14
(^1) FLOWER STRUCTURE
A typical flower develops inside a bud at the
end of a stalk. When the bud opens, it reveals
a ring of petals, each of which secretes nectar
from its base. At the centre of the flower lie the
male structures that produce pollen. These
surround the female structures that hold the
ovules, or egg cells. An outer ring of green
sepals may protect the flower when it is in bud.
Many plants produce beautiful flowers, often
vividly coloured and fragrant. These intricate
structures form the reproductive parts of plants, and
have evolved so that they attract insects and birds to
sip the sugary nectar at the flower’s centre. While
feeding, the insect or bird is dusted with pollen, which
is produced by the stamens and contain the male sex
cells. The pollen is deposited on the sticky stigma of
another flower. This is pollination. A pollen tube then
grows down the style to the ovary and fertilizes an ovule.
This is fertilization. Some plants, such as grasses and many
types of trees, rely on the wind to carry their pollen, and their
flowers do not need showy petals or fragrant nectar to attract
animals. Since this is a less efficient system, they must produce
far more pollen, which can fill the air and cause hay fever.
Flowers
(^2) CARPEL
An ovary, a style, and a stigma form the main
parts of a carpel. At the heart of the flower lie
the ovules, enclosed in a case called an ovary.
The top of each ovary extends into a style that
carries a sticky pad called a stigma. The flowers
of some plants have many carpels, each with
their own stigma, but this lily has just one.
Petals unfurl when the
flower opens, but
fall away once it
is fertilized
Bright reds and pinks
are more attractive to
birds than insects,
because not all insects
can see the colour red
Stamen is made up of an
anther and a filament
3
1
(^3) STAMEN
The tiny, dust-like pollen grains that
contain the male cells are produced
by stamens. These usually form a ring
around the central carpel or carpels.
Each stamen has a long filament,
which supports a club-like anther
that produces the pollen.
014_015_Flowers.indd 14 03/01/19 12:09 PM