Limiting factors of photosynthesis reduce yields of crops and other economically-important plants. Conditions can be set up in greenhouses and outside tunnels to reduce the effects of limiting factors.
Increasing the light intensity in greenhouses will increase the growth of crop or horticultural plants.
Plant growers can:
Artificial lighting systems can be used:
Many plants have the capacity to use additional carbon dioxide.
The table shows an example of data collected by Robb and Wittwer (1964) on plants grown in normal, and carbon dioxide-enriched greenhouses.
|Normal yield||Enriched yield|
|Lettuce||0.9 kg||1.1 kg|
|Tomatoes||4.4 kg||6.4 kg|
To increase the carbon dioxide concentration in a growing area, plant growers:
In greenhouses at higher temperatures, photosynthetic production declines, and carbon dioxide supplements have no effect.
Growers must find a balance as high humidity will promote the growth of pathogenic fungi.
Irrigation systems are also used outdoors.
Plants are sometimes grown in liquid systems called hydroponics. Hydroponics allow the grower to optimise mineral ions given to plants. Mineral ions are required to synthesise other essential molecules from the glucose produced during photosynthesis.
Heat is often used in greenhouses and makes plant growth possible when the weather is cold outside.
Increased temperatures in greenhouses increase the rate of photosynthesis. Temperature regulation is important – note that cooling may also be required.