Transport Systems Flashcards
Need for transport system
Roots only abs water and min and leaves only abs sugar
Pathways as water moves through root into xylem
Symplast= living cell,cyto,plasmode
Vacouloar= vacuoles
Apoplast= non living eg cell wall
Pass through space, carry solutes,
Casparian strip blocks and forces into symplast= as memb can control and all water to xylem
Transpiration stream
Root pressure high at bottom of x
Evap leaves- low pressure at top of xylem
Water moves by mass flow from high to low p, pulled up in a continuous column due to cohesion between water molecules and adhesion of water to the xylem walls, Capillary action - xylem narrow so water rises up
Transpiration
Consequence of gas exchange, loss of water
Eg stomata open for glucose, high wat inside so moves down wat potential grad and leaves
Factors affect transpiration
Light intensity= lighter, high as stomata open for co2 diffuse in
Temp= fast as water mol have more en to evap, inc wpg
Wind/ rel air mvt= air mol blows away water mol around stomata
High humidity = lots of air takes away water
Stomatal density, water availability
Translocation
Transport of assimilates eg sucrose(soluble and less reactive than gluc so not used up)and aa
Moves subs from source(loads eg leaf) to sink(unloads eg roots)
Active loading
At if h+ out of companion= c.grad
Facilitated diff of h+ back into comp
W sucrose by co transporter
Diffuse plasmodemsata from comp to sieve element
Mass flow hypo of translocation
At the Source sucrose enters the sieve tube, dec water potential= water moves in from the xylem by osmosis. Source= high hp
At the Sink sucrose diffuses out of the sieve tube into surrounding tissues (to be used for respiration or to be stored as starch). The loss of sucrose inc the wp inside, so water leaves tube by osmosis. This toCrape source. Sink= low hp
pressure gradient from the source to the sink. Assimilates move from source to sink down pg,by mf
