transport in plants

Question 1

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

Answer 1

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

Question 2

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

Answer 2

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

Question 3

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

Answer 3

provides support and flexibility to withstand bending forces on stem

Question 4

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

Answer 4

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

Question 5

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

Answer 5

provides strength to withstand pulling forces experienced by roots

Question 6

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

Answer 6

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

Question 7

state the meaning of transpiration

Answer 7

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

Question 8

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

Answer 8

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

Question 9

describe how water moves from cell to outside

Answer 9

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

Question 10

what are 5 environmental factors that increase transpiration rate

Answer 10

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

Question 11

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

Answer 11

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

Question 12

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

Answer 12

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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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

Question 15

how does the structure relate to function of stomata?

Answer 15

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

Question 16

how does a guard cell become turgid?

Answer 16

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

Question 17

explain when stomata open and close

Answer 17

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

Question 18

describe the movement of water form soil to root

Answer 18

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

Question 19

describe the movement of water from root to neighbouring cells

Answer 19

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

Question 20

describe the movement of water in the apoplast pathway

Answer 20

water flows through spaces in cell walls, not plasma membranes

Question 21

describe the movement of water in the symplast pathway

Answer 21

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

Question 22

describe the movement of water In vacuolar pathway

Answer 22

transfers through vacuoles

Question 23

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

Answer 23

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

Question 24

state the 3 ways water moves up the xylem

Answer 24

root pressure, transpirational pull, capillary action

Question 25

describe how root pressure moves water up xylem

Answer 25

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

Question 26

describe how transpiration pull moves water up xylem

Answer 26

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

Question 27

describe how capillary action moves water up xylem

Answer 27

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

Question 28

describe the movement of water from xylem to leaves

Answer 28

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

Question 29

what are assimilates?

Answer 29

substances that have become a part of the plant

Question 30

why is sucrose used by the plant ?

Answer 30

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

Question 31

explain the mechanism of transpiration

Answer 31

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.

Question 32

How does sucrose unload at the sink?

Answer 32

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

Question 33

How is sucrose transported along phloem ?

Answer 33

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 

Question 34

what is a hydrophyte ?

Answer 34

adapted to a water based habitat

Question 35

what is a xerophyte?

Answer 35

adapted to a dry habitat

Question 36

what is a halophyte ?

Answer 36

adapted to a salty habitat

Question 37

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

Answer 37

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

Question 38

What are five adaptions to a water lily?

Answer 38

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