Lesson OverviewLesson Overview24.2 Fruits and Seeds24.2 Fruits and Seeds

Lesson OverviewLesson Overview Fruits and SeedsFruits and Seeds

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.

Lesson OverviewLesson Overview Fruits and SeedsFruits and Seeds

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”

Lesson OverviewLesson Overview Fruits and SeedsFruits and Seeds

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.)

Lesson OverviewLesson Overview Fruits and SeedsFruits and Seeds

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.

Lesson OverviewLesson Overview Fruits and SeedsFruits and Seeds

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.

Lesson OverviewLesson Overview Fruits and SeedsFruits and Seeds

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.

Lesson OverviewLesson Overview Fruits and SeedsFruits and Seeds

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.

Lesson OverviewLesson Overview Fruits and SeedsFruits and Seeds

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

Lesson OverviewLesson Overview Fruits and SeedsFruits and Seeds

Seed Dormancy and Germination• Dormancy = a period during which the embryo is

alive but not growingoMany seeds will not grow when they first mature. o 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

Lesson OverviewLesson Overview Fruits and SeedsFruits and Seeds

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.

Lesson OverviewLesson Overview Fruits and SeedsFruits and Seeds

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.