xylem and phloem

Question 1

features of xylem

Answer 1

takes water and ions up plant
lignin strengthens walls
unaffected by poision or lack of co2 as passive

Question 2

explain cohesion tension

Answer 2

water evapourates from mesophyll cells in leaves from sun
creates tension
water forms h bonds which makes it cohesive and water moves up in columns

Question 3

transpiration factors

Answer 3

evapuration by water from plant leaves
light - lighter, faster
temp- hotter, faster
humidity- less humid, faster
air- windy, faster

Question 4

phloem features

Answer 4

transports sucrose
sieve plates
companion cells w lots of mitochondria for atp

Question 5

translocation

Answer 5

movement of solutes from source to sink. requires energy from atp. enzymes maintain conc grad where low at sink as its converted to starch there

Question 6

mass flow

Answer 6

1 sucrose actively transported sieve tubes in phloem via companion cells at source
2 this lowers wp in sieve tubes so water enters via osmosis
3 creates hp in sieve tubes at source generating mass flow
4 at sink, wp in sieve tues incr so water leaves via osmosis and lowers hp
5 pressure gradient pushes sucrose to the sink.

the higher the conc of sucrose the faster translocation

Question 7

sucrose into the sieve tubes

Answer 7

facilitated diffusion and co transport
sucrose made in chlorplasts during photosynthesis
then via fd moves into companion cells
h+ ions actively trans into companion cells against conc grad using atp
high conc f h+ of companion than in sieve, so h+ diffuse down grad, co transporting sucrose w it

Question 8

mass flow of sucrose to sink

Answer 8

osmosis and mass flow
higher conc of sucrose in sieve tubes at source which lowers wp so water osmoses in
water incr hp in sieve tube at source, and hp low at sink, so mass flow down hp grad, transporting sucrose into sink

Question 9

evidence for mass flow

Answer 9

pressure high in source low in sink
sucrose conc high in source low in sink
phloem stops at night or in shade
lack of co2 stops translocation
companion cells have lots of mitochondria

Question 10

against mass flow

Answer 10

sieve plates hinder mass flow

sucrose goes to all sinks, not ones who have low conc sucrose high wp

Question 11

tissue fluid formation

Answer 11

at arteriole end, hp inside capillaries higher than hp in tf
difference in hp- forces fluid out of capillaries and into spaces surrounding cells
bigger molecules stay in capillaries
as fluid leaves, hp reduces in capillaries and hp lower at venule end
wp at venule lower than tf
so water re enters capillaries from tf at venule end via osmosis

Question 12

tissue fluid return

Answer 12

excess to lymphatic system and returns to circulatory system