Transcript Lecture - Chapter 42 - Stems, Roots, and Leaves

Chapter #42 – Plant Anatomy
& Nutrient Transport
• 42.1 - How Are Plant Bodies Organized; How Do They Grow? p. 860
• 42.2 - The Tissues and Cell Types of Plants? p. 862
• 42.3 - The Structures, Functions of Leaves, Roots, & Stems? p. 865
• 42.4 - How Do Plants Acquire Mineral Nutrients? p. 873
• 42.5 - How Do Plants Move Water Upward from Roots to Leaves? p. 876
Plant Anatomy
Systems and Tissues
• How Are Plant Bodies Organized, and
How Do They Grow?
– Flowering Plants Consist of a Root
System and a Shoot System.
– As Plants Grow, Meristem Cells Give
Rise to Differentiated Cells.
Herbaceous Plants
• Soft-bodied plants with flexible stems.
• Most are annual (live only one year).
• Exhibit primary growth.
– e.g. lettuce, beans, grasses
Woody Plants
• Plants with hard,
thickened, woody stems
• Most are perennial (live
many years)
• Exhibit primary and
secondary growth
– e.g. trees, bushes
Leaves
Types of Leaves
• Simple leaves have
a single blade on
one petiole.
• Compound leaves
have multiple
leaflets on one
petiole.
Leaf Parts
• Two major parts to
the leaf:
• Blade
• Petiole
Leaf Microanatomy
• Epidermis and cuticle
slow evaporation.
• Guard cells regulate
gas exchange.
• Mesophyll carries out
photosynthesis
• Veins bring water,
move sugars.
Photosynthesis
• The purpose of photosynthesis is to
produce organic (carbon-based) molecules
(such as sugars).
• The plants use these molecules for two
purposes:
• As an energy source
• As building material
• Stop and think:
• On a piece of paper, list plant leaves or products
of plant leaves that you have used in the past few
days.
• What qualities of the leaves made them useful?
Roots
Types of Root Systems
• Taproot systems are
found in dicots, and
consist of a main
root with lateral
branches.
• Fibrous root systems
lose the primary root,
which is replaced by
many smaller roots.
Root Anatomy
• Parts of a Root:
•
•
•
•
Root cap
Root meristem
Zone of elongation
Zone of maturation
Root Anatomy:
Epidermis
• Root epidermis lacks a
cuticle, and is porous.
Usually has many root
hairs.
• Water enters through
membranes of
epidermal cells or
through spaces between
cells.
Root Anatomy:
Cortex
• The cortex layer is made
up of parenchyma cells.
• Sugars are linked to make
starch for food storage.
• Endodermis separates the
cortex from the vascular
cylinder.
Root Anatomy:
Vascular Cylinder
• Casparian strip
around endodermis
cells controls water
movement.
• Pericycle: layer of
parenchyma cells,
inside of endodermis,
from which branch
roots can arise.
Root Anatomy:
Vascular Cylinder
• Vascular Cylinder
contains:
• Phloem for moving
sugars.
• Xylem for moving
water and dissolved
minerals.
• Stop and think:
• On your own paper, list any roots that you have
used in the past few days.
• What qualities of the roots made them useful?
Stems
Stems:
Epidermis
• In herbaceous plants
and young woody
plants, the stem is
covered with
epidermis.
• Epidermis secretes
cuticle, has stomata,
and may be
photosynthetic.
Stems:
Cortex and Pith
• Cortex layer contains
parenchyma cells and
vascular bundles.
• Pith makes up the
center of the stem,
and is absent in
hollow stems.
Stems:
Vascular Tissue
• Vascular bundles are in
the cortex.
• While primary xylem
and phloem are made
by the apical meristem,
secondary xylem and
phloem come from
the vascular cambium,
another meristem
tissue.
Trunk:
Primary Growth
• Primary Growth is
primarily vertical.
• This kind of growth
gives the plant its
height.
Trunk:
Secondary Growth
• Secondary growth is
seen in woody plants.
• This kind of growth
produces stronger,
thicker stems from the
vascular cambium and
cork cambium.
• Horizontal Growth
Wood and Bark
• Xylem makes up the
wood of trees and
shrubs.
• Live phloem cells
form the green bark.
• Dead cork cells
make up the bark.
Annual Rings
• Trees in temperate zones
grow at different rates in
different seasons, causing
annual rings to form.
• In some parts of the
tropics, if seasons vary
little, tree rings are
indistinct.
• Stop and think:
• On your own paper, list any stems or products of
stems you have used in the last few days.
• What qualities of these stems made them useful?
Meristem Cells
• Meristem cells are
undifferentiated
cells; able to divide
as long as the plant
lives.
• Apical meristems
are located at tips
of roots and
shoots.
Meristem Cells
• Differentiated cells are mature cells
specialized for a specific function.
– Derived from meristem cells that lose
the ability to divide.
– Usually do not divide.
– Example: vessel elements and tracheids
of xylem.
Meristem Cells
• Meristems allow plants to grow throughout their
lives.
• Primary growth occurs by division of apical
meristem cells and differentiation of their
daughter cells.
– Responsible for growth in length of roots and
shoots of all plants.
Meristem Cells
• Secondary growth occurs by division of
lateral meristem cells and differentiation of
their daughter cells.
– Responsible for an increase in diameter of roots and
shoots of most conifers and dicots.
– Lateral meristems or cambia (singular, cambium)
run parallel to the long axis of roots and shoots.