1 Explain Why is it adaptive for some seeds to remain dormant before they germinate Apply Concepts The seeds of a bishop pine germinate only after exposure to the extreme heat of a forest fire. Evaluate the significance of this structural adaptation 2 Pose a Question A new angiosperm species is discovered. What questions would you ask before predicting how its seeds are dispersed- explain why you would ask each.

Ch 24 Plant Reproduction and Response 24.2 Fruits and Seeds

Seed and Fruit Development After fertilization, nutrients flow into the flower tissue and support the development of the growing embryo within the seed Fruit Mature angiosperm ovary, usually containing seeds Fruit isn’t limited to “fruits” like apples but also includes rice, corn, etc…

Ovary wall surrounding a fruit may be fleshy, (grapes and tomatoes) or tough and dry (shell that surrounds peanuts).

Dispersal by Animals Many seeds especially those in sweet, fleshy fruits are often eaten by animals Seeds are covered with tough coatings, allowing them to pass through an animal’s digestive system unharmed Seeds then sprout in the feces of the animal.

Dispersal by Animals Fruits provide nutrition for the animal Help the plant disperse its seeds Often to areas where there is less competition with the parent plants.

Dispersal by Animals Dry fruits sometimes have burrs or hooks that catch in an animal’s fur.

Dispersal by Wind and Water 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 Dandelion seed Coconut.

Dormancy Germination Embryo is alive but not growing Growth of plant embryo resumes.

How Seeds Germinate Seeds absorb water Causes food-storing tissues to swell and crack open the seed coat Young root emerges and begins to grow Shoot then emerges.

The Role of Cotyledons First leaves Store nutrients and transfers them to growing embryo as the seed germinates.

Monocots have one cotyledon Stays underground to nourish young plant Growing monocot shoot emerges from the soil protected by a sheath.

Dicot have two cotyledons Lack protection of a sheath for plant tip Upper end of the shoot bends to form a hook that forces its way through the soil Protects tip of plant, which straightens as it emerges into the sunlight.

Advantages of Dormancy Allow for long-distance dispersal Allow for seeds to germinate under ideal growth conditions Some seeds need cold temperature before seeds germinate.

The graph shows germination rates for Arisaema dracontium gathered at two locations. Interpret Graphs What effect does chilling have on germination of seeds from Ontario. How does it effect seeds from Louisiana Form a Hypothesis Describe how the different rates of seed germination might be explained in terms of adaptation to the local climate