Early spring is a tricky time for plants due to the combination of sunny but still quite cold days.
De-hardening in spring involves gradual re-hydration of the cells, recovery of photosynthetic capacity and a tight control of water loss.
High soil moisture leads to decreased photosynthesis.
In boreal upland forests, low soil moisture decreases the rate of photosynthesis.
What is the source of carbon that is assimilated in photosynthesis?
At low air humidity, a plant closes its stomata to prevent transpiration. The action also decreases photosynthesis
As plants respire, they release
Photosynthesis releases oxygen whereas respiration releases CO2.
Carbon becomes locked as part of the accumulating plant biomass as plants grow.
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.
A complex microbiota lives belowground, releasing carbon dioxide to the soil.
Photoinhibition means the decrease in photosynthesis due to
exposure to excess of light.
exposure to high temperature.
exposure to shortage of soil moisture.
exposure to excess of CO2.
exposure to excess of light
exposure to high temperature
exposure to shortage of soil moisture
exposure to excess of CO2
Plant respiration captures CO2.
Unlike photosynhesis, plant respiration captures atmospheric oxygen and releases carbon dioxide.
Photosynthesis of a tree canopy is driven or influenced by
photosynthetically active solar radiation (PAR).
air humidity (VPD).
air temperature (T).
soil moisture (REW).
the total leaf area (LAI).
The annual cycle of photosynthesis mainly follows
the changes in air temperature.
the changes in light.
the changes in soil temperature.
the changes in CO2 concentration.
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.
To transform atmospheric CO2 into organic molecules, plants can use the energy from