Download TRANSPORT IN PLANTS

TRANSPORT
TRANSPORT IN PLANTS
IN PLANTS
THE STEM STRUCTURE
TRANSPORT SYSTEM IN PLANTS
• Plants don’t have a circulatory system like animals, but they
have their own system to carry what they need (minerals,
food and water) in different parts of the plant.
• This can happen thanks to the transport tissue, which are two:
– Xylem
– Phloem
• They are both contained in the vascular tissue.
• Both of these systems are rows of cells that make continuous
tubes running the full length of the plant.
WHAT DOES PHLOEM DO?
• Phloem moves food substances from the leaves to
the rest of the plant.
• Its main function is to transport sugars and other
food materials such as amino acids from the leaves,
where they are produced, to all other parts of the
plant.
• Phloem tissue is usually found close to the other
transport tissue in plants, xylem.
WAHT DOES XYLEM DO?
• Xylem transports water and solutes from the roots to the
leaves.
• Its main function is to transport water and minerals as xylem
sap to the leaves.
• Xylem is made of vessels that are connected end to end to
move water around
• These xylem cells are dead and hollow, allowing rapid water
transport.
• When someone cuts an old tree down, they reveal a set of
rings. Those rings are the remains of old xylem tissue, one
ring for every year the tree was alive.
XYLEM RINGS
XYLEM in ROOT AND STEM
• Xylem cells have extra reinforcement in their cell walls, and
this helps to support the weight of the plant. This is why, the
transport systems are arranged differently in root and stem.
• Root:
It has to resist
forces that could
pull the plant out
of the ground.
• Stem:
It has to resist the bending and compression forces caused by the
weight of the plant and the wind.
XYLEM in LEAVES
The xylem
transports water
from the root
up the plant.
Phloem is the
living tissue that
carries organic
nutrients,
particularly
sucrose, a sugar,
to all parts of
the plant where
needed.
http://www.biology.ualberta.ca/facilities/multimedia/uploads/alberta/transport.html
ROOT HAIR CELLS
•The root hair cell has a large surface area but is a
delicate structure which can live up to 2 to 3 weeks.
•Plants absorb water from the soil by osmosis. Root
hair cells are adapted for this by having a large
surface area to speed up osmosis.
STRUCTURE AND FUNCTIONS:
1. Elongated structure - This is to increase the
surface area to volume ratio; thereby increasing
the rate of uptake of water from the soil to the
cell.
2. Large vacuole- The root hair cell has a large
vacuole to maximize the amount of water
capacity of the cell.
•
Absorbs water and mineral ions from the soil
THE WATER PATHWAY
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Water enters through the root hair cells and then moves
across into the xylem tissue in the centre of the root.
Water moves in this direction due to the tension caused by
the water loss from the leaves.
It gets in the stem and move upwards in the xylem tubes.
Water moves from xylem to enter the leaf tissues down water
potential gradient.
water evaporates from leaves and lowers the water potential
in the leaf tissue. This is called TRANSPIRATION.
TRANSPIRATION
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Plants lose gallons of water every day through the process of transpiration,
the evaporation of water from plants through pores in their leaves.
Water evaporates from the parts of the plant that are exposed to the
atmosphere.
The greatest loss of water takes place through the stomata (minute pores on
the leaf)which allow the uptake of Carbon Dioxide for photosynthesis.
They are the primary control mechanism that plants use to reduce water
loss.
Two specialized cells, called guard cells, make up each stoma.
Many stomata are usually found in the lower surface of the leaves, because
it is less exposed to warming effects of the Sun.
Water must be absorbed and drawn up through the plant to replace the
losses . This flow of water is called the transpiration stream.
http://www.sciencemag.org/site/feature/misc/webfeat/vis2005/show/transpiration.swf
TRANSPIRATION
FACTORS THAT AFFECT
TRANSPIRATION RATE
• LIGHT- in bright light transpiration increase.
Why? The stomata (openings in the leaf) open wider to allow more
carbon dioxide into the leaf for photosynthesis
• TEMPERATURE-Transpiration is faster in higher temperatures
Why? Evaporation and diffusion are faster at higher temperatures
• WIND-Transpiration is faster in windy conditions
Why? Water vapour is removed quickly by air movement, speeding up
diffusion of more water vapour out of the leaf
• HUMIDITY-Transpiration is slower in humid conditions
Why? Diffusion of water vapour out of the leaf slows down if the leaf is
already surrounded by moist air.
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QUESTIONS:
What are the functions of xylem and phloem?
What is transpiration?
State and explain two factors that affect the
transpiration rate.
CREATED BY: MARTINA