The relationship between light intensity and plant growth in the light incubator

Light intensity plays an important role in plant growth and morphological structure. Light has direct and indirect effects on plant growth. The direct effect refers to the role of light on plant morphogenesis, as far as the plant growth process itself, it does not need light. Plants can grow in the dark as long as there are enough nutrients. However, the morphology of plants grown in the dark is abnormal. For example, plants grown in the absence of light are yellowed seedlings. Indirect effects mainly refer to photosynthesis, which fixes carbon dioxide in the air to synthesize organic matter, which is the material basis for plant growth. For every 1 mol of CO2 fixed by a plant leaf, about 468.6 kJ (kilojoules) of light energy is required, so light affects plant growth by influencing the progress of photosynthesis. Therefore, providing the light necessary for plant growth ensures healthy plant growth. And light incubators do just that. Intelligent light incubator provides the appropriate light needed for plant growth, but also provides the temperature, humidity, illumination and so on, so that the plant grows and develops in the most suitable environment for growth.

Light can promote the differentiation of plant tissues and organs, and constrain the growth rate and development ratio of each organ. Strong light has an inhibitory effect on the growth of plant stems, but can promote tissue differentiation, which is conducive to the development of tree xylem. For example, trees grown under full light conditions generally have thick trunks, large crowns, and lower heights under branches, which have high ornamental and ecological values. Trees grown in high intensity light are shorter, but have increased dry weights and have an increased root to stem ratio. In addition, leaves are thicker and have more layers of fenestrated tissue. However, high light also causes photo-oxidation of chlorophyll, resulting in decreased protein synthesis and increased carbohydrate synthesis. Strong light often leads to high temperatures, which tends to cause water deficit, stomatal closure and insufficient CO2 supply, and also causes a decrease in photosynthesis, which affects plant growth; while insufficient light, long and upright branches with a strong growth potential are shown to be ungrowing and yellowing. In addition, light can promote cell enlargement and differentiation, control cell division and elongation, so to make the normal growth of trees, there must be a suitable light intensity.

Light intensity on the growth of tree roots can have an indirect effect, adequate light conditions are conducive to the growth of seedling roots, the formation of a larger root to stem ratio, the later growth of seedlings is beneficial; when the light is insufficient, there is an obvious inhibition of root growth, the amount of root elongation is reduced, the number of new roots occurring less, or even stop growing. Although the root system is growing in the soil under the condition of no light, its material source is still mostly from the assimilated material in the aboveground part. When the amount of assimilation is reduced due to insufficient light and the assimilated material is reduced, according to the principle of proximity distribution of organic matter transport, the assimilated material is firstly given to the above-ground part for use before it is sent to the root system, so the cloudy and rainy seasons have a great impact on the growth of the root system, and shade-tolerant trees form a low light compensation point to adapt to their environmental conditions. Trees show futility or yellowing due to the lack of light condition and poor root growth, which inevitably leads to poor maturation of upper branches, inability to successfully overwinter dormancy, shallow root system and low drought and cold resistance. In addition, light to some extent can inhibit disease activity, such as in the sunshine conditions on the ground growth of trees, the disease is significantly reduced.

Excessive light can cause sunburn, especially in continental climates, sandy areas and drastic changes in temperature between day and night are more likely to occur. After the leaves and branches are irradiated by strong light, the leaf temperature can be increased by 5-10 ℃, and the bark temperature can be increased by more than 10-15 ℃. When the trunk temperature is 50 ℃ or more or at 40 ℃ for more than 2 hours, sunburn will occur. Sunburn is closely related to light intensity, tree strength, crown part and branch thickness.

If the distribution of light intensity is uneven, it will make the tree branches and leaves to the direction of strong light growth luxuriant, to the direction of weak light growth is poor, the formation of obvious partial crown phenomenon. This phenomenon is very obvious in the urban garden tree species performance, due to the modernization of urban high-rise buildings, narrow streets, changing the distribution of light intensity, in the same streets and buildings on both sides, the light intensity will appear very different. Such as east-west street, the north side of the light by far more than the south side, so that due to the branches of the light growth will lead to tree bias crown. Trees and buildings are too close to each other, which can also lead to asymmetrical growth towards the center of the street.