Download Plant Form and Function

Plant Form and Function
Structure, Growth, and Development
The plant body has a
hierarchy of organs, tissues,
and cells
There are three
basic plant
organs:
Roots
Stems
Leaves
Roots
 Multicellular organs with important
functions
– Anchoring the plant
– Absorbing minerals and water
– Storing organic nutrients
 Type
– Fibrous Roots
– Tap Roots
– Mycorrhizae
– fungus that forms a symbiotic
relationship with some plants
Shoot System:
Stems and
Leaves
Reproductive shoot (flower)
Apical bud
Node
Internode
Apical
bud
 Stems – function
primarily to display
the leaves.
 Terminal Bud –
area of growth at
the top end of
stem
 Axillary Buds –
area of growth
located in the V
area between the
leaf and the stem
(branches)
 Leaves – main
photosynthetic
organ in plants
Vegetative
shoot
Leaf
Shoot
system
Blade
Petiole
Axillary
bud
Stem
Taproot
Lateral
branch
roots
Root
system
There are three basic groups
of plant tissues:
 Dermal Tissue
 Single layer of closely packed
cells
 Protects plant against water loss
and invasion by pathogens and
viruses
 Cuticle – waxy layer in leaves
 Vascular Tissue
 Xylem and phloem
 Ground Tissue
 Any tissue that’s not Dermal or
Vascular tissue
 Pith – ground tissue located
inside vascular tissue
 Cortex – ground tissue located
outside the vascular tissue
5 Major Cell Types
 Parenchyma
 Most abundant
 present throughout plant
 most metabolism (photosynthesis)
 Collenchyma
 Grouped in cylinders, supports growing parts of
plant
 Strings of celery (vascular tissue) is supported
by collenchyma cells
 Sclerenchyma
 Exists in parts of the plant that are no longer
growing
 Tough cell walls utilized for support
 Xylem
 Phloem
Fig. 35-10a
Parenchyma cells in Elodea leaf,
with chloroplasts (LM)
60 µm
Fig. 35-10b
5 µm
Collenchyma cells (in Helianthus stem) (LM)
Fig. 35-10c
5 µm
Sclereid cells in pear (LM)
25 µm
Cell wall
Fiber cells (cross section from ash tree) (LM)
Fig. 35-10d
Vessel
Tracheids
100 µm
Pits
Tracheids and vessels
(colorized SEM)
Perforation
plate
Vessel
element
Vessel elements, with
perforated end walls
Tracheids
Fig. 35-10e
Sieve-tube elements:
longitudinal view (LM)
3 µm
Sieve plate
Sieve-tube element (left)
and companion cell:
cross section (TEM)
Companion
cells
Sieve-tube
elements
Plasmodesma
Sieve
plate
30 µm
10 µm
Nucleus of
companion
cells
Sieve-tube elements:
longitudinal view
Sieve plate with pores (SEM)
Meristems generate cells for new organs
 Apical meristems
 Are located at the
tips of roots and in
buds of shoots.
 Sites of cell division
that allow plants to
grow in length
(primary growth)
 Lateral meristems
 results in growth
which thickens the
shoots and roots
(secondary growth)
Primary Growth
lengthens roots and
shoots
 Zone of cell division
 Includes apical
meristem
Cortex
Vascular cylinder
Epidermis
Key
to labels
Dermal
Root hair
Zone of
differentiation
Ground
Vascular
 New cells produces
Zone of
elongation
 Root cap is located
in root
 Zone of elongation
 Elongation of cells
Apical
meristem
 Zone of maturation
 Cell differentiation
 Cell become
functionally mature
Root cap
100 µm
Zone of cell
division
Secondary Growth add girth to stems
and roots in woody plants
 Two lateral meristems
 Vascular cambrium
 Produces secondary
xylem (wood)
 Secondary phloem
 Cork cambrium
 Produces tough
covering that replaces
epidermis early in
secondary growth
 Bark includes all the
tissues outside the
vascular cambrium.
Growth, morphogenesis, and
differentiation produce the plant
body
Morphogenesis
development of
body form and
organization.
This is the process
of cell
specialization