transport in plants Flashcards

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1
Q

what is the need for a transport system in a multicellular plant?

A

larger plant have a smaller SA:VOL so have an increased diffusion distance so it wouldn’t be quick enough to supply the volume of the plant with nutrients. sugars are made in leaves but will need to get to other parts of the plant, same for water in the roots

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2
Q

where are the vascular bundles in the stem ? xylem, phloem, cambium

A

round outside,
phloem =outer most layer
cambium = in-between phloem and xylem
xylem = innermost

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3
Q

what is the function of the vascular bundles in the stem ?

A

provides support and flexibility to withstand bending forces on stem

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4
Q

where are the vascular bundles in root? xylem, phloem, cambium

A

xylem - star like shape in middle
phloem - in-between the points of the star of the xylem
cambium - layer inside epidermis (pericycle)

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5
Q

what is the function of vascular bundle arrangement in a root?

A

provides strength to withstand pulling forces experienced by roots

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6
Q

where is the vascular bundles in a leaf? xylem, phloem

A

midrib of leaf watermelon shape
xylem = on top of phloem
phloem = round edge of xylem

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7
Q

state the meaning of transpiration

A

loss of water vapour from a plant to its environment by evaporation and diffusion form roots to leaves

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8
Q

describe how a water potential gradient is maintained during transpiration and causes a water movement to leaves

A

loss of water vapour from leaves creates a lower water potential in plants creating a concentration gradient between roots and leaves so water moves upwards towards leaves

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9
Q

describe how water moves from cell to outside

A

water evaporates out of spongy mesophil into air spaces as water vapour where it diffuses out of stomata down a water potential concentration gradient

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10
Q

what are 5 environmental factors that increase transpiration rate

A

high wind, high light intensity, high temp, high water availability, low humidity

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11
Q

how does an increase in wind cause transpiration rate to increase?

A

blow away water vapour in air surrounding leaf, increases water vapour potential gradient out o leaf so maintains steep concentration gradient

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12
Q

how does an increase in light intensity cause transpiration rate to increase?

A

increased rate of photosynthesis, more stomata open to allow more co2 in so more water vapour is able to diffuse out

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13
Q

how does an increase in temperature cause transpiration rate to increase?

A

water molecules have more kinetic energy so will evaporate into air spaces quicker so therefore increases water vapour potential gradient and rate of diffusion out increases
hotter air can hold higher concentration of water vapour

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14
Q

how does an decrease in humidity cause transpiration rate to increase?

A

more water molecules in surrounding air, decrease concentration gradient from in to out of leave and therefore decreasing rate of diffusion

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15
Q

how does the structure relate to function of stomata?

A

thick inner wall- so doesn’t change shape when tugged so stays convex
thin outer wall - moves outwards when turgid so both will create an opening gin the centre for gases

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16
Q

how does a guard cell become turgid?

A

potassium ions are brought into the cell to lower water potential so water then moves in to make it turgid

17
Q

explain when stomata open and close

A

open - day as photosynthesis ongoing from sunlight present reactants present
close-night as to reduce water loss, can’t photosynthesis as sunlight is limiting reagent

18
Q

describe the movement of water form soil to root

A

mineral ions flow into root by active transport because there is a higher conc in root than soil, this lowers w.p in root therefore water moves in via osmosis, root has large SAand thin walls to maximise osmosis

19
Q

describe the movement of water from root to neighbouring cells

A

there is a more negative w.p in next cell because there is an abundance of water In currant cell, so water moves to next cell via osmosis
can now take 3 routes, apoplast, symplast, vacuolar through cells

20
Q

describe the movement of water in the apoplast pathway

A

water flows through spaces in cell walls, not plasma membranes

21
Q

describe the movement of water in the symplast pathway

A

enters cytoplasm through plasma membrane then goes to next cell via the plasmodesmata (gaps in cell wall which connects two cells

22
Q

describe the movement of water In vacuolar pathway

A

transfers through vacuoles

23
Q

describe the movement of water from cells in root to xylem vessel

A

water from any pathway reaches casparian strip (waxy, waterproof made of Suberin) and all water has to enter symplast pathway. plasma membrane contains transporter proteins which actively pump mineral ions from cytoplasm of cortex cells to medulla and xylem, xylem now has lower w.p so water moves into vessel via osmosis

24
Q

state the 3 ways water moves up the xylem

A

root pressure, transpirational pull, capillary action

25
Q

describe how root pressure moves water up xylem

A

water going from endodermis to xylem it lowers water potential in endodermis so draws water into xylem. pressure in root medulla increases and forces water into xylem which forces water up xylem

26
Q

describe how transpiration pull moves water up xylem

A

water molecules are attracted to each other by cohesion, this force is strong enough to form acolumn of water, water lost at top so more is pulled up, pull creates tension so walls are reinforced with lignin so doesn’t collapse

27
Q

describe how capillary action moves water up xylem

A

water molecules are attracted to each other via cohesion this also attracts the molecules to the side of the xylem (adhesion) vessel is narrow so adhesion pulls molecules up sides

28
Q

describe the movement of water from xylem to leaves

A

movement of water from xylem to leaves creates low hydrostatic pressure so water evapourates from sub-stomatal air spaces therefore lowering w.p in these cells so water is drawn in down conc grad from xylem to cell by osmosis

29
Q

what are assimilates?

A

substances that have become a part of the plant

30
Q

why is sucrose used by the plant ?

A

non-reducing so more unreactive and it contains glucose and fructose which Is used by fruits so more effective

31
Q

explain the mechanism of transpiration

A

H plus ions are pumped out of companion cell into mesophyll cells by active transport . they then move back into companion cell down a concentration gradient because there is a high concentration of H plus ions in mesophyl cells. They move back into companion cell through co transporter proteins but they only allow them through if they’re attached to sucrose so they move by facilitated diffusion. There is a buildup of crows inside companion cells therefore it moves by diffusion into tube elements and concentration is increased in the sieve tube of sucrose. This lowers the water potential in the tube so water now moves into safe tube by was Moses from surrounding cells. This increases of pressure inside causing movement of water and stimulates by mass flow from source to sink.

32
Q

How does sucrose unload at the sink?

A

Citrus diffuses or by active transport into cell surrounding sift tube elements at the sink through plasmodesmata. The removal of crows makes water potential higher so water moves out of tube into surrounding cells by osmosis. This reduces hydrostatic pressure in phloem at the sink so maintains mass flow inside of phloem

33
Q

How is sucrose transported along phloem ?

A

Sucrose actively loaded into sieve tube element and reduces water potential, water flows in by osmosis and increases hydrostatic pressure, sap moves from high to low hydrostatic pressure. Sucrose is removed by surrounding cells and increases water potential in sieve tube so water then moves out and lowers hydrostatic pressure 

34
Q

what is a hydrophyte ?

A

adapted to a water based habitat

35
Q

what is a xerophyte?

A

adapted to a dry habitat

36
Q

what is a halophyte ?

A

adapted to a salty habitat

37
Q

What are five adaptions to plants living on land to reduce water loss?

A

Waxy cuticle on leaf- reduce water loss by evaporation
Stomata found on under side of leaf- reduces operation by direct sunlight
Stomata shut at night -no need to photosynthesise as there’s no sunlight
Deciduous plants lose leaves in winter - the ground is frozen less water available temperature is too low for photosynthesis
Deep roots- to find water and stabilise soil

38
Q

What are five adaptions to a water lily?

A

Big leaf surface area-flow on surface and attract and poor sunlight as water is not a limiting factor
Stomata on upper side - only way to release water vapour and get access to gaseous exchange
Small roots - don’t need to forage for water so don’t need to waste energy uses energy to strengthen stem and leaf
Leaves and stems have wide airspaces internally- less dense than the water so floats, allows oxygen to diffuse quickly around plant