B2 - plant transport systems and transpiration Flashcards
(22 cards)
the phloem …
transports food (mainly dissolved sugars) both up and down the stem
phloem tubes are made up of …
columns of sieve cells
these have perforated end-plates
no nucleus
translocation is …
the movement of food substances around the plant
the xylem …
takes water and minerals from roots to leaves
xylem tubes are made up of …
dead cells with no end walls
hole (lumen) down the middle
companion cells …
carry out living functions for sieve cells (in phloem)
Why is the xylem strong?
thick side walls made of cellulose
strengthened with lignin
provides support for plant
transpiration is …
loss of water from a plant
How does transpiration work?
water evaporates and diffuses from a plant’s surface
this causes a slight water shortage
so more water drawn up from roots
transpiration benefits the plant because …
water keeps plant cool
provides a constant supple of water for photosynthesis
creates turgor pressure in cells - supports plant
minerals brought up with water
transpiration is affected by …
an increase in light intensity
an increase in temperature
an increase in air movement
How does light intensity affect transpiration?
brighter light –> greater rate of transpiration
increases photosynthesis rate
stomata open to let CO2 in
water can escape
How does temperature affect transpiration?
warmer –> greater rate of transpiration
water has more energy to evaporate and diffuse
How does air movement affect transpiration?
lots of air movement –> greater rate of transpiration
when air is still, water vapour surrounds leaf
so high concentration both in and out of leaf
so less diffusion
stomata are found …
on the lower surface of a leaf
darker and cooler here
slows down diffusion of water from leaf
the waxy cuticle …
covers upper epidermis
make leaf waterproof
the more stomata …
the more water is lost
stomata close when …
supplies of water start to dry up
when guard cells are turgid …
stoma opens
when guard cells are flaccid …
stoma closes
What are guard cells’ walls like?
thick outer wall
thin inner wall
helps them open and close
a potometer is …
a piece of equipment used to estimate transpiration rate
