Download Chapter 12

Chapter 12
Plants
Section 1
Could you survive without plants in your life? What about the paper you write on, the
furniture you may sit on, the table you eat on, the money you may spend, the salad you
may eat, the OXYGEN you breathe. As you can see our lives revolve around plants. We
could not survive without plants.
Plants are Producers: Plants make their own food through photosynthesis. Plants have
chlorophyll in chloroplasts of their cells. The chlorophyll captures the energy (light) from
the sun to carry out photosynthesis.
Plants have a protective covering. Plants have a cuticle, which is a waxy layer that covers
the stems, leaves, and other parts of the plant exposed to the air that are susceptible to
drying out.
Plants have Cell Walls: the cell walls provide support for the plants, which allows them
to grow tall. Once the cells stop growing, a second cell wall may form that provides more
strength.
Plant Reproduction: You should think of plants as having two parts to their life cycle.
Plants will spend some of their life in a stage that produces spores and another part of
their life producing sperm and egg cells. The stage in which spores are produced is called
the sporophyte stage. The stage in which sperm and egg are formed is called the
gametophyte stage. (Sperm and Egg are gametes: You should have remembered this from
reproduction chapter). Spores that land in a suitable habitat are capable of growing into
new plants, the sperm and egg must unite (fertilization) in order for a new plant to grow.
The Origin of Plants
Hundreds of millions of years ago there were no plants on land. Scientists believe there
were green algae that as time passed had adaptations to occur that allowed the algae to
survive in land based habitats. The green algae have the same type of chlorophyll as
plants and they also have two phases of their life cycle. This is why scientists think that
green algae gave rise to plants.
There are close to 275,000 species of plants that we have classified today. We group
them into two categories: 1) vascular and 2) non-vascular.
The non-vascular plants include mosses and liverworts. The term non-vascular simply
means they do not have “vessels” to carry water and nutrients. These plants depend on
diffusion to get all the water they need and all of the nutrients they need. RECALL:
Diffusion – substances moving from an area of high concentration to an area of low
concentration. Because they rely on diffusion to get materials into and out of their
system, the plants do not get very large. Remember diffusion only works well if you have
only a few layers of cells to cross.
The vascular plants do not have to rely on diffusion alone. These plants have a “pipe”
network to carry water and nutrients. These are special tissues called vascular tissues. We
group vascular plants into two groups: 1) seed producers and 2) do not produce seeds.
The plants that do not produce seeds include the ferns, horsetails and club mosses.
We also divide the seed producers into two groups: 1) Gymnosperms and 2)
Angiosperms. Gymnosperms do not produce flowers, and Angiosperms do produce
flowers. You are probably most familiar with angiosperm plants because you can often
see the flowers they produce.
SECTION 2
SEEDLESS PLANTS
There is one group of non-vascular plants that do not make seeds and one group of
vascular plants that do not makes seeds. The non-vascular group is the mosses and
liverworts, and the vascular seedless plants are the ferns, horsetails and club mosses.
Mosses and Liverworts: These plants are small and are found growing on the sides of
trees, surfaces of rocks, and on some soils. Remember they get their nutrients and water
they need by diffusion. They do not have true roots, stems, or leaves like other plants.
Mosses often resemble “carpet” because they grow in dense mats many times. Each moss
plant has a structure called a rhizoid that serves as roots which anchors the moss to the
structure it is growing on. The life cycle of a moss alternates between the gametophyte
stage and the sporophyte stage.
Liverworts: they are nonvascular and small. The liverworts live in damp or moist habitats
(around streams). Liverworts also have a gametophyte and sporophyte stages of their life
cycle. The gametophyte stage looks like a small leafy structure and the sporophyte stage
resembles an umbrella or very small palm tree. Liverworts also have rhizoids that anchor
them into place.
Mosses and liverworts are pioneer species (often the first to inhabit an area). They often
“capture” soil particles that are being eroded away and help the soil become established
on the new site. Mosses provide some species of bird with nest building materials. In
some locations the mosses have been growing so long there are dead peat mosses that
humans harvest (peat moss is available in bags from gardening centers). Some of the peat
is allowed to dry and then burned as fuel in some countries.
FERNS, HORSETAILS, and CLUB MOSSES
Remember these plants are also non-seed producers, but they are vascular.
Ferns: grow in many places varying from tropical rain forests to the cold climates of the
arctic. The underground “stem” of the fern is called a rhizome, which anchors the fern in
place. The rhizome produces the “leafy” structures called fronds. (We see the fronds
above ground). There are also small structures that look like small violins or fiddles
called fiddleheads. As the fiddleheads mature and open, they become the fronds. The
ferns have a gametophyte stage and a sporophyte stage during their life cycle. The
sporophyte stage is the most recognizable (it is the fern we see). During the sporophyte
stage, the fern produces spores which will grow into the gametophyte stage (heart-shaped
structure that produces sperm and egg). When a sperm and egg unite (fertilization) a new
sporophyte (fern that we recognize) grows.
The sporophyte stage produces the spores and the clusters of spores can be found on the
underside of the fronds. They will appear like small “bumps” in rows along the main
“rib” of the fronds.
Horsetails: Scientists have found many fossils of what they believe are horsetail plants,
but there are only about 15 species existing today. The horsetails are small vascular
plants that are found in wet marshy habitats. The plants are round and the stems are
hollow with a “cone-like” structure on the tip of the horsetail plant. The cone-like
structure produces spores. Think of a drinking straw with a cone-like structure on the top,
this would resemble a horsetail. The stems are green and carry out photosynthesis. The
inside of the hollow stem is covered with silica, which feels very abrasive. Early settlers
used the horsetails to scrub pots because of their abrasive properties.
Club Mosses: These plants are short and grow in woodland habitats. They are NOT true
mosses because club mosses are vascular. They were probably very common millions of
years ago.
Seedless Vascular Plant Benefits: since most of these are small, they trap soils that would
be eroded away and hold the soil in place. Ferns are often kept as house plants and the
small fronds (called fiddleheads) are sometimes collected and cooked to be eaten. One of
the most important aspects of these seedless vascular plants happens to be the ones that
survived millions of years ago. When these plants died they often formed coal, which is a
fossil fuel we relay on for many reasons (produce electricity, some countries use it as a
heating source in their houses, run steam engine trains and other steam driven
machinery).
SECTION 3
PLANTS WITH SEEDS
There are two groups of vascular plants that produce seeds: 1) Gymnosperms and 2)
Angiosperms. Gymnosperms are trees and shrubs that produce their seeds in cones or
fleshy structures on stems. Examples of gymnosperms are pines, spruces, firs, cedars, and
ginkgo trees (these are all evergreens, except for the ginkgo). Examples of angiosperms
include cherry trees, peach trees, rose bushes, and any plant that you know produces a
flower. Many flowers are hard to see or are so small you never notice them.
Characteristics of Plants That Produce Seeds
1) The seed plants produce their seed inside structures that the sporophyte is protected
and nurtured (protected). 2) The gametophyte and sporophyte stages occur on the same
plant, they are not independent of each other (the gametophyte is protected by the
sporophyte). 3) The male gametophyte uses the wind or air currents to be dispersed
instead of water. These male gametophytes are called pollen.
These characteristics allow the plants to grow just about anywhere. For this reason, seed
plants are the most common type of plants on Earth.
Seeds develop after an egg and sperm have united (fertilization). The seed consists of
three parts, 1) the young sporophyte or young plant, 2) stored energy (food), and 3) a
seed coat that surrounds the young plant for protection.
When the young plant starts growing (germinates) it has its own food or energy source
from the seed. The young plant uses the food source until it can establish all the parts of a
plant to carry out photosynthesis (roots, stem, and leaves). This is an advantage over a
spore, which must start growing in a suitable habitat it can carry out photosynthesis
immediately.
Gymnosperms (non-flowering seed plants)
Gymnosperms produce their seeds which are not enclosed in a fruit. Gymno means naked
seed in Greek. There are four groups of gymnosperms: conifers, cycads, ginkgos, and
gnetophytes. You are probably most familiar with conifers (cone bearing trees).
Gymnosperms also have two a sporophyte and gametophyte life cycle. Conifers have two
types of cones: 1) male and 2) female. The male cones produce the male gamete or sperm
we call pollen and the female cones produce the female gamete called the egg. The
sporophyte produces the cones and the egg and sperm make up the gametophyte. In
simpler terms, a pine tree that you see is the sporophyte and the cones are producing the
gametophyte stage or gametes. Pollen is dispersed by wind and when it lands onto a
female cone of the same or different tree of the same species, fertilization occurs except
with pollen, we call it pollination. The male cones of conifers are small and often go
unnoticed. The large “woody cones” are the female cones.
Conifers are very important economically, because we harvest them to make lumber to
build things, soap, turpentine, some inks, and paint.
Angiosperms: (flowering seed plants).
Flowering plants are the most numerous plants today. All flowering plants are vascular
and they come in a wide variety of shapes and sizes. These plants produce gametes and
after pollination (fertilization – egg and sperm union) they form a fruit that covers the
seed. Examples of flowering plants include orange trees, apple trees, oak trees, orchids,
tomatoes, cucumbers, watermelons, and other foods many people think of as vegetables.
The Function of Flowers
One of the first things you notice about flowers is their coloration. The flowers also
contain the male and female gametes. The coloration attracts certain insects or animals
that serve as carriers of pollen (pollinators). The insect may get some pollen on it and
transfer it to another flower and fertilization occurs. Flowers may also create a specific
scent that attracts specific pollinators.
The Importance of Fruits
The fruits will provide protection for the seeds and help provide transportation for the
seeds to new places in which to begin growing. Some fruits have structures that allow
them to be carried in the wind to new places. Other fruits may have prickly structures that
allow the fruit to attach to the fur of animals and fall off later into new areas. Some fruits
may be eaten by animals and the seeds transported somewhere else in the digestive
system of the animal.
There are Two Groups of Angiosperms (Monocots and Dicots)
The Monocots and Dicots differ in the number of cotyledons their seeds contain.
Cotyledon – is a seed leaf that is found inside the seed. Monocots have one seed leaf.
Mono means one. Dicots have two seed leaves. Di means two.
Examples of monocots include grasses, corn, orchids, onions, and plants that have the
leaf veins running parallel to each other. Examples of dicots include roses, beans, peas,
and other plants that have leaf veins that form a net pattern.
Angiosperms are important to land dwelling animals because they produce a tremendous
amount of food for them. Some may eat the plants directly, like a mouse eating grass and
some animals may eat the mouse that had eaten the grass. Humans also depend on
flowering plants for the majority of their food need, whether eating the plants directly of
indirectly (eating organisms that eat the angiosperms directly). We also get many of our
medicines from flowering plants, as well as other material to use in our daily activities.
SECTION 4
The Structures of Seed Plant (Roots, Stems, and Leaves)
Remember when we studied the different body systems of humans? Well, plants also
have systems to carry out specific functions. Plants have root and shoot systems to supply
the plant with the resources it needs to survive. The root system is made up of roots and
the shoot system is composed of stems and leaves. Both systems are dependent on each
other. There are two kinds of vascular tissue: 1) Xylem, which transports water and
minerals through the plant and 2) Phloem, which transports sugars through the plants.
The Functions of Roots
1) Roots supply the plants with the water they need and the dissolved minerals they
absorb from the soil.
2) The roots anchor the plant into the soil and help prevent the plant from falling
over.
3) The roots also act as a storage system for the excess sugars produced during
photosynthesis.
Root Structure
The outer layer of the root is covered with epidermis and small root hairs extend
off the main root. The root hairs increase the amount of surface area for absorption of
water and minerals. The tip of the root has some specialized cells that make up the root
cap. The root cap releases a moist material that allows the root to penetrate deeper into
the soil.
Root Types
There are two types of roots 1) taproots and 2) fibrous roots. The taproot is the
main root that grows down through the soil. The fibrous roots grow off of the taproot and
spread out away from the taproot. These are often right under the soil and pull in water
near the surface of the soil.
Above the roots of the plant you will find stems. Plants of different types will have
different stems, but most plant stems are above ground.
Stem Functions
The stems of plants support the plant body (could be branches, flowers, leaves).
Also, the stems transport materials between the root and shoot systems. Remember
Xylem carried water and minerals upward from the roots to other parts of the plant.
Phloem will be carrying the sugars produced from photosynthesis to the roots and other
parts of the plant. Some stems also serve to store materials (cactuses store water in their
stems to survive long droughts in desert regions).
Types of Stems
1) Herbaceous stems are flexible and are found on plants like wildflowers, many
vegetable crops, and houseplants. The xylem and phloem of herbaceous stems
are in clusters if you viewed the cross section of a herbaceous stem.
2) Woody Stems are not flexible, the phloem only occurs under the outer layer
(like right under the bark of trees) and the xylem is all the other tissue inside
the plant. The xylem of woody stems will stop growing and only be used to
transport. The woody stems produce growth rings that indicate periods of fast
growth compared to periods of slow growth.
Food Production in Plants
Remember: plants use chlorophyll to capture the sunlight energy and carry out
photosynthesis.
Leaf Function: The main function of leaves is to produce food for the plant by capturing
carbon dioxide, water, and the sun’s energy and making glucose and oxygen. Leaves
have specific layers we need to know.
The upper surface and lower surface of a leaf is covered with cells that make up the
epidermis (the top is upper epidermis and the bottom is lower epidermis). These are
covered on their outer surface with cells that make up the cuticle. Under the upper
epidermis we find a layer called the palisade layer and below the palisade layer we find
the spongy layer. So if we labeled a leaf from the top surface to the lower surface we
would find the following layer pattern. Cuticle, Upper epidermis, palisade layer, spongy
layer, lower epidermis, and cuticle. The lower cuticle and epidermis have special cells
called guard cells that allow carbon dioxide into the cell and oxygen out of the cell.
The palisade layer consists of cells closely together that carry out photosynthesis. The
spongy layer consists of cells with “air spaces” between them, which allows the carbon
dioxide to move more freely between them. We also find phloem and xylem tissue in the
leaf to transport the needed materials. Remember: Xylem – transports water and minerals,
Phloem transports sugars.
Special Leaf Adaptations
Some leaves of plants have other functions rather than just carrying out
photosynthesis. Some leaves may have thorns that prevent organisms from eating the
leaves. Others may have special structures to capture insects (Venus Flytrap) and release
chemicals that breakdown the insects and allow the plant to take in nutrients from the
decomposed insects.
Flowers
The main purpose of flowers appears to be to attract pollinators to the flowers and
carry out pollination. This may be by being a specific color or having a specific
fragrance. The many shapes of the flowers will determine the type of pollinator that is
effective and attracted to the flower.
Parts of a Flower
1) Sepals – the green structures that resemble leaves on the outside base of the
flower.
2) Petals – the colorful portion of the flower that is readily visible.
3) Stamens – the male reproductive structure on the flower that has the pollen
grains on the tips. The stamen is made up of the filament (stalk) and the anther
(portion where pollen is located).
4) Pistil – the female reproductive portion of the flower. The pistil has the 1)
Stigma on the end which serves as the receptacle for pollen, the 2) Style
which is the tube the pollen travels to reach the ovary 3) Ovary, which is the
location of fertilization between the sperm (pollen) and egg (ovule). The ovary
develops into the fruit of the plant. The fruit will contain the seeds.
Adaptations of Flowers
Color – attracts specific pollinators.
Fragrance – may again attract specific pollinators.
SECTION 1 STUDY GUIDE
1. _______________________ captures the light energy from the sun.
2. The waxy layer of the surface of stems and leaves that serves as protection is
called the _________________________.
3. The ___________________ __________________ of plants provides strength,
support and protection of plants.
4. The ___________________________ is the stage of a plant’s life cycle in which
spores are produced.
5. The ____________________________ stage is when the plant produces gametes
(sperm and egg) for sexual reproduction.
6. Scientists believe plants originated from green ________________.
7. ____________________________ plants are limited on how large they grow
because they lack tissues that transport needed resources. They must rely on
diffusion for obtaining their resources.
8. ______________________________ have tissues that deliver resources to all
parts/places in a plant. You could think of these plants as having a plumbing
system for transport.
9. Non-flowering plants are ______________________ and flowering plants are
____________________________.
10. There are two groups of vascular plants, those that produce _______________
and those that do not produce ________________.
SECTION 2 STUDY GUIDE
1. Mosses and Liverworts are ___________________________ plants and do not
produce _____________________.
2. The gametophyte stage produces __________________ and _______________
for the reproduction of mosses.
3. The _____________________ serve as roots for mosses.
4. The three examples of plants that are vascular, yet do not produce seeds are the
____________________, ______________________, and the _____________
______________________.
5. The “root” system of ferns is actually called a ___________________.
6. The rib with leaves attached on a fern is called the _______________________.
7. The immature fronds are called _______________________ because they
resemble a fiddle in shape.
8. _______________________ are thought to be the common link to modern plants.
They resemble straws in the fact that their stems are hollow and the tip has a
cone-like structure. The cone-like structure contains ___________________.
9. ______________________ __________________ resemble mosses, but they
have a cone-like tip that releases spores for reproduction.
10. We get one major fossil fuel from the seedless vascular plants that died millions
of years ago. What fuel are we talking about? _______________________
SECTION 3 STUDY GUIDE
1. Seed plants also have a two part life cycle of a _____________________ and
________________________ stage.
2. The seed protects the young ________________________ and provides
nourishment until the young plant can carry out photosynthesis.
3. The sporophyte and gametophyte stage are found on the same plant of
___________ plants.
4. The male gametophyte of seed producing plants is in the dust-like structures we
call __________________. Many people have allergies to these dust-like
structures.
5. The three parts of a seed is the ________________ coat, ________________
food, and the _____________________ plant.
6. When a seed begins to grow we say the seed is undergoing _________________.
7. _________________________ produce seeds, but do not have flowers.
8. The most common group of gymnosperms is probably _________________.
9. The pine tree is an example of a sporophyte stage that produces male and female
_________________, which make up the gametophyte stage.
10. The transfer of pollen to a female cone is known as _____________________.
11. _________________________ are flowering plants that produce seeds.
12. Angiosperms can be divided into two groups: 1) _________________ which only
has one leaf inside the seed, and 2) ______________________ which have two
leaves inside the seed.
13. Flowers often have specific colors or fragrances to attract specific
_________________________.
SECTION 4 STUDY GUIDE
1. Plants can be divided into three systems, the _______________,
_______________, and ____________________ system.
2. The ___________________ system takes in water and minerals from the soil in
most plants.
3. In plants, the ____________________ transports water and minerals that are
dissolved in the soil.
4. The ___________________ carries sugars that the plant has produces.
5. Roots have three functions. They can transport needed materials, serve as an
______________ to keep the plant from falling over and the roots can also
_________________ surplus food made during photosynthesis.
6. Roots are covered with _________________________ and have small root
____________ growing off the main root system.
7. The root type that has one main root is the ________________ system and the
type with many roots branching out is called the _____________________ root
system.
8. The _________________________ of most plants is located above ground and
holds the plant body up.
9. There are _________________ types of stems. One stem is _________________,
which is soft and pliable (bendable). The other type of stem is woody and is not as
pliable.
10. Many plants have growth _________________ when there are periods of
alternating slow and fast growth.
11. The main function of a leaf is to carry out ______________________, which is
the process of taking in carbon dioxide and water and capturing the suns energy
and making glucose and oxygen.
12. ________________________ cells open and close the stomata which is the
location of gas exchange in a leaf. Water can also be lost through the stomata
opening.
13. The male portion of a flower is the ____________________, which is made up of
the filament and anther.
14. The female portion of a flower is the ___________________, which consists of
the stigma, style, and ovary.
15. The ____________________ are found inside the ovary and turn into seeds after
they are fertilized.
16. The ovary of a flowering plant turns into a ______________________.
17. The colorful portion of a flower is known as the _________________________.
18. The green portion under the petals that resemble small leaves are known as
____________________.