Parts of a Plant
You need only to be concerned with the three main
parts of a plant: the roots,
the stems, and
the leaves.
The Roots
The magic chemistry of plant growth starts at
the roots. Roots send nutrients (in exchange for sugar) up through
leaf stems to the leaves for final processing. They are also
large storage sites for excess energy from the leaves, which
is stored as starch. The roots and their capacity to store starch
will decide how well a plant will grow and how much the plant
will yield.
Root size: A research Rye plant
in a 12-inch pot had 14 billion root hairs that, if placed end
to end, would have stretched 6,200 miles (almost 10,000 kilometres).
The root hairs alone would have covered a square area of 180
ft by 180 ft (about 55 m by 55 m)! The more extensive the root
system, the better the plant will grow. This is because roots
storing much energy are able to exchange lots of nutrients up
to the leaves, and so the leaves can send down more sugar, etc.
Thus, root growth is directly affected by moisture, oxygen,
temperature, and sugars sent down from the leaves.
Root medium is important for plant growth. The
less energy the roots use to absorb water and nutrients from
their surrounding medium, the more they can use that energy
to grow and to help send nutrients up to the plant. Most of
a plant's water is taken in by the root hairs. 99% of the water
taken in by a plant is transpired out through the leaves. A
plant will fall over and wilt as a result of its roots not being
able to extract any more water from the surroundings. (See Mediums
for Growing)
Air roots: in a plant's natural
life in the earth, its roots get moisture from rainfall. After
rain, the soil water soon sinks down and the topsoil dries quickly.
For this reason, the top 1/3 of plant roots are air specialized
and the bottom 1/3 are water roots. One must be careful not
to keep the air specialized roots constantly wet or the plant
will drown. The bottom section of roots can be constantly wet
provided that the water has oxygen in it. Stagnant water will
soon kill the plant. The roots should always look crisp and
white. If the roots develop brown tips or general browning,
the problem is usually lack of oxygen, and infection will soon
follow.
A plant can function quite well with its roots
exposed to light as long as they do not dry out. However, the
light encourages alga growth, which causes odors, and the alga
competes with the plant for nutrients in the light period and
oxygen in the dark period.
Oxygen is the most important
root requirement because the roots need oxygen to convert sugar
to energy. The more oxygen available to the roots, the more
energy they can transfer to the plant.
Temperature also affects root growth and function.
The roots do a great deal of their storage developing at night
when the green sections of the plant are not being pressured
by the light to produce and distribute the day's excess sugar
to the roots. Roots function more efficiently when they are
warm, so roots in warm dark period develop better structures
than those grown in cool dark period. As an illustration, a
cycle of warm dark 77°F (25°C) and day 59°F (15°C)
would develop better roots than a cycle of cool dark 59°F
(15°C) and day 77°F (25°C). In essence, plants will
grow better with a high average 24-hour root temperature that
is constant rather than fluctuating.
Roots: the root hair zone is relatively small
and starts just behind the growing root cap. This zone advances
with the
growing roots and as the new hairs near the tip emerge, the
older hairs die I
off. Here is where most water and nutrients are absorbed. So
for fast growth, plant roots must not be allowed to become rootbound
but be kept healthy and advancing at maximum throughout the
entire life of the plant. When growing in pots that are too
small, it is better to have the roots trim themselves by coating
the inside of pots with a special copper paint rather than letting
the roots circle and girdle themselves. In general, pots are
not oxygen efficient for super plant growth. Remember that plant
yield is proportional to root size.
The Stems
The stems serve as supply pipes between the roots
and the leaves. Shorter stems are better because the nutrients
have less distance to travel between
. the roots and the leaves. This affects the whole plant since
it does not have to lift the water too high, the plant conserves
energy - that energy can then be used for extra yield.
The Leaves
The leaves are the sugar
(energy) producing factories of a plant. They produce plant
sugars by using light to combine water and nutrients with carbon
dioxide (C02) from the air. Provided that the leaves have adequate
light and enough carbon dioxide (the air has about 400 PPM parts
per million - of CO2), the plant will grow well. You should
read the section on The Magics Here - Photosynthesis, where
the workings of the leaves are described in detail.
To let in CO2, leaves have on their underside
breathing holes called stomata. Stomata are on the underside
for obvious reasons:
(a) They remain shaded.
(b) Dirt does not settle on them and block them.
(c) Fungal spores do not settle into them. There could be from
20,000-40,000 of
these small holes in an area equal to a thumbnail.
Only in the light do leaves produce sugars and
starches, which become the energy for the plant. Good leaf growth
provides lots of sugar energy for the plant.
As mentioned before, evaporation at the leaves
causes water to be drawn up from the roots. In this way, the
leaves exchange sugars for nutrients with the roots. Good leaf
growth makes it possible to draw up lots of nutrients and have
lots of excess sugars to send down to the roots. However, the
yield of a plant is not directly proportional to the amount
of leaves it has. The leaves are only the plant's potential.
The roots are far better indicators of the energy produced.
Leaves: the leaves are constantly
sending out energy to the plant and to the roots; when stimulated,
they are kept at absolute maximum production. The leaves are
now processing so much starch that they have to store a great
deal of it in their tissues.
At night, the leaves transfer as much stored energy as possible
to the roots. The healthier the leaves and the leaf stems are,
the more energy they have to transfer into storage within the
plant.
The leaves are the visible part of a plant, and
the health of a plant can be easily seen in them. Leaves do
not repair themselves, so the life of a plant can be read by
its leaves. Regular gardening books can explain how various
nutrient deficiencies can be identified when examining the plant
leaves.
