Biologist ______Date ______
24-2 PowerPoint Notes – Seeds and Fruits
Seed and Fruit Development
Once fertilization of an ______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 ______.
Fruits vary in their ______.
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 ______.
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 ______. (The peanuts themselves are the seeds.)
Dispersal by Animals
The seeds of many plants, especially those encased in sweet, fleshy fruits, are often eaten by ______.
The seeds are covered with tough coatings, allowing them to pass through an animal’s digestive system ______.
The seeds then sprout in the feces ______from the animal.
These fruits provide nutrition for the animal and also help the plant disperse its seeds—often to areas where there is ______competition with the parent plants.
Animals also ______many dry fruits, but not necessarily by eating them.
Dry fruits sometimes have burrs or ______that catch in an animal’s fur, enabling them to be carried many miles from the parent plant.
Dispersal by Wind and Water
Seeds dispersed by wind or water are typically contained in ______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.
A ______seed, for example, is attached to a dry fruit that has a parachute-like structure, allowing the seed to glide considerable distances away from the parent plant.
Some seeds, like a ______, are dispersed by water.
Coconut fruits are buoyant enough to float in seawater for many weeks, enabling the seeds to reach and colonize even remote islands.
Seed Dormancy and Germination
Many seeds will not grow when they first mature. Instead, these seeds enter a period of ______, during which the embryo is alive but not growing.
______is the resumption of growth of the plant embryo.
Environmental factors such as ______and moisture can cause a seed to end dormancy and germinate. The effect of temperature on the germination of Arisaema seeds is shown in the graph.
How Seeds Germinate
Before germinating, seeds absorb water, which causes food-storing tissues to swell and crack open the seed ______.
Through the cracked seed coat, the young root emerges and begins to ______.
The shoot—the part of the plant that will emerge above ground—emerges next, as seen in the ______corn seed.
The Role of Cotyledons
Cotyledons are a flowering plant’s first leaves. They store nutrients and then transfer them to the growing ______as the seed germinates.
Monocots have a single cotyledon, which usually remains underground while it passes nutrients to the young ______.
The growing monocot shoot emerges from the soil protected by a ______.
In ______, which have two cotyledons, there is no sheath to protect the tip of the young plant.
Instead, the upper end of the shoot bends to form a hook that forces its way through the soil.
This protects the ______tip of the plant, which straightens as it emerges into the sunlight.
Advantages of Dormancy
Seed dormancy can allow for long-distance dispersal, and for seeds to germinate under ______growth conditions.
For some species, a period of cold temperatures during which the seeds are dormant is required before growth can begin.
The period of cold that is required is long enough that seeds will not germinate until the ______winter season has passed.
Sometimes, only ______environmental conditions can end seed dormancy.
Some pine trees, for example, produce seeds in cones that remain sealed until the high temperatures generated by forest ______cause the cones to open.
The high temperature both ______and releases the seeds, allowing the plants to reclaim the forest quickly after a fire.