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Reproduction in Angiosperms. Angiosperms are flowering plants. They produce seeds in flowers Ovules are borne in the ovaries. What is a flower …. A complete flower has a green calyx, a corolla of petals, a male androecium and female gynaecium. Floral structure ….
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Reproduction in Angiosperms Angiosperms are flowering plants. They produce seeds in flowers Ovules are borne in the ovaries.
What is a flower … • A complete flower has a green calyx, a corolla of petals, a male androecium and female gynaecium.
Floral structure … • An incomplete flower has both the vegetative whorls (calyx and corolla), but only one of the reproductive whorls i.e. either the androecium or the gynoecium.
Male and female parts • Male: The stamen consists of the anther which produces pollen grains in which the male gametes are found. • Female: the carpel consists of the stigma, style and ovary. The ovules are the eggs found inside the ovary and develop into the seeds when fertilised.
POLLEN, BEARERS OF MALE GAMETES • Stamens consist of an anther with a filament. • The anther produces pollen in the pollen sac. • The pollen grains contain the male gametes.
Pollination is the transference of pollen grains containing the male gamete to the receptive stigma
POLLINATION is the transfer of ripe pollen from an anther to a receptive stigma..
Selfplollination 2. Same plant , different flower • 3. Different plant of same species
The pollen grain germinatesno detail required • Meiosis occurs in the pollen grain. • The male gametes are haploid. • When the ripe pollen grain lands on a receptive stigma, it will germinate. • The pollen grain germinates and form a pollen tube.
The female pistil no detail required • The ovary contains the ovule(s) with female gametes (n). • The pollen tube grows down the style, through the micropyle and into the embryo sac. • Double fertilisation occurs.
The ovary develops into the fruit, the ovule into the seed. • The fruit develops from the following layers: • Fruit wall from ovary wall. • Seed from ovule.
A SEED … • A seed consists of a 1. Seed coat – outer layer of ovule (pericarp). 2. Embryo – from fertilised egg cell (zygote undergoes mitosis).
A SEED … Endosperm – result of double fertilization. Endosperm is food for embryo – also why we eat seeds for food.
Germination of a seed: • The radicle or first root grows out to seek water
When a seed germinates • The cotyledons contain food for the embryo in some seeds. • In beans the cotyledons are responsible for photosynthesis after germination before first leaves are formed.
SEEDS NEED TO BE DISTRIBUTED BY DIFFERENT AGENTS COCO DE MER
CONFUSION ABOUT FRUIT AND AND SEED • The seed develops from the ovule when it is fertilised and will germinate and develop into the new plant • The fruit develops from the ovary and can break open to release seeds or be dispersed with seeds
1. Asexual reproduction • Angiosperms mainly reproduce sexually in their life cycle. But some species can also reproduce asexually, iethe daughter plants are genetically identical to the parents. They usually undergo natural asexual reproduction by vegetative growth. There are three basic forms that occur naturally: no detail required
RUNNERS • Strawberry can extend its runners, horizontal aboveground stems, to other places. New stems and roots are developed at every node on the runners and hence many new genetically identical individual plants are reproduced.
CORMS • For Corm, a type of vegetative growth, for example, new individual daughter plants can develop from the auxiliary buds on the short, thick and vertical underground stems in Gladiolus.
RHIZOMES • Potatoes can extend their stems into the soil to form rhizomes. Nutrients are transported to the tip of the rhizomes. The storage of these nutrients can enlarge the rhizomes to form a storage organ called tuber. New stems and roots develop from the tuber by using the stored nutrients in it.
Describe how pollen can be transferred between flowers. • Pollen can be transferred by: 1. Wind 2. Insects 3. Birds
