Plants and Plant Adaptations

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Plants and Plant Adaptations

• How is the plant kingdom different from other
  kingdoms?
• 4/21/08

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Principle Organs

• Roots? absorb water and dissolved nutrients, hold
  plant upright
• Stems? support plant body and transport nutrients
• Leaves? carry out photosynthesis and protect
  against water loss

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Tissue Systems

• 3 tissue systems
• Dermal tissue? outermost layer
• Cuticle? thick waxy layer covering outer surface
  of epidermal cells
• Roots have root hair
• Leaves contain guard cells
• Vascular tissue? transports nutrients throughout
  plant
• 2 types xylem and phloem
• Ground tissue? Between dermal and vascular
  tissues
• Parenchyma- packed with chloroplasts
• Collenchyma- help support larger plants
• Sclerenchyma-make ground tissue tough and strong
• Meristematic tissue? tips of shoots and roots
  responsible for growth

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Xylem

• Water conducting tissue consisting of tracheids
  and vessel
• Used to get water and minerals up through the
  plant

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Phloem

• Food conducting tissue consisting of sieve tube
  elements and companion cells
• Carries food from leaves to roots or stems

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Meristematic Tissue

• Plants grow as long as they live
• Meristematic tissue is the only tissue that
  produces new cells
• Apical meristem? group of undifferentiated cells
  that divide to produce increased length of stems
  and roots

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Structure and Growth
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Roots

• 2 types
• Taproots (dicots)
• One large primary root with small secondary roots
  
• Fibrous roots (monocots)
• Branch off in equal sizes

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Types of roots
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Root Structure

• Three layers of tissue in a root
• Epidermis outer layer
• Root hairs increase surface area
• Vascular tissue central cylinder
• Ground tissue tissue that lies between the
  others

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Root Structure cont

• Root cap protects meristematic tissue
• Cortex? spongy layer inside epidermis
• Endodermis? encloses the vascular tissue in the
  center

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Root Functions

• Anchor plant to ground
• Absorb water and nutrients from soil
• Endodermis surrounded by waterproof strip called
  Casparian strip
• Once water/minerals in cant get out
• Puts pressure on water causing it to rise inside
  xylem b/c no place to go.

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Root function
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Stems

• 3 important functions
• Produce leaves, branches, and flowers
• Hold leaves up in the sunlight
• Transport substances between roots and leaves
• 3 things stems have
• Nodes? leaf is attached
• Internodes? regions between nodes
• Buds? underdeveloped tissue that can produce new
  stems and leaves

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Stem function and structure
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Monocot vs Dicot Stems

• Monocot
• Vascular bundles scattered throughout stem
• Three tissues
• Vascular
• Epidermis
• Ground tissue
• Dicot
• Vascular tissue arranged in a cylinder (ring
  pattern)
• Parenchyma cells inside vascular bundles called
  Pith
• Parenchyma cells outside vascular bundle called
  Cortex

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Monocot Dicot
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Stem types
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Growth of Stems

• Primary
• Growth that occurs at the end of plants (increase
  length)
• Apical meristem
• Secondary
• Increase in width (lateral growth)
• Lateral meristematic tissue called vascular and
  cork cambium

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Leaves

• Structure
• Optimized for absorbing light and carrying out
  photosynthesis
• Cuticle waterproof outer covering
• Vascular bundles surrounded by parenchyma and
  sclerenchyma cells
• Blades? flattened sections that collect sunlight
• Petiole? thin stalk that attaches the blade to
  the stem

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Leaves

• Functions
• Photosynthesis
• Transpiration
• Gas Exchange

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Leaves

• Functions
• Photosynthesis
• Mesophyll? packed with chloroplasts and carries
  out photosynthesis
• Transports carbohydrates to phloem
• Stomata? opening allows carbon dioxide and oxygen
  to diffuse in and out of leaf
• 2 guard cells control opening and closing of
  stomata
• Open during dayphotosynthesis
• Closed at night water loss

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Leaves

• Functions
• Transpiration? water loss from a plant through
  its leaves
• Water is replaced by water drawn into leaf from
  xylem
• Gas Exchange
• Between air spaces in the spongy mesophyll and
  opening stomata
• Plants keep stomata open just enough to allow
  photosynthesis to take place

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Transport of Water

• Capillary Action
• Tendancy of water to rise in a thin tube
• Water forms H bonds with one another
• Transpiration
• Major force in water transport
• Controlled by water moving into and out of spongy
  mesophyll
• Water enters guard cells open stomata
• Water lost guard cells close stomata

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Nutrient Transport

• Phloem
• Pump sugars into a plants fruits or into roots
• Pumps sugars back out in spring to aid in growth

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Nutrient Transport

• Source to Sink
• Source? where sugars are produced
• Sink? where sugars are stored

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Reproduction with Cones and Flowers

• Alternation of Generations
• Sporophyte (diploid)begins with zygote
• Gametophyte (haploid)forms gametes
• Life cycle of Gymnosperms
• Reproduction takes place in cones
• Two types of cones
• Pollen and Seed Cone
• Near the base of scale are two ovules (female
  gamete)

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Reproduction with Cones and Flowers cont

• Pollination
• Gymnosperms life cycle takes two years to
  complete
• Male cones release pollen in spring
• Sticky secretion on female cone called
  pollination drop (catches pollen)
• Fertilization and Development
• Pollen lands near ovule begins to grow a pollen
  tube? two haploid sperm nuclei

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Reproduction with Cones and Flowers cont

• Structure of Flowers
• Four types of specialized leaves
• Sepals, petals, stamens, carpels
• Sepals and Petals
• Sepals? outermost circle of floral parts
• Petals? brightly colored found just inside sepals
• Sterile leavesno reproductive cells

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Reproduction with Cones and Flowers cont

• Stamens and Carpels
• StamenAnther and Filament (male Gametophyte)
• Filamentlong thin stalk that supports an anther
• Anther oval sac where meiosis
• Carpel or pistal? female gametophyte
• Ovarybroad base of the carpel (contains eggs)
• Style stalk that rises from the ovule
• Stigmatop of style

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Parts of a Flower
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Parts of a flower
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Reproduction with Cones and Flowers cont

• Life cycle of Angiosperms
• Reproduction takes place inside flower
• Pollination
• Most angiosperms are pollinated by animals

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Seed and Fruit Development

• Ovary walls thicken form fruit
• Fruit? applies to any seed enclosed within embryo
  wall
• Example of fruits
• Peas, corn, beans, rice, tomatoes, cucumbers,
  apples, grapes, strawberries

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Plant Hormones Continued

• Auxins
• Stimulate cell elongation
• Gibberellins
• Produce increases in size, particularly in stems
  and fruit
• Ethylene
• Stimulates fruits to ripen

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Plant Hormones

• Cytokinins
• Plant hormone that are produced in growing roots
  and in developing fruits and seeds
• Stimulate cell division and the growth of lateral
  buds
• Cause dormant seeds to sprout

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Tropisms

• Phototropismresponse of plant to light
• Plants to bend toward the light
• Gravitropism response of plant to gravity
• Roots grow toward gravity, shoots grow away
• Thigmotropismresponse of plant to touch
• Photperiodism responsible for the timing of
  seasonal activities such as flowering and growth.
• Dormacy
• Leaf Abscissionlayer of cells seal the leaf from
  the plant at the petiole

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Types of Plants

• Carnivorouseat insects to gain nitrogen needed
• Soil usually to acidic and lack nitrogen
• Parasites extract water and nutrient from host
• Harms host
• Epiphytes grow directly on the bodies of other
  plants
• Make own food and gather water

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Defense Mechanisms

• Chemical
• Plants manufacture compounds that effect insects
• Hormones disrupt reproductive and growth cycles
  of some insects
• Nicotine in tobacco plant is thought to act as a
  natural insect repellent
• Disrupts the nervous system of the plant