1. Lesson Overview
24.2 Fruits and Seeds

2. Seed and Fruit Development
Once fertilization is complete, nutrients flow into the flower tissue and support the development of the growing embryo within the seed
A fruit is a matured angiosperm ovary, usually containing seeds.

3. Seed and Fruit Development
The term fruit applies to the sweet things we usually think of as fruits, such as apples and strawberries.
However, foods such as peas, corn, rice, and tomatoes, which we commonly call vegetables, are also “fruits”

4. Seed and Fruit Development
The ovary wall surrounding a fruit may be fleshy, as it is in grapes and tomatoes, or tough and dry, like the shell that surrounds peanuts. (The peanuts themselves are the seeds.)

5. Dispersal by Animals
The seeds encased in sweet, fleshy fruits, are often eaten by animals.
The seeds are covered with tough coatings, allowing them to pass through an animal’s digestive system unharmed.

6. Dispersal by Animals
The seeds then sprout in the feces eliminated from the animal.
These fruits provide nutrition for the animal and also help the plant disperse its seeds—often to areas where there is less competition with the parent plants.

7. Dispersal by Animals
Animals also disperse dry fruits, but not by eating them.
Dry fruits have burrs or hooks that catch in an animal’s fur, enabling them to be carried many miles from the parent plant.

8. Dispersal by Wind and Water
Seeds dispersed by wind or water are typically contained in lightweight fruits that allow them to be carried in the air or in buoyant fruits that allow them to float on the surface of the water.

9. Dispersal by Wind and Water
Dandelion seed = dry fruit that has a parachute-like structure, allowing the seed to glide considerable distances away from the parent plant
Coconut fruits = buoyant enough to float in seawater for many weeks, enabling the seeds to reach and colonize even remote islands

10. Seed Dormancy and Germination
Dormancy = a period during which the embryo is alive but not growing
Many seeds will not grow when they first mature.
Environmental factors such as temperature and moisture can cause a seed to end dormancy and germinate.
Germination = the resumption of growth of the plant embryo

11. Advantages of Dormancy
Allow for long-distance dispersal
Seeds germinate under ideal growth conditions
Sometimes, only extreme environmental conditions (hot/cold) can end seed dormancy.

12. Advantages of Dormancy
Some pine trees, for example, produce seeds in cones that remain sealed until the high temperatures generated by forest fires cause the cones to open.
The high temperature both activates and releases the seeds, allowing the plants to reclaim the forest quickly after a fire.