TRANSLOCATION Flashcards
TRANSLOCATION
1) movement of assimilates (sugars and chemicals) from leaf through phloem
2) for storage, utilization, and consumption by the plant
IMPORTANCE OF TRANSPORT SYSTEM
1) for cells deep within plant tissues to receive nutrients
=> roots can obtain water but not sugar
=> leaves can produce sugar, but can’t get water from air
2) sugars are required for metabolism
PRODUCTION OF SUGARS
1) by source tissues
2) during light period
MOVEMENT OF TRANSLOCATION
1) source to sink (short term)
2) storage tissue to young tissues (long term)
SUCROSE
1) principal photosynthetic product
2) important storage of sugar
3) major form for translocation of carbon
OTHER COMPOUNDS THAT ARE TRANSLOCATED
1) sugars
2) amino acids
3) organic acids
4) protein
5) potassium
6) chloride
7) phosphate
8) magnesium
SOURCE
(DIRECTION OF TRANSLOCATION)
releasing sucrose to phloem
=> leaves
SINK
(DIRECTION OF TRANSLOCATION)
removes sucrose from phloem
=> root
ALLOCATION
channelling of fixed carbon to various pathways within organs or tissues
SOURCE ORGAN
(PURPOSE OF ALLOCATION)
1) metabolic utilization within chloroplast
2) synthesis of starch within chloroplasts
3) synthesis of sucrose for export to sink
SINK ORGAN
(PURPOSE OF ALLOCATION)
1) metabolic utilization and growth processes
2) storage
PARTITIONING
distribution of assimilates to competing sinks
=> lower mature leaves feed the roots
=> higher mature leaves feed young leaves and shoot apex
SOURCE LEAVES
(PARTITIONING)
preferentially supply sink organs with which they have vascular connection
=> flower of fruit that is directly above or below them
=> basis for flower and fruit thinning
MECHANISMS OF TRANSLOCATION OF PHOTOSYNTHATES
1) mass or bulk flow (munch pressure flow hypothesis)
2) diffusion (slow)
3) cytoplasmic streaming (within cytoplasm through plasmodesmatal connections)
4) others
=> facilitated diffusion
=> active transport
APOPLAST PATHWAY
1) requires active transport (utilizes ATP)
2) water moves through spaces within cells and the cell wall
