Plants can grow only within a certain temperature range. Temperature has a comprehensive effect on growth. It can affect plant growth not only by affecting photosynthesis, respiration, transpiration and other metabolic processes, but also by affecting the synthesis and transport of organic matter.
Because the activities of enzymes involved in metabolic activities vary at different temperatures, the effects of temperature on plant growth also have the lowest, the best and the highest temperature namely three basic points. Plants can only grow in the range of the lowest temperature and the highest temperature. Although the optimum temperature for growth refers to the fastest growing temperature, it is not the most robust temperature for plant growth. Because at the optimum temperature, the plant consumes too much organic matter, and the plant grows slender and weak. Therefore, in production practice, the cultivation of robust plants often requires a temperature below the optimum temperature, which is called the optimum temperature of coordination.
The three basic points of temperature are different for different plants. This is related to the climatic conditions of plant origin. The plants originating from tropical or subtropical zones have higher temperature three base points, which are 10℃, 30-35℃and 45℃ respectively; the plants originating from temperate zones have lower temperature three base points, which are 5℃, 25-30 ℃and 35-40 ℃ respectively; the plants originating from cold zones have lower temperature three base points, and the plants growing in Arctic or alpine zones can be below 0 ℃ or 0 ℃. Temperature growth, the optimum temperature is rarely more than 10 ℃.
The three base points of temperature of the same plant also vary with organs and growth stages. Generally, the temperature of root growth is lower than that of bud. Eg, the lowest temperature for apple root growth is 10 ℃, the optimum temperature is 13 – 26 ℃, and the highest temperature is 28 ℃. The above ground part is higher than this temperature. The optimum temperature for primary roots and hypocotyl elongation was 33 ℃ at seed germination, but after a few days, the root decreased to 27 ℃, while the hypocotyl elongation increased to 36 ℃. In most annual plants, the optimum temperature for growth is gradually increasing from the initial stage of growth through flowering to fruiting. This requirement is just in line with the temperature change from spring to early autumn. Sowing too late makes the seedlings too long and weak, and if the temperature is not high enough in summer, it will also affect the growth and delay the maturation.
The experimental data of the artificial climate chamber prove that the vegetative growth of plants is the best among the periodic changes of higher daytime temperature and lower night temperature. For example, tomato plants grow faster under the temperature difference between day and night of 26 ℃ and 20 ℃ than under the constant temperature condition of 25 ℃. Under natural conditions, there are also periodic variations of higher daily temperature and lower night temperature. The response of plants to this periodic change of temperature during the day and night is called the thermoperiodic phenomenon of growth.
Higher day temperature and lower night temperature can promote vegetative growth of plants, mainly due to higher daytime temperature, which is conducive to the increase of photosynthetic rate under strong light and provides sufficient material for growth; lower night temperature can reduce the consumption of organic matter by respiration. In addition, lower night temperature is beneficial to root growth and cytokinin synthesis, thus increasing the growth rate of the whole plant.By the day&night mode of Gloreen Smart Climate Control System,the grower can set different temperatures during the day or at night base of the plants’ condition to promote productivity.
So in greenhouse or greenhouse cultivation, the grower should pay attention to change the day and night temperature so that under natural conditions, water, mineral, light, temperature and other factors have a cross-cutting and comprehensive impact on plant growth.
