plant transport Flashcards

Question

what are two ways in which water can move across a root into the dylem

Answer 1

sympoplast pathway apoplast pathway

Answer 2

continuous cytoplasm of plant cells connected by PLASMODESMATA

Answer 3

water moves through the simplast by osmosis —> root hair cell had a higher water potential than the next cell along - as water has diffused in by osmosis making cytoplasm more dilute —> this continues until water reaches xylem • as water leaves root hair cell by osmosis into symplast —> leaves lower water potential —> so maintains steep conc gradient for more water to diffuse in

Answer 4

cell walls and intercellular spaces

Answer 5

water moves through apoplast --> water fills spaces between cellulose fibres in the cell wall •as water moves through xylem -molecules pulled through apoplast due to cohesion between water moleculees —> creates a CONTINUOUS flow —> with little/no resistance

Answer 6

band of waxy material (suberin) tht runs around endodermal cells —> creating a waterproof layer

Answer 7

forces water from apoplast into the symplast pathway —> water has to pass through selectively permeable membranes —> removes any potentially toxic solutes in the soil water / excess soil solutes from reaching tissues

Answer 8

water potential of cytoplasm of ENDODERMAL cells is high compared to cells in xylem + endodermal cells move minerals into xylem water moves into xylem by osmosis down water potential gradient from endodermis THROUGH SYMPLAST PATHWAY •when waters in xylem —> water moves BACK INTO APOPLAST

Answer 9

active pumping of mineral ions into xylem by root cells that produces a movement if water into xylem by osmosis

Answer 10

• some poisons e.g. cyanide affect production of ATP —> if cyanide is applied to root cells, root pressure disappears —> as no energy is supplied for active transport • root pressure increases when temp increases and vice versa —> suggests chemical reactions are involved —> HOWEVER, not very good evidence as increasing temp also increases rate of passive processes • levels of O2/ respiratory substrates fall -root pressure falls —> as less ATP produced •xylem sap exudes from cut ends of stems(guttation) —> root pressure independant of transpiration

Answer 11

symplast pathway: •relies on osmosis as water moves through cell membranes and cytoplasm * Water moving in from soil by osmosis into root hair cell raises water potential compared to next cell so water moves again by osmosis * Active transport of ions needed to move water from endodermis to xylem by osmosis Apoplast pathway: •water moves through cellulose cell walls by cohesive forces between water molecules and as result of transpiration pull up xylem •moves into symplast pathway in endodermis as a result of Casparian strip and needs active pumping of ions into xylems followed by osmosis before water moves back to apoplast pathway in xylem.

Answer 12

•loss of water vapour (from leaves/stems) •as a result of —> evaporation if cell surfaces inside the leaf —> diffusion down a conc gradient —> out through stomata

Answer 13

movement of water through a plant from the roots until its lost by evaloration from the leaves

Answer 14

•water molecules evaporate from surface of mesophyll cells into air spaces —> move out of stomata into surrounding air down concentration gradient • this lowers water p of mesophyll cells —> water moves into cell from adjacent cell —> via both symplast and apoplast pathways •this repeats across leaf to the xylem —> water moves out of the xylem by osmosis • h20 forms bonds with carbs in walls of xylem vessels = ADHESION •h20 forms bonds with itself —> so tend to stick together =COHESION •combined effects of ADHESION + COHESION —> water exhibiting capillary action •water is drawn up xylem in a continuous stream (transpirstion pull) —> to replace water lost by evaporation • transpiration pull results in TENSION in xylem —> helps move water across the roots from the soil

Answer 15

•when xylem is broken —> most times air is drawn in, rather than water leaking out •When xylem is broken and air is being pulled in —> plant csnt move water up the stem - as continuous stream has been broken so water isnt being pulled up • changes in diameter if trees —>when transpiration is at its highest in the day time —> tension in xylem is at its highest - vice versa is true for nighttime —> as a result, tree shrinks in diameter

Answer 16

• delivers water/mineral ions •evaporation of water from leaf cell —> cools the leaf down = no heat damage

Answer 17

``` •water loss —> amount of water available is often limited •in high intensity sunlight —> high rate of photosynthesis —> high rate of gaseous exchange —> stomata open for longer time —> more water lost ```

Answer 18

turgor driven process • when turgor is low —> asymmetric guard cell walls close pore when conditions are favourable • guard cells pump in solutes by active transport —> increasing turgor —> inner wall if guard cells less flexible than outside —> cell becomes bean shaped —> opens pore

Answer 19

• light intensity —> higher light intensity increases no. open stomata • relative humidity - high humidity =SLOWS —> reduced water potential gradient outside if stomata —> opposite for dry air •temp -as temp increases —> Ek of h20 increases => rate of evaporation increases - as temp increases —> conc of water that water vapour can hold increases before it becomes saturated (so decreases relative humidity) • air movement —>leaves have a still layer of air around them —> decreases movement close to the leaf —>water vapour accumulates here —> increases water p outside • soil- water availability —> amount of water in soil —> very dry - rate reduced

Answer 20

the movement of organic solutes around a plant via the phloem

Answer 21

regions plabts that oroduce assimilated by photosynthesis or from storage organs * green leaves and green stems * storage organs —> tubers/tap roots unloading their stores * food stores in seeds when they germinate

Answer 22

regions of pants that require assimilates to supply their metabolic needs •roots growing/ actively absorbing minerals •meristems dividing •any parts tbat are laying down storage organs —> developing seeds, fruits

Answer 23

products of photosynthesis

Answer 24

it isnt used in metabolism as much as glucose so therefore less likely to he metabolised suring transport

Answer 25

apoplast route

Answer 26

sucrose travels through cell walls to companion cells and sieve element by diffusion —> mainstained by sucrose being removed into phloem vessels

Answer 27

* H+ ions actively transported out of the companion cell using ATP * hydrogen ions return to companion cell down conc gradient via a co- transport protein •sucrose is co transported with h+ ions into companion cells •as a result of the build up of suctose in companion cells and sieve elements —> water moves in by osmosis —> leads to a build up of turgor pressure due to rigid cell walls, reducing pressure in companion cells • the water carrying the assimilates moves into tubes of sieve element

Answer 28

* have many infoldings in cell membranes to give increase SA for active transport of suctose into cytoplasm * many mitochondria to supply ATP needed for the transport pumps

Answer 29

solute accumulation in source leads to increased turgor pressure —> forces sap to regions of lower pressures (in sinks)

Answer 30

main mechanism if phloem unloading —> diffusion of sucrose from phloem - sucrose rapidly moves onto other cells - and is converted into other respiratory substrates(glucose) —> loss of solutes leads to rise in water p in phloem —> water moves out of phloem

Answer 31

•advances in microscopy —> see adaptions of companion cells for active transport • if mitochondria of companion cell poisoned—> translocation stops • flow of sugsrs is much fadter in phloem than by diffusion alone • aphids can be used to show -+ve pressure in phloem that forces sap out of the stylet

Answer 32

plant with adaptions that allow them to survive in dry habitats / when water availability is low

Answer 33

• THICK WAXY CUTICLE ``` •SUNKEN STOMATA —>refuces air movemnet —>creates microclimate of still air —> which becomes RELATIVELY HUMID —> reduces water p gradient ``` • REDUCED NO. STOMATA —>reduces water loss —>also reduces gaseous exchange (not ideal) •REDUCED LEAVES —> reduces leaf area •HAIRY LEAVES —>creates microclimate of still air —> which becomes RELATIVELY HUMID —> reduces water p gradient •CURLED LEAVES —> confines stomata into microenvironment of still air —> which becomes humid due to transpiration —> reduces water p gradient •SUCCULENTS —> they store water in special parenchyma tissue in stems/roots •LEAF LOSS - plants lose leaves when water isn’t available •ROOT ADAPTIONS - eg —>long tap roots grow several metres into the ground —> mass of widespread shallow roots w/ large surface area

Answer 34

conifers marram grass cacti

Answer 35

plants with adaptions that enable them to survive in wet habitats or submerged in water

Answer 36

•VERY THIN/NO WAXY CUTICLE —> dont need ti conserve water loss •MANY OPEN STOMATA ON UPPER SURFACES —> maximising gaseous exchange —> stomata open at all times •REDUCED STRUCTURE TO THE PLANT —>water supports the leaves and flowers so there is no need for supporting structures •WIDE FLAT LEAVES —> eg lilies have these spread across water to capture as much light as they can • SMALL ROOTS —> water can diffuse directly into stem/leaf tissue •LARGE SA OF STEMS/ROOTS UNDERWATER —> maximised area for photosynthesis + oxygen to diffuse into plants •AIR SACS —> enables leaves to float on water •AERENCHYMA —> specialised parenchyma —>many latge air spaces - formed by apoptosis in parenchyma - makes leaves/stens more buoyant - forms low resistance internal pathways for o2/ other substances underwater —> helps cope with anoxic conditions eg in mud with very little o2