mass flow theory Flashcards
what is the aim of mass flow theory
to provide sucrose for respiring cells at the sink
what does mass flow rely on the idea of
active loading
where is sucrose transported from and where does it end up
from source to sink
where does sucrose go first
companion cells
how does sucrose enter the companion cells
facilitated diffusion down conc. gradient into companion cells
how does the sucrose leave the companion cell
the hydrogen ions are actively transported from companion cells into cell wall using ATP
what happens now hydrogen is emmbeded in the cell wall
it diffuses via facilitated diffusion into the companion cell
once the hydrogen is in companion cell how is sucrose released
hydrogen ions move via co-transport with sucrose from companion cell into sieve tube elements
what does movement of sucrose to companion cells in active loading stimulate
mass flow of water as water moves in from xylem into phloem creating hydrostatic pressure
when sucrose is in sieve tubes what happens
it diffuses down to the sink where
what happens to sucrose at the sink
it is actively transported into respiring cells
what does the movement of sucrose from sink into cells mean
lower water potential in cells so water moves via osmosis from sieve tube elements and into cells
