Transport In Plants at Birmingham City University | Flashcards & Summaries

Lernmaterialien für transport in plants an der Birmingham City University

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TESTE DEIN WISSEN

define transpiration

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this is the loss of water vapour by evaporation and this is an inevitable consequence of gas exchange through the stomata

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explain the need for plant transport systems

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  • plants need substances- like water, minerals and sugars to live. they also need to get rid of waste substances 
  • big size- this means plants plants need very effective transport systems to move substances up and down from the tip of the root to the top - and so exchanging substances by direct diffusion could be too slow to meet their metabolic needs 
  • plants are multicellular- so have a small SA:V ratio 
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TESTE DEIN WISSEN

name factors in which affect the transpiration rate

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  • light intensity - increasing no. of open stomata increasing the rate of water vapour diffusing out and therefore increasing the evaporation from the surfaces of the leaf 
  • humidity- high humidity means low transpiration because of the reduced water vapour potential gradient between the inside of the leaf and the out the air spaces of the left side of the air 
  • temperature- increase kinetic energy increases the rate of evaporation from the spongy mesophyll cells into the air spaces of the leaf. 
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TESTE DEIN WISSEN

state features of hydrophytes to adapt

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  • thin or no waxy cuticle - no need to conserve water as there is plenty available water for loss by transpiration 
  • many open stomata - maximising the number of stomata maximises gas exchange . this plant there is no risk to the plant of loss of turgor as there is abundance of water so the stomata always open all the time for gas exchange 
  • large surface area of stems and roots - maximises the area for photosynthesis 
  • air sacs this enables the leaves to float on the surface of water 
  • aerenchyma - large air spaces, make the stems and leaves more bouyant
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TESTE DEIN WISSEN

explain the process of transpiration

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TESTE DEIN WISSEN
  • carbon dioxide moves from the air into the leaf and oxygen moves out by gas exchange by diffusion down concentration gradient through microscopic pores in the leaf on the underside of the leaf called stomata and
  •  these stomata can be opened and closed by guard cells which surrounds the stomatal opening 
  • when the stomata are open to allow an exchange of carbon dioxide and oxygen between the air inside the leaf and the external air water vapour moves out by diffusion and is lost . 
  • this loss of water vapour is transpiration 
Lösung ausblenden
TESTE DEIN WISSEN

give examples of strategies xerophytes use to conserve water

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TESTE DEIN WISSEN
  • thick waxy cuticle helps minimise water loss
  • sunken stomata located in pits which reduces air movement producing a moist climate that reduces the water vapour potential gradient and so reduces transpiration 
  • reduced no. of stomata reduce water loss by transpiration , also reduce the gas exchange 
  • reduced leaves- reducing leaf area water loss can be greatly reduces in transpiration 
  • hairy leaves same for waxy cuticle 
  • curled leaves this confines within a microenvironment of still humid air to reduce diffusion of water vapour from the stomata 
  • succulents plants store water in the parenchyma tissue in their stems and roots - water is stored when it is in plentiful supply and then used in times of droughts 
  • leaf loss - preventing water loss through their leaf loss by losing their leaves when water is not available 
  • root adaptations that allow the to get as much water as possible from the soil - a mass of wide spread shallow roots with a large surface  area able to absorb any available water before a rain shower evaps
Lösung ausblenden
TESTE DEIN WISSEN

explain the process of translocation in phloem loading

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TESTE DEIN WISSEN

there are two ways in which plants load assimilates into the phloem for transport 

phloem loading- apoplast pathway 

  1. hydrogen ions pumped out of the companion cells through the proton pump by active transport using ATP
  2. the hydrogen ions return to the companion cell down a concentration gradient via  a co- transporter protein with sucrose being co-transported 
  3. this increases sucrose concentration in the companion cell so diffuse in the sieve tube elements by plasmodesmata between two linked cells 
  4. this decreases the water potential in the sieve tube so  water moves in by osmosis and this leads to a build up in turgor pressure . the water carrying assimilates moves  moves up or down the plant by mass flow to areas of low pressure (the sink)
Lösung ausblenden
TESTE DEIN WISSEN

explain the process of translocation in phloem unloading.

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TESTE DEIN WISSEN

the mass flow of assimilates as they flow from source to sink down a pressure gradient 

  • the mechanism of phloem unloading is diffusion of the sucrose from the phloem into the surrounding cells 
  • the sucrose rapidly move on into other cells or convert into another substance to maintain a steep concentration gradient between the contents of phloem and the surrounding cells
  • the loss of assimilates from the phloem leads to a rise in water potential of the phloem so water moves into the surrounding cells by osmosis or some water is drawn into the transpiration stream in the xylem
Lösung ausblenden
TESTE DEIN WISSEN

Define translocation

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TESTE DEIN WISSEN

this is the transport of assimilates from the source to the sink in plants

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TESTE DEIN WISSEN

define xerophytes

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TESTE DEIN WISSEN

these are plants that live in a dry habitat that have evolved in a range of adaptations that enable them to live and reproduce in places where water availability is very low indeed. for example, conifers, marram grass and cacti etc

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TESTE DEIN WISSEN

explain the process of transpiration (in depth)

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TESTE DEIN WISSEN
  • water molecules evaporate from the surface of mesophyll cells into the air spaces in the leaf and move out the stomata unto the surrounding air by diffusion down a concentration gradient
  • the loss of water by evaporation from a mesophyll cell lowers the water potential of the cell so water moves into the cell from an adjacent cell by osmosis along both the apoplast pathway and symplast 
  • this is repeated across the leaf to the xylem. water moves out of the xylem by osmosis into the cells of the leaf 
  • water molecules from hydrogen bond with the carbohydrates in the walls of the xylem vessel- adhesion
  • water molecules also form hydrogen bonds with each other and so stick together - cohesion. this combined effects of adhesion and cohesion result in water exhibiting a capillary action. water is drawn up the xylem in a continuous stream to replace the water lost by evaporation. this is known as the transpiration pull. 
  • this transpiration pull results in a tension in the xylem which in turn helps to move water across the roots from the soil
Lösung ausblenden
TESTE DEIN WISSEN

Define Hydrophytes

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TESTE DEIN WISSEN

These are plants that live in water examples include , water lilies etc

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Q:

define transpiration

A:

this is the loss of water vapour by evaporation and this is an inevitable consequence of gas exchange through the stomata

Q:

explain the need for plant transport systems

A:
  • plants need substances- like water, minerals and sugars to live. they also need to get rid of waste substances 
  • big size- this means plants plants need very effective transport systems to move substances up and down from the tip of the root to the top - and so exchanging substances by direct diffusion could be too slow to meet their metabolic needs 
  • plants are multicellular- so have a small SA:V ratio 
Q:

name factors in which affect the transpiration rate

A:
  • light intensity - increasing no. of open stomata increasing the rate of water vapour diffusing out and therefore increasing the evaporation from the surfaces of the leaf 
  • humidity- high humidity means low transpiration because of the reduced water vapour potential gradient between the inside of the leaf and the out the air spaces of the left side of the air 
  • temperature- increase kinetic energy increases the rate of evaporation from the spongy mesophyll cells into the air spaces of the leaf. 
Q:

state features of hydrophytes to adapt

A:
  • thin or no waxy cuticle - no need to conserve water as there is plenty available water for loss by transpiration 
  • many open stomata - maximising the number of stomata maximises gas exchange . this plant there is no risk to the plant of loss of turgor as there is abundance of water so the stomata always open all the time for gas exchange 
  • large surface area of stems and roots - maximises the area for photosynthesis 
  • air sacs this enables the leaves to float on the surface of water 
  • aerenchyma - large air spaces, make the stems and leaves more bouyant
Q:

explain the process of transpiration

A:
  • carbon dioxide moves from the air into the leaf and oxygen moves out by gas exchange by diffusion down concentration gradient through microscopic pores in the leaf on the underside of the leaf called stomata and
  •  these stomata can be opened and closed by guard cells which surrounds the stomatal opening 
  • when the stomata are open to allow an exchange of carbon dioxide and oxygen between the air inside the leaf and the external air water vapour moves out by diffusion and is lost . 
  • this loss of water vapour is transpiration 
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Q:

give examples of strategies xerophytes use to conserve water

A:
  • thick waxy cuticle helps minimise water loss
  • sunken stomata located in pits which reduces air movement producing a moist climate that reduces the water vapour potential gradient and so reduces transpiration 
  • reduced no. of stomata reduce water loss by transpiration , also reduce the gas exchange 
  • reduced leaves- reducing leaf area water loss can be greatly reduces in transpiration 
  • hairy leaves same for waxy cuticle 
  • curled leaves this confines within a microenvironment of still humid air to reduce diffusion of water vapour from the stomata 
  • succulents plants store water in the parenchyma tissue in their stems and roots - water is stored when it is in plentiful supply and then used in times of droughts 
  • leaf loss - preventing water loss through their leaf loss by losing their leaves when water is not available 
  • root adaptations that allow the to get as much water as possible from the soil - a mass of wide spread shallow roots with a large surface  area able to absorb any available water before a rain shower evaps
Q:

explain the process of translocation in phloem loading

A:

there are two ways in which plants load assimilates into the phloem for transport 

phloem loading- apoplast pathway 

  1. hydrogen ions pumped out of the companion cells through the proton pump by active transport using ATP
  2. the hydrogen ions return to the companion cell down a concentration gradient via  a co- transporter protein with sucrose being co-transported 
  3. this increases sucrose concentration in the companion cell so diffuse in the sieve tube elements by plasmodesmata between two linked cells 
  4. this decreases the water potential in the sieve tube so  water moves in by osmosis and this leads to a build up in turgor pressure . the water carrying assimilates moves  moves up or down the plant by mass flow to areas of low pressure (the sink)
Q:

explain the process of translocation in phloem unloading.

A:

the mass flow of assimilates as they flow from source to sink down a pressure gradient 

  • the mechanism of phloem unloading is diffusion of the sucrose from the phloem into the surrounding cells 
  • the sucrose rapidly move on into other cells or convert into another substance to maintain a steep concentration gradient between the contents of phloem and the surrounding cells
  • the loss of assimilates from the phloem leads to a rise in water potential of the phloem so water moves into the surrounding cells by osmosis or some water is drawn into the transpiration stream in the xylem
Q:

Define translocation

A:

this is the transport of assimilates from the source to the sink in plants

Q:

define xerophytes

A:

these are plants that live in a dry habitat that have evolved in a range of adaptations that enable them to live and reproduce in places where water availability is very low indeed. for example, conifers, marram grass and cacti etc

Q:

explain the process of transpiration (in depth)

A:
  • water molecules evaporate from the surface of mesophyll cells into the air spaces in the leaf and move out the stomata unto the surrounding air by diffusion down a concentration gradient
  • the loss of water by evaporation from a mesophyll cell lowers the water potential of the cell so water moves into the cell from an adjacent cell by osmosis along both the apoplast pathway and symplast 
  • this is repeated across the leaf to the xylem. water moves out of the xylem by osmosis into the cells of the leaf 
  • water molecules from hydrogen bond with the carbohydrates in the walls of the xylem vessel- adhesion
  • water molecules also form hydrogen bonds with each other and so stick together - cohesion. this combined effects of adhesion and cohesion result in water exhibiting a capillary action. water is drawn up the xylem in a continuous stream to replace the water lost by evaporation. this is known as the transpiration pull. 
  • this transpiration pull results in a tension in the xylem which in turn helps to move water across the roots from the soil
Q:

Define Hydrophytes

A:

These are plants that live in water examples include , water lilies etc

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