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STUDY GUIDE:
PLANTS
The study of plants is called botany, and the scientist who studies plants is called
a botanist.
Plants have five main characteristics:
1. They are multicellular organisms. This means that they are composed of several
cells instead of just one cell.
2. They do not move by themselves.
3. They have a cell wall surrounding the cell membrane of each cell.
4. They are autotrophs, which means they produce their own food by a process called
photosynthesis. Photosynthesis is the scientific process whereby plants produce food
by utilizing solar energy. Chlorophyll in the leaves traps the sunlight’s energy to
produce carbohydrates for its own nourishment.
5. They have chloroplasts within their cells that contain chlorophyll to aid in
photosynthesis. Besides aiding in photosynthesis, chlorophyll gives plants their green
color.
Plants are divided into two main groups according to their structure. They may be
nonvascular or vascular plants.
Nonvascular plants are plants that have no internal tube-like structures to carry
the sugar, water, and minerals throughout the plant. They also lack true roots, stems, and
leaves.
There are two main types of nonvascular plants:
MOSSES and LIVERWORTS
Vascular Plants are plants that have a system of tube-like cells that carry
materials throughout the plant. There are two types of vascular tissue in a vascular plant.
The phloem carries food from one part of a plant to another. Food is produced in the leaf
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and travels downward to the root and to other parts of the plant through phloem. The
other type of vascular tissue is the xylem. The xylem carries water and dissolved
minerals upward from the roots to the stem and leaves. Vascular plants do have true
roots, stem, and leaves. Vascular plants tend to be taller than nonvascular plants, because
they are able to transport materials longer distances through their tube-like vascular
systems.
All plants EXCEPT mosses and liverworts are vascular plants.
Because they have a simpler structure, let’s examine the nonvascular plants first.
Mosses and liverworts are nonvascular plants that belong to the phylum bryophyta.
Bryophytes are small land plants that produce spores and live in a moist environment.
Bryophytes do not have true roots. They are held in the ground by a mass of root-like
threads called rhizoids. Water travels through the rhizoids and to all parts of the plant by
osmosis. The rhizoids are connected to the green, stalk-like part of the plant.
Surrounding the stalk are green, leaf-like parts that contain the chloroplasts and carry on
the photosynthesis. Once the food is manufactured, it is carried to the other parts of the
plant by diffusion. Both osmosis and diffusion are very slow processes. A capsule is
located at the top of each stalk. This is the spore case of the moss.
The life cycle of moss is unique. Moss undergoes an asexual stage as well as a
sexual stage during its life cycle. During the asexual stage, the moss capsule produces
spores. When these are scattered by natural forces, such as wind and water, they
sometimes land in moist soil. If so, they germinate, meaning they sprout into a new
plant. When this new plant matures, it develops sex organs at the top of the leaf-like
parts and begins the sexual phase of its life. The male sex organ produces the sperm,
which swims through the inherent moisture, such as rainwater or dew, and fertilizes the
egg of a nearby female sex organ. This fertilized egg is called a zygote. It develops into
an embryo that remains in the moist female sex organs for protection. Here it develops a
stalk and a capsule, and the process starts over again.
OTHER VOCABULARY RELATED TO MOSSES:
1. Gametes are the sex cells.
2. Gametophytes are the stage in the life cycle that produces the gametes.
3. Sporophytes are the stage in the life cycle that produces spores, the cells which are
capable of reproducing into a new entity.
Liverworts are another nonvascular plant and are very similar to mosses.
Vascular plants are divided into two main types: those that are seedless, such as
club mosses, horsetails, and ferns, and those that have seeds, which are then subdivided
into the gymnosperms and angiosperms. Gymnosperms include conifers, cycads, and
gingkoes, and angiosperms include the flowering plants.
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The club moss is a vascular seedless plant. It lives in tropical regions or on forest floors
in the cooler climates. It reproduces by producing spores called gametes. It is not a true
moss because it has scale-like leaves, and mosses do not have leaves. Horsetail are very
similar to club mosses. Both were much more widespread in the past.
Another vascular seedless plant is the fern. Like all vascular plants, ferns have
true leaves, stems, and roots. They are often grown as houseplants. The other parts of a
fern are the:
Rhizomes:
The part of the plant between the roots and the young leaves.
Fronds:
The large feathery leaves.
Fiddleheads: The young leaves that are coiled up. They uncoil and become
mature fronds and the plant ages.
Sporanzia: The structure in which reproductive cells are produced.
Sori (Sorus): The term for the clusters of spore cases that develop on the
underside of a fern frond. Spores released from the sori are carried by the wind
and water.
Ferns were the first plants to evolve vascular tissue and the first to evolve true roots,
stems, and leaves.
Vascular plants with seeds are subdivided into the gymnosperms and the
angiosperms. Gymnosperms are plants that produce seeds but do not have flowers.
Most trees and shrubs are gymnosperms. Like all vascular plants, gymnosperms have
true roots, stems, and leaves. Conifers are gymnosperms that have needle-like leaves
and produce seeds in cones. Pines, spruces, and sequoias are examples of conifers.
Reproduction in Conifers:
1. The small, male cones produce pollen, a yellow powder that produces sperm.
2. The wider female cone has two ovules near its base that produce one or more eggs.
The ovules protect the eggs.
3. Pollen is released from the male cones in the spring.
4. The pollen is carried to female cones by the wind, other weather conditions, or
animals.
5. The pollen lands on the female cone. It slides down the scales of the female cone and
is caught in the sticky substance released by the ovules. Pollination has occurred, and
the sperm fertilizes the egg.
6. The fertilized egg grows into an embryo that becomes a seed.
7. The seed coat is a tough, outer covering that protects the seed, which is finally
released in the second autumn after pollination.
Cycads and ginkgoes are also gymnosperms.
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Angiosperms are vascular plants with seeds that produce flowers. There are two types
of angiosperms.
1. The first type is monocotyledons (monocots). Monocots have the following
distinctive characteristics:
a.
b.
c.
d.
e.
One seed leaf (cotyledon).
Parallel leaf veins.
Scattered vascular bundles inside its stems.
Fibrous roots.
Flowers that occur in multiples of three parts.
2. The second type is dicotyledons (dicots). Dicots have the following distinctive
characteristics:
a.
b.
c.
d.
e.
Two seed leafs (cotyledon).
Veins that have a netlike pattern or are palmates.
Vascular bundles that form a ring pattern in the stems.
Tap roots.
Flowers that occur in multiples of four or five.
ANGIOSPERMS have eight distinct parts.
1.
2.
3.
4.
5.
6.
7.
8.
Stamens are the male reproductive organs of the flower.
Pistils are the female reproductive parts.
Stigma refers to the sticky surface on the pistil that traps the pollen.
Sepals are usually green. They are leaf-like and are found at the base of the flower.
They enclose the flower before it blooms and protect it.
Filaments are the long stalk-like parts of the stamen that support the knob-like
anthers where the pollen is produced.
The style is the section of the pistil that links the stigma to the ovary.
Ovules are the female reproductive organs of the flower that produce the eggs.
Ovaries contain the ovules.
Angiosperms are grouped according to the length of their growing periods. They can
be annuals, biennials, or perennials. Annuals are plants that complete their life cycle in
one year. Biennials are plants that require two years to complete their growth and life
cycle. Perennials are plants that grow year after year and reproduce many times.
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ROOTS
There are two main types of roots: fibrous roots and tap roots. Both types of
roots are covered with root hairs. Root hairs are tiny hairs that gather water and
nutrients from the soil. They also help anchor the plant into the ground. The roots of
some plants store food.
Fibrous roots are slender and branch out in many directions. They are often found
in such food crops as wheat, barley, and beans.
A taproot is a single, large root that grows straight down into the ground. It has
tiny root hairs that shoot out form its core. Its purpose is to store a large amount of food.
The carrot is an example of taproot.
ROOT STRUCTURE
The epidermis, an outer layer of cells, protects the root. Inside this layer is
vascular tissue, which includes two types of cells, the phloem and the xylem. The
function of the phloem is to transport food from one part of the plant to another. The
function of the xylem is to carry water upward from the roots to the rest of the plant.
STEMS
There are two main types of stems: herbaceous and woody. An herbaceous stem
is soft, green, and flexible. Woody stems are hard, strong, and firm.
The purpose of stems is to transport the food from the leaves to the roots, and to
hold the plants erect, so the leaves can capture light, and thus undergo photosynthesis.
Stems are composed of xylem, phloem, and cambium. Xylem is found towards
the core of the stem, and phloem is found closer to the outside. The cambium is a layer
of cells that manufactures new xylem and phloem. When you look at the growth rings of
a tree, you are actually looking at its xylem! Bark is the outer protective layer found on
woody stems.
LEAVES
Leaves are the part of the plant that manufacture the food. The flat part of the leaf
is called the blade, and the veins are actually bundles of xylem and phloem.
OTHER LEAF PARTS INCLUDE:
A. The epidermis is the outer protective coating of cells on the leaf.
B. The mesophyll: the middle part of the leaf containing the chlorophyll and the part of
the leaf where most of the food is actually made.
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C. The cuticle is the waxy layer found on some leaves that keeps the plant from losing
water through evaporation.
D. The palisade layer contains long cells under the epidermis (in the mesophyll) that aid
in the process of photosynthesis.
E. The spongy layer contains irregularly shaped cells that also help during
photosynthesis.
F. Stomata (Stomates) are the openings on the underside of the leaf where carbon
dioxide enters the leaf and oxygen exits the leaf during photosynthesis.
G. Petioles are stalk-like particles that attach the leaves to the stem.
LEAF VEIN PATTERNS
There are three main leaf vein patterns:
1. Pinnate: The veins in a pinnate leaf pattern resemble the veins in a feather. One
main vein, called the midrib, goes up the center of the leaf. Several smaller veins
branch off from the midrib. Elm leaves have a pinnate leaf pattern.
2. Parallel: Grass has a parallel vein pattern. The veins tend to run parallel to each
other. They never touch or intersect each other until they get to the very tip where
they taper toward the point of the leaf.
3. Palmate: There is not one main midrib in the palmate vein pattern. Three to five
larger veins branch outward from one point near the bottom of the leaf, resembling
fingers on a hand. Other small veins then branch from these larger veins. Maple
leaves have palmate leaf patterns.
PHOTOSYNTHESIS
Photosynthesis is the food-making process in the plant. The four things needed
for photosynthesis are carbon dioxide, chlorophyll, water, and light energy.
Photosynthesis takes place in the leaf of the plant. Carbon dioxide is brought into the
plant through the stomata on the leaves, and the roots gather water and transport it
upward to the leaves. The following steps then occur.
1. The chlorophyll captures and traps the light from the sun.
2. The captured energy is split into two parts. One part is stored in the compound ATP
and will be used for other cell purposes. The other part is split apart to release the
hydrogen and oxygen. The oxygen is released into the air through the stomates, or
tiny holes, on the underside of the leaf. The hydrogen remains in the chloroplasts.
3. Enzymes and energy that has been stored as ATP then combine with carbon dioxide
to create a simple sugar, called glucose that is used by the plant to perform its life
processes.
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RESPIRATION
Respiration is the process where the energy stored within the newly manufactured
glucose is released from the glucose. Contrary to photosynthesis, which occurs only
during the daylight, respiration occurs continuously. It is the opposite of photosynthesis
in that it uses some of the oxygen produced in photosynthesis and releases carbon dioxide
and water.
TROPISMS
Tropisms are the processes in which a plant grows toward a particular stimulus.
There are four different types of tropisms:
Phototropism: The plant responds and grows toward a light source.
Geotropism: The plant responds to downward gravity. If a plant is placed
upside down, with the roots extending upward, those same roots with gradually
turn and grow downward due to gravity.
Thigmotropism: Plants respond and grow toward touch. They may wind around
a wooden stake, or grow along a wall.
Hydrotropism means that the plants respond and grow toward water.
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OTHER PLANT VOCABULARY TERMS
Auxins are hormones that determine stem growth. They are connected with tropisms.
Bulbs are the underground portions of the plant that put down roots.
Cross-pollination occurs when pollen is transferred from the anther of one flower to the
stigma of another flower by the action of weather conditions or insects.
Dormancy is the time period during which a plant does not grow.
Embryo is a term for the young plant that develops from the zygote.
Endosperm is the material which turns into stored food for the seed.
Epiphytes are plants that grow on trees but do not leech food from the tree or harm the
tree in any way. For example, in some tropical forests, ferns may grow on the sides of
taller trees.
Fruit is the name given to the ripened ovary that surrounds and protects the seeds.
Germination refers to the beginning of growth.
Gnetophytes are a group of plants that possess characteristics of both gymnosperms and
angiosperms. Included in this category are tropical vines and several desert plants.
Grafting is the science through which a bud of one plant is inserted into an existing stem
or trunk of another, where it grows as a permanent part of that plant.
Hydroponics is the science of growing plants in water as opposed to the traditional
method of planting them in soil.
Pollination is the process by which pollen is transferred from the male reproductive
structure (stamen) to the female reproductive structure (ovule).
The Radicle is the root part of an embryo seedling.
The Seed Coat is the outer casing that protects the seed.
Self-pollination occurs when pollen from the stamen is transported to the pistil in the
same flower.
Tuber refers to the short, fleshy part of an underground stem from which new plants
develop.
Vegetative reproduction occurs when a new plant grows from the root, stem, or leaf of
another parent plant.