Transport in Plants Flashcards
describe the structure of xylem (6)
dead cells cell joined end to end waterproof hollow plasmodesmata in walls one direction flow
which tissue has end walls
phloem
which tissue has no nucleus
phloem
describe the structure of phloem (3)
has companion cells
flows in all direction
sieve elements cells make up tissue
purpose of xylem
mechanical support and transport of amino acids and water
cells that make up xylem
vessel elements and tracheid, sclerenchyma fibres, parenchyma cells
how sieve plate is formed
two sieve elements meet
adaptations of the companion cell
high number of mitochondria/ribosomes/plasmodesmata in cell wall
peripheral cytoplasm for less resistance
which part of the phloem has the highest concentration of sucrose
sieve element cells
describe the process of translocation (7)
H+ ions move out of companion cell by active transport
H+ diffuse back in with sucrose via.facilitated diffusion
through cotransporter protein
sucrose diffuses into sieve tube element by plasmodesmata
water enters by osmosis
hydrostatic pressure builds up
unloads at sink
definition of transpiration
the loss of water vapour from leaves to its environment
describe the process of transpiration (7)
water diffuses by osmosis from xylem to mesophyll cells
water evaporates from mesophyll cells into air spaces of spongy mesophyll cells
water diffuses out of stomata
water potential reduced
reduces hydrotatic pressure
water pulled by adhesion/cohesion
capillary action
high light intensity affects transpiration
stomata opens more = high rate
describe apoplastic pathways
movement of water through cell wall by osmosis
when does apoplastic pathways normally occur
transpiration rate is high
describe symplastic pathways
movement of water through plasmodesmata
process when apoplastic pathways reaches endodermis
apoplastic pathway blocked by casparian strip
forced to use symplastic pathways
suberin blocks both ways
passage cell used for symplastic pathway
structure of root hair cells (3)
thin permeable cellulose cell wall, more concentrated solution in vacuole, multiple root hair cells
describe xerophytes
plants living in environment with short water supply
what happens to sucrose in translocation after loading in sink
turns into glucose + fructose
used for storage - starch
used for growth - cellulose
respiration
characteristics of xerophytes (4)
sunken stomata
rolled leaves
hairy leaves
thick waterproof cuticle
purpose of xerophytes characteristics (4)
steeper gradient
trapping moist air
protection from sun
greater distance for diffusion
why do plants require transport systems (4)
distance is too great
cells require substances
respiration
large organisms
describe epidermis
thin continuous layer outside the plant
