transport in plants

Question 1

what adaptations of plants increase SA:V?

Answer 1

some plants have a branching body type
leaves are flat and thin
roots have root hair

Question 2

what is mass flow

Answer 2

the bulk movements of materials

Question 3

How is mass flow helpful to cells?

Answer 3

help to bring substances quickly from one exchange site to another
maintain the diffusion gradients sites between cells and their fluid surroundings
ensure cell activity by keeping the immediate fluid environment of cells within a suitable metabolic range

Question 4

what is the function of the xylem?

Answer 4

because the vascular tissue carries dissolved minerals and water up the plant
structural support
food storage

Question 5

function of phloem tissue?

Answer 5

transport organic compounds, particularly sucrose, from source to the sinks

Question 6

what 4 tissues make up xylem?

Answer 6

tracheids( narrow tapered cells with pits)
vessel elements (large w/ thickened cell walls and no end plates when mature)
xylem parenchyma (can store water)
schlerenchyma cells (fibres & sclereids)

Question 7

describe the structure of a xylem

Answer 7

• lignified cell walls
• no end plates
• no protoplasm
• pits in wall
• small diameter of vessels

Question 8

draw a diagram for xylem and vessel in roots

Answer 8

check google

Question 9

draw a diagram for xylem and vessel in leaf

Answer 9

check google

Question 10

draw a diagram for xylem and vessel in stems

Answer 10

check google

Question 11

describe the structure of a sieve tube element in the phloem

Answer 11

• sieve plates with sieve pores
• cellulose cell wall
• no nucleus, vacuole or ribosomes in mature cells (some ER & mitochondria are present)
• thin cytoplasm

Question 12

describe the structure of a companion cell

Answer 12

• nucleus and other organelles present
• transport proteins in plasma membrane
• large numbers of mitochondria
• plasmodesmata (channels in the cell wall)

Question 13

what is a transpiration stream?

Answer 13

refers to the movement of water from the roots to the leaves

Question 14

what is transpiration?

Answer 14

the loss of water vapour from a plant to its environment by evaporation and diffusion

Question 15

why is transpiration useful?

Answer 15

• provides a way to cool down plant via evaporative cooling
• helpful in uptake of mineral ions
• turgor pressure of the cells provides support to leaves and
  stem of non woody plants

Question 16

describe the process of transpiration (2 steps)

Answer 16

1. evaporation of water molecules from the surface of mesophyll cells to air space (H2O(l) -> H2O(g))
2. diffusion of water vapour out of stomata when there is a concentration gradient

Question 17

how does humidity affect the rate of transpiration

Answer 17

humidity -> water content in air so the water potential gradient is created

Question 18

how does air movement affect rate of transpiration

Answer 18

air movement -> maintaining conc. gradient to replace saturated/ humid air

Question 19

how does temperature affect rate of transpiration

Answer 19

temperature -> temp ↑ leads to thermal energy ↑ so kinetic energy ↑ so evaporation is higher

Question 20

how does light intensity affect rate of transpiration

Answer 20

light intensity -> signals guard cells to open and close stomata so the SA of transpiration ↑

Question 21

what factors affect the rate of transpiration

Answer 21

light intensity, temperature, air movement and humidity

Question 22

what two pathways that move water along the cortex?

Answer 22

apoplastic pathway and symplastic pathway

Question 23

what does the apoplastic pathway do?

Answer 23

through cell wall by diffusion. can occur from cell wall to cell wall directly or through intracellular spaces

Question 24

what is the casparian strip made of and purpose?

Answer 24

it is made of suberin and is a thick, waterproof and a waxy band. stops the apoplastic pathway

Question 25

what is the symplastic pathway?

Answer 25

when water is transported through osmosis in the cytoplasm and plasmodesmata of the cells

Question 26

what is the cohesion-tension theory?

Answer 26

cohesion is the idea of attraction between H2O molecules and adhesion is the idea of the attraction to the xylem vessel. when water moves through xylem due to these properties of H2O

Question 27

what is the role of the stomata?

Answer 27

the guard cells open when turgid and close when they lose water. helps the process of transpiration

Question 28

describe the process of water movement through a lead (5 steps)

Answer 28

1) water vapour diffuses from air spaces through stoma by transpiration lowering the water potential
2) water evaporates from a mesophyll cell wall into the air spaces, creating a transpiration pull
3)water moves out through the apoplastic pathway to symplastic pathway
4)water leaves xylem vessel through a non lignified area (pit)
5) water moves up the xylem vessel (transpiration stream)

Question 29

what is translocation?

Answer 29

the transport of assimilates via the phloem from sources to sinks which requires the input of metabolic activity

Question 30

list some examples of sources for assimilates

Answer 30

-> green leaves and green stem
-> storage organs (e.g.tubers and tap roots)
-> food stores in seeds