When using artificial light, we must choose the natural light closest to the photosynthetic conditions of plants. The light source should have the following characteristics:
1. Efficient conversion of electrical energy into radiant energy
2. High radiation intensity, especially low infrared radiation (thermal radiation), within the effective range of photosynthesis
3. The radiation spectrum of the bulb conforms to the physiological requirements of plants, especially in the effective spectrum region of photosynthesis.
The energy conversion effect of sodium lamp is twice as high as that of mercury lamp. Sodium lamp is the most effective light source in greenhouse which affects plant photosynthesis and proper growth. Tube sodium lamp can reach 150lm/w of high light efficiency radiation, is currently the most favorable choice for the growth of various crops. Increasing the sodium vapor pressure in ceramic arc tubes expands the spectrum of blue and red light, which is the high wavelength range sought. PLANTASTAR(OSRAM), son-t AGRO (PHILIPS), LUCALOX XO(GE) are recommended for high pressure sodium lamps used in horticultural products. They differ by increasing the blue light range by a much higher 0-40%, which activates the plant's chlorophyll. In order to achieve the highest radioactivity, all sodium lamps are side-mounted in a lamp shade. At present, most factories in China generally use sodium lamps as street lamps.
Light environment is one of the most important physical environmental factors for plant growth and development.
Effects of spectral range on plant physiology:
280nm ~ 315nm has little influence on morphology and physiological process
The chlorophyll absorption of 315 nm~ 420nm is low, which affects the photoperiod effect and prevents stem elongation
The absorption ratio of chlorophyll and carotenoids was the largest at 420 nm~ 500nm (blue), which had the largest effect on photosynthesis
The absorption rate of 500 nm~ 620nm pigment is not high
The "high" chlorophyll absorption rate of 620nm ~ 750nm (red) has a significant effect on photosynthesis and photoperiod effect
The low absorption rate of 750nm ~ 1000nm can stimulate the prolongation of cells and affect the flowering and germination of seeds
>1000nm converted to heat
For most growers, plant sodium and metal halide lamps are the best alternatives to sunlight. Metal halide lamp rich in blue light is suitable for the growth of early plant branches and leaves.