How Do Plants Feed and Breathe?
Plants nourish themselves not only with
nutrients found in the soil and water but also with
the energy found in light. Just as some bacteria and
algae do, photosynthesis
is the way plants capture the energy of sunlight to
produce food. The process is rather complex but basically,
plants convert CO2 (carbon dioxide) into carbohydrates
and oxygen with the use of water and energy (provided
by light). During the day, light is absorbed by different
pigments, especially chlorophyll. Since chlorophyll
does not absorb the wavelength of green light, it is
reflected by the leaves. This is why most plants are
Carbohydrates are chemical forms of energy
necessary to feed living organisms. Oxygen is necessary
for respiration of living organisms, including plants.
During plant respiration, carbohydrates combine with
oxygen which are reduced to carbon dioxide and water,
the reverse of photosynthesis. This process goes on
night and day, but is counterbalanced by photosynthesis
Of course, plants also need small amounts
of mineral nutrients they absorb along with water through
their roots. Carnivorous plants have developed
an original way of ingesting nutrients by capturing
insects and feeding on their decomposing bodies.
Try an experiment with two same-size
potted plants (you can sow your own peas or beans and
wait until they are a few weeks old to do this experiment).
Since plants need light and carbon dioxide for photosynthesis,
you can demonstrate this by depriving some of the plants
of these vital elements and then observe the effects.
Deprive light from one and leave the other one as a
control plant in order to compare the results.
The "no light" plant should be put in
a dark closet or anywhere where the plant will get no
light. Observe and water the plants for two weeks to
see the effects of these experiments. You can also keep
a daily log of this experiment and note all the changes
as well as the time span. You can also take pictures
of the two potted plants at various stages of your experiment
and include them in your log.