Effect of Spectrum on Plant Growth

Have you ever thought about what kind of plant lamp to choose for your plant?

Do you know what kind of plant lamp your plant is suitable for?

In fact, the spectrum of different plant growth lamps is different. This article will explain the principle of plant spectrum and its interaction with plants, and provide some practical suggestions for you. Choosing the right light will get twice the result with half the effort for the growth of your beloved plants.

Principle of plant spectrum

Ground plants have obvious spectral reflection characteristics, which are different from soil, water and other typical ground objects. The response of vegetation to electromagnetic waves is determined by its chemical characteristics and morphological characteristics, which are closely related to the development, health and growth conditions of vegetation.

Within the visible wavelength band, various pigments are the main factors governing the spectral response of plants, with chlorophyll playing the most important role. Within the two spectral bands centred at 0.45 μm (blue) and 0.65 μm (red) respectively, chlorophyll absorbs most of the incoming energy and between these two chlorophyll absorption bands, a reflection peak forms near 0.54 μm (green) due to the low absorption effect.

Hence the green appearance of many plants. In addition to this, chlorophyll and lutein have an absorption band near 0.45 μm (blue), but as the absorption band of chlorophyll is also within this region, these two yellow pigments play a dominant role in the spectral response pattern.

What spectrums are needed for plant growth

The sensitivity of plants to spectrum is different from that of human eyes. The most sensitive spectrum of human eyes is 555 nm, which is between yellow and green light. It is less sensitive to blue light and red light. Plants, on the other hand, are most sensitive to red light spectrum and less sensitive to green light.

However, the difference in sensitivity is not as great as that of human eyes. The most sensitive area of plants to spectrum is 400-700nm. This part of the spectrum is usually called the effective energy region of photosynthesis. About 45% of the energy of sunlight lies in this spectrum.

Therefore, if the artificial light source is used to supplement the light quantity, the spectral distribution of the light source should also be close to this range.

The energy of the photons emitted by a light source varies depending on the wavelength. For example, a wavelength of 400 nm (blue light) is 1.75 times more energetic than 700 nm (red light).

For photosynthesis, however, the effect of both wavelengths is the same. The excess energy in the blue spectrum that cannot be used for photosynthesis is converted into heat.

In other words, the rate of plant photosynthesis is determined by the number of photons absorbed by the plant in the 400-700 nm range, and not by the number of photons sent out by each spectrum.