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UNIT III: PLANT FORM AND FUNCTION

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Title: UNIT III: PLANT FORM AND FUNCTION


1
http//www.csdl.tamu.edu/FLORA/hdwimages1/
  • UNIT III PLANT FORM AND FUNCTION
  • Plant structure and growth
  • Plant nutrition
  • Plant reproduction and development

Cardinal Flower
Red Maple
Arabidopsis thaliana
2
Purves et al 2000
3
Purves et al 2000
Evolutionary relationships among the Angiosperms.
The monocots and eudicots are the largest
monophyletic groups among the angiosperms. (The
other groups remain to be placed accurately on
the phylogenetic tree).
4
Monocotylenous and Dicotyledonous Plants
  • Monocots
  • 65,000 species
  • Lilies, irises, orchids, cattails, all the
    grasses and grains
  • Monocot lineage, taxon, is monophyletic evolved
    from dicot ancestor
  • Dicots
  • 175,000 species
  • Most trees and shrubs
  • Most annual plants mints, sunflowers, peas,
    snapdragons
  • Most dicots are in members of the Eudicot lineage
    a monophyletic taxon

5
Palms
Grasses
Lilies
Purves et al 2000
Examples of Monocot angiosperms
6
Purves et al 2000
Cactus
Flowering Dogwood
Rose
Examples of Dicots (more specifically, Eudicots)
7
Source Freeman (2002)
Phylogenetic relationships among Angiosperm
lineages
Angiosperms
Several lineages related to magnolias
Oldest living angiosperm lineages
Eudicots
Monocots
Non-Angiosperms
Lineages in green are traditionally called dicots
- the seeds of these lineages have two seed
leaves. Dicots dont form a monophyletic
group -- ie monocots are descended from a dicot
lineage Eudicots are a monophyletic group that
includes much of the angiosperm diversity
8
Phylogenetic relationships of the orders of
flowering plants (AGP, 1998)
  • Monocots apparently diverged from dicots early in
    the history of the phylum

http//www.csdl.tamu.edu/FLORA/newgate/cronang.htm
9
ANNUAL, BIENNIAL AND PERRENIAL PLANTS Annual
Plants Life cycle (vegetative growth and
reproduction) occurs in the course of a single
year die after single year of growth. Most are
entirely herbaceous, ie, lack secondary growth,
secondary tissue (wood) some (eg sunflowers)
produce poorly developed secondary tissues. Many
crop plants (incl. corn, wheat, soybeans) are
annuals. Biennial Plants Narrow definition life
cycle takes two years to complete. Generally,
vegetative growth in the first year flowering
and senescence in the second year. Many
bienniels flower in year 3 or later, but all
flower only once before dying. Much less common
than annuals. Crop plants include carrots,
cabbage. Wild plants include evening primrose,
queen annes lace Perennial Plants Life cycle
extends for for multiple, often many years
flower repeatedly and live for many years. Most
vascular plants are perennials. Many are
herbaceous plants (eg wildflowers of prairie,
wetlands and woodlands) that usually lack
secondary growth in stems stems die back each
year following food accumulation, often in
substantial roots Trees and shrubs have secondary
growth and are perennial, they are either
deciduous (shed leaves at particular time of
year) or evergreen (leaves drop throughout year,
plant never appears leafless)
Desert annuals (above) and a giant redwood (below)
Sources Raven Johnson 1999, Purves 2000)
10
PLANT STRUCTURE AND GROWTH
  • The Angiosperm Body
  • root and shoot systems adaptations to
    terrestrial life
  • structural adaptations of protoplasts and cell
    walls specialized functions
  • plant tissue systems dermal, vascular and ground
  • Plant Growth
  • meristems continuously generate cells for new
    organs
  • Primary growth apical meristems
  • (Secondary growth lateral meristems)

11
  • BASIC ORGANIZATION OF PLANT BODY ADAPTATION TO
    TERRESTRIAL LIFE
  • Root system anchor absorption transport of
    water, ions, dissolved mineral nutrients food
    storage
  • Shoot system stem is scaffold for photosynthetic
    leaves and reproductive structures transport of
    sugars from photostynthetic to non-photosynthetic
    parts of plant

Shoot
Solomon et al 1999
Campbell et al 1999
Root
Roots
Shoots
12
Biological Organization in Plants Cells Plant
cells are eukaryotic, with some unique
modifiations, including the cell wall. Cell
types include Parenchyma, Collenchyma
Schlerenchyma, Tissues Tissues plant cells are
organized into tissues groups of cells that form
a structural and functional unit. Simple plant
tissues consist of single cell type. Complex
plant tissues consist of two or more kinds of
cells. Tissue systems Groups of tissues that
extend throughout plant body Three main tissue
sytems ground, vascular, dermal Organs Roots,
stems. leaves, flower parts, and fruits are
referred to as organs because each is composed of
several different tissues. The tissue systems of
different plant organs fornm an interconnected
network througout the plant.
Shoot
Root
13
CELL SPECIALIZATION STRUCTURAL ADAPTATION IN
CELL WALLS AND CELL PROTOPLAST
In plant cell division, daughter cells secrete a
middle lamella that will adhere the adjoining
cells Each the secretes a primary cell wall of
cellulose and other polysaccharides, which grows
with growing cell Depending on cell
specialization, after growth to final size, cell
may lay down a secondary cell wall of
polysaccarides and, depending on cell type,
lignin (characteristic of wood) or suberin
(characteristic of cork, bark) Secondary cell
walls typically function in structural support or
waterproofing Protoplast cell contents
exclusive of cell wall
Purves et. al. 2000
14
CELL SPECIALIZATION STRUCTURAL ADAPTATION IN
CELL WALLS AND CELL PROTOPLAST
  • In addition to other features of Eukaryotic
    cells, plant cells have
  • cell wall
  • chloroplasts
  • central vacuole,

15
Raven Johnson 1999
Cell plate formation between two nuclei, during
plant cytokinesis
16
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17
Raven and Johnson 1999
18
  • PLANT CELLS ARE ORGANIZED INTO TISSUE SYSTEMS
  • Plant organs have three tissue systems that are
    continuous throughout the plant body. The tissue
    systems derive from meristem tissue localized
    regions of cell division
  • Meristems apical lateral meristems give rise
    to all cells and tissues
  • Ground tissue system storage, secretion,
    photosynthesis mostly parenchyma cells
  • Vascular tissue system conduct water minerals
    (xylem), carbohydrates, amino acids, hormones
    (phloem)
  • Dermal tissue system outer protective covering
  • We will discuss specialized reproductive tissue
    in a later lecture

19
THE THREE TYPES OF CELLS AND GROUND TISSUES IN
PLANTS
  • Parenchyma
  • Parenchyma cells are relatively unspecialized
    large vacuoles, thin primary wall (no secondary)
  • most common type of plant cell responsible for
    most of plant metabolic functions - primary sites
    of photosynthesis, starch storage.
  • Fleshy tissue of most fruits
  • Collenchyma
  • Collenchyma cells provide support to growing
    stems and leaves thickened primary cell walls
  • Relatively flexible, allowing organs to bend
    without breaking
  • Sclerenchyma
  • Sclerenchyma cells have tough, thick secondary
    walls, often impregnated with lignin
  • Two types specialized for support fibers and
    sclereids. Both function to strengthen tissue in
    which they occur

(Solomon et al 1999)
cross-section of a young elderberry branch
cross-section from grass blade
cluster of sclereids (stained red) in pulp of pear
20
Raven and Johnson 1999
Vascular tissue functions in the movement of
water, dissolved inorganic materials and
carbohydrates through a plant
21
Cell Types in Vascular Tissue System
  • Xylem cells
  • Tracheids vessel elements both function in
    water transport both modified sclerenchyma cells
  • Both have secondary cell walls and are dead at
    functional maturity
  • Dual function in gymnosperms water transport,
    structural support (structural support in
    angiosperms provided mainly by fiber cells

22
  • Tracheids
  • long, thin cells with tapered ends
  • water moves between cells across pits
  • function in support secondary walls hardened
    with lignin
  • Vessel Elements
  • usually wide, short, oblique ends, thin-walled,
    compared to tracheids
  • perforated end walls facilitates water flow

23
VESSEL ELEMENT Photomicrograph shows longitudinal
section of two vessel elements from an unknown
woody dicot
Solomon et al 1999
24
longitudinal section
transverse section
  • Phloem Cells
  • Sieve-tube members Food-conducting cells,
    arranged end to end with porous walls (sieve
    plates) between them cells living at functional
    maturity, but lacking nuclei, ribosomes
  • Companion cells Nucleated companion cell lies
    along side each sieve-tube member

25
SELECTED CELL TYPES OF THE PLANT DERMAL TISSUE
SYSTEM
  • Epidermal Cell
  • living parenchyma cell with thin primary wall
  • outer wall usually thickened and covered by an
    extra-cellular waxy cuticle
  • reduces water loss protects surface of plant
    body
  • epidermis is usually one cell layer thick
  • Guard Cell
  • specialized epidermal cells on leaves that
    function in pairs stoma (pore) is a gap between
    two guard cells
  • guard cells, stoma, regulate gas exchange and
    water loss (transpiration)

solomon et al 1999
26
  • PLANT GROWTH Meristems generate cells for new
    organs throughout the lifetime of a plant
  • Primary plant growth
  • -Apical meristems extend roots and shoots by
    giving rise to the primary plant body
  • Secondary plant growth
  • -Lateral meristems add girth by producing
    secondary vascular tissue and periderm

27
Apical and Lateral Meristems Apical meristems
produces primary plant body lateral meristems
produce the secondary plant body
28
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29
Raven and Johnson 1999
Vascular tissue functions in the movement of
water, dissolved inorganic materials and
carbohydrates through a plant
30
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31
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