1. The effect of light on plant growth:
In the natural spectrum, the effects of different wavelength bands on plant physiology are as follows:
280 ~ 315nm has little effect on morphology and physiological process;
315 ~ 400nnm chlorophyll absorbs less, which affects the photoperiod effect and prevents stem elongation;
400 ~ 520nm (blue light) The absorption ratio of chlorophyll and carotenoids is the largest, which has the greatest impact on photosynthesis;
The absorption rate of 520 ~ 610nm pigment is not high;
610 ~ 720nm (red light) The absorption rate of chlorophyll is low, which has a significant impact on photosynthesis and photoperiod effect;
720 ~ 1000nm absorption rate is low, stimulating cell extension, affecting flowering and seed germination;
>1000nm is converted into heat.
From the previous analysis, we know that different wavelengths have different effects on the growth and development of plants. When the stem growth of plants is to be inhibited, ultraviolet light can be irradiated. When the benefits of plant photosynthesis are to be increased, the intensity of blue light can be strengthened. Flowering or seed germination can be achieved by adjusting the proportion of red light.
2. The advantages of LED light source as plant light:
LED has the advantages of small size, light weight, solid state, long life, special wavelength, low driving voltage, high optical efficiency, low energy consumption, safety, reliability and durability, and not easy to color decay. luminous flux. In addition, the luminescence of LED is the luminescence of group III and V compounds, which has a narrow spectrum. The half-width of the spectrum ranges from a few nanometers to several tens of nanometers. At about ±20 nm, the wavelength is exactly the same as the spectral range of plant photosynthesis and photomorphogenesis. match. Therefore, the use of LEDs as special plant lighting will have advantages over traditional light sources in terms of efficiency and efficacy, because traditional light sources are generally full-band, if fluorescent lamps are used as light sources, it is necessary to add a filter to obtain the required specific wavelength of light. , which will reduce the utilization of the light and will possibly convert it to the form of heat for the filtered light source.
3. If LED is used as plant light, how to choose LED light source parameters:
3.1 Selection of the ratio of red LED to blue LED
From the perspective of plant growth’s demand for red light and blue light, the chromatographic ratio of red and blue light of plant lights is generally between 5:1 ~ 10:1, and the ratio of 7 ~ 9:1 is usually selected. Of course, different plants have different needs for red and blue light, and different plant lights use different red and blue LEDs. Therefore, the best ratio should be selected according to the type of plants and the performance of the LED.
3.2 The choice of light intensity of LED light source
When designing the intensity of the plant light, it is necessary to refer to two key points of plant photosynthesis, one is the light compensation point, and the other is the light saturation point.
The light compensation point means that with the decrease of light intensity, the photosynthetic rate decreases accordingly. When the light intensity decreases to a certain value, the photosynthetic rate of the leaves is equal to the respiration rate, and the net photosynthetic rate is zero. The light intensity at this time is called light compensation. point. At this point, to continue photosynthesis in plants, additional light compensation is required.
The light saturation point refers to above the light compensation point. With the increase of light intensity, the photosynthetic rate increases accordingly. When a certain light intensity is reached, the photosynthetic rate no longer increases with the increase of light intensity. This phenomenon is called light intensity. saturation phenomenon. The light intensity at which the maximum photosynthetic rate begins to be reached is called the light saturation point. If the external light intensity is greater than the light saturation point of the plant, the waste of light will be formed.
The light compensation point and light saturation point of photosynthesis and the values of some main vegetables at these two points are introduced above. The specific function is to set the light intensity (or power) when preparing the plant light according to different plants.
