Unit 2: Organisation - Plant Tissues, Organs, and Organ Systems Flashcards
how do specialised plant cells get formed?
they are formed from a process called differentiation
draw and label a diagram of a root hair cell
what is the function of a root hair cell
- they help to absorb water by osmosis
- they absorb mineral ions by active transport and diffusion
what are the adaptations of a root hair cell
- Root hair - increases surface area for osmosis and diffusion of mineral ions
- Thin cell wall - short diffusion distance
- Vacuole - contains cell sap which gives cell low water concentration (maintains gradient for osmosis)
draw and label a diagram of a xylem cell
what is the function of a xylem cell
- transports water + mineral ions
- UP the plant, roots to shoots/leaves
- via the TRANSPIRATION STREAM
what are the adaptations of a xylem cell
- the cells are dead and hollow (empty)
- cells are elongated
- cell walls are strengthened by lignin
draw and label a diagram of a phloem cell
what is the function of a phloem cell
- transports sugar solution
- UP and DOWN plant (bidirectional)
- via TRANSLOCATION
what are the adaptations of a phloem cell
- cells are living (sugars move by active transport)
- sieve plate (pores) allow sugar solution to move from cell to cell
- cells are elongated
what do epidermal tissues do
they cover the plant
what does the palisade mesophyll do
it is the main site of photosynthesis
what does the spongy mesophyll do
it has air spaces for diffusion of gases and some photosynthesis
what do the xylem and phloem do
they transport substances around the plant
where is meristem tissue found
at growing tips of shoots and roots
what happens in the meristem tissue
cells divide by mitosis and then differentiate into specialised cells
what is the cuticle
a layer of wax (not a tissue)
draw and label a diagram of leaf
give an example of a plant organ
vascular system
what is the vascular system made up of
phloem tissue and xylem tissue
How is water absorbed?
It is absorbed by osmosis from the soil.
definition of transpiration
the loss of water vapour from the surface of plant leaves
how does transpiration occur
water vapour is mainly lost via open stomata
some get lost via cuticle
draw a diagram of an open and closed guard cell
when is the stoma opened
in daylight
when is the stoma closed
at night (no transpiration occurs)
describe the mechanism of stomatal opening during the day
The rate of transpiration is highest during the day
The active transport of H+ ions causes the stomata to open
The absoption of K+ ions cause the guard cells to need more water as it lowers its water potential
Water is transferred to guard cells from nearby cells via osmosis
The uneven thickening of cellulose lets the cells change shape
The guard cells bow and form an opening
When the stomatal openings are largest, it is known as ‘turgid’
what is a bubble potometer used for
to measure the rate of transpiration
describe how the potometer is used to measure the rate of transpiration
When water is transpired from the leaves, the shoot absorbs water from the potometer
The distance the air bubble moves in a certain period of time can be used to calculate the rate of water uptake.
The apparatus can be reset - to investigate the effect of a different environmental factor
What are some benefits of using a potometer
it is set up underwater to avoid air bubbles
the junction at shoot is sealed with vaseline to prevent air leaks
the reservoir allows appartus to be reset.
why is the capillary of the potometer narrow
- easier to see bubble move
- bubble will move further
formula for rate of transpiration
cross sectional area of capillary tube x distance travelled by the bubble = volume of water lost.
what factors affect the rate of transpiration
temperature
humidity
air movement
light intensity
what is the assumption for potometer
the water uptake = water lost in transpiration
Describe wilting
The plant does not have enough water, as all the water has been transpired
The rate of water loss > water uptake
Plant cells have lost turgor pressure (they are now flaccid)
The plant cells are plasmolysed, they can no longer support the plant.
as temp increases, the rate of transpiration _____
increases
explain how temperature affects the rate of transpiration
As the temperature increases, the kinetic energy of the water molecules increases.
This increases the rate of evaporation.
This increases the rate of diffusion of water vapour out of the leaf
as humidity increases, the rate of transpiration _________
decreases
explain how humidity affects the rate of transpiration
More humid air = more water vapour present (so smaller gradient for diffusion)
Increasing humidity increases the concentration gradient between the inside and the outside of the leaf.
This decreases the rate of diffusion, and therefore the rate of transpiration decreases.
as air movement increases, the rate of transpiration __________
increases
explain how air movement affects the rate of transporation
Air movement blows away the diffusion shell around the leaf.
This increases/maintains the diffusion gradient.
as light intensity increases, the rate of transpiration __________
increases
explain how light intensity affects the rate of transporation
As light intensity increases, the rate of photosynthesis increases.
There is more stomata open for gas exchange (CO2 into the leaf)
This increases the rate of diffusion
which part of the leaf usually has the most stomata
on the lower surface the leaf
rate of transpiration increases when:
- temp increases
- air movement increases
- light intensity increases
- humidity decreases
- more stomata (stomata density)
- more leaves/ bigger leaves
