Sexual Reproduction in Plants

Learning Goals:

To identify the parts of a flower.

To understand the function of each of the parts of a flower in sexual reproduction.

Plant - flower

Pollen

+

Ovules

Pollination

Fertilisation

Seed Formation

Dispersal

Germination

Plant Life Cycle

Plant - flower

Pollen

+

Ovules

Pollination

Fertilisation

Seed Formation

Dispersal

Germination

Plant Life Cycle

♁

♂

Parts of a Flower

PISTIL

STYLE

Petals: Modified leaves that attract pollinators

Stamens: the male parts of the flower – they are made of the anther and the filament. The anther makes the pollen.

Pistil: the female part - made of the stigma, style and ovary. In the ovary are ovules which have the female egg cell.

Parts of a Flower

♂

♁

STYLE

Flowers come in many shapes, colours and sizes. They are usually specially adapted to particular types of pollination.

Pollination: the transfer of pollen from the anther to the sticky stigma by wind, animals/insects or water.

Pollination

Cross pollination: when pollen goes from one plant to another of the same type. This results in stronger plants.

Self pollination: where the pollen goes from the anther to the stigma of the same plant. This can result in a genetically weaker plant

Pollination

Most Common Types of Pollination

Once pollination has occurred, the nucleus of the male sex cell (pollen) moves down the pollen tube to the female sex cell (egg) in the ovary

Fertilisation: when the nucleus of the male sex cell fuses with the nucleus of the female sex cell and becomes a seed

Fertilisation

Australian Honey Possum

The Australian honey possum is one of the only mammal species, other than bats, known to eat nectar and pollen as the mainstay of its diet.

Brazilian Birthwort

The Brazilian birthwort uses insects as pollinators. The putrid odor of this species—like that of rotting flesh—especially attracts flies, which enter the plant and become trapped overnight. While they are trapped, they become completely dusted with pollen. They escape the following day as the plant withers and are attracted to other Brazilian birthworts, which they then inadvertently pollinate as they enter and again become trapped.

Worker Honey Bee in the Field

As they fly from flower to flower, worker honey bees collect pollen grains and pack them onto their hind legs in special hair-fringed pockets known as pollen baskets (shown here holding a glob of yellow pollen on the hind leg). Nectar, the sweet liquid produced by flowers, is sucked into the honey stomach, an internal storage sac. In the hive, field bees deposit their pollen pellets into empty storage cells of the comb and regurgitate nectar to waiting hive bees. The hive bees mix some nectar with the pollen to make bee bread, a spoilage-proof larval food, and gradually concentrate the rest of the nectar into honey by dehydration.

Butterfly Pollinating a FlowerMany species of butterflies eat plant nectar. When these butterflies land on a series of flowers in search of food, they brush their bodies against both male and female floral organs, inadvertently transferring pollen from one flower to another.

Lawson Cypress Branch

The Lawson cypress, like all other coniferous trees, is wind pollinated. The tiny male “flowers” are located at the ends of the small branchlets, where the wind can easily pick up and distribute their pollen.

Rose Hip

When rose hips become ripe, they change in color from green to red. Attracted by the red color, both birds and other mammals eat the rose hips as a part of their diet. The individual seeds of the rose hip have a tough outer skin that allows them to pass through the digestive tract of an animal undigested, ensuring successful wide-ranging dispersal.

Dorling Kindersley

"Rose Hip," Microsoft® Encarta® 97 Encyclopedia. © 1993-1996 Microsoft Corporation. All rights reserved.

Lesser Burdock Plant

The lesser burdock plant has a fruit that is encased in a burr covered with hooks. These hooks enable the burr to easily attach to the fur of passing

animals, which ensures wide-ranging dispersal of the seeds.

DINGBATS – SAY WHAT YOU SEEReproduction in plants

rs

H

-nd

- bok

n

- 5

A