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.

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.

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

Cotyledon

Plumule

Radicle

Micropyle

Seed coat or testa

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

GERMINATIONGERMINATION

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

CONDITIONS FOR GERMINATIONCONDITIONS 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

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

EVENTS IN GERMINATIONEVENTS IN GERMINATION

1. absorption of water through a tiny hole called the microphyle.

2: mobilization of reserve food. 3: respiration and release of energy4: breaking down of the seed coat5: emergence of the embryo 6: radical develops7: The plumule emerges above the ground and leaves

begin to form

1. Seeds aborb water and begins to grow

2. Radicle bursts out through the testa and grows down

3. The plume becomes visiable and the cotyledon grows

4. the plumule grows up through the soil and its delicate leaves are protected by the plume because it is “hooked” over

6: The cotyledon shrivel as food is transferred from them

7: once above ground the plume straightens up and produces leaves

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

2. 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

Epigeal: growth of the cotyledon above soilHypogeal: growth of the cotyledon below soil

Produce oxygen for the atmosphere

Produce lumber for building Provide homes and food for

many organisms Prevent erosion Used for food

Produce wood pulp for paper products

Source of many medicines Ornamental and shade for

yards Fibers such as cotton for fabric Dyes