|Why Plants Have Flowers
Flowers are a way some
plants reproduce, making new, young plants that are a little bit
different from the parent plants. If every plant was the same and
conditions changed - a new disease showed up or the climate got colder -
the species might disappear. By constantly making new mixes of the
parent plants' different properties, a species is more likely to have
some individuals that can survive.
does this work? Cells, called pollen, from one flower have to get to
another flower. The flower that gets the pollen can ripen into a fruit
with seeds. The seeds then can grow into plants which have a mixture of
the properties of both the plant that made the pollen and the plant that
got the pollen.
How Does Pollen Move?
are several different ways for the pollen to move from one flower to
another. The most common pollen movers in New York State are wind and
insects. Wind pollinated flowers are usually not very showy to look at,
but make huge amounts of pollen. That way at least a little of it might
be blown to another flower of the same kind of plant. Grasses and ragweeds use the wind to move their pollen, giving some people hay fever when they are in flower.
pollinated flowers have to advertise so that insects will find them.
They also have to bribe the insect with some food so the insect will
want to visit several flowers. Insects may eat some of the pollen. Many
plants also have some sugar water called nectar in their flowers which
insects can eat. Most plants that have pretty flowers are advertising
parts of a flower are arranged like circles, inside each other. Some
flowers have 4 different kinds of circles. For drawings of flowers with
parts labeled, visit Mendel Web. Our own Fast Plant Flower Close-ups page (see left navigation) has photographs.
many flowers, the outside circle is made of green, leaf-like parts.
These are called sepals and they probably protect the flower some when
it is in the bud.
The next circle is
the petals. Showy insect pollinated flowers have bright colored petals
which help get the attention of pollinators. They may have markings
which show insects where the nectar is or may be shaped in a way that
sends the insect past the pollen.
flower makes pollen, its next circle is the stamens which make pollen
and hold it where insects or wind can move it. The knob at the top of
the stamen which has pollen in it is called the anther and the stem
which holds the anther up is called the filament.
a flower receives pollen, it has a pistil at its center. The pistil has
a sticky surface at the top for the pollen to land on and begin to
grow. This sticky or hairy top is called the stigma. It is at the top of
a stem called the style. At the bottom of the style is a swelling which
has the future seeds in it. This swelling is called the ovary.
How It Works:
wind or an animal moves grains of pollen to a flower's stigma, they
stick there. Each grain of pollen grows a tube down the style to try to
fertilize a part inside the ovary. Then these parts, called ovules, can
develop into seeds. If you have ever seen the silk on an ear of corn,
you have seen very long pollen tubes which grew down into the corn
flowers to pollinate each of the kernels on the ear of corn.
Why Do Plants Have Flowers?
are one way some plants reproduce. They help a plant population in an
area mix its properties enough to be ready to survive changes in the
For More Information:
Partners in Pollination is a Web site with lessons on pollination.
See also the ESP Flowers page.