Transport in flowering plants Flashcards
topic 2 H .2
the phloem and xylem make up the transport system of
vascular plants
the role of the xylem is to
transport water and mineral ions from the roots to the shoots of the plant
the xylem is formed from
dead cells reinforced by lignin
the cell wall in the xylem is
broken down
the walls in the xylem are thickened by
lignin
the xylem has contents of
continuous column of water
role of the phloem is to
transport sucrose and amino acids throughout the plant
phloem is formed by
living cells forming a tube with small holes through which substances can move
root hair cells contain _____ which releases energy for active transport
mitochondria
root hair cells increase ___ ____ of plant roots, increasing the rate at which water and minerals can be taken up
surface area
how do root hair cells take up mineral ions and water from the soil
by active transport and osmosis
water moves into the root hair cells by
osmosis
water moves into the root hair cells through the __ ___ and into the ___
root cortex
xylem
once water has gotten into the xylem, it is carried up to the ___ where it enters ____ cells
leaves
mesophyll
pathway of water through plants
root hair cells
root cortex cells
xylem
leaf mesophyll cells
transpiration is defined as
The loss of water by evaporation from the leaves of plants
loss of water occurs through ___ at the surfaces of ___ ____ cells
evaporation
spongy mesophyll
after the evaporation of water from spongy mesophyll cells, ___ of water ___ through the stomata happens
diffusion
water vapour
functions of transpiration in plants (4)
- transporting mineral ions
- Providing water to keep cells turgid in order to support the structure of the plant
- Providing water to leaf cells for photosynthesis
- Keeping the leaves cool as heat energy is removed from the leaves when water evaporates
factors affecting transpiration (4)
- air movement
- humidity
- temperature
- light intensity
how does wind affect transpiration rate
As wind speed increases, the transpiration rate increases
When it is windy, water molecules that diffuse out of stomata are quickly blown away from the leaf; this creates a concentration gradient and more water vapour diffuses out of the leaf
when it is windy, transpiration rate ____
increases
when temperature increases, transpiration rate ___
increases
why does rate of transpiration increase when temperature increases
When temperatures are high water vapour molecules have more kinetic energy and move around faster, so they are more likely to move out of the stomata by diffusion
when humidity increases, rate or transpiration ___
decreases
why does transpiration decrease when humidity increases
Humid air contains a high concentration of water vapour; this reduces the diffusion gradient between the inside of the leaf and the outside air, so less water vapour diffuses out of the leaf
when light intensity increases, rate of transpiration ___
increases
why does rate of transpiration increase when light intensity increases
Increased light intensity increases the rate of photosynthesis, so the stomata open to allow gas exchange; when this happens, water vapour diffuses out of the stomata
PRACTICAL FACTORS AFFECTING TRANSPIRATION
Cut a shoot underwater
To prevent air entering the xylem and place in tube
Set up the bubble potometer, and make sure it is airtight, using Vaseline to seal any gaps
Dry the leaves of the shoot
Wet leaves will affect the results as stomata will be blocked
lift the tube from the beaker of water to allow a single air bubble to form and place the tube back into the water
Allow the plant to adapt to the new environment for 5 minutes
Record the starting location of the air bubble
Leave for 30 minutes
Record the end location of the air bubble
Reset the bubble by opening the tap below the reservoir
Repeat the experiment
Calculate the rate of transpiration by dividing the distance the bubble travelled by the time period
The further the bubble travels in the same time period, the greater the rate of transpiration
the lignin that reinforces xylem vessels provides what
a route for the column of water to move through the plant by transpiration
root hair cells are
specialised cells found in plants
root hair cells are adapted to
absorb water and mineral ions from soil
adaptations of root hair cells (2)
root hairs
mitochondria
why do root hair cells have root hairs
they increase the surface area for absorption
why do root hair cells have mitochondria
they release energy for active transport
when minerals are taken up by active transport, how does this allow water to be taken up
because it reduces the water potential in the cell, so water can move in by osmosis
how is water lost
evaporation of water through the spongy mesophyll layers into the air spaces
water then diffuses into the surrounding air through the stomata
if you wanted to investigate light intensity on rate of transpiration, what would you do
you would just do the same investigation, but change the distance between the potometer and the lamp
