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Plant%20Structure,%20Growth%20

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Title: Plant%20Structure,%20Growth%20


1
Plant Structure, Growth Development
  • Packet 35
  • Chapters 35 38

2
The Plant Body
3
Introduction
  • Genes and the environment affect plant structure.
  • Plants exhibit structural responses to their
    specific environment.
  • Plasticity
  • Explains why no two plants are identical.
  • Mangroves and cacti

4
Introduction II
  • Plants are multi-cellular, have organs that are
    composed of different tissue (previously
    covered), and tissue which are composed of
    different cell types (previously covered).

5
Roots, Stems Leaves
6
Introduction
  • The basic morphology of plants reflects
    adaptations that have developed so that an
    organism can inhabit and obtain resources from
    soil and air.
  • Two systems
  • Subterranean root system
  • Aerial root system
  • Stems and leaves
  • Neither system is independent of the other

7
Introduction II
  • Most absorption occurs near the root tips
  • Vast number of root hairs found
  • Increase the surface area of the root
  • Extensions of epidermal cells
  • Previously covered
  • Adventitious tissue is any tissue that grows in
    an atypical location
  • Roots that develop out of above ground stems or
    leaves are called adventitious roots
  • Provide additional support for taller plants.

8
Root System
  • Roots are generally underground, obtains water
    and dissolved nutrient minerals for the plant and
    stores food.
  • Anchors the plant firmly in place.
  • Fibrous root systems
  • Observed in seedless vascular plants and most
    monocots.
  • Mats of thin roots that spread out through the
    soil
  • Grasses and mangroves

9
Root System
  • Taproot System
  • Make up many eudicots and gymnosperms
  • Consist of one large vertical root that produces
    many smaller lateral or branch roots
  • Firmly anchors the plant in the soil
  • Some store food (starch) that can be consumed by
    the plant when the plant is fruiting or flowering
  • Most tree species

10
Modified Roots
11
Modified Roots I
  • Prop Roots
  • Develop from branches, or a vertical stem and
    grow downward into the soil to help support
    certain plants in an upright position
  • Fichus tree South Florida?
  • Buttress Roots
  • Swollen bases or braces that support certain
    tropical rainforest trees that have shallow root
    systems

12
Modified Roots II
  • Pneumatophores
  • Aerial breathing roots that may assist in
    getting oxygen to submerged roots
  • Contractile Roots
  • Roots that grow into the soil and then contract
  • Pulling plant deeper into the soil
  • Corms
  • bulbs

13
Mutualistic Relationship Between Roots Other
Organisms
14
Relationships
  • Mycorrhizae
  • Mutually beneficial associations between roots
    and soil fungi
  • Root nodules
  • Swellings that develop on roots of legumes and
    house millions of rhizobia (nitrogen fixing
    bacteria)
  • Root Graft
  • Natural connection between the roots of trees
    belonging to the same or different species.

15
Shoot System
16
Introduction I
  • Shoots consist of stems and leaves
  • Vegetative
  • Leaf bearing
  • Reproductive
  • Flower bearing

17
Stems
  • Stem
  • Alternating system of nodes
  • Locations where the leaves are attached
  • Internodes
  • Stem segments between nodes
  • Auxiliary Bud
  • Angle, or axil, formed by each leaf of the stem
  • Has the potential to form a branch
  • Most though are dormant

18
Stems II
  • Growth of a young shoot is usually concentrated
    at its apex (tip), where there is a terminal bud
    with developing leaves and a compact series if
    nodes and internodes
  • The presence of terminal bud prohibits the growth
    of the axillary bud
  • Apical dominance
  • evolutionary response that directs growth toward
    light

19
Modified Stems
  • Stolons/Runners
  • Grow on the surface of the ground
  • Increase surface area
  • Can colonize asexually if plant is fragmented
  • Strawberry
  • Rhizomes
  • Horizontal stems that grow underground
  • Ginger
  • Tubers
  • Swollen ends of rhizomes specialized for storing
    food
  • Potato
  • Bulbs
  • Vertical, underground shoots consisting mostly of
    swollen bases of leaves that store food
  • onions

20
Leaves
  • The main photosynthetic organ
  • Consist of a flattened blade and a petiole
  • Stalk
  • Joins the leaf to the node on the stem
  • Leaves are in various sizes, shapes and
    arrangement of leaves.

21
Differences Between Plant Animal Growth
22
Differences Between Plant Animal Growth
  • Growth in plants, unlike animals, is localized in
    specific regions called meristems, and involves
    three processes
  • Cell division
  • Cell elongation
  • Cell differentiation
  • Plant growth is not limited to an embryonic
    period
  • Most plants have indeterminate growth

23
Life Cycles
24
Life Cycles
  • Annuals
  • Complete their life cycle from germination to
    flowering and seed production and death in one
    year or less
  • Wildflowers
  • Biennials
  • Live for two years
  • There is a dormant period between vegetative
    growth and flowering
  • Carrots
  • Beets
  • Perennials
  • Long lived plants and include trees, shrubs and
    some grasses.

25
Indeterminate Growth
  • Unrestricted growth in stems and growth
  • This pattern of growth depends in the location of
    the meristems
  • Meristems are regions of undifferentiated,
    embryonic cells. Initially, the cells are
    totipotent and can differentiate/mature into any
    other type of cell.
  • Apical meristems
  • Responsible for primary growth
  • Located at the tips of roots, shoots and within
    the buds of stems

26
Indeterminate Growth
  • Lateral meristems
  • Cylinders of dividing cells that extend along the
    length of the roots and shoots provide for an
    increase in girth
  • Responsible for secondary growth
  • Vascular cambium
  • Cork cambium

27
Primary vs. Secondary Growth
28
Primary Growth
  • Increase in stem or root length
  • Occurs in all plants
  • Restricted to the youngest part of the plant.

29
Primary Growth
  • Fig 34.12
  • Primary Growth of Root
  • Fig 35.15
  • Primary Growth of Shoot

30
Secondary Growth
  • Increase in stem or root girth
  • Typically occurring in long cylinders of
    meristematic cells throughout the length of older
    stems and roots
  • Occurs in all gymnosperms, most eudicots and
    rarely in monocots.

31
Secondary Growth IILateral Meristems
  • Vascular cambium
  • Produces secondary xylem (wood) and secondary
    phloem
  • Secondary xylem
  • Interior
  • Secondary phloem
  • Exterior
  • Cork Cambium
  • Produces thick, tough covering (cork cells) for
    stems and roots that replace the epidermis
  • Recall what wood is composed of?
  • Tracheids
  • Vessel elements
  • Fibers

32
  • An overview of primary and secondary growth
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