4.4

Question 1

xylem

Answer 1

water and disolved mineral ions
from roots to leaves
one way transport
dead cells
cell walls with lignin
hollow
pits
dead

Question 2

phloem

Answer 2

living tissues
sucrose
from leaves (where produced) to where it is needed
mass flow
translocation
no lignin
no pits
companion cells and sieve plates

Question 3

cambium

Answer 3

layer of unspecialised cells that divide, giving rise to more specialised cell that in turn form both the xylem and the phloem

Question 4

formation of the xylem

Answer 4

starts as living tissue
first xylem to form is protoxylem - streches and grows because the walls are not fully lignified
cellulose microfibrilis withstands the pressure of compression
as the cells age increasing amount of lignin is joined to the cell wall
the cells then become inpermeable to water and die
this lignified xyem is a metaxylem
the end walls mostly break down so the xylem is a hollow tube

Question 5

xylem support

Answer 5

pays important role in larger plants.
as the plants age more xylem is lignified to increase support

Question 6

support in small plants

Answer 6

non woody
turgid parenchyma cells
sclerenchyma
collenchyma

Question 7

evidence of the xylem

Answer 7

dye can be seen moving through a plant

Question 8

parenchyma

Answer 8

thin walls of cellulose

Question 9

collenchyma

Answer 9

cell walls with thickened areas of additional cellulose

Question 10

sclerencyma

Answer 10

have lignified cell walls
2 types - sclereids and fiber (long and thin) cells
support

Question 11

symplast pathway

Answer 11

water moves down concentration gradient from hair to the xylem through cytoplasm of cells
moves through plasmodesmata gaps in cellulose walls
living
slower
osmosis

Question 12

apoplast pathway

Answer 12

water is pulled in by the attraction between water across adjacent cell walls from root hair to xylem
up to half of cell wall can be filled with water
water moves across cells walls until it reaches the endodermis which contains the waterproof layer called the casparian strip - then enter cytoplasm
non living
faster
diffusion

Question 13

translocation

Answer 13

movment of substances arount plants
passive process in xylem
active in phloem

Question 14

transpiration

Answer 14

loss of water vapour from the surface of the plant

Question 15

xylem movments

Answer 15

xylem proved by josef using porous pot
transpiration
water lost from leaves
lower water potential
cohesion - water polat
adhesion of water to xylem

Question 16

transpiration
light

Answer 16

stoma open in light and closed in dark
so rate increase with light intesity untill all stoma open

Question 17

transpiration
temp

Answer 17

temp increases evaporation
increases amount of water vapour before saturation
increase conc gradient
so increased rate
eventualy there will be a limiting factor

Question 18

transpiration
wind

Answer 18

reduces shell of air
increases conc gradient
increased rate

Question 19

transpiration
humidity

Answer 19

lowers rate as reduced conc gradient

Question 20

translocation

Answer 20

phloem transports assimilate
mass transport system
- sap is the transport medium

Question 21

guttation

Answer 21

when transpiration rates are low and drops of water are forced out of the leaves

Question 22

sources

Answer 22

site of sugar production

Question 23

sinks

Answer 23

where sugar is used or stored

Question 24

phloem loading

Answer 24

1.sympast pathway - sucrose moves by diffusion down a conc gradient into companion cells through cytoplasm and into seive cells then water moves by osmosis into seive tube causing positive hydro static pressure - passive
2.apoplast pathway - moves by diffusion down a conc gradient through cell wall to companion cell across membranes by active transport producing a high conc in the cytoplasm of companion cells , passes into seive tubes through plasmodesmata. water then moves due to os producing positive hydrostatic presssure

Question 25

unloading

Answer 25

into sink cells by diffusion then sucrose moves rapidly into the other cells maintaing the diffusion gradient

Question 26

evidence for transclocation

Answer 26

use radioactivity (carbon 14) to measure where glucose goes

Question 27

limitations of mass flow model

Answer 27

• dosent take active loading of sucrose in to phloem seive cells into account, this changes the conc gradient, rate of osmosis and even direction
  -translocation is continous
  -water can move in at any point
• return route of water is xylem
• pressure flow is better

Question 28

transport through the phloem

Answer 28

moves as a solution
sucrose actively pumped into phloem at the source
sucrose moves out the phloem into the sink tissues
and moves to a region of lower hydrostatic pressure

Question 29

stomata

Answer 29

guard cells become larger
inner wall is less flexible than the outer

Question 30

minteral ions into plant

Answer 30

active transport through carrier proteins in the cytoplasm root cells

Question 31

gas exhange in roots

Answer 31

CO2 out
O2 in

Question 32

gas exchange surface in woody plant

Answer 32

lenticel

Question 33

slowest conditions for water uptake

Answer 33

cold, humid and dark
low wijnd speed

Question 34

movement of sugards

Answer 34

sugars pumped in phloen so water enters
pressure in phloem increases
sugars converted to starch in root cells
increase in water potential so water moves out

Question 35

aerenchyma

Answer 35

when parenchyma is modified to create tissues with air spaces for buoyancy or aeration of tissues,