no 
THE VEGETATIVE FUNCTIONS OF PLANTS 
thus see that there is a continuous circulation of carbon 
in nature, known as the carbon cycle (Fig. 71). A com- 
parison between the two processes is shown in Table II. 
TABLE II. COMPARISON OF RESPIRATION AND PHOTOSYNTHESIS 
[ . Photosynthesis 
Changes inorganic 
matter into plant- 
f oods (carbohy- ' 
drates), which are 
To supply energy 
for work, 
To repair waste 
(Nutrition), 
In the construction 
of new parts 
All of these proc- 
esses are depend- 
ent upon Oxida- 
tion within the 
^ cells. 
2. Respiration, 
which involves 
The taking in of 
oxygen, 
The oxidizing of 
oxidizable mat- 
Assimilated and 
used by the plant 
(Development), in- 
cluding Reproduc- 
tion. 
This process of 
oxidation is 
called. . . . 
ter, 
The release of 
all products of 
these oxidations. 
Photosynthesis 
1. Takes place only in cells contain- 
ing chlorophyll. 
2. Requires light. 
3. CO2 absorbed, O set free. 
4. Carbohydrates formed. 
5. Plant gains in dry weight. 
6. Kinetic energy of sunlight be- 
comes potential energy. 
Respiration 
1. Takes place in all active cells. 
2. Can proceed in darkness. 
3. O absorbed, CO 2 set free. 
4. Carbohydrates consumed. 
5. Plant loses in dry weight. 
6. Potential energy becomes kinetic 
energy. 
113. Plant and Animal Respiration. There is probably 
no erroneous notion about plants more tenaciously held, 
nor more widespread, than the belief that plant respira- 
tion is the reverse of animal respiration. This error is 
due entirely to a confusion of the two processes of respira- 
tion and photosynthesis. From what has preceded, how- 
ever, it should now be clear that plants respire in the same 
way as animals, using up oxygen in the processes of oxida- 
tion within their tissues, renewing the supply from the 
surrounding air (or, in anaerobic respiration, from the 
breaking down of chemical compounds rich in oxygen), and 
