Geoscience Reference
In-Depth Information
Chapter 11
How the Plants Nourish Themselves
We have already mentioned that plants are sort of “natural factories” that have the
capacity to produce very complicated organic molecules from a simple form of
carbon (carbon dioxide, CO
2
). The process of this transformation is called photo-
synthesis. The term has its root in Greek,
phôs
meaning light, since light is the
energy needed to arrange carbon atoms to enter manifold bonds in organic mole-
cules. This conserved energy is released when we burn wood, coal, or dried grass,
and everybody has the opportunity to feel some of this released energy as warm air
around the fl ames.
The plants, however, are not satisfi ed by accepting solely carbon dioxide and
dissociated water during photosynthesis. They require many other additional ele-
ments known as plant nutrients that are indispensable for their life and growth.
These required elements, also denoted as biogenic elements, are easily and simply
identifi ed from the chemical analysis of ash after burning the plant's body. The
name was derived from the Greek
bios
meaning life and
genos
meaning race or kin
and also Latin
genus
meaning descent, family, or type. Autotrophic plants accept
carbon from the atmospheric CO
2
that gets into contact with the plant cells in micro-
scopic windows called stomata openings. They can be opened or half closed or
completely closed like real windows, as we have mentioned in Sect.
10.3.2
.
Photosynthesis begins when CO
2
moves into the plant through these windows. The
term autotrophic is derived from two Greek words,
autos
meaning self and
trofe
meaning nutrition. A second and somewhat opposite term is heterotrophic that is
formed from the Greek
heteros
meaning another. A heterotrophic process occurs
during the germination stage of plants' growth from seeds. The emerging plant
sprouts are nourished heterotrophically by required matter inside of the seeds up to
the time when green organs capable of photosynthesis evolve. With such develop-
ment, a transitional stage occurs when the plants begin and eventually completely
sustain the process of photosynthesis utilizing the infl ow of elements pumped into
their bodies by their fi ne roots. Subsequently, even the roots are kept alive heterotro-
phically. Living without photosynthesis, microorganisms, fungi, and small animals
frequently contribute to the heterotrophic nutrition of plants.
