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Seed Dispersal and Germination. Mr. Chapman Biology 20. Animals, Wind & Water Can Spread Seeds. Seeds can get around in a lot of different ways thanks to several evolutionary adaptations. Different Types of Seed Plants.
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Seed Dispersal and Germination Mr. Chapman Biology 20
Animals, Wind & Water Can Spread Seeds Seeds can get around in a lot of different ways thanks to several evolutionary adaptations.
Different Types of Seed Plants • Remember that cone-bearing plants do not produce fruits as reproductive structures. • Cone-bearing plants rely on the wind, as well as gravity, in order to spread their seeds. • Flowering plants have fruit to help disperse their seeds. • Don’t forget that fruit is the mature ovary of the flower. • The ovary is the bottom part of the pistil, the female reproductive structure of flowering plants. Cone-bearing Plants Flowering Plants
Seed Dispersal is Important • Seed dispersal is basically the process of spreading seeds to a great area. • It is important for a plant to be able to do this. If a plant drops its seeds nearby, the resulting plants that grow from it will have to compete for food and sunlight with the parent plant. • The new plant will also have to compete for space and water, as well as all the nutrients in the soil
Fruits Play an Important Role • Fleshy fruits, like apples and berries, attract animals with their fragrant, nutritious offerings. • When the animal eats the fruit, it digests everything except for the seed. The seed has a tough outer coating that protects it from the animal’s digestive juices. • Once the animals graces nature with his fragrant excrement, the seeds are released along with an ample supply of fertilizer.
Fruits Play an Important Role • Often, this results in the release of the seed far from the place that it was originally ingested, allowing the plants to be spaced well apart from each other. • Some plants have fruits that can stick to animals instead, such as burrs. Eventually, the burrs fall off of the animal, hopefully some distance away from where they caught on.
Seeds Dispersed by Wind • A lot of the time, seeds that are dispersed by the wind have fruits attached to them that act like parachutes or wings. This allows them to travel great distances in the wind before they hit the ground. • Some plants that grow near water produce fruits that float. The coconut, for example, is a fruit that is designed to be able to float on the water, and travel to islands that are thousands of miles away.
Seeds Grow When Conditions are Favourable • Once a parent plant releases its seeds, it could be weeks, months, or even years until the seeds begin to grow into new plants. • Scientists recently found a 2000-year-old seed that came from an extinct species of tree. When they gave it the proper conditions to grow, it became a new plant.
How Does Dormancy Work? • A seed is in a state of dormancy when the embryo has stopped growing. • Different seeds require different conditions to come out of dormancy. For many, all that is required is for the seed to be exposed to proper temperature, moisture, oxygen and light levels. • For other seeds, such as the strawberry plant, the outer seed coat must be mostly digested by an animal before it exits dormancy. Can you think of why this is?
Germination • Germination occurs when there are certain changes in temperature, moisture, or light levels. During germination, the embryo breaks out of the seed coat and begins to grow into a seedling. • This only occurs when the conditions for growth are proper for the young plant to grow. Because of this, seeds can survive many harsh conditions that young plants could not. • The process begins when water begins to swell the sed, causing it to crack the seed coat.
Germination • Water comes in through the cracks and activates enzymes that allow the embryo to break down its endosperm into sugar, giving it a source of energy. • The plant continues to grow upwards, with details that you don’t need to know. Once the leaves emerge and begin to make food through photosynthesis, the young plant is called a seedling instead of an embryo.
