Temperature is a key factor in plant growth and development. Along with the levels of light, carbon dioxide, air humidity, water and nutrients, temperature influences plant growth and ultimately crop yields. All these factors should be in balance. Temperature influences the plant in the short term as well as the long term.
Differences between air temperature and plant temperature:
Most biological processes will speed up at higher temperatures, and this can have both positive and negative effects. For example, faster growth or fruit production is one benefit, in most cases. However, the excessive respiration that occurs is adverse because it means that there is less energy for fruit development and the fruits will be smaller. Some effects are short term, while others are longer term. The plant's assimilation balance, for example, is influenced by the temperature and is affected immediately. Flower induction, on the other hand, is determined by the climate over a much longer period.
Plant temperature and air temperature are not equal because plants are able to cool off through evaporation and warm up through irradiance. Plants seek to reach their optimal temperature, and a balance between air temperature, relative humidity and light is important in this. If light levels are high, the plant will heat up, resulting in a difference between plant temperature and air temperature. To cool down, the plant's transpiration rate must increase. As well as temperature, the transpiration rate depends on environmental conditions such as light, the level of atmospheric CO2 and relative humidity, but also on the plant species.
Plants consist of different parts which all react differently to temperature. The temperature of the fruit is closely in line with that of the air; when the air temperature rises, fruit temperature also rises and vice versa. However, the fruit temperature will fluctuate less than air temperature and it will also take longer (sometimes a couple of hours longer) to rise or fall than the air temperature does. The temperature of the flowers, by contrast, is higher than air temperature or leaf temperature, and the petals transpire at a much lower rate than leaves. The plant temperature at the top of the canopy will undergo larger fluctuations than that at the bottom of the canopy. The top will also heat up more easily through irradiance and therefore reach higher temperatures than the air when light levels are high.
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