Transport in Plants

Question 1

what are the properties of water

Answer 1

1. it’s an important metabolite
2. it’s a good solvent
3. relatively large latent heat of vaporisation
4. relatively high heat capacity
5. has strong cohesion between molecules

Question 2

what’s metabolic reaction

Answer 2

process that occurs in living cells

Question 3

what’s a metabolite

Answer 3

a substance involved in a metabolic reaction

Question 4

what’s the function of the stomata

Answer 4

tiny pores on the leaf where gases diffuse in and out

Question 5

what’s the function of the xylem

Answer 5

transports water and mineral ions up the plant

Question 6

what’s the function of the spongy mesophyll

Answer 6

contains air spaces for gaseous exchange

Question 7

what’s the function of the epidermis

Answer 7

transparent layer on top of the leaf allows sunlight through the leaf for photosynthesis

Question 8

what’s the function of the waxy cuticle

Answer 8

Wax layer on top of the leaf, prevents transpiration

Question 9

what’s the function of the palisade mesophyll

Answer 9

long cylinderal cells where photosynthesis occurs

Question 10

what’s the function of the phloem

Answer 10

transports dissolved sugars/assimilates up and down the plant

Question 11

what direction does water move in the roots

Answer 11

from an area of high water potential to area of low water potential

Question 12

what’s the apoplast pathway

Answer 12

when water moves through the cell walls of the cells in the roots

Question 13

what’s the symplast pathway

Answer 13

water moves through the cytoplasm via the plasmodesmata of the cells in the roots

Question 14

what’s the vacuolar pathway

Answer 14

water moves through the vacuole of the cells in the roots

Question 15

how is the apoplast pathway stopped

Answer 15

by the endodermis cells as they contain suberin
this is a waterproof substance doesn’t allow water molecules to move through it
this is called the casparian strip

Question 16

what’s the function of a xylem vessel

Answer 16

• elongated tubes formed from dead cells
• no end walls between cells
• thick walls made of lignin
• gaps in the cell wall called pits

Question 17

what does lignin do in the xylem walls

Answer 17

allows water to leave the vessels
prevent collapsing

Question 18

what’s transpiration

Answer 18

the loss of water vapour from the aerial parts of the plant

Question 19

what’s the transpiration stream

Answer 19

the flow of water from the root, through the xylem to the leaves

Question 20

explain the cohesion-tension theory

Answer 20

1. water evaporates due to heat from sun (transpiration)
2. increase in water tension pulls more water to the leaf - transpiration pull
3. when some are pulled into the leaf other molecules follow
4. pulling a column of water in the xylem
5. water enters the stem through the roots

Question 21

evidenced for cohesion-tension theory

Answer 21

• changes in tree diameter
• cut flower
• broken xylem

Question 22

what are the factors effecting transpiration

Answer 22

1. light intensity
2. temperature
3. humidity
4. air movement

Question 23

what’s the formula for measuring the rate of transpiration

Answer 23

πr²h

Question 24

what are some adaptation of xerophytes

Answer 24

• sunken stomata
• rolled leaves
• thicker waxy cuticle
• stomatal hairs
• extensive root systems

Question 25

what are some adaptations of hydrophytes

Answer 25

- roots as anchors - air sacs - wide flat leaves - no/thin waxy cuticle acting as a water resistor - stomata on upper surface

Question 26

what's the structure of the phloem

Answer 26

- tube formed from elongated living cells (sieve tubes) - no nucleus, just thin layer of cytoplasm - sieve tubes are supported by companion cells

Question 27

what's a source

Answer 27

produces or releases glucose and converts it into sucrose

Question 28

what's a sink

Answer 28

any part of the plant that's metabolically active

Question 29

why do plants transport sucrose rather than glucose

Answer 29

it's more stable and less reactive, glucose would get used up quicker

Question 30

explain mass flow hypothesis

Answer 30

1. source releases sucrose into phloem -> high sucrose concentration, decreseing water potential 2. mass flow of solutes -> turgor pressure gradient created between source and sink 3. sink removes sucrose from phloem -> low sucrose concentration, increases water potential in sieve tubes

Question 31

define translocation

Answer 31

transport of assimilates from source to the sink

Question 32

how are companion cells adapted for active loading

Answer 32

have many mitochondria to produce ATP

Question 33

what principle does mass flow work in sieve tubes work

Answer 33

tugor pressure difference

Question 34

what principles does phloem unloading work

Answer 34

diffusion of sucrose by converting it to glucose

Question 35

what's the role of hydrogen ions in active loading

Answer 35

they're pumped out of the companion cells, creating a hydrogen ion concentration gradient across the cell membrane