Early spring is a tricky time for plants due to the combination of sunny but still quite cold days.
The annual cycle of photosynthesis mainly follows
the changes in air temperature.
the changes in CO2 concentration.
the changes in light.
the changes in soil temperature.
When there is low soil moisture, plants close its stomata pores which then decreases photosynthesis.
Plant respiration captures CO2.
Unlike photosynhesis, plant respiration captures atmospheric oxygen and releases carbon dioxide.
To transform atmospheric CO2 into organic molecules, plants can use the energy from
The effect of light on photosynthesis has a clear saturating pattern: more light results in more photosynthesis but eventually leaves cannot take full advantage of all the extra light.
De-hardening in spring involves gradual re-hydration of the cells, recovery of photosynthetic capacity and a tight control of water loss.
At low air humidity, a plant closes its stomata to prevent transpiration. The action also decreases photosynthesis
Transpiration decreases as air becomes drier.
In general, the more carbon dioxide that is available to the plant, the faster the rate of photosynthesis - if other factors are favourable.
The rate of respiration decreases with temperature.
What is the source of carbon that is assimilated in photosynthesis?
Photosynthesis of a tree canopy is driven or influenced by
air temperature (T).
the total leaf area (LAI).
air humidity (VPD).
soil moisture (REW).
photosynthetically active solar radiation (PAR).
Leaf area increases with stand age, resulting in a decreasing rate of photosynthesis in the stand.
An increment in leaf area increases also the photosynthesis of a tree stand. However, the relationship is saturating.
Almost half of the total biomass of a tree may be allocated to the roots.