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translocation - movement of organic compounds around a plant - Coggle…
translocation - movement of organic compounds around a plant
phloem loading (apoplast route)
high concentration in mesophyll cells of hydrogen leads to it moving back into cc, co-transported with sucrose (diffusion)
build up of sucrose in companion cells so sucrose diffuses into sieve tube elements
companion cells contain many mitochondria for ATP needed
water potential in sieve tube is lower, so water moves in via osmosis
hydrogen ions are pumped out of companion cells by active transport
hydrostatic pressure inside elements is increased so water + assimilates move by mass flow
phloem unloading
concentration of sucrose between phloem + surrounding cells is maintained)
it can also be converted into another substance (glucose/starch)
sucrose mainly diffuses out of the phloem into other cells
source --> sink
assimilates = products of photosynthesis that are transported (mainly sucrose)
sinks are where sugars are used + stored
sources are where sugars are made + mobilised
mass flowcffcq
symplast route
sucrose moves from source through cytoplasm of mesophyll cells + plasmodesmata to sieve tubes
via diffusion
mostly passive