Download Unit 4 Lesson 3

Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
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• Nonvascular plants are simple plants that lack
vascular tissue, which easily transports water from
the ground into the plant.
• They grow in damp places and almost never grow
taller than 10 cm.
• Nonvascular plants move materials by absorbing
nutrients and water in the same way that a
sponge absorbs water.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
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• Vascular plants have vascular tissues that allow
them to move water, nutrients, and sugars across
long distances.
• Vascular tissue contains tiny tubes, which move
water and nutrients up a plant in the same way
that water moves up a straw.
• Most plants, including trees, grasses, and shrubs,
are vascular plants.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
Tubes for Transport
• Vascular plants have true leaves and roots.
• Vascular tissue includes two kinds of smaller
tubes. Xylem carries water and nutrients from the
roots to the other parts of the plant.
• Phloem carries sugar from the leaves to the rest
of the plant.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
No Seeds, Please!
• A spore is a single reproductive cell that can grow
into a new plant.
• Both nonvascular plants, such as mosses and
liverworts, and vascular plants, such as ferns, use
spores to reproduce.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
No Seeds, Please!
• All of these plants have a sexual generation and
an asexual generation in their life cycles.
• For example, the sexual generation of moss has
male parts producing sperm and female parts
producing eggs. When sperm and egg combine,
the fertilized egg grows into a stalk.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
No Seeds, Please!
• The stalk is the asexual generation of moss. A
capsule grows at the end of the stalk, forming
spores that shoot out when the capsule opens.
• These spores land on the ground and develop into
threadlike plants that form buds, which turn into
green “leafy” structures.
• The “leafy” sexual generation of moss, the most
familiar form of the plant, makes food and rootlike structures that anchor the plants to the
ground.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
No Seeds, Please!
• Like mosses, ferns also use spores to reproduce.
In ferns, the reproductive spores form inside
clusters on the underside of the leaflets.
• The spores are released and fall to the ground
when the pockets burst.
• The spores then grow into a tiny fern plant. This
structure releases sperm and egg cells that, once
fertilized, grow into a young fern.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
No Seeds, Please!
• The young fern grows into the large, upright fern
plant, called the frond. This is the asexual
generation of the fern.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
Seed Power!
• While spores need to stay moist and sprout soon
after release, seeds have a covering that protects
them until conditions are right for sprouting.
• Gymnosperms are plants that do not produce
seeds in flowers. Gymnosperm seeds have a
protective seed coat, but are not enclosed by fruit.
• Cone-producing plants, called conifers, are the
most common gymnosperms. Conifers include
pine, fir, spruce, and cedar trees.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
Seed Power!
• Angiosperms are plants that produce seeds in
flowers.
• Since angiosperm seeds are often enclosed in
fruit, they are easily spread when animals eat the
fruits.
• Gymnosperm seeds may also be spread by
animals, but typically fall to the ground and grow
where they land.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
From Flower to Fruit to Seed
• Typical flowers have both male and female
reproductive parts.
• A male part, the anther, produces pollen, or the
sperm.
• The female parts include the stigma and the
ovary, which contains eggs in ovules.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
From Flower to Fruit to Seed
• Flowers produce nectar that organisms may eat.
When an organism gathers nectar, pollen may
brush onto it.
• The organism carries this pollen when it moves to
the next flower. This process is called pollination.
• When the pollen reaches the stigma, it travels
down to the ovary and fertilizes the ovules. This
process is called fertilization.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
From Flower to Fruit to Seed
• Fertilized ovules develop into seeds, and the ovule
wall becomes a seed coat. The ovary that holds the
seeds develops into the fruit, such as a pumpkin.
• The development of a pumpkin seed into a mature
pumpkin fruit follows a sequence of events.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
From Flower to Fruit to Seed
• Pollen enters the flower’s ovary and fertilizes the
ovules. The ovary grows and the petals fall off.
The ovules develop into seeds inside the ovary.
• Finally, the outer layer of the ovary thickens to
form a fruit around the seeds. The mature
pumpkin is filled with seeds.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
From Flower to Fruit to Seed
• Identify the following parts of a flower: anther,
ovary, ovules, petals, stigma.
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Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
How Seeds Grow
• Seeds have a hard outer coat that protects them
and allows them to rest until the environment is
right for growing.
• Many plant seeds rest during winter and then
germinate, or start to grow, when the ground
becomes warm and moist in the spring.
• A dormant seed lies in the soil until conditions are
right for growing. The seed germinates by absorbing
water and breaking through the seed coat.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 3 How Do Plants Grow and Reproduce?
How Seeds Grow
• The embryo continues to grow and a stem pushes
upward. Cotyledons provide energy for growth and
roots form and begin growing downward.
• Leaves mature and the plant starts absorbing more
energy from sunlight. It continues to grow as the
shoot pushes upward.
• The plant grows and matures until it produces
flowers and fruit.
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