3.1.3 transport in plants

make seeds that contain 2 cotyledons

dicotyledonous plants

a series of transport vessels running through the stem, roots and leaves

vascular bundle

-vascular bundles are around the edge
-give strength and support

stems

-vascular bundles are in the middle of the root
-withstand the tugging strains that result as the stems and leaves are blow in the wind

roots

-vascular bundles are in the main vein in the midrib of the dicot
-helps support the structure and transport in the leaf through small branching veins

leaves

xylem _ packs around the xylem vessels, storing food and contains tannin deposits

parenchyma

___ is a bitter, chemical that protects plant tissues from herbivores

tannin

____ pathway-the continuous cytoplasm of the living plant cells connected through the plasmodesmata

symplast

-the root hair cell has a ___ water potential than the next cell so water moves into the next cell by ____
-this repeats till the xylem is reached
-once water leaves the cell the water potential ____ again so a water potential is remained

higher, osmosis, decreases

___ pathway-cell walls and intercellular spaces

apoplast

-water fills the spaces between the network of fibres in the cell wall
-as water molecules move into the xylem, more water molecules are pulled through the apoplast due to ____ forces between water molecules
-creates ____ that allow for a continuous flow of water through the cell wall that has little resistance

cohesive, tension

_ is a band of waxy material, suberin, that runs around each of the endodermal cells forming a waterproof layer

Casparian strip

at the Casparian strip, the water in the apoplast pathway cannot go further so it is forced in the ____
-it then passes through a selectively permeable cell surface to the surface membrane excluding any toxic solutes as they have no carrier proteins to admit them
-joins the ____ pathway
-the solute conc in the cytoplasm is dilute and the endodermal cells move mineral ions into the xylem cells by ______
-the water potential of xylem cells is lower that the water potential of endodermal cells
-the rate of water moving into the xylem by ___ down a water potential gradient

cytoplasm, symplast, active transport, osmosis

outside the vascular bundle water returns to the ___ pathway
-water enters the xylem and moves up the plant, the active pumping of mineral into the xylem due to produce movement of water by osmosis
-this results in ____ and gives a push up the xylem but is not a major factor

apoplast, root pressure

evidence for the role of __ in root pressure
-poisons such as cyanide affect the mitochondria to prevent the production of ATP so if cyanide is applied, there is no energy supply, root pressure disappears
-root pressure increase with a rise in temp and falls with a fall in temp
-if O2 falls, root pressure falls
-xylem sap may exude from stems when transpiration is low

active transport

transpiration

the loss of water vapour from the leaves and stems of plants

-water enters the root of the plant by osmosis and is transported up in the xylem until it reaches the leaves
-in the leaves water leaves by diffusion in the ___ pathway and it evaporates form the freely permeable cellulose cell wall of the mesophyll cells into the ____ ____
-the water vapour move into the external air through the stomata along a diffusion gradient
-this lowers the ___ ___ of the cell so water moves into the adjacent cells by osmosis along both apoplast and symplast pathways

apoplast, air spaces, water potential

cohesion-tension theory
-the water molecules from _____ bonds with the carbohydrates in the walls of the narrow xylem vessels due to ____
-water molecules form hydrogen bonds with each other and stick together due to ____
-the adhesion and cohesion causes exhibiting ____ _____ so allows water to rise up the tube: transpiration pull
-the transpiration pull results in tension in the xylem which helps water move across the root from the soil

hydrogen, adhesion, cohesion, capillary action

evidence for the cohesion-tension theory
-the diameter of trees _____ during the night as the tension in the xylem decreases
-when the xylem is broken, water doesn't leak out
-if a xylem is broken, water cannot be pulled up the plant as the cohesive forces have been broken

decreases

source
-green leave and stems
-storage organs like tubers
-food stores in seeds when they germinate

parts of the plant from which assimilates are loaded into the phloem

sink
-growing roots
-dividing meristems
-laying down stores of the plant

parts of the plant from which assimilates are unloaded into the phloem

symplast route-__
-diffusion from mesophyll cells to sieve tubes through ___
-sucrose ends up in sieve tube elements
-water follows by osmosis which creates a pressure of ___
-this move sucrose through the phloem by mass flow

passive, plasmodesmata, water

apoplast-___
-in companion cells sucrose is move into the cytoplasm by an active process
-H+ ions are pumped out of the companion cells using ____ and return down a conc gradient by a co-transport protein
-sucrose is co-transported so the sucrose conc increases in companion cells and in sieve elements
-the build of sucrose causes ___ to move by osmosis
-this causes ___ pressure to build up due to rigid cell walls
-the water carrying assimilates move into the sieve elements, reducing the pressure in the companion cells
-the water moves by ___ ___ to areas of lower pressure

active, ATP, water, turgor, mass flow

phloem unloading
-mainly by , sucrose moves rapidly so that a con gradient is maintained
-the loss of solutes lead to the water potential in the phloem _
-this causes water to move out of the phloem into surrounding cells

diffusion, increasing

evidence for translocation
-microscopes allow for adaptations of the companion cells to be seen
-if mitochondria in companion cells are poisoned, translocation is ___
-the flow of sugars are faster than diffusion could do
-conc of sucrose in phloem sap is higher near to the source than sink

stopped

___ ____ cuticle- reduces transpiration from leaf surfaces
stomata found on the underside-prevent loss of water vapour

thick waxy

___ ____-reduce air movement which reduce the water vapour potential gradient

sunken stomata

___ ____-reduce the water vapour potential gradient and minimise the loss of water by transpiration

hairy leaves

__ ___-reduces water loss by transpiration as it confines all the stomata to reduce the diffusion of water vapour

curled leaves

very thin or no waxy cuticle-do not need to conserve water as transpiration is not an issue
always-open stomata on the upper surface-maximises the number of stomata
reduced structure-the water support the plant so structures are not needed
wide, flat leaves-spread across the surface area of the water to capture as much light as possible
small roots-water can diffuse into stem so less uptake by roots
large surface area under water-maximises the area for photosynthesis and oxygen to diffuse into plants
air sac-enables plants to float on water
aerenchyma-specialised parenchyma which causes buoyant and provides a low-resistance pathway for substances underwater

hydrophytes