Transcript Nerve activates contraction - University of Indianapolis

Lecture 19:
Plant Structure and Function
Plant structure can be divided into two
systems: roots and shoots
The Root System
• Parts under ground
• Used for anchorage
• Used for absorption
of water and
nutrients
Fibrous root
Tap root
Roots are often covered with root hairs
which increase the surface area for
absorption
Epidermal cell
Root hair
Modified roots
The Shoot System
• Stems, leaves, buds
• Nodes are places on
the stem where
leaves are attached
and buds form.
Figure 35.5 Simple versus compound leaves
Figure 35.19 Leaf anatomy
Figure 35.6 Modified leaves: Tendrils, pea plant (top left); spines, cacti (top right);
succulent (bottom left); brightly-colored leaves, poinsettia (bottom right)
Figure 35.4 Modified shoots: Stolons, strawberry (top left); rhizomes, iris (top right);
tubers, potato (bottom left); bulb, onion (bottom right)
Plant structures are composed of 3
types of tissues
• ground tissue -- bulk of
plant body
• vascular tissue -distribution of water and
solutes
• dermal tissue -covering, protection of
plant surface.
Vascular tissue: xylem and phloem
Plant growth occurs at localized regions called
meristems
• Meristem cells are
undifferentiated and can
divide through mitosis
• Continued divisions of
meristem cells keeps a plant
growing throughout it's life =
indeterminate growth.
• apical meristems -- results
in increase in length of
stems and roots
• lateral meristems -- growth
produces thickening of
stems and roots
Growth at apical meristems = primary growth
• As a stem or root grows, primary
meristems develop behind the
growing tip
• These differentiate into the three
tissue systems:
• Dermal tissue comes from:
• protoderm --> epidermis (waxy
covering in shoots)
• Vascular tissue comes from:
• procambium --> vascular
cambium--> primary xylem and
phloem
• Ground tissue comes from:
• ground meristem -> ground
tissues--> cork cambium
Figure 35.17 The terminal bud and primary growth of a shoot
Growth at lateral meristems: Secondary growth
• In woody plants vascular
cambium forms a ring
• each growing season a
new layer of xylem is
produced which pushes
the cambium and all
outer tissues further out.
• Old phloem cells are
crushed and only a thin
strip of newly- formed
phloem remains alive.
Figure 35.22 Anatomy of a three-year-old stem
Figure 35.23 Anatomy of a tree trunk
• As the stem expands, it
ruptures the epidermis
• Bark is composed of
phloem and ground
issue cells called cork
cells
Tree Girdling
If you hammer a nail into a tree 10 feet
above the ground, and wait 20 years,
where will the nail be?
?
10 feet
Angiosperms are often divided into the
monocots and dicots
Monocots
Dicots