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Plant Structure
Plant Body Plan
• The apical–basal
pattern and the
radial pattern
are parts of the
plant body plan
• They arise
through orderly
development
Plant Body Plan
• Plant development differs from that
of animals
• The plant body is modular, and the
growth of stems and roots is
“indeterminate”
• Leaves, flowers, and fruits show
“determinate” growth.
•
•
Plant Cells
Some produce a thick secondary wall
Adjacent cells are connected by plasmodesmata
extending through both cell walls
Angiosperms
Monocots
–
–
–
–
have a single cotyledon
narrow leaves with parallel veins
flower parts in multiples of three
stems with scattered vascular bundles
Dicots (eudicots)
–
–
–
–
have two cotyledons
broad leaves with netlike veins
flower parts in fours or fives
vascular bundles in a ring
Monocots & Dicots
Figure 34.1
Figure 34.1
Plant Tissue Systems
• Vascular tissue
system conducts
water, minerals, and
the products of
photosynthesis
• Dermal tissue system
protects the body
surface
• Ground tissue system
produces and stores
food materials;
serves as “anchor”
Vegetative Organs
Include:
• roots, which
form a root
system
• stems and
leaves,
which form
a shoot
system
Leaves
Plant Body Plan
• Meristems are
localized regions
of cell division
• Apical meristems
at the tips of
stems and roots
produce the
primary growth of
those organs
Plant Body
Plan
• Shoot apical
and root
apical
meristems
give rise to
primary
meristems
Plant Body Plan
• In some plants, the products of primary
growth make up the entire plant body
Other plants show secondary growth
• Two lateral meristems, the vascular
cambium and cork cambium, are
responsible for secondary growth
Plant Body Plan
• Young roots
have apical
meristems that
gives rise to the
root cap and 3
primary
meristems
• 3 primary
meristems
produce the
three tissue
systems
Plant Body Plan
• Root tips have
three zones:
the zones of
cell division,
cell elongation,
and cell
differentiation
Plant Body Plan
• The dermal
tissue system
consists of the
epidermis, part
of which forms
root hairs
responsible for
absorbing water
and minerals
Roots
• The cortex of a young root surrounds the
endodermis which controls access to the
stele (pericycle, xylem, phloem)
Roots
• Lateral roots arise in the pericycle
• Monocot roots have a central pith region
Real Images - Roots
Dicots
Monocots
Real Roots
Stems
• Vascular tissue in young stems is
divided into vascular bundles, each
containing xylem and phloem
• Pith occupies the center of the
eudicot stem
• Cortex lies to the outside of vascular
bundles in eudicots, and pith rays lie
between them.
Stems
Monocots:
vascular bundle
scattered
Dicots:
vascular bundle
in a ring
xylem
phloem
Stems – real images
Dicots
Monocots
Stems and Roots
• Many dicot stems
and roots show
secondary growth,
in which vascular
and cork cambiam
give rise to
secondary xylem
and phloem
• As secondary
growth continues,
wood and bark are
produced
Secondary Growth
Figure 34.19 –
Part 2
Figure 34.19 – Part 2
Photosynthesis
• Mesophyll is the
photosynthetic
tissue of a leaf
• Veins bring
water and
minerals to the
mesophyll and
carry products
of
photosynthesis
to other parts of
the plant body
Photosynthesis
• A waxy cuticle
prevents water loss
from the leaf, but
is impermeable to
carbon dioxide
• Guard cells control
opening of stomata,
leaf openings that
allow CO2 to enter
and water to escape
Cross-section of Leaf
Figure 34.23
Figure 34.23
Stomata