plant transport (brain exercise!)

Question 1

state a way that leaves are adapted for gas exchange?

Answer 1

leaves thin = short diffusion distance.

Question 2

why do plants have a lower demand for oxygen than animals?

Answer 2

because they have a lower metabolic rate

Question 3

is parenchyma living or non living? how do we know?

Answer 3

living - has a nucleus!

Question 4

what is the function of parenchyma

Answer 4

packaging tissue - for storage and support

Question 5

difference between xylem and phloem walls

Answer 5

xylem has no end walls, whereas phloem is divided into sieve tube elements with sieve plates.

Question 6

why is it beneficial that xylem has no end walls?

Answer 6

to allow continuous column of water during transpiration

Question 7

function of the xylem other than transport of water and mineral ions?

Answer 7

mechanical support for stems, roots, and leaves (due to lignin)

Question 8

why is lignin beneficial to xylem walls?

Answer 8

adds strength and rigidity - prevents collapse under tension/transpiration pull forces

Question 9

why is it beneficial that the xylem is narrow?

Answer 9

to ensure column of water doesn’t break

Question 10

what is the function of the non lignified pits in the xylem walls?

Answer 10

to allow lateral flow of water

Question 11

why is the cytoplasm pushed to the sides in sieve tube elements?

Answer 11

becomes a thin layer SO less resistance to flow

Question 12

what are amyloplasts?

Answer 12

starch grains

Question 13

function of sieve plate

Answer 13

keeps tubes open ( for support ) and allows tube to be blocked incase of infection

Question 14

what is function of callose?

Answer 14

prevents loss of sap + spread of infection

Question 15

if a phloem is cut, how do the sieve tube elements react?

Answer 15

rapidly block the sieve pores so sucrose accumulates above where it is cut (swelling)

Question 16

what are cytoplasmic strands and what is their function?

Answer 16

• connect companion cell with sieve tube element
• facilitate movement of substances between cells (sucrose)
• enable cell signalling

Question 17

what can cambium produce?

Answer 17

new xylem + phloem cells

Question 18

function of collenchyma

Answer 18

extra support

Question 19

state order of the layers of ‘chyma’ starting from inwards to outwards of a stem

Answer 19

-sclerenchyma
-parenchyma
-collenchyma

Question 20

features of meristematic cells (4)

Answer 20

• thin cell walls
• little cellulose
• no vacuole
• no chloroplasts

Question 21

what 3 organelles do phloem sieve tubes not have?

Answer 21

• ribosomes
• vacuole
• golgi

Question 22

definition of mass flow

Answer 22

bulk transport of material from one point to another as a result of pressure differences between two points

Question 23

why do root hair cells have short diffusion distances?

Answer 23

hair was thin surface layer

Question 24

how can root hair cells carry out active transport of minerals

Answer 24

have many mitochondria to provide ATP

Question 25

how do minerals move from soil to roots?

Answer 25

pumped in via active transport

Question 26

what wall blocks apoplast pathway of water?

Answer 26

casparian strip (suberin)

Question 27

active pumping of mineral ions causes...

Answer 27

root pressure

Question 28

what is another term for capillary action?

Answer 28

cohesion-tension hypothesis

Question 29

how does water availability affect transpiration

Answer 29

cells surrounding stomata lose turgidity so stomata may close to prevent water loss

Question 30

state how number of leaves affect transpiration

Answer 30

more leaves = more stomata to lose water water from therefore increase transpiration

Question 31

how does presence of cuticle affect water loos? (transpiration)

Answer 31

the thicker the cuticle the slower the rate of transpiration. (thicker leaves in younger + shaded plants)

Question 32

what safety procedures must be taken into account when using a potometer?

Answer 32

- glass tubing - secateurs (sharp) - allergies (wear gloves)

Question 33

in a potometer test, why must you put vaseline on the joints?

Answer 33

to make the leaf airtight + watertight

Question 34

why must you leave the potometer experiment set up for a good 5 minutes before you start recording

Answer 34

to allow plant to acclimatise

Question 35

why is it advantageous that cacti have spines instead of leaves?

Answer 35

reduces surface area for water loss

Question 36

explain the adaptation of stomata in cacti?

Answer 36

they close at the hottest times when transpiration would be highest in order to retain water

Question 37

function of the hairs on marram grass

Answer 37

to trap humid air to decrease water potential

Question 38

why are pits in marram grass adapted to have sunken stomata?

Answer 38

shelters from wind + traps moist air = decreasing water potential gradient = slower transpiration

Question 39

why do marram grass have rolled leaves? (3)

Answer 39

-minimise surface area of moist tissue exposed to air -protects leaves from wind -funnel rainwater to the roots

Question 40

what does a xerophyte have that a hydrophyte lacks?

Answer 40

waxy cuticle is absent

Question 41

what is the function of aerenchyma (airspaces) in a hydrophyte?

Answer 41

males leaves buoyant = float to surface for light

Question 42

hydrophytes are wide and flat - how is this beneficial for photosynthesis?

Answer 42

increases surface area = more light captured = increasing gas exchange.

Question 43

list the three features that reduces loss of water vapour in xerophytic leaves

Answer 43

- hair leaves - rolled/curled up - thick waxy cuticle

Question 44

definition of translocation

Answer 44

movement of dissolved substances (solute) like sucrose and amino acids to where they are needed in a plant

Question 45

what molecule is soluble and metabolically inactive?

Answer 45

sucrose

Question 46

name the 3 stages of translocation

Answer 46

1. phloem loading (active) 2. mass flow (passive) 3. phloem unloading

Question 47

in active loading, how do protons move through the cell surface membrane of a companion cell?

Answer 47

proton pump (active)

Question 48

what happens during mass flow

Answer 48

bulk transport of sucrose and amino acids down pressure gradient from source to sink

Question 49

what happens during phloem unloading

Answer 49

sucrose -> moves into sink cells and is used up

Question 50

what process supplies energy to pump H ions out of companion cells?

Answer 50

ATP hydrolysis

Question 51

sucrose and H ions are transported by co-transporter protein via which process?

Answer 51

facilitated diffusion

Question 52

how does sucrose diffuse into sieve tube elements?

Answer 52

via the plasmodesmata

Question 53

effects of cyanide on plants

Answer 53

poisons mitochondria = no energy = no active loading of sucrose = no translocation

Question 54

what is sucrose used for at the sink end?

Answer 54

converted into glucose for respiration or storage of starch

Question 55

how is mass flow maintained?

Answer 55

decrease hydrostatic pressure at sink allows pressure gradient for mass flow to be maintained

Question 56

why is concentration gradient for sucrose being maintained?

Answer 56

because its constantly being used up by sink cells.