B8 - Transport in Plants Flashcards
What is the function of the xylem? [2]
- transport water and mineral ions
- support
What is the structure of a xylem vessel like? [3]
- made up of dead cells
- no end walls between cells
- cells are strengthened with lignin
What is the function of the phloem? [1]
- transport of sucrose and amino acids
What is the structure of a phloem vessel like? [3]
- made up of living cells
- end walls have perforated sieve plates
- cells walls made of cellulose
How are the minerals in the xylem vessel transported? [1]
via active transport
How is water moved to the roots? [1]
via osmosis
What do xylem vessels not have? [2]
- no cell wall
- no cell membrane
Where does the xylem vessel transport to and from? [2]
- transports to the stems, leaves and flowers from the roots
What structure do the xylem and phloem form? [1]
vascular bundles
What are vascular bundles used for? [2]
- transport
- support
What is the flowage like in a xylem vessel? [1]
one-way flow only
- from root to the rest of the plant
What is the flowage like in a phloem vessel? [1]
two-way flow movement
What is unique about the cells in a phloem vessel? [1]
cells are living but they need support from companion cells
What are perforated sieve plates? [1]
it lets some things in and not others
Why are companion cells used in phloem vessels? [2]
- phloem cells are living but have no nucleus and very little cytoplasm
- they are supported by companion cells that have all the cell organelles
What are 3 differences between xylem and phloem vessels? [3]
- xylem = no end plates whereas phloem = perforated sieve plates
- xylem = one-way flow of movement whereas phloem = two-way flow of movement
- xylem = made up of dead cells whereas phloem = made up of living cells
Where is the xylem and phloem located in the roots? [2]
- middle = the cross
- outside the cross
Where is the xylem and phloem located in the stem? [2]
- the inside = small dots
- the outside = one dot
Where is the xylem and phloem located in a leaf? [2]
- up = thicker and bigger
- down = smaller
What is transpiration? [2]
the loss of water from plant leaves by evaporation of water at mesophyll cells and then diffusion of water vapour through the stomata
How is water lost from the leaves? [3]
- from the leaves
- to the air
- out of the stomata
What are adaptations of root hair cells? [2]
- large surface area
- increases the rate of absorption of water by osmosis
How does water travel to the leaves? [2]
- up the stem
- in the xylem
Where is water absorbed from and by? [2]
- absorbed from soil
- absorbed by roots
How do minerals in the water get into the roots? [1]
via active transport
What does active transport require? [3]
- energy
- ATP
- carrier protein
Where does the process of evaporation occur? [1]
from cells to air space
Where does the process of diffusion happen? [1]
from stomata to atmosphere
How does water move from the roots to the leaves? [3]
- loss of water in leaves reduces tension in the xylem vessels in the leaf
- water moves up the xylem tube from high to low pressure
- water molecules stick together as they are cohesive
What is the Cohesion Tension? [1]
- water molecules are stuck together
Which has a lower water potential: soil or root hair cell? [1]
root hair cell
What is the transpiration stream? [2]
the movement of water through the plant from the root to the leaves
What are the different places water moves through in the transpiration stream? [6]
- root hair cells
- root cortex cells
- xylem vessel
- mesophyll cells
- air space
- stomata
What is the path taken of the movement of water through a plant (transpiration stream)? Explain. [5]
- water enters the root hair cell by osmosis
- water enters xylem from root cortex cells by osmosis
- water enters mesophyll cells by osmosis
- water evaporates from mesophyll cells into air spaces
- water vapour leaves the leaf by diffusion through the stomata
How is water pulled up the xylem? [1]
by tension and cohesion
What are the factors affecting transpiration? [4]
- light intensity
- wind speed
- temperature
- humidity
How is brighter light advantageous for transpiration? [4]
- causes more stomata to open up
- more water can diffuse out
- stomata close in the dark to reduce water loss
- when all stomata are open = transpiration rate at its max
How is a higher temperature advantageous for transpiration? [2]
- the faster water evaporates from cells of the leaf
- diffusion of water vapour out of the leaf increases
How is the windier the weather advantageous for transpiration? [3]
- the more water vapour molecules are blown away from the leaf
- steeper the concentration gradient between leaf and surrounding air
- water diffuses more quickly out of the leaf
How is humidity disadvantageous for transpiration? [3]
- more humid = more water vapour in the air
- the smaller the concentration gradient between leaf and surrounding air
- water diffuses more slowly
What is the method when using a potometer? [4]
- lift up tube from beaker to take in an air bubble
- air bubble moves towards the plant as water moves into the shoot and is lost via evaporation from the leaves
- measure the distance the air bubble moves in a period of time
- refill the tube using the reservoir and repeat the measurements
What is the method when using a balance? [6]
- place a cut shoot from a plant in a measuring cylinder
- pour layer of oil or use bung
- weigh the whole apparatus
- leave for a period of time
- weigh again
- calculate change in mass
What is wilting? [1]
- the result of a water deficit in the plant
When does wilting occur? [2]
when water loss through transpiration exceeds water uptake by the roots
What does the loss of water in wilting lead to? [1]
- a loss of turgor pressure in the plant cells
- cells become flaccid
What is translocation? [2]
movement of sucrose and amino acids in the phloem from sources to sinks
What is a source? [2]
parts of the plant that release sucrose and amino acids
What is a sink? [2]
parts of the plant that use or store sucrose and amino acids
What are the sources and sinks in summer? [2]
- sources: leaves
- sinks: flowers, fruits, roots, bulbs, tubers
What are ths sources and sinks in winter? [2]
- sources: storage organs like roots, bulbs, tubers
- sinks: newly growing leaves
Why can plant organs be both sources and sinks? [3]
- depends on the season
- in summer more photosynthesis happens in the leaves so nutrients from the leaf go to the roots, etc
- in winter there’s less light so less photosynthesis so the roots store nutrients from previous photosynthesis reactions and so nutrients go from roots to leaves
