Plant Organ Systems
Section 2.2
Homework
Pg. 76 #1-6
Quick review
1. How many organ systems are in a plant?
2. Identify the organs in each of these systems.
3. What are xylem and phloem?
a) How are they similar?
b) How are they different?
4. Cross-section of a leaf:
http://www.purchon.com/biology/flash/leaf.swf
Plant organ systems
ROOT SYSTEM
• anchor the plant
• absorb water and
minerals from soil
• store food
SHOOT SYSTEM
•
•
•
•
photosynthesis
support
transport substances
produce flowers for
sexual reproduction
Vascular tissue allows
transport between
the root and shoot
system.
Xylem
Phloem
Dead, hollow tissue
Living tissue
Transports water
and minerals
upwards from roots
Transports sugars
produced by leaves,
to the rest of the plant
The importance of water
...in plants:
• turgor pressure in cells
• dissolving/transporting nutrients
• reactant for photosynthesis
Transport of Water
Transport of H2O from roots to shoots through the
xylem occurs by two forces, which act in the
same direction:
Water
transport
Pushing
force
root pressure
Pulling
force
capillary action
1) Root pressure: The pushing force
• Water and dissolved minerals move into roots
by osmosis.
▫ generates pressure to push water upwards
Tiny root hairs
increase the
surface area of
the root.
2) Capillary action: The pulling force
• Capillary action - The ability of liquids to
move against gravity through narrow spaces
Transpirational Pull
Cohesion and
Adhesion
Both of these factors influence
the water’s ability to move up
the xylem against gravity
Transpiration – The evaporation of water vapour
from the leaf, through the stomata
▫ pulls on water at the top of the plant
Transpirational pull is
felt even at the roots.
How? It is enhanced by
the properties of water:
cohesion and adhesion
Two properties of water:
• Cohesion
Allows water to
move upwards by
capillary
action.
▫ Water molecules stick to
other water molecules.
▫ This is due to dipole – dipole
interactions
• Adhesion
▫ Water molecules stick to
sides of the xylem.
Guard cells control when the
stomata are open and closed.
When do the guard cells close?
• when the plant cannot afford to lose too much
water
▫ hot, dry days
▫ high wind speeds
Effect of various factors on
transpiration
http://www.knowledgebank.irri.or
g/ewatermgt/courses/course1/mod
ules/module02/m02l03.htm
Transport of sugars
a) What chemical process produces sugars
in the plant?
photosynthesis
a) Where are these sugars produced?
leaves (palisade cells - chloroplasts)
Plants photosynthesize to convert the Sun’s energy
into a useable form - glucose.
CO2+ H2O + light energy glucose + O2
The energy in glucose is then accessed by
cellular respiration (in mitochondria).
glucose + O2  CO2+ H2O + energy
Cells in every part of the plant need glucose.
Glucose must be transported to all organs of the plant.
Glucose produced in leaves
POSSIBLE FATES
OF GLUCOSE
used right away
by nearby cells
transported to
other parts of the
plant (as sucrose);
used right away
stored in the
roots (as starch)
when needed
In the spring, sucrose from
the roots flows upward to
help nourish leaf buds.
In the summer and fall, leaves
produce glucose that moves
downward to be stored in the
roots.
Glucose
Glucose
Sucrose
Sucrose
Starch
Starch
Transport in plants: Recap
Video
Section 2.2
Concepts to be reviewed:
• the function and characteristics of the root and shoot systems
• the function and properties of xylem and phloem tissue
• the tissues and processes involved in moving water and nutrients
• the movement and storage of the products of photosynthesis
Homework
Read 2.2
• Pg. 76 #1-6