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Photosynthesis
Green plants [that is plants containing chlorophyll] make their own basic food by the process of
photosynthesis. This process can be represented by the following summary equation –
Carbon dioxide
6CO2
+
water
6H2 O
light
sugar
C6H12O8
+
oxygen
6 O2
Photosynthesis is one the most important processes on earth since it is the only process that makes food from
substances that are not foods. Thus photosynthesis is the ultimate source of food, not only for green plants,
but for animals and non-green plants as well. If all photosynthesis should suddenly stop it would not take long
until there was universal starvation and the extinction of life on earth [except for a very few chemo-synthetic
bacteria and the few small animals they could supply with food].
Photosynthesis is the only source of oxygen in the atmosphere; before photosynthetic plants appeared on
earth there was no oxygen in the air. Though yeasts and a few other fungi and bacteria can survive in the
absence of atmospheric oxygen through anaerobic respiration, the vast majority of plants and animals
suffocate and die in the absence of oxygen.
Though photosynthesis is the only natural process adding oxygen to the air, oxygen is removed from the air by
many processes including respiration, rusting, combustion and weathering of rocks.
Photosynthesis is also the only natural process that converts any appreciable amount of the energy from the
sun into energy useable by living organisms.
Greulach, Victor A [1968] Botany Made Simple. Doubleday & Co, New York