A Level Biology- Transport In Plants

Front 1

Define vascular bundle

Back 1

Vascular system in plants

Consists of 2 transport vessels. The xylem and the phloem

Front 2

Describe the structure and function of the vascular system in the roots of dicotyledons

Back 2

Xylem arranged in an X shape to provide

resistance against force

Phloem found as patches between the arms

Surrounded by

endodermis aiding water passage

Front 3

Describe the structure and functions of the vascular system in the stem of plants

Back 3

Vascular bundles

organised around a central pith

Xylem on the inside of the bundle to provide support and flexibility, phloem on the

outside

Cambium is found

between the 2

Front 4

What structure in plants is adapted for the uptake of water and minerals

Back 4

Root hair cells

Front 5

How is water taken up from the soil

Back 5

Root hair cells absorb minerals by active

transport, reducing the water potential of the root

Water potential of root hairs cells is lower than that of the soil

Water moves into the root by osmosis

Front 6

How are plant roots adapted for the adsorption of water and minerals

Back 6

Contain lots of root hair cells which have:

Long hairs that extend from the cell body,

increasing the surface area for absorption

Many mitochondria which produce energy for the active transport of mineral ions

Front 7

What are the 3 pathways by which water moves through the root

Back 7

Apoplast pathway

Symplast pathway

Vacuolar pathway

Front 8

Describe the apoplast pathway

Back 8

Water moves through intracellular spaces

between cellulose molecules in the cell wall

It diffuses down its water potential gradient by osmosis

Front 9

What is the symplast pathway

Back 9

Water enters the cytoplasm through the plasma membrane and moves between adjacent cells via plasmodesmata

Water diffuses down its water potential gradient by osmosis

Front 10

What is the vacuolar pathway

Back 10

Water enters the cytoplasm through the plasma membrane and moves between vacuoles of

adjacent cells

Water diffuses down its water potential gradient by osmosis

Front 11

What is the structure and function of the endodermis

Back 11

Saturated with suberin which forms the

casparian strip

Innermost layer of the cortex or a dicot root

Endodermal cells actively transport mineral ions into the xylem

Front 12

What is the function of the casparian strip

Back 12

Blocks the apoplast pathway, forcing water through the symplast route

Enables control of the movement of water and minerals across the root into the xylem

Front 13

What molecule makes up the casparian strip

Back 13

Suberin

Front 14

Relate the structure of the xylem to its function

Back 14

Long, continuous columns made of dead tissue, allowing the transportation of water

Contain bordered pits, allowing the sideways movement of water between vessels

Walls lined with lignin, providing structural

support

Front 15

Define transpiration

Back 15

The loss of water vapour from the parts of a plant exposed to the air she to evaporation and diffusion

Consequences of gaseous exchange, occurs when the plant opens the stomata to exchange O2 and CO2

Front 16

What is the transpiration stream

Back 16

The flow of water from the roots to the leaves in plants, where it is lost by evaporation to the environment

Front 17

How does water move up the stem?

Back 17

Root pressure

Cohesion tension theory

Capillarity

Front 18

What is root pressure

Back 18

The force that drives water into and up the xylem by osmosis due to the active transport of

minerals into the xylem by endodermal cells

Front 19

What is the cohesion tension theory

Back 19

Water molecules form hydrogen bonds with each other, causing them to stick together

Surface tension of the water also creates this sticking effect

Therefore as water is lost through transpiration, more is drawn up the stem from the roots

Front 20

Define capillarity

Back 20

The tendency of water to move up the xylem, against gravity, due to adhesive forces that prevent the water column dropping back

Front 21

What factors affect the rate of transpiration

Back 21

Light

Temperature

Humidity

Air movement

Front 22

How does temperature affect the rate of transpiration

Back 22

A higher temp increases random motion and the kinetic energy of the water molecues and rate of evaporation therefore increasing rate of

transpiration

Front 23

How does light affect the rate of transpiration

Back 23

A higher light intensity increases the rate of

photosynthesis, causing more stomata to open for gas exchange, therefore increasing rate of transpiration

Front 24

How does humidity affect the rate of transpiration

Back 24

High humidity means the water content of the air next to the leaf is high

This reduces the concentration gradient, therefore decreasing rate of transpiration

Front 25

How does air movement affect the rate of transpiration

Back 25

Large amounts of air movement bl8w moist air away from the leaves, creating a steep concentration gradient

Rate of transpiration increases

Front 26

What is a hydrophyte

Back 26

A plant that is adapted to lice and reproduce in very wet habitats

Water lilies

Front 27

What adaptations of hydrophytes allow them to live in wet conditions

Back 27

Thin or absent waxy cuticle as no need to conserve water

Stomata often open and on upper surface as lower surface is submerged

Wide flat leaves, poorly developed xylemas no need to transport water

Air spaces for buoyancy and act as reservoirs of gas

Front 28

What is a xerophyte

Back 28

A plant that is adopted to live and reproduce in dry habitats where water availability is low

Cacti and marram grass

Front 29

What are the adaptations of xerophytes that allow them to live in dry conditions

Back 29

Small/rolled leaves reduces area of leaf exposed directly to air

Densely packed mesophyll

Thick waxy cuticle reducing water loss by evaporation from epidermal tissue

Stomata often closed, or sunken, reducing diffusion gradient and therefore water loss

Stiff interlocking Hairs to trap moist air inside rolled leafe, reducing water potential gradient and therefore waterloss

Front 30

What are mesophytes

Back 30

Terrestrial plants adapted to live in environments with average conditions and an adequate water supply

They have features that enable their survival at unfavourable times of the year

Front 31

Relate the structure of the phloem to its function

Back 31

Seive tube elements transport sugars around the plant

Companion cells designed for active transport of sugars into tubes contain many

mitochondria forATP and the organelles for proteinsynthesis.

Plasmodesmata allow communication and the exchange of substances between sieve tubes and companion cells

Front 32

What are cytoplasmic strands

Back 32

Small extensions of the cytoplasm between adjacent sieve tube elements and companion cells

Front 33

Define the function of cytoplasmic strands

Back 33

Allow communication and the exchange of materials between sieve tube elements and companion cells

Hold the nucleus in place

Front 34

With is translocation

Back 34

The movement of organic compounds in the phloem from sources to sinks

Front 35

What is the mass flow hypothesis of translocation?

Back 35

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.

Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissues

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Glucose produced furing photosynthesis is too reactive for transport so converted into sucrose.Sucrose actively loaded into sieve tubes through companion cells Lowers water potential, causing water to move in from the xylem by osmosis Hydrostatic pressure increases, causing sugars to move towards the sink They are unloaded into the tissuesLowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Lowers water potential in the tissues of the sink so water moves out of phloem by osmosis Excess water, then enters the xylem

Front 36

What evidence is there for the mass flow hypothesis

Back 36

Sap is released when the stem is cut so there must be pressure in the phloem

Sap exuding from the stylet of an aphid

inserted into sieve tubes provides evidence that sugars are carried in the phloem

There is a higher sucrose concentration in the leaves than the roots

Autoradiographs produced using carbon

dioxide labelled with radioactive carbon

provide evidence for translocation in the phloem

Front 37

What is autoradiography?

Back 37

A technique used to record the distribution of radioactive material within a specimen

Front 38

What is a potometer

Back 38

An apparatus used to measure water uptake from a cut shoot

Front 39

What are adaptions of mesophytes

Back 39

Closed stomata at night to decrease water loss

Shed leaves in unfavourable conditions

Underground organs and dormant seeds survive winter

Front 40

Why must the leafy shoot be cut underwater in the potometer practical

Back 40

To prevent air bubbles from forming in the vascular tissue

Front 41

Why should the cut of the shoot be slanted in the potometer practical

Back 41

To increase the surface area available for water uptake

Front 42

How do we setup the potometer practical

Back 42

Set up the potometer

Clamp the capillary tube into the stand. Place the bottom of the capillary tube into the beaker of water

Smear petroleum jelly around the join to maintain airtight conditions

Leave for 5 mins for a bubble to be drawn into the capillary tube

Measure the movement of the bubble along the capillary tube in a certain length of time

Repeat the experiment and change the abiotic variable

Front 43

How is the rate of transpiration calculated

Back 43

Measure the distance travelled by the bubbles in the capillary and the radius of the capillary

Find the volume of water taken up by using pi r^2

Divide the volume by time

Front 44

How is light intensity controlled

Back 44

By changing the distance between the lamp and potometer

Front 45

How can wind speed be controlled

Back 45

By placing a fan near the potometer with different speeds

Front 46

How can humidity be controlled

Back 46

By wrapping a plastic bag around the plant to maintain a humid environment

Front 47

What are some limitations of the potometer practical

Back 47

The plant is dying when the stem is cut, rate or water uptake is lower than normal

Front 48

Why is it important that no air bubbles enter the apparatus?

Back 48

This will affect the rate of water uptake in the xylem

Front 49

How do we ensure no air bubbles enter the

apparatus

Back 49

Cut the shoot under water

Assemble the potometer underwater

Front 50

What experimental evidence is there for the mass flow hypothesis

Back 50

Ringing experiments (removal of phloem) show accumulationof sucrose products on leaf side of the ring but none on rootside. Movement of sucrose was blocked by removal of phloem.Therefore, phloem is the route of transport.

2. Using aphids to sample sap from the phloem. An aphid stylusextends into sieve tube elements. If a laser is used to remove thestylus from the body, the stylus then becomes a micropipetteand sap drips out. This can be analysed to show that sucrose andamino acids are carried in the phloem, both above and

belowleaves.

Radioactive labelling of carbon dioxide which will becomeincorporated into sucrose can be used in conjunction with theabove technique to determine the rate of transport in the phloem

Sources and sinks can be determined by

autoradiographyusing radioactively labelled carbon dioxide