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