Plants
(^1) GERMINATION
A bean plant begins life as a seed
with two halves, called cotyledons.
In spring when the weather is mild,
the seed starts to absorb water
through a minute hole in its outer
coating (the testa). The seed swells
and about three days later a root
grows to hold the plant in place, and
a shoot appears above the ground.
This process is called germination.
(^2) ROOTS
The plant’s roots absorb water from
the soil. The water is used by the
leaves to make food. The water
also contains dissolved mineral salts,
such as nitrates and phosphates,
which are essential for growth.
(^3) STEM
The strong stem of the plant
supports its leaves in the sunlight.
It also contains bundles of tubes or
veins. These allow water containing
dissolved nutrients to flow up from
the roots to the leaves, and also
carry sugary food from the leaves
to other parts of the plant.
Seed is covered by a
testa, which protects it hard coat called the
from fungi and bacteria
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(^4) LEAVES
The leaves are the plant’s food
factories. They act like solar panels,
as the green chlorophyll enables the
plant to absorb the energy of sunlight
and use it for photosynthesis – the
process in which the plant takes carbon
dioxide from the air, and combines it
with water drawn up by the roots to
make sugar. Oxygen is also produced
in the process and released into the air.
(^5) TRANSPIRATION
As sunlight warms a plant, water in the
leaves is lost as water vapour, through
pores called stomata. The leaves then
take in water from the stem, which in
turn draws more water up into the
plant from the roots. The water carries
nutrients from the soil with it.
All green plants use the energy of sunlight to make sugary
carbohydrate food from water and carbon dioxide in the air.
This is why they grow well only in sunlit, moist places. The
food fuels growth and is used to make cellulose – the tough,
fibrous tissue that helps support all the various parts of the
plant, from its stems and leaves to its flowers.
Cotyledons become the
first leaves of the plant,
once above the ground
Strong ribs kept rigid
by water pressure
delicate leaf tissuesupport the thin,
More leaves are
produced as the plant
continues to grow
Shoot sprouts from
the testa to form
a root, with two
seed leaves, called
cotyledons, at its tip
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010_011_Plants.indd 10 03/01/19 12:09 PM