Environmental Engineering Reference
In-Depth Information
Respiration
During darkness, turf plants do not produce carbohydrates but still need
some energy to maintain essential functions. Although photosynthesis
stops at night, respiration continues (Fig. 1.6). Carbohydrates stored
during the day are broken down during the night by respiration, which
releases energy, water and carbon dioxide. High temperatures increase
respiration, especially at night. Warm-season grasses are adapted to these
conditions and can tolerate hot days as well as nights without negative
effects. Under the same conditions, cool-season grasses may suffer severe
harm. Respiration also increases when photosynthesis is reduced, e.g.
during periods of drought or after mowing.
Growth
Growth can be described as irreversible increase in size. Grasses grow by
cell division (the process in which individual cells divide in two, produ-
cing more cells) and by cell elongation (in which individual cells stretch
or lengthen). Growing cells synthesize carbohydrates, proteins, fats,
DNA and other nucleic acids, and many other compounds, a process
that requires a sizeable amount of energy derived directly from photo-
synthesis. Again, efficient synthesis of these compounds by warm-season
grasses is almost unlimited at high temperatures. As long as moisture
and light are unrestricted, growth is unrestricted as well.
Storage
Carbohydrates and sometimes proteins are stored for use later when
needed. For example, storage products are used whenever the plant is
Photosynthesis
Carbon dioxide + Water + Solar energy
6CO
2
+ 12H
2
O + Light
Glucose + Water + Oxygen
C
6
H
12
O
6
+ 6H
2
O + 6O
2
Respiration
Carbon dioxide + Water + Chemical energy
6CO
2
+ 12H
2
O + Chemical energy
Glucose + Water + Oxygen
C
6
H
12
O
6
+ 6H
2
O + 6O
2
Fig. 1.6. Respiration is the reverse of photosynthesis. In order for the plant to grow,
production of carbohydrates must exceed their breakdown.
