transport in plants

why do plants have a transport system

to move substances between leaves, stems and roots

how to metabolic demands have an affect on the transport system

many internal parts of the plant do not make their own glucose through photosynthesis, so they need glucose and oxygen to be transported to them

explain how a root would appear under a microscope

• xylem in a cross in the middle with phloem surrounding it

• the endodermis

• cortex

• epidermic

• exodermis

• root hair cell

explain how a vascular stem would appear under a microscope

explain how vacular bundle in a leaf would appear

describe the structure of the xylem

made of dead cells, long hollow structures, made by several columns of elongated cells fusing end to end. They are impregnated with lignin ( stiff and strong )

what adaptations do xylem cells have due to lignin

• lignin which strengthens them, to resist forces generated by water

• lignin makes them waterproof

• different types of lignin enabiling plant gowth

how to pits help with xylems

allow water to move laterally from vessel to vessel

describe the structure of the phloem

2 cells: companion and sieve cell.

companion cells supply the energy, then move through plasmodesmata into the sieve cell where it gets transported.

describe the structure of sieve cells

very few organelles, no cytoplasm or nucleus

they have sieve pore plates, which allow the sugars to move

the DONT HAVE LIGNIN

describe the structure of companion cells

living cells that are found next to sieve tubes

connected to sieve cells by plasmodesmata

they are alive

they support sieve tubes

they load sugar into the sieve tubes

what is turgor pressure

result of osmosis in plants, giving plants their shape.

what is transpiration

the movement of water out of plants via the xylem

what is translocation

the movement of food ( sugars and amino acids ) around the plant via phloem

how are root hair cells adapted to their function

each hair has a large SA:V

each hair is thin

maintains a steep concentration gradient

how is water taken up by root hair cells

• They take up mineral ions via active transport, which lowers the w.p in the cell

• this means water from outside will then enter the cell by osmosis, because there is a higher w.p outside the cell.

describe the symplast pathway

water movement through the cytoplasm and plasmodesmata, by osmosis

describe the apoplast pathway

water movement through the cell walls and the intercellular spaces, by diffusion . until it reaches the casparian strip

what is the casparian strip

made up of suberin. It forces water from cell walls to enter cells. They do this the filter out any pathogens

what three ways of movement of water up the xylem are there

• root pressure

• capillarity

• transpiration pull

what is root pressure

active transport into xylem drives water into roots

pressure forces water up xylem

what is capillarity

cohesion water molecules stick to eachother due to hydrogen bonding

adhesion water molecules bond with the carbohydrase in the walls of xylems

the narrower / finer the xylem the gretaer the effect

what is transpiration pull

transpiration is evaporation of water from leaves

this draws water up the xylem as a continuous column of water

the pull exerted produces tension ( and inward pressure ) in the xylem creating a pulling effect

what evidence is there of the cohesion tension theory

changes in diameter of trees. Higher the tension the smaller in diamter the trees are

when xylem vessles break water isnt los, instead air is taken in, however this then means that water can no longer be pulled up the xylem in a continous stream because the cohesion tension has been broken

describe the movement of water within a leaf

• H2o is drawn from leaf xylem to mesophyll cells

• from mesophyll cells to intercellular spaces

• water then leaves via stomata down the water potential gradient via DIFFUSION

what effects the rate of transpiration

tempurature

humidity

wind speed

light intensity: stomata stay open

how do stomata work

when the turgor is low the guard cells walls close the pore, when the turgor is high the guard cell walls open the pores. This is beauces the gaurd cells have a thicker cell wall on one side allowing it to open like a bean

name some examples of sources

a source is somthewhere the food comes from

green leaves and green stems

storage organs

name some examples of sinks

tissues that need the sugars

things that are growing

meristem that are actively dividing

seeds, fruits or storage organs

explain the movement of sucrose through mesophyll cells

sucrose diffuses down the concentration gradient through channel proteins in the cell membranes and along the plasmodesmata

sucrose can also diffuse along the apoplast pathway through cell walls

explain how sucrose moves from the apoplast region to the companion cell

1. hydrogen ions are actively pumped against their concentration gradient OUT of companion cells using ATP

2. the H+ are then in High Con, outside the cells in the apoplast region

3. hydrogen ions will then diffuse down their concentration gradient

4. however they can only do this when they have a sucrose, the two particles will pass through the channel together ( cotransport)

5. the concentration of sucrose inside the cell increases

6. then can move into the sieve cells by diffusion

explain the mass flow hypothesis

• the high conc of sucorse in sieve cells lowers the water potencial

• water moves into the sieve tubes from xylem by osmosis

• sucrose is then given to the sink

• sucrose conentration falls so water potential increases

• so water moves out by osmosis and moves back into xylem

what pieces of evidence are there for translocation

• we can see the adaptation in the phloem under a microscopes

what is a hydrophyte ?

plants that have adaptation so that they can live in extremely wet conditions

what are three types of hydrophytes and give examples of them

• submerged hydrophytes: duck weed

• floating hydrophytes: water lilie

• marginal hydrophtes: on river banks/ bogs

why do hydrophytes need adaptation

water logging is a major problem in hydrohpytes, the air spaces of the plant need to be full air not water to survuve

why do hydrophytes have a waxy a very thin or no waxy cuticle

they dont need to conserve water as there is always plenty avaiblabe so water loss by transpiration is not an issue

why are the stomata always open and founf on the upper surfaces of hydrophytes

• maximising the amount of stomata maximises gaseous exchange.

• due to there being no fear of turgor loss, the stomata can always stay open to

• in floating hydrophytes they need to be on the top in order to be in contact with the air

why is there a reduced structure in hydorphytes

the water supports the leaves and the flowers so there is no need for string supporting structure

why do hydrophytes have wide flat leaves

increase surface area across the water to capture as much sunlight as possible

why do hydrohpytes have small roots

so water can dissfuse directly into the stem and leaf tissue so there is less need for uptake by roots

why do some hydrophytes have air sacs

to enable the leaves and/or flowers to float to the surface of the water

what does aerenchyma mean

specilased parenchyma ( packiging ) tissue with thin walls and large intrcellulat spaces form. Make leaves and stems more bouyant and form a pathway for internal gas circulation

what do arecnhyma enable plants to have

• make stems and leaves buoyant

• forming a low resistnace internal patheay for the movement of substances, helping plants to cope with really low levels of oxygen