shorter and have smaller leaves compared to plants grown without blue light. This is because blue light suppresses extension growth. Plants use a photoreceptor called cryptochrome to see blue light. If there are high levels of blue light, cryptochrome dampens the operation of auxin. Auxin is a plant hormone that regulates plant stem growth. Auxin controls the ‘apical dominance’, making buds create subsidiary branches instead of getting entwined. Therefore, when plants are exposed to blue light, they create more side stems and stay shorter. By supplementing blue light to greenhouse lighting and indoor lighting, growers are able to regulate plant growth.

Regulate flowering

Blue light can regulate flowering by increasing bud size and the timing of flowering. Take cannabis as an example. Flowering is strongly related to plant size and bud size. Blue light can increase the bud size and promote photosynthesis. Plants that accumulate more resources can produce large and dense flowers. Blue light is essential for cannabis cultivation. Another way that blue light regulates flowering is by controlling the flowering time. High intensity blue light can promote flowering of long-day plants and inhibit flowering of short-day plants. However, low intensity blue light does not regulate flowering for most day-length sensitive plants.

Blue light is essential for plant growth. It not only regulated vegetative growth but also flowering. Blue light affects chlorophyll formation, the opening and closing mechanism of stomata, extension growth, and flowering. It is usually used with red light to increase photosynthesis. Conjunction with other lights such as green light, far-red light, and UV light have further benefits for plant growth. Therefore, full-spectrum LED grow lights are the ideal choices for most plants. To achieve specific cultivation goals, a customized light spectrum is required. If you need any horticulture lighting solutions, don’t hesitate to contact us.