Plant Growth and Differentiation

Organ Systems

  1. Root Organ System Functions

       1. anchoring the plant in the soil    2. absorbing water and nutrients from the soil    3. storing food and nutrients for future use.

  1. Shoot Organ Sytem Functions

       1. leaves do photosynthesis    2. transporting water and nutrients    3. producing flowers and fruits for reproduction.

Organs

  1. Root Organ Function

       1. anchoring the plant to the ground    2. absorbing water and nutrients from the soil    3. stores food and nutrients

  1. Stems Organ Function

       1. support to the Shoot (leaves, flowers, fruit)    2. conduit between root and shoot    3. main site of growth

  1. Leaves Organ Function

       1. site for photosynthesis

\ \ Taproot: 1 giant root

Fibrous root: many tiny branching roots

Adventitious root: come from organ other than the root (stem/leaf), ex: fibrous root

Nodes: point where leaves are attached

Internode: stem space between 2 nodes

Apical bud:

  1. terminal bud
  2. at shoot tip
  3. elongation of young shoot

Apical Dominance:

  1. apical bud (top) blocks the growth of lateral buds (side)
  2. plant growing taller rather than wider.
  3. central stem dominates side stem

Petiole: stalk in leaf that joins leaf to node

Cotyledon: Monocot

Dicotyledon: Dicot

Monocot:

  1. 1 seed leaf
  2. parallel viens
  3. lateral/fiber roots

Dicot:

  1. 2 seed leaves
  2. branching veins
  3. tap root

Dermal Tissue: protection to plants

Epidermis: dermal tissue in non-woody plants

Periderm: corky, dermal tissue in woody plants

Vascular Tissue: transport water and nutrients

Xylem: moves water and dissolved minerals up from root to shoot

Phloem: transports organic nutrients from where they are made to where they are needed

Ground tissue: storage, photosynthesis, support

Pith: internal to vascular tissue in stem, ground tissue

Cortex: external to vascular tissue in stem, ground tissue

Parenchyma Cells:

  1. thin flexible primary walls
  2. no secondary walls
  3. least specialized
  4. perform most metabolic functions
  5. can divide and differentiate

Collenchyma Cells

  1. grouped in strands
  2. support young parts of plant shoot
  3. no secondary walls
  4. thick uneven cell walls
  5. flexible support, don’t restrict growth

\ Sclerenchyma Cells

  1. rigid thick secondary walls
  2. dead at functional maturity
  3. two types: sclereids and fibers

\ Sclereids: short, irregular shape, thick secondary walls

Fibers: long, slender, in threads

\ Tracheid’s and Vessels

  1. water conducting cells of Xylem Vascular Tissue
  2. transport water and minerals to shoot
  3. dead at maturity

\ Sieve elements

  1. sugar conducting cells of Phloem Vascular Tissue
  2. transport sugar to root of plant
  3. alive at maturity but lack organelles

\ Meristem:

  1. generate new cells
  2. two types made: initials and derivatives

\ Initials: cells stay in meristem and keep its cell supply in check

Derivatives: cells migrate away from meristem and undergo differentiation to become specialized

\ Indeterminate growth: growth throughout life

Determinate growth: stop growing at a certain size

\ Primary growth:

  1. lengthens root and shoot
  2. longitudinal growth, adds thickness

\ 3 Zones of Primary Growth in Root:

  1. Cell Division
  2. Elongation
  3. Maturation

\ Root cap: covers root tip and protects apical meristem

\ Secondary growth:

  1. in stems and roots of woody plants, rare in leaves
  2. adds girth

\ Secondary plant body is tissue produced by:

  1. vascular cambium: meristematic cells 1 cell thick
  2. cork cambium protective cover, periderm

\ Cell Division: increases number of cells = growth

Cell Expansion: actual increase in plant size

Cellulose microfibrils: in cell wall and restrict direction of elongation

Cytoplasmic microtubules: big role in cell division and expansion

Morphogenesis:

  1. development of body form and organization
  2. controlled by homeotic genes

Pattern formation:

  1. development of specific structures in specific locations
  2. determined by positional information

Polarity

  1. having structural or chemical differences at different ends of organism
  2. determines positional information

Polarization: started by first asymmetrical division of plant zygote

Cellular Differentiation:

  1. cells in developing organism synthesize different proteins and diverge in structure/function
  2. depends on positional information
  3. affected by homeotic genes

\ Phase change: developmental phases from juvenile to adult

Flower formation:

  1. vegetative to reproductive growth
  2. meristem identity genes switched on

Organ identity genes:

  1. plants homeotic genes
  2. regulate development of floral pattern

Mutation in plant organ identity:

  1. abnormal floral development

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