The Parts of a Flower

• Most flowers have four parts:

• sepals,• petals,• stamens,• carpels.

The parts of a flower

• Sepals protect the bud until it opens.

• Petals attract insects.

• Stamens make pollen.

• Carpels grow into fruits which contain the seeds.

Stamen (male)

• Anther: pollen grains grow in the anther.

• When the grains are fully grown, the anther splits open.

Pistil (female)

• Stigma• Style• Carpel (ovary)• Ovules (eggs)

Pollination

• Flowering plants use the wind, insects, bats, birds and mammals to transfer pollen from the male (stamen) part of the flower to the female (stigma) part of the flower.

Pollination

• A flower is pollinated when a pollen grain lands on its stigma.

• Each carpel grows into a fruit which contains the seeds.

Fertilisation

• Pollen grains germinate on the stigma, growing down the style to reach an ovule.

• Fertilised ovules develop into seeds.

• The carpel enlarges to form the flesh of the fruit and to protect the ovary.

Wind pollination

• Some flowers, such as grasses, do not have brightly coloured petals and nectar to attract insects.

• They do have stamens and carpels.

• These flowers are pollinated by the wind.

Seed dispersal

Seeds are dispersed in many different ways:

• Wind• Explosion• Water• Animals• Birds• Scatter

How birds and animals help seed dispersal

• Some seeds are hidden in the ground as a winter store.

• Some fruits have hooks on them and cling to fur or clothes.

How birds and animals help seed dispersal

• Birds and animals eat the fruits and excrete the seeds away from the parent plant.

Sexual Reproduction

• Calyx-the outermost and often green color. Individual calyx-sepals-Protects inner whorls at bud stage

• Corolla-next inner whorl and is often colored brightly, -Individuals-Petals

• Anther has 4 pollen sacs, one in each lobe. Pollen sacs contain the mother cells, which undergo meiosis. Each microspere mother cell produces 8 sperm cells.

Asexual Reproduction• In some species, stems arch over

and take root at their tips, forming new plants. The horizontal above-ground stems (called stolons) of the strawberry (shown here) produce new daughter plants at alternate nodes.

• Underground stems • rhizomes • bulbs • corms and • tubers• are used for asexual reproduction

as well as for food storage. Irises and day lilies, for example, spread rapidly by the growth of their rhizomes.

Asexual Reproduction

• This photo shows the leaves of the common ornamental plant Bryophyllum (also called Kalanchoë) . Mitosis at meristem along the leaf margins produce tiny plantlets that fall off and can take up an independent existence

Asexual Reproduction• Some plants use their roots for asexual reproduction. The

dandelion is a common example. Trees, such as the poplar or aspen, send up new stems from their roots. In time, an entire forest of trees may form — all part of a clone of the original tree.

• Apple seeds are planted only for the root and stem system that grows from them. After a year's growth, most of the stem is removed and a twig (scion) taken from a mature plant of the desired variety is inserted in a notch in the cut stump

• Citrus trees and many other species of angiosperms use their seeds as a method of asexual reproduction; a process called apomixis.

• In one form, the egg is formed with 2n chromosomes and develops without ever being fertilized.

• In another version, the cells of the ovule (2n) develop into an embryo instead of the fertilized egg.