Agriculture Reference
In-Depth Information
Howplantsmaketheirownfood
Photosynthesis is the process where the green
parts of the leaf (chloroplasts) interact with
light energy from the sun, carbon dioxide
(CO 2 ) from the atmosphere and water via the
xylem to create simple sugars. There is no life
on Earth that does not depend on this
process.
The chemical equation is:
6CO 2 +6H 2 O + light energy =
C 6 H 12 O 6 + 6O 2
which means:
Six carbon dioxide molecules plus six water
molecules plus light energy creates one
molecule of sugar and six molecules of oxygen.
This simple sugar, combined with nutrients
and water from the soil or growing media,
supplies all the materials to make the plant
and all other life on Earth.
Figure 1.6 The inside of this dense Buxus gets hardly any
light, therefore it cannot support leaves.
The exposure of leaves to light is imperative.
Look at the inside of a dense shrub; there are
no leaves (see Figure 1.6).
Note the small bumps on the stem of the box
plant in Figure 1.6. These are old
meristematic sites (from leaves or small
stems) that have gone into dormancy due to
lack of light. Cutting back to these growth
points and allowing light in can reactivate the
meristems creating new growth.
Only the external parts of the shrub that
receive light produce leaves (see Figure 1.7).
Photosynthetic surfaces may not always be
what we think they are. It is the green
pigments found in chloroplasts that perform
photosynthesis. Chloroplasts are found not
Figure 1.7 The outside of the bush is well clothed with
leaves due to their exposure to the light.
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