Three tissue systems make up the plant body

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Three tissue systems make up the plant body

• A tissue system consists of one or more tissues
  organized into a functional unit
• Roots, stems, and leaves are made of three tissue
  systems
• The epidermis
• The vascular tissue system
• The ground tissue system

Leaf
Stem
Root
Epidermis
Groundtissue system
Vasculartissue system
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The epidermis covers and protects the plant

• The cuticle is a waxy coating secreted by
  epidermal cells that helps the plant retain water
• The vascular tissue contains xylem and phloem
• It provides support and transports water and
  nutrients
• The ground tissue system functions mainly in
  storage and photosynthesis
• It consists of parenchyma cells and supportive
  collenchyma and sclerenchyma cells

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• The ground tissue system of the root forms the
  cortex

• The cortex consists mostly of parenchyma tissue
• The selective barrier forming the innermost layer
  of the cortex is the endodermis

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TISSUE SYSTEMS IN A YOUNG DICOT ROOT
Xylem
VASCULARTISSUESYSTEM
Phloem
EPIDERMIS
GROUNDTISSUESYSTEM
Cortex
Endodermis
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These microscopic cross sections of a dicot and a
monocot indicate several differences in their
tissue systems

• (vascular and ground tissue systems different)

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• The three tissue systems in dicot leaves

• The epidermis consist of pores called stomata
  (singular, stoma involved in water loss) flanked
  by regulatory guard cells (regulate size of
  stomata, allow gas exchange)

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• The vascular tissue consists of a network of
  veins composed of xylem and phloem

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• The ground tissue system of a leaf is called
  mesophyll and is the site of photosynthesis

Figure 31.6D
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Plant growth Primary growth lengthens roots and
shoots

• Most plants exhibit indeterminate growth
• They continue to grow as long as they live
• In contrast, animals are characterized by
  determinate growth
• They cease growing after reaching a certain size

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• Annuals complete their life cycle in a single
  year or growing season

• Examples wheat, corn, rice, and most wildflowers
• Biennials complete their life cycle in two years,
  with flowering occurring in the second year
• Examples beets and carrots
• Perennials live and reproduce for many years
• Examples trees, shrubs, and some grasses

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• Growth in all plants originates in tissues called
  meristems
• Meristems are areas of unspecialized, dividing
  cells
• Apical meristems are located at the tips of roots
  and in the terminal buds and axillary buds of
  shoots
• They initiate primary growth, lengthwise growth
  by the production of new cells
• Roots and stems lengthen further as cells
  elongate and differentiate

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LOCATION OF APICAL MERISTEMS, RESPONSIBLE FOR
PRIMARY GROWTH
Terminal bud
Axillary buds
Arrows directionof growth
Roottips
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PRIMARY GROWTH

• ENABLES ROOTS TO PUSH THROUGH THE SOIL
• ALLOWS SHOOTS TO INCREASE EXPOSURE TO LIGHT AND
  CARBON DIOXIDE

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SECONDARY GROWTH INCREASES THE GIRTH OF WOODY
PLANTS
An increase in thickness secondary growth It
involves cell division in two cylindrical
meristems Vascular cambium Cork cambium
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• Vascular cambium thickens a stem
• It first appears between the primary phloem and
  the primary xylem
• Then it gives rise to secondary phloem and
  secondary xylem
• Larger than the previous layer
• Therefore, it thickens the root or stem

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VASCULAR CAMBIUM DEVELOPS INBETWEEN PRIMARY XYLEM
AND PHLOEMTHEN, VASCULAR CAMBIUM DEVELOPS INTO
SECONDARY XYLEM AND PHLOEM
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VASCULAR CAMBIUM EXPLAINS RINGS ON TREES CAN
DETERMINE THE AGE

• SECONDARY XYLEM MAKES UP THE WOOD OF A TREEWOOD
  GETS THICKER AS VASCULAR CAMBIUM PRODUCES
  SECONDARY XYLEMRINGS APPEARS BECAUSE OF UNEVEN
  GROWTH DURING THE YEAR LITTLE GROWTH DURING
  WINTER

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UNLIKE XYLEM, THE EXTERNAL TISSUES DO NOT
ACCUMULATE OVER THE YEARS

• EXTERNAL LAYERS EPIDERMIS AND CORTEX ARE THE
  RESULT OF PRIMARY GROWTH
• SECONDARY GROWTH EPIDERMIS FALLS OFF AND
  REPLACED BY AN OUTER LAYER CORK
• CORK PRODUCED BY CORK CAMBIUM WHICH FORMS FROM
  CELLS IN THE CORTEX
• BARK EVERYTHING EXTERNAL TO THE VASCULAR
  CAMBIUM CORK, CORK CAMBIUM AND SECONDARY PHLOEM

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ORIGINAL CORK AND CORK CAMBIUM FALL OFFNEW CORK
CAMBIUM FORMS FROM THE PHLOEM
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Plant reproduction The structure specfic to
reproduction is the flower

• The angiosperm flower is a reproductive shoot
  consisting of
• sepals
• petals
• stamen
• carpels

Stigma
Carpel
Anther
Ovary
Stamen
Ovule
Sepal
Petal
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• Sepals are usually green and resemble leaves in
  appearance

• Sepals enclose and protect the flower bud before
  the flower opens
• Petals are often bright and colorful
• They attract insects (pollinators)

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• Stamens are the male reproductive organs of plants

• Pollen grains develop in anthers, at the tips of
  stamens meiosis occurs in the anthers
• Carpels are the female reproductive organs of
  plants
• The ovary at the base of the carpel houses the
  ovule which contains the developing egg
• At the tip of the carpel is the stigma which is
  the receiving surface for pollen grains brought
  from other flowers or the same flower -
  pollination

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The life cycle of an angiosperm involves several
stages

• Fertilization occurs in the ovule (inside the
  ovary) then maturation into a seed containing
  the embryo
• The ovary also develops into a fruit which
  protects the seed
• The seed grows and the embryo develops into a
  seedling
• The seedling grows into a mature plant

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The sexual life cycle of a flowering plant
Ovary, containingovule
Embryo
Fruit,containing seed
Seed
Mature plant withflowers, wherefertilization
occurs
Seedling
Germinating seed
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The development of pollen and ovules culminates
in fertilization

• The plant life cycle alternates between diploid
  (2n) and haploid (n) generations
• What does diploid and haploid mean?
• What is mitosis and meiosis?

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• ANGIOSPERM LIFECYCLE

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• Sporophyte
• diploid plant body
• produces anthers (male) and ovules (female)
• this is where meiosis occurs
• Haploid spores result and then divide by mitosis
  producing a multicellular gametophyte
• Male produce 2 cells 1 for fertilization and 1
  for double fertilization
• Female produce a haploid egg for fErtilization
  and a large central cell with 2 haploid nuclei
  for double fertilization

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TWO TYPES OF FERTILIZATION

• 2 sperms produced
• 1 sperm fertilizes the egg producing a zygote
• fertilization
• 1 sperm contributes its haploid nucleus to the
  large central cell of the embryo sac
• Produce a cell with a triploid nucleus (3n)
• Produce tissue that nourishes the embryo
  (endosperm)
• Double fertilization

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Life cycle of an angiosperm
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The ovule develops into a seed

• After fertilization, the ovule becomes a seed
• The fertilized egg (zygote) within the seed
  divides into two cells then after repeated
  divisions it become an embryo
• From double fertilization - the other fertilized
  cell develops into the endosperm, which stores
  food for the embryo
• A resistant seed coat protects the embryo and
  endosperm

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The zygote undergoes cell divisions becomes an
embryo and then a seed

• The triploid cell becomes the endosperm
• A seed coat also develops

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There will be no more growth until the seed
germinatesSeed dormancy is an important
evolutionary adaptation in which growth and
development are suspended temporarily

• It allows time for a plant to disperse its seeds
• It increases the chance that a new generation of
  plants will begin growing only when environmental
  conditions favor survival

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• At the same time that seed development is
  occurring, fertilization triggers hormonal
  changes that causes a flowers ovary to mature
  into a fruit
• The fruit protects seeds and helps disperse them
  from the parent plant

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DIFFERENT PARTS OF THE FLOWER DEVELOP INTO
DIFFERENT PARTS OF THE FRUIT
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There is a correspondence between flower and
fruit in a pea plant

• The wall of the ovary becomes the pod
• The ovules develop into the seeds
• The sepals of the flower become the base of the
  pea pod
• The carpel remains at the other end of the pod

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Seed germination continues the life cycle

• A seed starts to germinate when it takes up
  water, expands, and bursts its seed coat
• Metabolic changes cause the embryo to resume
  growth and absorb nutrients from the endosperm
• An embryonic root emerges, and a shoot pushes
  upward and expands its leaves

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Asexual reproduction produces plant cells

• Asexual reproduction vegetative propagation
• Offspring are derived from a single parent
• Asexually produced identical organism clone
• Advantages
• Can produce a large number of offspring
• Can also perform plant cell cultures -
  genetically alter plants, foreign genes can be
  inserted