mass transport in plants Flashcards
(16 cards)
what is lignin?
a substance which stiffins xylem walls
what is a vascular bundle?
a bundle of transportation vessels in the stem, made up of xylem and phloem vessels
what is the stele?
transportation vessels in the roots
how does transpiration work?
due to the cohesive nature of water, when one molecule evaporates from the leaves, another is drawn up from the roots, creating a continuous stream of water up the plant
what two methods can water move through the leaf by?
the cell wall pathway and the cytoplasmic pathway
what is translocation?
the process by which organic molecules and mineral ions are transported around the plant
what does sap flow through?
the sieve tube element of phloem vessels
where does sap flow from and to?
source to sink
what is pressure flow theory?
the process by which sap flows, water is drawn into the phloem from the xylem due to the high sucrose concentration, this raises the pressure and causes the sap to move downward
how does sugar move into a fruit sink?
active transport due to a high concentration of sucrose in fruit
how does sugar move into a root sink?
diffusion, as sucrose is stored there as starch
what are the pores between companion cells and the sieve tube element of phloem vessels called?
plasmodesmata
how does water move in and out of phloem vessels?
it is drawn into the sieve tube element at the top of the plant via osmosis, and moves to an area of lower hydrostatic pressure, where it is drawn back into the xylem vessel via osmosis
what is a ringing experiment?
the selective removal of phloem vessels by cutting a shallow ring around a stem, causing a swelling above the ring and therefore supporting pressure flow theory
what are aphid helpers?
aphids (which pierce phloem tissue and suck out sap) used to study translocation
what is a tracer experiments?
one leaf is exposed to radioactive CO2 14 and the plant is placed on photographic film to see where the radiation has spread to
