Effect of temperature and humidity on the respiration rate of crops

The growth and development of crops directly depend on the balance between respiration and photosynthesis. This balance is influenced by both internal factors (plant age, volume of available substrates) and external conditions. For an agronomist, air temperature and tissue moisture content are of key importance, as they determine the rate of consumption of accumulated sugars.

• Standard temperature coefficient Q10 — 2
• Temperature of respiration cessation — 45–50 °C
• Moisture content of dormant seed — 10–12 %
• Moisture content at full seed maturity — 14 %

Within a normal physiological range, the respiratory activity of plants follows van 't Hoff's rule: for every 10 °C increase in temperature, the intensity of respiration doubles (the temperature coefficient Q10 equals 2). However, this growth is limited by the capacity of the enzyme system. With short-term heating, respiration accelerates to peak values at 35–40 °C, but prolonged exposure to high temperatures leads to thermal inhibition.

In the process of adaptation, different species have developed their own temperature minimums. While herbaceous crops die during frosts, overwintering organs and woody plants are capable of reducing respiration to a minimum. Weak gas exchange in their tissues is maintained even at significantly negative temperatures. Specific temperature boundaries of respiration are not static and depend on the developmental stage of the plant and its overall condition.

How tissue moisture affects respiration

The water content in cells regulates stomatal aperture, membrane structure, and the activity of oxidative enzymes such as cytochrome oxidase. At the same time, the dependence of respiration on humidity is not linear. A slight moisture deficit in leaves initially stimulates respiration, but further dehydration inhibits it. Excess water is also harmful: waterlogging of tissues leads to the filling of intercellular spaces with water, which blocks oxygen access to cells.

Controlling humidity during seed maturation and storage is critically important. As maturation progresses, the water content in the grain drops, which naturally reduces the intensity of respiration. In the full maturity phase, when humidity drops to 14 %, only tightly bound water remains in the seed, and respiration sharply subsides, ensuring the preservation of the harvest.