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Biology > M3 chapter 9: Transport in plants > Flashcards

M3 chapter 9: Transport in plants Flashcards

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1
Q

what does the xylem transport?

A

water and mineral ions from roots to leaves

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2
Q

what are the xylem and phloem responsible for?

A

transport of reactants and products of chemical reactions around the plant

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3
Q

what is lignin?

A

waterproofs xylem and provides reinforcement to stop xylem collapsing. lignification leads to death of xylem cells

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4
Q

what is capillary action?

A

forces of attraction such as cohesion and adhesion pull water up the xylem vessels.

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5
Q

what is parenchyma?

A

packing tissue which fills spaces between xylem and phloem.

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6
Q

what does phloem transport?

A

cell sap which is sucrose dissolved in water
amino acids

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7
Q

what are some features of the sieve tube elements?

A

don’t contain a nucleus
have little cytoplasm
perforations between sieve tubes

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8
Q

what are companion cells?

A

carry out active processes which are needed to add assimilates into the sieve tubes.

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9
Q

what are plasmodesmata?

A

thin strands of cytoplasm that links content of adjacent cells which allows assimilates to flow between cells

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10
Q

how are root hair cells adapted to their function?

A

have a large surface area and lots of mitochondria to provide energy for active transport and draw more water into a plant

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11
Q

what is the epidermis?

A

outermost layer of a cell of a plant which contains root hair cells

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12
Q

how does water enter the root hair cell?

A

mineral ions move into the root hair cell by active transport which then lowers the water potential in the root hair cell, which then causes the water to move into the cell via the water potential gradient

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13
Q

what is the symplast pathway?

A

where water enters the cytoplasm through the plasma membrane and passes from one cell to the next through plasmodesmata, the channels
which connect the cytoplasm of one cell to the next.

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14
Q

what is the apoplast pathway?

A

where the water moves through the water filled spaces between cellulose molecules in the cell walls. In this pathway, water doesn’t pass through any plasma membranes therefore it can carry dissolved mineral ions and saltswhere the water moves through the water filled
spaces between cellulose molecules in the cell walls.

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15
Q

what is the casparian strip?

A

part of the root called the endodermis, it encounters a layer of suberin which is known as the Casparian strip, which cannot be penetrated by water.

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16
Q

what is the vacuolar pathway?

A

Movement of water molecules in plant cells via the vacuoles located in the cytoplasm of the cell.

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17
Q

what is the endodermis?

A

cylinder of cells that forms the final boundary between the cortex and inner region of plant

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18
Q

how do ions get from the casparian strip to the xylem?

A

transport proteins actively pump mineral ions into the medulla

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19
Q

what is transpiration?

A

movement of water in a plant

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20
Q

why is transpiration inevitable?

A

the stomata have to remain open during the day due to needing light for photosynthesis

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21
Q

how does the plant make up for the water lost by transpiration?

A

water moves up the xylem known as transpiration pull

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22
Q

what 3 forces that contribute to transpiration pull?

A

cohesion
tension
adhesion

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23
Q

what is cohesion?

A

attraction between water molecules caused by hydrogen bonds formed between negative oxygen and positive hydrogen molecules. this holds the water molecules together in a long chain

24
Q

what is tension?

A

pulling force which pulls the collum of water up the xylem

25
Q

what is adhesion?

A

attraction between the water molecules and walls of xylem vessel. xylem vessels are narrow so forces can pull water up by capillary action

26
Q

what is root pressure?

A

force that pushes the fluids (mostly water) upwards into the xylem vessels in the stem from the roots

27
Q

how does water get into root hair cells?

A

via osmosis

28
Q

how does water get into the stem from the roots?

A

via root pressure

29
Q

how does water travel up the xylem?

A

capillary action (adhesion) pulls water to sides of xylem. cohesion holds the collum of water together which is then pulled up the plant by tension

30
Q

why is there a constant flow of water through the xylem?

A

as transpiration occurs it creates a transpiration pull so water is needed to replace the water lost

31
Q

what is sub stomatal air space?

A

area of air spaced just above the stomata

32
Q

how much water is lost during transpiration?

A

around 95%

33
Q

how is water vapour formed in a leaf?

A

water evaporates from the spongy mesophyll to form water vapour in the air pockets

34
Q

how does water vapour move out of the leaf?

A

as a result of water evaporation, the water vapour potential increases so it will move to an area of low water potential and diffuse out of the leaf via the stomata.

35
Q

what is translocation?

A

Moves food substances from leaves to rest of plant and from stores such as in the roots

36
Q

what has to happen before the phloem can transport assimilates?

A

actively load them into the sieve tubes to be transported

37
Q

what protein is used in the process to actively load assimilates into the sieve tubes?

A

co transporter proteins which moves 2 molecules into a cell together one goes down the conc gradient and one goes against the conc gradient

38
Q

what is hydrostatic pressure?

A

pressure exerted by a fluid on its container at a given point. this creates a pressure gradient so fluid moves to area of less pressure from source to sink

39
Q

how are assimilates moved into the sieve tubes bfrom the companion cells?

A

-atp is hydrolyzed to form adp. this is used to actively transport h+ions out of the cell
-sucrose and h+ ions enter the cell using cotransporter proteins
-high conc of sucrose in companion cell so moves down conc gradient by plasmodesmata into phloem
-this lowers the water potential in sieve tube so water moves in
-this creates cell sap and due to hydrostatic pressure moves it towards the ‘sink’

40
Q

what cells determine if stomata are open or closed?

A

guard cells

41
Q

how does water move into the guard cells?

A

via osmosis down the water potential gradient

42
Q

why is a hole (stomata) created by guard cells?

A

they have an assymetric configuration so the inner wall is thicker than outer wall. when there is lots of water this causes it to swell and bend creating a pore in the middle aka the stomata

43
Q

what increases the rate of transpiration?

A

air movement
relative humidity
temperature
light intensity
soil water availability

44
Q

how does air movement affect transpiration rate?

A

air pockets can get trapped below leaf near stomata, which can trap H2O in them. this lowers the water potential gradient so so more water will diffuse out of the stomata. if it is windy this wouldn’t happen as pockets of air are constantly moving away which maintains a steep water potential gradient

45
Q

how does relative humidity affect transpiration rate?

A

less humidity means less moisture in the air which increases the rate of transpiration ad there is a steeper water potential gradient and water is more likely to move.

46
Q

how does temperature affect transpiration rate?

A

increases temperature means the H2O molecules have more kinetic energy therefore they will move faster out of the leaf, increasing the rate of diffusion and transpiration

47
Q

how does light intensity affect transpiration rate?

A

stomata open when its light so increased light means more stomata are open so more holes for water to diffuse out of. increased transpiration rate

48
Q

how does soil-water availability affect transpiration rate?

A

is a plant has less water it is more liekly to be under water stress so will conserve water as much as possible for photosynthesis and other processes. this lowers the rate of diffusion

49
Q

how can we measure transpiration rate?

A

using a potometer, this measures water uptake which can show how much water is used and evaporated by a plant (transpiration) by how far the air bubble moves in the capillary tube

50
Q

what is a xerophyte?

A

plant adapted to survive in dry conditions

51
Q

what is a hydrophyte?

A

plant adapted to live in wet conditions

52
Q

what is an example of a xerophyte?

A

marram grass which is found on beaches and sandy areas
cacti which are found in desserts

53
Q

what adaptations do xerophytes have?

A

-very big roots to find water over a large SA
-leaves are rolled up longitudinally which -traps humid air, lowering the rate of water loss
-waxy cuticle on outer side of leaf reducing evaporation
-stomata on inner surface and in pits which reduces air movement
-spongy mesophyll is very dense so less air pockets so less room for evaporation
-ribbed stems so it can expand to accommodate and store more water
-no leaves so no water can be lost that way (in cacti)

54
Q

what is an example of a hydrophyte?

A

water lillies

55
Q

how are hydrophytes adapted?

A

-large air spaces to keep afloat to get sunlight and CO2 for photosynthesis
-stomata are on the upper epidermis so they are exposed to the air so water can evaporate
-leaf stems have large air spaces which allows O2 to diffuse quickly to roots for respiration and to keep plant afloat
-have hydathodes which release water droplets which lowers the water potential in the leaves generating a transpiration pull

Biology (15 decks)

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