The Introduction of Plant Grow Light
According to the natural law of plant growth and the principle that plants use sunlight for photosynthesis, plant grow light is a lamp that uses grow light instead of sunlight to provide the light source required for plant growth and development. In some cases, plant grow lights replace sunlight. As we all know, plants need photosynthesis. When they grow, they will supplement grow light energy to the greatest extent and carry out photosynthesis under the action of light. However, in order to improve agricultural efficiency, plant grow lamps are now used in many cases to replace sunlight and strengthen plant photosynthesis.
Plants can grow only when photosynthesis is greater than respiration. This critical point is called light compensation point. For example, the light compensation point of tomato is 51.6 μ mol/s/m ²， Then the effective radiation of photosynthesis must be greater than 51.6 μ mol/s/m ² To work.
Lux is the intensity of human eye perception. For plants, it is measured by the intensity of the spectrum effective for photosynthesis contained in the grow lamp. This is called photosynthetic effective radiation, referred to as par or PPF for short. PPF and lux cannot be converted. PPFD is the unit area strength of PPF
When PPFD reaches this point, the photosynthesis rate of plants is the fastest, but beyond this point, it will not increase, or even have reaction. The light saturation point of tomato is 1998 μ mol/s/m ²， At present, the grow lamp with the maximum power in application is 1000W double ended agricultural sodium grow lamp, PPF 2100 μ Mol / s, when hanging in a 6-meter-high greenhouse, the PPFD is only 200 μ mol/s/m ² Around noon in summer, the sunshine PPFD is more than 2000 μ mol/s/m ² Therefore, no artificial light source on earth can replace sunlight.
The LED form of plant grow light is usually made up of a specific proportion of red LED and blue LED, making the form of lamp cup and spotlight. Although the current LED technology has been able to achieve higher luminous efficiency (100lm/w), the luminous efficiency of red LED and blue LED used in plant growth lamps can only reach about 20lm/w, much lower than that of ordinary fluorescent grow lamps (50-90lm/w), and the price per unit power is much higher than that of fluorescent grow lamps. According to the calculation, if we want to use LED grow light in the area of 40cm to reach the illumination that can meet the normal growth of plants, it will take about LED grow light of 1000W and cost more than 10000 yuan. In this way, it is better to use fluorescent lamp or microwave sulfur lamp.
The experiment also shows that the fluorescent grow light source will cause significant temperature rise to the plant and cultivation medium within a distance of tens of centimeters, and lead to drying. The main cause of temperature rise is radiation, so it is not easy to block. At the same time, the temperature of a single fluorescent grow lights in stable operation has reached 60-90 ℃. If a large number of fluorescent grow lamps are densely installed in order to improve the illumination, effective heat dissipation measures must be taken for the lamps themselves. Although LED grow light for indoor plants has the advantage of low heating, high-power LED and LED grow lights group also need to consider heat dissipation.
In fact, it is more effective for plant growth to provide a higher concentration of carbon dioxide (gas and fertilizer) in addition to plant lighting grow lamps.