1. Seed Development in Angiosperms
While pollen tube is growing, cells inside ovule prepare for its arrival.
Once the sperm cell meets the egg, a zygote is formed.
Other cells in the ovule develop into the cotyledon which contains food.
Zygote now goes through mitosis to form an embryo.

2. Sexual Reproduction of Gymnosperms
The life cycle is similar to angiosperms.
Gymnosperms do not bear flowers.
These plants are called conifers.
Usually male and female cones are produced in the same trees.
Seeds contain an embryo, food supply, and a coat - but no fruit.

3. Seed Dispersal in Angiosperms
The fruit of an angiospern aids in its dispersal.
Dispersal is the transport of the seed away from the parent.
Some launch their own fruits
Some need help from outside agents
Wind, animals, water

4. Seed structure
Cotyledon
Plumule
Radicle
Micropyle
Seed coat or testa

5. radicle: a young root
Plumule: Part of a seed embryo that develops into the shoot, bearing the first true leaves of a plant.
Cotyledon: is a significant part of the embryo within the seed of a plant. Usually becomes the first leaves of the young seedling
Micropyle: a small opening in the seed that allows water to enter
Testa: the outer covering

6. Germination
Germination is the - growth of the embryo after a period of dormancy if the environmental conditions are suitable

7. Conditions for germination
Water is needed to allow enzyme reactions to occur – the seeds absorb water from the soil
Oxygen is needed for aerobic respiration
A suitable temperature is needed to allow enzyme reactions to take place
Dormancy must be complete
Light may or may not be required

8. Seed viability
Viability: When a seed is capable of germinating after all the necessary environmental conditions are met.
Average life span of a seed 10 to 15 years.
Some are very short-lived e.g. willow (< 1 week)
Some are very long-lived e.g. mimosa 221 years
Conditions are very important for longevity

9. Events in germination
absorption of water through a tiny hole called the microphyle.
2: mobilization of reserve food.
3: respiration and release of energy
4: breaking down of the seed coat
5: emergence of the embryo
6: radical develops
7: The plumule emerges above the ground and leaves begin to form

10. The stages in seedling growth Cotyledons remain below the soil – Broad beans
Seeds aborb water and begins to grow
Radicle bursts out through the testa and grows down
The plume becomes visiable and the cotyledon grows
the plumule grows up through the soil and its delicate leaves are protected by the plume because it is “hooked” over

11. The stages in seedling growth Cotyledons remain below the soil – Broad beans
6: The cotyledon shrivel as food is transferred from them
7: once above ground the plume straightens up and produces leaves

12. The stages in seedling growth Cotyledons move above the soil – Sunflower seeds
This form of germination is similar to the previous form with the following differences:
The region between the emerging radicle and the cotyledons (hypocotyl) grows causing the emerging cotyledons to be carried above the soil
Once above the soil, the fruit wall (pericarp) falls to the ground, the cotyledons open out and become green and photosynthetic. The plumule emerges from between the cotyledons and forms the first foliage leaves

13. Epigeal: growth of the cotyledon above soil
Hypogeal: growth of the cotyledon below soil

15. Plant Uses

16. Why We Can’t do Without Plants!
Produce oxygen for the atmosphere
Produce lumber for building
Provide homes and food for many organisms
Prevent erosion
Used for food

17. More Reasons We Can’t do Without Plants!
Produce wood pulp for paper products
Source of many medicines
Ornamental and shade for yards
Fibers such as cotton for fabric
Dyes