Temperature refers to the thermal state of matter, which is determined by the average
kinetic
energy of its molecules. Radiation in the wavelength range of 800 to 5000 nm provides thermal
energy and thereby regulates the speed of biological processes (in plants, this is nearly the sole
regulator, as they generate very little internal heat—unlike animals).
Temperature conditions as an environmental factor depend on:
- Microclimate, i.e., geographic latitude
and proximity to oceans (warm, temperate, cold,
maritime, continental).
- Microclimate, i.e., slope aspect
and inclination (exposure, inclination), soil properties (color,
moisture content).
- Nano-climate, i.e., the temperature
of the air layers near the ground and/or within the soil. The
soil acts as a thermal buffer.
Temperature influences plant growth through:
- Its effect on all metabolic processes.
A key parameter for this influence is the Q10 value,
which indicates the factor by which a reaction rate increases with a temperature rise of 10 K
(most common range: 2–3).
- Specific processes:
Germination
Biomass accumulation
(temperature-dependent interplay between photosynthesis and
respiration)
Nutrient uptake
(metabolism-dependent) and water uptake (viscosity of water)
Induction of processes
(dormancy periods in potatoes and onions can be shortened by
increasing temperature; cold treatments—vernalization, jarovization—can break seed
dormancy).
Cold damage in crop plants is often caused by the crystallization of
water, leading to dehydration
of cell compartments and membrane damage. Heat damage results from irreversible plasma
damage and protein denaturation.
