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Plant Life
Unit 2: Life Science
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In This Section:
 We consider seeds and how they grow, how new
plants can be started from plant parts, how
environmental conditions affect plants, how plant
parts work, and how plants respond to their
environment. A brief, final section takes up the tiny
plantlike organisms called molds.
Copyright (c) 2011 by Pearson Education, Inc.
Children and Plants
 Throughout the elementary years, it is important
that children build an understanding of biological
concepts through direct experiences with living
things.
 Plants are excellent sources for observational
activities, classification tasks, and experimentation.
Copyright (c) 2011 by Pearson Education, Inc.
Seeds
 “Where do seeds come from?”
 Seeds are produced in the ovary, in the central part of
the flower. As the ovary ripens, its seeds become
enveloped either by a fruity pulp, a pod, or a shell,
depending on the kind of plant.
 “What are some examples of seeds?”
 Pears and peaches are fruits whose pulp we eat. Beans,
peas, and peanuts are examples of seeds enclosed in
pods. When we “shell” string beans, lima beans, peas, or
peanuts, we are removing these seeds from their pods.
Walnuts, pecans, and coconuts have hard outer shells.
Copyright (c) 2011 by Pearson Education, Inc.
Seed Plants
 Seeds come in many shapes, colors, and sizes.
Still, they have three things in common:
 A protective seed cover
 A baby plant (embryo)
 A food supply that nourishes the seed as it pushes up
through the soil and grows into a young plant.
 The growth process from seed to seedling is called
germination.
Copyright (c) 2011 by Pearson Education, Inc.
Survival Conditions
 Some flowering plants produce thousands of seeds a year.
However, a variety of factors enable only a small
percentage of wild seeds to grow:
 Birds, insects, bacteria, and other organisms destroy
seeds.
 Unless proper conditions of moisture, temperature, and
oxygen are present, seeds remain dormant.
Copyright (c) 2011 by Pearson Education, Inc.
How Seeds Travel
 Children can learn that seeds travel in several ways.
 Some are scattered through the actions of animals
and people.
 The wind blows many seeds.
 Water can carry seeds from place to place because
many seeds float.
 The capacity of seeds to disperse widely and in
different ways is another survival feature.
Copyright (c) 2011 by Pearson Education, Inc.
Sprouting Seeds
 Some easy-to-grow seeds are kidney beans, lima
beans, pinto beans, whole green peas, and yellow
peas.
 To ensure that only live, healthy seeds are planted,
make sure you soak them and plant them while still
moist. A method for treating seeds can be found in
the textbook.
Copyright (c) 2011 by Pearson Education, Inc.
Soil
 Instruct students to plant seeds only slightly deeper than the
seed length. But always follow instructions on the seed
package for seed store varieties. Because it takes energy to
push through the soil, a small seed planted too deeply runs out
of food before it reaches the surface.
 Keep the soil somewhat loose so that air can get to the roots.
 Ensure that there is proper drainage by either using a container
with small holes, placed in a saucer or placing a layer of rocks
in a container before adding soil.
Copyright (c) 2011 by Pearson Education, Inc.
Vegetative Reproduction
 Many people think that only seeds produce new
flowering plants. Yet, some of the most useful and
interesting ways to grow new plants are through the
propagation of roots, stems, and even leaves. This
technique is called vegetative reproduction.
 Why not just use seeds?
 Vegetative reproduction results in faster growth.
 Some plants do not have seeds (ex: seedless oranges).
 Quality control (a seedling’s growth is unpredictable;
however, if vegetative reproduction is used, we can ensure
that the new plant will be very similar to its parents).
Copyright (c) 2011 by Pearson Education, Inc.
Roots
 Consider the orange-colored taproot of the carrot plant (the
part we eat):
 If left in sunlight, the taproot will sprout leaves, stems,
flowers, and seeds.
 Parsnips and beets grow in the same way.
 New plants may be grown from taproots in the classroom
by embedding them in moist sand or garden soil.
Copyright (c) 2011 by Pearson Education, Inc.
Stems
 Most ground-cover plants, such as grass,
strawberry, and ivy, spread quickly after planting.
These plants send out stems or runners that take
root, push up shoots, and develop into new plants.
These lateral stems may spread above ground, as
the strawberry plant and Bermuda grass do, or
below ground, as quack grass does.
Copyright (c) 2011 by Pearson Education, Inc.
Leaves
 Even some leaves may develop into whole plants.
 Suggestions for using an African violet, echeveria,
and bryophyllum plant are in the textbook.
Copyright (c) 2011 by Pearson Education, Inc.
Environmental Conditions
 Plants grow and flourish only when the environment
provides proper amounts of minerals, water, light,
temperature, and—more indirectly—space.
 Because the classroom is an artificial habitat, or home, for
plants, children will need to furnish the conditions the
plants need for survival.
Copyright (c) 2011 by Pearson Education, Inc.
Growth Conditions
 Excess watering causes plants to die of oxygen deprivation or
disease. Not enough watering usually results in droopy,
malnourished plants. The absence of vital soil minerals and
extremes in temperature also has a weakening, or even fatal,
effect on plants.
 Crowding of plants is harmful to growth largely because
competition deprives individual plants of enough of what they
need for good growth.
 Green plants need light energy, but not necessarily sunshine, to
manufacture their own food. Electric lights may be substituted.
Plants generally grow faster when exposed to light for increased
time periods, but overexposure retards growth and delays normal
blooming times.
Copyright (c) 2011 by Pearson Education, Inc.
Three Habitats
 It may be difficult for us to take children directly to different
habitats such as deserts and woodlands. It is possible, though,
to bring several habitats to the classroom in miniature form.
 The terrarium is a managed habitat for small land plants and, if
desired, small animals likely to be found with the plants. Three
basic kinds are the woodland, the marsh, and the desert
terrariums.
 Teachers can create these terrariums with any large clear
container such as an aquarium.
Copyright (c) 2011 by Pearson Education, Inc.
Plant Roots
 Roots:
 Anchor the plant
 Absorb soil water
 Store food
 Root hairs absorb all of the water for the plant
because they are able to grow in the tiny spaces
between soil particles and make direct contact with
water and air trapped within the soil.
Copyright (c) 2011 by Pearson Education, Inc.
Stem
 Water absorbed by the roots goes into the stems,
through which it is transported by narrow tubes to
all parts of the plant.
 Cohesion and adhesion work together to move
water molecules through the plant.
Copyright (c) 2011 by Pearson Education, Inc.
Leaves
 Inside leaves is a green chemical called
chlorophyll. Chlorophyll enables a leaf to
chemically combine carbon dioxide from air with
water to form a simple sugar.
 The energy needed to power this process,
Photosynthesis, comes from sunlight, which is
absorbed by the chlorophyll.
Copyright (c) 2011 by Pearson Education, Inc.
Leaves, cont’d
 Carbon dioxide is taken up in photosynthesis, and
oxygen is released as a waste product. But when a
plant consumes the food stored in its cells, it takes
up oxygen and gives off carbon dioxide as a waste
product.
 Fortunately for us, much more oxygen is released
to the air through photosynthesis than is used by
plants in oxidizing their stored food. In fact, green
plants are the chief source of the world’s current
oxygen supply.
Copyright (c) 2011 by Pearson Education, Inc.
Stomata
 How do these gases enter and leave the leaf? Thousands
of microscopic openings, called stomata, may be found in
a green leaf.
 In land plants, these are largely, but not exclusively,
located in the leaf’s underside.
 Water in the leaf evaporates into the air through the
stomata, a process called transpiration.
 Regulation of these openings has great survival value. In
dry spells and at night, the stomata stay closed, thereby
preventing any appreciable loss of water.
Copyright (c) 2011 by Pearson Education, Inc.
Flowers
 The flower is the reproductive system of a flowering
plant. Its two principal organs are the pistil, which
contains unfertilized egg cells, and stamens, which
produce dust-like pollen cells.
 It is best to examine single flowers, such as tulips
and sweet peas, with children rather than
composite flowers, such as daisies and sunflowers
which have very minute parts that are difficult to
observe.
Copyright (c) 2011 by Pearson Education, Inc.
Pollination
 Self-pollination happens when pollen from a
flower’s own stamens fertilize its ovules.
 Cross-pollination occurs when pollen from another
flower perform this function.
 Pollen must be from the same type of flower,
however, for fertilization to take place.
 Pollen may travel through wind, insects, or even
just gravity.
Copyright (c) 2011 by Pearson Education, Inc.
Life Cycles
 Many garden flowers and vegetables grow from seeds,
then blossom, produce seeds, and die in one growing
season. These are known as annuals.
 Examples are petunias, zinnias, beans, and tomatoes.
 Those that live two seasons are biennials.
 Examples are hollyhocks, forget-me-nots, carrots, and turnips.
 Plants that live more than two growing seasons are
perennials.
 Trees and most shrubs fit into this classification.
Copyright (c) 2011 by Pearson Education, Inc.
Tropisms
 A plant’s responses to environmental stimuli are
called plant tropisms.
 Geotropism- The plant’s response to gravity.
 Example: A plant grows towards a light source.
 Hydrotropism- The plant’s response to water.
 Example: A plant’s roots growing towards a water
source.
Copyright (c) 2011 by Pearson Education, Inc.