Seeds
You have learned that after a zygote is formed, cell division produces an embryo within a seed. Then seeds become dormant for awhile. Dormancy is a period of time when the embryo is not actively growing. Chemical changes occur that prepare the embryo for further growth.
When fruits and cones drop from seed plants, the seeds grow into new plants if conditions are right. The early growth of a plant from a seed is called germination . Moisture, oxygen, and a favorable temperature must be present for germination to occur. Then the embryo within the seed begins to develop.
Every seed contains a seed coat and embryo. Angiosperm seeds have seed leaves called cotyedons . Seeds with one cotyledon are monocots. Seeds with two cotyledons are dicots. Cotyledons contain food that the embryo uses during its early growth.
Few seeds would produce new plants if they all began to grow in the same spot. There would be too much competition for water, minerals, and sunlight. Seed dispersal increases the chances of a seed growing into a new plant. Seed dispersal means seed are carried away from the plant that produce them. Animals, wind, and water aid in seed dispersal.
Seeds eaten by animals may be carried great distances away from a plant. Many plant fruits have tiny hooks that cling to the fur or feathers of animals. Milkweed seeds have silky hairs that cause them to be carried by wind. A coconut may be carried far from a coconut palm tree by ocean currents.
แหล่งข้อมูล: FOCUS ON LIFE SCIENCE. Page 184.
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