The glass greenhouse is the fifth generation smart greenhouse. It not only has a crystal clear appearance, but is also suitable for larger density planting and has a high degree of mechanization. Under the influence of future changeable weather and the cultivation and planting model of glass greenhouse plant factories, smart greenhouses will become more and more accepted. With the maturity of planting technology and the improvement of cultivation technology, greenhouse output has also made a qualitative leap.

Unlike other types of greenhouses, what is pursued during the construction process of glass greenhouses is light transmittance. Although crops are grown inside a greenhouse, the ideal situation is to maximize photosynthesis of plants throughout the day. Let the plants grow in the greenhouse under lighting conditions that are very close to those grown in the open air. Other temperature, humidity, and carbon dioxide levels are adjusted using the greenhouse.

While smart glass greenhouses pursue light transmittance, they naturally cannot avoid the choice of glass. The glass currently used in agricultural greenhouses is mainly divided into eight specifications, three types of glass, and two categories;

The two major types are ordinary float glass used on the side walls of the glass greenhouse and standard ultra-white scattering tempered glass on the top.

The three types of glass are ordinary float glass, ultra-white scattering glass, and ultra-white coated anti-reflective glass.

The eight specifications: 0, 10, 20, 30, 40, 50, 70, and 75 respectively correspond to the eight haze specifications of the greenhouse top scattering glass;

In the greenhouse industry, it is understandable that the side walls of glass greenhouses use insulating float glass. There are many questions about the glass on the top of the greenhouse;

First of all, the standard glass on the top of the greenhouse is diffuse scattering glass and coated anti-reflective glass. This is certain. What makes a difference is what color is the glass on the top of the greenhouse?

The definite answer is colorless and transparent, that is, ultra-white; let’s talk about the specific reasons.

Due to its wide range of uses, glass greenhouses can not only be used as plant factories, but also can be used for sightseeing, experiments, seedlings, scientific research, etc. There are also a wide variety of crops grown inside the greenhouse. Currently, there is no clear regulation in the industry as to what type of crops must be grown in what kind of greenhouse. Therefore, it is meaningless at this time to choose the color of the scattering glass on the top of the greenhouse.

We can be sure that the intensity of different color bands of light has an impact on the growth of plants. For example, blue light, purple light, and red light among the seven colors of light will be more favored by plants; different lighting will indeed affect the growth of plants. But it is also for the different growth stages of plants. During the special growth stages of plants, we can completely use fill lights to solve the problem, instead of changing the color of the glass on the top of the greenhouse to adjust. Take tomatoes as an example;

<1> Compared with white light, red light significantly promotes the growth of seedling plant height and stem diameter, but root growth is hindered, root activity decreases, and seedling strength index decreases; seedling growth is significantly inhibited under purple light, and chlorophyll content decreases; red and blue combined light (3:1) seedlings grow vigorously and have the highest seedling strength index.

<2> Compared with white light, violet light reduces the net photosynthetic rate (Pn), RuBP carboxylase activity and carbohydrate content of seedling leaves; red and blue combined light (3:1) significantly increases Pn and RuBP carboxylase activities and increases carbohydrate content. Compound accumulation; Different light qualities increase the activity of sucrose synthase (SS), with the highest activity under red and blue combined light (3:1); the highest activity of acid invertase (AI) under red light, and the lowest under blue light; red, blue, and purple light All reduce the activity of sucrose phosphate synthetase (SPS). Red light reduces the total nitrogen content of leaves and the activities of nitrate reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT); purple light, blue light, and red-blue combined light (3:1) significantly increase GS , GOGAT activity and free amino acid and soluble protein content.

<3>Compared with white light, tomato flowering time advances under red and blue combined light (1:1) and blue light; red and blue combined light (1:1) increases fruit soluble sugar and lycopene content, while blue light increases Vc and protein content; the tomato yield under red and blue combined light (1:1) was higher than red light and blue light, but there was no significant difference from the control, and the yield under blue light was the lowest.

<4> During the development of tomato fruits, the activities of acid invertase (AI) and neutral invertase (NI) gradually increase, the activity of sucrose synthase (SS) gradually weakens, the starch content gradually decreases, and the glucose and fructose contents gradually increase. In the young fruit stage, fruit SPS and SS activities are strongest under white light, which promotes the synthesis and accumulation of sucrose, fructose, and glucose; blue light increases the AI and NI activities of fruits in the color-changing stage, and increases fructose and glucose content; red light, and red-blue combined light ( 1:1) improves the AI and NI activities of fruits at maturity, increases fructose and glucose content, and the carbohydrate content under red and blue combined light (1:1) is higher than red light.

It is true that when we build a glass greenhouse, it is best to use ultra-white scattering tempered glass or ultra-white anti-reflective glass on the top of the greenhouse. According to the different growth stages of the plants, if we want strict control, we can use different fill lights to adjust. There is absolutely no need to change the color of the glass on top of your greenhouse.

The best color for glass used in greenhouses is ultra-white.