Download Ch. 23 Plant Book Notes


Plants have 3 main organs: roots, stems, & leaves
 Roots
– absorbs water and dissolved nutrients, anchors the
plant, protect the plant from bad soil, and transports water
to rest of the plant
 Stems – support system for the plant body, transport system
for water and nutrients
 Leaves – plants main photosynthetic system
Plants
rely on specialized tissue, called
vascular tissue, to transport water,
nutrients, and the products of
photosynthesis around the plant.
The
2 types of vascular tissue are xylem
and phloem.
What is xylem? Transports water from the roots up to the
rest of the plant in one way flow.
What are tracheids? Hollow cell in xylem with
thick cell walls that resist turgor pressure
Water rises through the thin tubes by a process called
capillary action (cohesion of h20 molecules and
adhesion to solid surface). The thinner the tube, the
higher the water will rise.
 Plants lose water through their stomata in a process
called transpiration. As the leaves lose water, more
is drawn up the plant (like liquid through a straw).
 The actions of these two forces, along with root
pressure (Root pressure occurs in the xylem when the soil

moisture level is high either at night or when transpiration is low
during the day),
allows water to be delivered to the
entire plant, even to ones that are a hundred feet
tall.
 Vascular
tissue that transports sugars (glucose)
produced by photosynthesis to plants in a two-way
flow to the roots of the plant.
-dripping sap(sugars) coming from a tree is usually from the
phloem
 When
nutrients are pumped into or removed
from the phloem system, the change in
pressure causes a movement of nutrients in
that same direction. As a result, phloem is
able to move nutrients in either direction to
meet the nutritional needs of the plant.
Functions:
 absorb water and nutrients from the soil
 anchor plants in the ground
 hold soil in place and prevent erosion
 protect plant from harmful soil bacteria and fungi
 hold plants upright against forces such as wind and
rain.
 Taproot




Typical in Dicots
Single large root
Able to penetrate to deep water source
Ex. Radishes and Dandelions
 Fibrous



Root
Typical in Monocots
Many branched roots of similar length
Prevents soil erosion
Adventitious Roots
Cypress trees have root
“knees” that extend
above ground.
Prop Roots: Mangrove Islands
More Prop Roots
Contractile Roots
Root Structures
•
Roots have root hairs, which
increase the surface area of
roots, thus increasing the
amount of water absorbed.
•
Refer to the picture to view a
root’s apical meristem.
Meristem tissue is the only plant
tissue that produces new cells
by mitosis. Thus, roots only
grow from the tips (apical)
where the meristem tissue is
located.
Xylem and Phloem in Plant Roots
One of the reasons
Angiosperms are divided
into monocots and dicots is
there roots.
In Dicots, the xylem makes an X in the
center of the root, and the phloem fills
around it. In Monocots, the xylem makes
a ring, rather than an X, and is
surrounded by a ring of phloem.
Dicot root (notice the X).
The vascular tissue in the dicot is spread throughout the
root while the vascular tissue in the monocot is just
around the outer ring of the root.
 Composed
of a Node,
Internode, and Bud
 Three main functions of a
stem:
1.
2.
3.
Produce leaves,
branches, and flowers
Hold leaves up to
sunlight (support)
Transport substances
between roots and
leaves
Apical
meristem
of shoot
Leaves
Stem Buds
Leaves attach to stems at areas
called nodes. Internodes are
the areas between the nodes,
and buds contain undeveloped
tissue that will produce new
stems and leaves.
Like roots, stems have apical
meristems for growth. The apical
meristems contain hormones that
cause the stems to grow in height. If
the apical meristems are removed, the
plant grows side branches instead.
Stems
Tubers- stems that store
food (usually grow
underground)
Potato
Bulbs – made of a central stem
surrounded by short, thick leaves. The
leaves wrap around and protect the stem
and also store food. It may remain
dormant for a long time.
Beets
Onion
 Monocot

Vascular bundles are scattered
 Dicot

Vascular bundles are in a ring
Functions:
 most photosynthesis takes place here
 absorb sunlight
 contain pores for gas exchange
General Structure
 Blade-
thin, flattened
surfaces of leaves that
increase surface area
for absorption of
sunlight.
 Petiole-
thin stalk that
attaches the leaf blade
to the stem.
Dicot – makes an X in
the middle
Monocot – makes a ring
around outer edge.
 Monocot
Vascular bundles
are scattered

Dicot
* Vascular bundles
are in a ring
Cuticle
Guard Cells
Stomata (stoma)
Epidermis
Chloroplasts
Vascular bundle (vein)
Guard cells:
• cells that open and
close the stoma
Stomata: openings in
underside of leaf’s
surface; when open:
• GAS EXCHANGE:
Allows CO2 in & O2
out of leaf
• TRANSPIRATION:
Allows excess H2O
out of leaf
GUARD CELL WITH STOMATA
1. Transpiration: loss
of excess water from plant
leaves
2. Significance:
a. Transpiration causes
enough pressure to help
pull water (& required
nutrients) up stem from
roots.
b. As part of the water cycle,
trees transpire water back
into the atmosphere.
c. Transpiration provides
much of the daily rain in
rainforest.
A average size maple tree can
transpire 200 liters of water
per hour during the summer.
Transpiration is the #1 driving
force for pulling water up
stems from roots.