Respiration consists of a series of reactions that occur primarily within the mitochondria of plant cells. Respiration converts oxygen and the sugars generated during photosynthesis into carbon dioxide, water and energy. In addition to the type of plant, several environmental factors affect a plant cell's rate of respiration.
Tissue Age/Life Stage
Younger tissue has a higher respiration rate than older tissue. So the root tip and young leaves have higher respiration rates than older root segments and leaves.
When a seed first absorbs water, the respiration rate of cells rises rapidly but levels off after around 20 minutes.
Ripening fruits host a burst of respiratory activity, which culminates when fruits reach peak ripeness.
The rate of respiration in a plant cell decreases when temperature decreases until respiration nearly or completely halts around freezing temperatures. Respiration increases with increasing temperatures until very high temperatures are reached and result in tissue deterioration.
Temperature greatly affects respiration for maintenance (much more than cells dedicated to plant growth). Plants in temperate climates have much lower respiration rates in winter than during warm summers.
The respiration rates of fruits can be controlled by storing fruit in cool, dry places. Lower storage temperatures are able to slow the respiration and ripening of fruit.
Respiration decreases with decreased available oxygen. Under circumstances where no oxygen is present, like in poorly draining soil, anaerobic respiration (fermentation) occurs. Anaerobic respiration results in carbon dioxide, some energy, and ethanol. This type of respiration is also used to create alcohols.
The rate of respiration for most plants peaks around the normal oxygen level in the atmosphere.
Carbon dioxide, one of the waste products of the respiration equation, also affects respiration The higher the concentration of carbon dioxide, the lower the rate of respiration.
Respiration increases in both directly infected and surrounding cells when plant tissue is damaged or infected.
Often, when there is a worm hole in an apple, a small brown bruise surrounds it--this is an indication of increased respiration in the area around the damaged cells.
Lack of Water
Dry tissue has a lower respiration rate than hydrated tissue. Although drought has a much greater impact on the process of photosynthesis in plant cells, lack of available water also negatively affects respiration.
An increase in available sugars from photosynthesis generally leads to an increased rate of respiration. Respiration rates in the upper-canopy leaves will often be higher than lower-canopy leaves because upper-canopy leaves produce more sugar.
- Texas A&M Horticultural Science and Practices: Factors Affecting Respiration
- "Plant Physiology"; Effects of Water Stress on Respiration in Soybean Leaves; Ribas-Carbo, M, et.al. September 2005.
- "Physiology of Woody Plants"; Stephen G. Pallardy, Theodore Thomas Kozlowski; 2008
- Photo Credit Jordan Siemens/Photodisc/Getty Images The apple image by nsa1977 from Fotolia.com fall yellow leaves and red dogwood leaves image by Jorge Moro from Fotolia.com
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