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structure + function of xylem + phloem + root + stem + leaf - Coggle…
structure + function of xylem + phloem + root + stem + leaf
Transport systems in dicotyledonous plants (p198-201)
Xylem
Made of dead cells
Only runs upwards
Long and hollow
There are two types of xylem tissue: Tanin which is used for protection from herbivores and Parenchyma which stores food and gives the xylem thick walls
transport of water and dissolved minerals
Phloem
Made of living cells
runs up and down the plant
Supplies cells with sugars and amino acids
In areas between the cells sieve plates form which let phloem contents through
Vascular Bundle
Responsible for transport systems, structural support and includes the xylem and phloem
Different parts of the vascular bundle have different amounts of xylem and phloem, for example the roots have a much high concentration of xylem to transport the water from the roots to the rest of the plant
A plants needs for transport systems:
Metabolic demands
Different parts of the plant demand different things therefore the plants must have advanced transport systems to facilitate this movement of substances
Size
Plants continue to grow through out their lifetime and some can get over 100m tall therefore there transports systems have to be capable to transport substances across the plant
SA : V Ratio
Although leaves have a high surface area to volume ratio with other parts of the plants factored in, it has a relatively low SA : V ratio so it cannot rely on simple diffusion
Two transport systems
Transpiration
Xylem vessel
Passive process - No energy required
movement of water and dissolved minerals
Translocation
Phloem vessels
Active process - energy required
Movement of sugar and amino acids
root
root hair cells absorb water
root hair cells have a high contact surface with the soil
used for absorption of water and minerals and excretion of waste products
soil has a higher water potential compared to the low water potential of the roots
the cell membrane is partially permeable allowing water absorption via osmosis
carrier proteins in the cell membrane allow mineral uptake via active transport
stem
structure
the xylem is on the inside of the root and the phloem is on the outside and are separated by the cambium
The epidermis surrounds the stem and the cortex surrounds the inner parts
function
Provides structure
contains xylem and phloem (vascular bundle)
provides strength
leaf
carries out photosynthesis
waxy cuticle to reduce water loss
high surface area to volume ratio
thin to allow for easy diffusion
contains stomata which open and close via guard cells to allow for gas exchange
Useful Website for structure and function