9.2 Flashcards
why is water important in plants?
provides turgor pressure keeping the plant upright
evaporation cools the plant down
water is needed for photosynthesis
water carries mineral ions
how does water move into the root?
through root hair cells
how are root hair cells adapted to their role?
- have hairs with a large SA:V ratio
- hairs have a short diffusion distance so faster osmosis
- mitochondria to provide ATP for active transport of ions
why do root hair cells pump in ions?
by pumping in ions it reduces the water potential in the root hair cell which allows water to move down the concentration gradient into the root hair cell by osmosis
what are the two pathways water takes in the roots?
symplast
apoplast
what is the symplast pathway?
water moves through the cytoplasm and through the plasmosdesmata
what is the apoplast pathway?
water moves through the cellulose cell wall
why can water move with the cell wall?
because the cell wall can form hydrogen bonds with the water molecules
what is the endodermis?
cells which surround the vascular bundle?
what forces the apoplast pathway into the symplast pathway?
the Casparian strip which is made up of suberin which is waterproof
why is water forced into the symplast pathway?
in order for all the water to pass through the endodermis which contains a cell surface membrane which would prevent toxic molecules from passing through
how does water move from the endodermis into the xylem?
the endodermal cells pump ions into the xylem to lower the water potential which allows water to moved down the concentration gradient by osmosis and into the xylem
what evidence is there for the role of active transport in root pressure?
when cyanide is added to the root cells, root pressure disappears
root pressure rises with temperature
root pressure falls when oxygen levels fall
where is the casparian strip found?
at the endodermis
