Animal, Plant

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Animal, Plant Soil Science E4-2Plant
Internal Structure and Growth
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Interest Approach

• Take the students outside to see a small tree,
  bring a small tree to class, direct attention
  toward a small tree outside the window, or show
  an image of a small tree. Identify a small lower
  limb on the tree. Then, ask the students where
  that limb will be in 50 years if the tree
  continues to grow. Students often assume that a
  tree grows from the ground and that it begins by
  enlarging at the ground level they fail to
  realize that growth occurs from meristem tissues.
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3
Objectives

• 1 Review the functions of plant cell components.
• 2 Examine the role of cell division, cell
  elongation, and cell differentiation in plant
  growth and the different types of plant tissue.
• 3 Identify and describe the basic types of plant
  cells.
• 4 Compare and contrast primary and secondary
  plant growth.

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Terms

• _ apical meristem
• _ bud primordia
• _ cell
• _ cell differentiation
• _ cell division
• _ cell elongation
• _ cell wall
• _ cellulose
• _ chlorophyll
• _ chloroplasts

• _ chromatin
• _ chromosomes
• _ collenchyma cells
• _ companion cells
• _ cork cambium
• _ cork cells
• _ cytoplasm
• _ dermal tissues

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Terms

• _ endoplasmic reticulum
• _ fiber
• _ genes
• _ golgi complex
• _ ground tissue
• _ lateral meristem
• _ leaf primordia
• _ lignin
• _ meristems
• _ mitochondria

• _ nucleolus
• _ nucleus
• _ organelles
• _ parenchyma cells
• _ periderm
• _ phloem
• _ pith
• _ plasma membrane

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Terms

• _ plastids
• _ primary plant growth
• _ ribosomes
• _ rough endoplasmic reticulum
• _ sclereid
• _ sclerenchyma cells
• _ secondary plant growth
• _ sieve tube member

• _ smooth endoplasmic reticulum
• _ tracheid cells
• _ vacuole
• _ vascular cambium
• _ vascular tissues
• _ vessel elements
• _ xylem

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What are the functions of plant cell components?

• I. The cell is the most basic unit of life. It is
  the smallest unit that can perform functions of
  life. Plant cells are composed of the following
  items.
• A. The cell wall is made of multiple layers of
  cellulose, which is a polysaccharide or complex
  sugar molecule. The layers of cellulose offer
  great strength. Therefore, it is no surprise that
  cellulose is the primary ingredient of wood. Once
  a cell has stopped growing, the cell wall
  thickens and becomes rigid.

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What are the functions of plant cell components?

• B. The feature that really defines a cell is the
  plasma membrane or cell membrane, which is a thin
  sheet that holds the contents of the cell
  together and serves as a protective barrier from
  the surrounding environment. The fluid mosaic
  model of the plasma membrane consists of a lipid
  bi-layer in which proteins are imbedded. While
  the plasma membrane restricts the movement of
  some materials, it allows and even initiates the
  movement of other materials into and out of the
  cell.

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What are the functions of plant cell components?

• C. Cytoplasm is the living semi-fluid material
  inside the cell membrane and is home to a number
  of specialized structures called organelles.
• D. Organelles are small structures inside the
  cell that carry out the physiological processes
  of the organism.

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What are the functions of plant cell components?

• 1. Plastids are organelles that produce and store
  food.
• a. Chloroplasts are a type of plastid that
  contains green pigments called chlorophyll.
  Chlorophyll traps light energy for
  photosynthesis. Chloroplasts are found in cells
  exposed to light, so they are abundant in leaves
  and absent from root cells.
• b. Chromoplasts are plastids that give flowers
  and fruits their color.

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What are the functions of plant cell components?

• 2. The endoplasmic reticulum (ER) is an internal
  network of membranes extending throughout the
  cytoplasm. The endoplasmic reticulum contains
  many types of enzymes that catalyze different
  types of chemical reactions. There are two
  distinct forms of endoplasmic reticulum smooth
  and rough.
• a. The smooth endoplasmic reticulum is the site
  for the production of lipids (fats) and hormones.
  It is also a site that breaks down toxic
  chemicals.
• b. The rough endoplasmic reticulum produces the
  proteins for the cell secretion and cell
  membranes.

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What are the functions of plant cell components?

• 3. Proteins are processed, sorted, or modified in
  the golgi complex. These processes result in the
  complex molecules needed for plant growth. Many
  proteins manufactured in the ER pass through the
  golgi complex.
• 4. Mitochondria convert sugar into energy through
  cellular respiration. With mitochondria, the
  plant is able to convert the food that it has
  made and stored into a form of energy.

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What are the functions of plant cell components?

• 5. The nucleus is the command center of the cell.
  It holds the genetic information for a cells
  activities within a nuclear membrane.
• a. The nucleus is surrounded by a nuclear
  membrane. Flowing through the nuclear membrane
  are materials needed for protein synthesis and
  fluids carrying chemical messages between the
  cytoplasm and the nucleus.
• b. Chromosomes contained in the nucleus hold the
  genetic blueprint of the organism and direct all
  functions of the cell, including protein
  synthesis. Chromosomes are made of chromatin.
• (1) Chromatin is a complex of deoxyribonucleic
  acid or DNA molecules (35 percent), RNA (5
  percent), and protein (60 percent).
• (2) Segments of chromosomes, or genes, are units
  of hereditary data that dictate the activity and
  structure of a cell. Each chromosome contains
  thousands of genes.
• c. A nucleolus is a specialized structure in a
  nucleus that is the site of ribosome synthesis.

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What are the functions of plant cell components?

• 6. Ribosomes are bead-like structures found on
  the endoplasmic reticulum. Ribosomes are the
  major site for the assembly of amino acids into
  proteins.
• 7. The vacuole is a large sac bound by a
  membrane. It may occupy up to 90 percent of the
  cell. It serves to transport and store water,
  foods, salts, minerals, pigments, proteins, and
  wastes.

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What are the functions of plant cell components?

• E. The organelles within a cell have thin
  membranes used to compartmentalize or isolate
  different conditions from other organelles. For
  example, mitochondria and chloroplasts are bound
  with membranes. Different intracellular pH,
  enzyme systems, and more can be noted within each
  organelle. This enables the cell to perform
  different metabolic activities at the same time.

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What is the role of cell division, cell
elongation, and cell differentiation in plant
growth? What are the different types of plant
tissue?

• II. Growth of higher plants takes place through
  three essential processes, and vascular plants
  have three types of mature tissues.
• A. Cell division is simply the increase in the
  number of cells, which is accomplished through
  mitosis.
• B. Cell elongation is the enlargement of the
  individual cells, which results in growth of the
  entire tissue or organ. Auxins and gibberellins
  are responsible for cell elongation.

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What is the role of cell division, cell
elongation, and cell differentiation in plant
growth? What are the different types of plant
tissue?

• C. Cell differentiation allows cells to take on
  specific functions. Cell differentiation is
  important to multicellular plants, whereas
  single-cell plants have no need to have different
  cell types. The cells of the higher plants are
  programmed to become specialized and make up the
  various plant organs. Some cells specialize as
  root cells that absorb water and nutrients. Some
  conduct water and minerals throughout the plant.
  Others become leaf cells containing chloroplasts
  and function to produce food for the plant.

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What is the role of cell division, cell
elongation, and cell differentiation in plant
growth? What are the different types of plant
tissue?

• D. Vascular plants have three types of mature
  tissues.
• 1. Dermal tissues consist of the epidermis or
  external covering of the leaves, stems, and
  roots. Dermal tissues offer a barrier to
  infectious organisms and other invaders.
• a. The epidermis is made of closely packed cells
  that secrete a waxy cuticle to reduce water loss.
  The epidermis is a single layer of cells
  associated with plants that exhibit primary
  growth. Specialized epidermal cells called guard
  cells control the opening and closing of the
  stomata through which the diffusion of carbon
  dioxide, oxygen, and water vapor is allowed.
• b. Dermal tissue on secondary woody growth is a
  few too many cells thick and forms the familiar
  bark of trees.

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What is the role of cell division, cell
elongation, and cell differentiation in plant
growth? What are the different types of plant
tissue?

• 2. Vascular tissues are the conductive vessels of
  the plant. They transport water, minerals, food,
  and hormones. Specialized vascular tissues
  include the xylem, which conducts water and
  minerals upward from the roots, and the phloem,
  which transports food.
• 3. Ground tissue (fundamental tissue) includes
  all the parts of the plant other than dermal or
  vascular tissues. The bulk of a plant consists of
  ground tissue consisting of parenchyma,
  collenchyma, and sclerenchyma cells.

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What are the basic types of plant cells?

• III. Genetic information and environmental
  conditions determine the types of cells that a
  plant produces. With the appropriate signals,
  various types of cells are produced.
• A. Parenchyma cells are found throughout a plant
  and typically lack a secondary cell wall
  associated with rigid strength for support. The
  palisade layer and spongy mesophyll cells in
  leaves are parenchyma cells. Modified parenchyma
  cells compose a large portion of the pith (the
  center part of a stem). There they serve as
  storage facilities for starch, oil, water, and
  salt. The pith is very evident in corn and sugar
  cane.

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What are the basic types of plant cells?

• B. Collenchyma cells are located under the
  epidermis of the stem, along leaf veins, and at
  corners of angular stems. They have thick, yet
  flexible cell walls that provide structural
  support for the plant.
• C. Sclerenchyma cells are found throughout a
  plant and function as a support. These cells have
  a hard, thick secondary cell wall composed, in
  part, of a material called lignin, which is a
  molecule that provides strength and rigidity to
  the cell. A long type of sclerenchyma cell is
  called fiber. Fiber cells are abundant in wood
  and bark. A form of sclerenchyma cell that is
  short and cubical is the sclereid. It is found in
  the shell of nuts and the stones of fruit, such
  as peaches.

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What are the basic types of plant cells?

• D. Tracheid cells are one of four types of cells
  found in the xylem. The others are vessel
  elements, parenchyma, and fibers. Tracheids are
  long and tapering in shape. They are dead cells
  and hollow. Their role is to conduct water and
  minerals throughout the plant. Water passes from
  one cell to another through thin places in the
  cell wall called pits. Tracheids also contribute
  to the structural support of the plant.

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What are the basic types of plant cells?

• E. The vessel elements are found in the xylem
  where they conduct water and minerals and provide
  structural support for the plant. Vessel element
  cells are hollow. At the end of the cell walls,
  there are perforations or holes that allow the
  free flow of water from one cell to the next.
  Vessel cells also have pits along the sides of
  the cells that permit the lateral movement of
  water.

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What are the basic types of plant cells?

• F. The sieve tube member is a major element of
  the phloem. Other cells that compose phloem
  tissue are companion cells, parenchyma, and
  fibers. Sieve tube members are stacked end to end
  to form sieve tubes. There are holes at the end
  of each cell called sieve plates through which
  sugars are moved. Sieve tube members are living
  cells at maturity, but many organellesincluding
  the nucleus, vacuole, and ribosomesvanish as the
  cell matures.

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What are the basic types of plant cells?

• G. Companion cells are associated with sieve tube
  members. They have many connections with adjacent
  sieve tube members. Companion cells do not
  conduct sugar throughout the plant. They do,
  however, play an important role in transporting
  sugars from photosynthetic parenchyma cells to
  the sieve tube members.

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What are the basic types of plant cells?

• H. Cork cells are produced to the outside of the
  cork cambium and result in the outer covering of
  secondary growth. Cork cells have waterproof
  characteristics and fire-retardant attributes.

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How do primary and secondary plant growth
compare?

• IV. The growth of a plant takes place in
  specialized areas of the plant called the
  meristems. The meristem tissue consists of
  unspecialized cells that are capable of mitosis.
  Two types of growth result from cell division in
  meristem regions primary and secondary growth.
• A. Primary plant growth occurs in areas called
  apical meristems. Apical meristem tissue is found
  at the tips of roots and at the end of stems.
  Growth at the apical meristem increases the
  length of the plant. Primary growth occurs in
  herbaceous and woody plants.

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How do primary and secondary plant growth
compare?

• 1. The meristem of a root is located right behind
  the root cap, which is a layer of cells that
  protect the meristem as the root grows through
  the soil. Just behind the root cap is the area of
  cell division. Further back is an area of cell
  elongation. As the cells in the root mature, they
  differentiate to perform specific functions. In a
  root system, the cells might become root hairs,
  xylem, phloem, etc.
• 2. The meristem of the shoot has areas of cell
  division, cell elongation, and cell maturation.
  The structure of the stem apical meristem differs
  from the root apical meristem in that it has
  embryonic leaves known as leaf primordia and
  embryonic buds called bud primordia. As the cells
  in these immature structures divide, elongate,
  and mature, they become the leaves and stems of
  the plant.

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How do primary and secondary plant growth
compare?

• B. Secondary plant growth takes place only in
  woody plants. It takes place in the lateral
  meristem this tissue is found on the sides of
  roots and stems. Secondary plant growth involves
  cell division in layers ringing the stem. The
  result is an increase in the width of the stem or
  trunk of the plant. Two lateral meristems are
  involved in secondary growth.

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How do primary and secondary plant growth
compare?

• 1. Vascular cambium is a layer of meristematic
  tissue found between the wood and the bark. It
  produces secondary xylem to the inside of the
  vascular cambium and secondary phloem to the
  outside. Cell division occurs only when the plant
  is actively growing, primarily during the spring
  and summer.
• 2. The cork cambium is located in the outer bark
  region, and the cells produced there form the
  periderm (the outer bark). Cork cambium produces
  cork cells that replace the epidermis present
  during primary growth. The periderm ranges from
  several cells in thickness to many cells.
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REVIEW

• 1. What are the functions of plant cell
  components?
• 2. What is the role of cell division, cell
  elongation, and cell differentiation in plant
  growth? What are the different types of plant
  tissue?
• 3. What are the basic types of plant cells?
• 4. How do primary and secondary plant growth
  compare?