2546374
Description
Mind Map by tasnia.a.98, updated more than 1 year ago
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Created by tasnia.a.98
about 9 years ago
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Plants: Exchange and Transport
- Xylem and Phloem
- Xylem
- transport water and
minerals from the roots up
to the leaves.
- Xylem vessel
- dead cells, thick
walls and lignin
(waterproofs the
walls of the cell)
- Lignin allows the stem to be
flexible due to the patters in the
cell wall, e.g. spiral or reticulate.
- some places lignification is not complete which
leaves pores called pits. this allows water to
leave one vessel and enter another, or into
living parts of a plant.
- dead cells, thick
walls and lignin
(waterproofs the
walls of the cell)
- Adaptations
- dead skin cells
aligned end to
end to form
column
- narrow tubes, capillary
action is effective
(tubes don't burst)
- pits in lignified walls to
allow water movement to
adjacent vessels
- lignin deposited in
walls in spiral,
annular or reticulate
patterns to allow
xylem to stretch
- no nucleus, cell contents, end
wall or cytoplasm; good flow of
water
- dead skin cells
aligned end to
end to form
column
- transport water and
minerals from the roots up
to the leaves.
- Phloem
- transport sugars from one
part of plant to another
- 2 types of cell.
- Sieve Tubes
- not true cells as they do not have a
nucleus and very little cytoplasm
- sucrose is transported (cells lined end-end) ,
sucrose dissolved in water to form sap.
- cross walls at intervals called sieve plates,
perforated by pores to allow sap to flow
- thin walls and 5-6
sided
- not true cells as they do not have a
nucleus and very little cytoplasm
- Companion Cells
- in between sieve tubes with large nucleus
and dense cytoplasm
- numerous mitochondria to produce
ATP. They carry out metabolic
processes needed by sieve tube
elements.
- includes using ATP as a source of
energy to load sucrose into sieve
tubes
- includes using ATP as a source of
energy to load sucrose into sieve
tubes
- cytoplasm of cell and sieve tube
elements are linked through
plasmodesmata (gaps in cell walls
allowing communication and flow of
substances)
- in between sieve tubes with large nucleus
and dense cytoplasm
- Sieve Tubes
- transport sugars from one
part of plant to another
- Xylem
- Water
- Water Potential
- measure of tendency of water
molecules to diffuse from one
place to another
- water moves from
high water potential
to low potential
- pure water has a water
potential of zero.
- cells have a negative
water potential
- because they contain
dissolved salts and
sugars
- because they contain
dissolved salts and
sugars
- lower water potential: more negative;
higher water potential: less negative
- cells have a negative
water potential
- turgidity and plasmolysis
- when water leaves a cell the
cytoplasm and vacuole shrink.
The cytoplasm loses contact
with the cell wall, this is known
as plasmolysis
- when water enters a cell the
water pressure exerts pressure on
the cell wall. The cell wall
becomes full with water, this is
known as being turgid.
- when water leaves a cell the
cytoplasm and vacuole shrink.
The cytoplasm loses contact
with the cell wall, this is known
as plasmolysis
- pathways water molcules can take
- apoplast pathway
- cellulose cell walls have many water filled
spaces between cellulose molecules,
water does not pass through any plasma
membranes which means dissolved
mineral ions and salts can be carried with
the water.
- cellulose cell walls have many water filled
spaces between cellulose molecules,
water does not pass through any plasma
membranes which means dissolved
mineral ions and salts can be carried with
the water.
- symplast pathway
- water enters cytoplasm through plasma
membrane, (passes through plasmodesmata
from one cell to the next), water can move
through the continuous cytoplasm from cell to
cell.
- Plasmodesmata: gaps in the cell wall that contain a thin strand
of cytoplasm
- Plasmodesmata: gaps in the cell wall that contain a thin strand
of cytoplasm
- water enters cytoplasm through plasma
membrane, (passes through plasmodesmata
from one cell to the next), water can move
through the continuous cytoplasm from cell to
cell.
- vacuolar pathway
- water enters cytoplasm, and passes through the
vacuole back out into the cytoplasm and a vacuole of
an adjacent cell
- water enters cytoplasm, and passes through the
vacuole back out into the cytoplasm and a vacuole of
an adjacent cell
- apoplast pathway
- measure of tendency of water
molecules to diffuse from one
place to another
- Water Potential
- Transpiration
- the loss of water from
the aerial parts of a plant
due to evaporation
- water vapour diffuses
down a water potential
gradient
- 3 processes are involved in
transpirartion
- 1. osmosis from the xylem to
mesophyll cells
- 2. evaporation from the surface of
the mesophyll cells into the
intercellular spaces
- spongy mesophyll cells have large
air spaces between them which
help water vapour diffuse
- spongy mesophyll cells have large
air spaces between them which
help water vapour diffuse
- 3. diffusion of water vapour from the
intercellular spaces out through the
stomata
- 1. osmosis from the xylem to
mesophyll cells
- water that is lost needs to be
replaced, water is useful in a
number ways
- water keeps the cells turgid
- required for photosynthesis
- flow of water carries essential
nutrients and minerals
- water keeps the cells turgid
- potometer
- estimates the rate
of water loss
- cut the shoot
underwater to prevent
any air bubbles getting in
- what affects the rate of transpiration?
- wind speed
- surface area
- temperature
- humidity
- size and position of stomata
- light
- waxy cuticle
- wind speed
- estimates the rate
of water loss
- xerophytes
- plant that is adapted to reduce water
loss so that it can survive in very dry
conditions
- structural and behavioural adaptations to reduce water loss
- smaller needle
like leaves:
reduces total
surface area
- densely pack spongy mesophyll:
reduces surface area exposed to
the air
- pits containing stomata: trap air which
can become saturated with water
vapour (water vapour potential has
been reduced)
- rolled up leaves so lower epidermis is
not exposed: traps air so it can
become saturated (water vapour
potential has been reduced)
- hair on the surface:
traps air so it becomes
saturated (water
vapour potential has
been reduced)
- smaller needle
like leaves:
reduces total
surface area
- plant that is adapted to reduce water
loss so that it can survive in very dry
conditions
- the loss of water from
the aerial parts of a plant
due to evaporation
- Translocation
- transport of assimilates
throughout the plant, in
the phloem tissue
- sugars are transported in the
phloem in the form of sucrose
- source and sink
- source
- releases sucrose into the phloem
- water potential reduces at the sieve
tube element as sucrose enters
- water molecules move into the
sieve tube element by osmosis
- this increases the hydrostatic pressure in the sieve tube (at the source)
- this increases the hydrostatic pressure in the sieve tube (at the source)
- releases sucrose into the phloem
- sink
- removes sucrose from the phloem
- sucrose molecules move by diffusion or
active transport from the sieve tube into
surrounding cells
- this increases the water potential in the sieve tube
- this increases the water potential in the sieve tube
- water molecules move into the
surrounding cells by osmosis
- this decreases the hydrostatic pressure in
the sink (at the phloem)
- this decreases the hydrostatic pressure in
the sink (at the phloem)
- removes sucrose from the phloem
- source
- sucrose can be
converted to starch
from storage or used in
a metabolic process;
e.g. respiration
- reduces sucrose concentration
in cells
- reduces sucrose concentration
in cells
- mass flow
- a flow of water in the phloem is produced
by the water moving down the hydrostatic
pressure gradient
- the flow of water carries sucrose
and other assimilates along the
phloem
- it can flow in any
direction and at the
same time
- a flow of water in the phloem is produced
by the water moving down the hydrostatic
pressure gradient
- transport of assimilates
throughout the plant, in
the phloem tissue
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