transport in plants QP2 PMT Flashcards
(14 cards)
The sap in phloem sieve tubes is moved by mass flow
state two adaptations of sieve tubes that enable mass flow to occur
-elongated elements;
-elements joined end to end to form a column;
-sieve plates/pores in end walls/ perforated end plates/ sieve pores;
-little cytoplasm/ cytoplasm pushed to cell edges;
-no nucleus/ few organelles;
describe how assimilates are moved into the phloem
-active transport of H+ out of companion cells;
-creates hydrogen ion/ concentration/diffusion gradient;
-(facilitated) diffusion of H+ back into companion cells.
-sucrose/assimilates move in with H+
-by cotransport/ through cotransport protein
-sucrose/assimilates (diffuse) through plasmodesmata from companion cells into sieve tube element
describe why smoke could pass from one end of the xylem and out the other end
-its hollow and contains no organelles
-it has no cross walls and is continuous
-lignified
-(bordered) pits in walls
describe and explain how transpiration contributes to the mechanism of water transport up the stem
-water loss from leaf is replaced;
-via apoplast/symplast/vacuolar pathway;
-down a water potential gradient;
-lost water replaced by water from xylem;
-in the xylem loss of water causes low/ negative (hydrostatic) pressure at the top of leaf OR creates a pressure gradient;
-water moves from a high pressure to a low pressure down a pressure gradient;
-under tension/ pulled up/drawn up;
-by mass flow;
-cohesion/ attraction between molecules
-column/chain of water molecules
suggest why a bunch of flowers may survive for longer if their stems are removed immediately before being placed into water
-bubbles/air (present/being removed);
-(blockage) in xylem
-restore (continuous) column of water in xylem
define apoplast pathway *
describe and explain how water is moved up the xylem from the roots to the leaves
-water moved into the xylem down a water potential gradient ; (water pot lowest in xylem)
-root pressure/ high hydrostatic pressure at bottom of the xylem;
-water vapour loss/ transpiration/ evaporation at leaves at the top of the plant;
-creating a low hydrostatic pressure at the top of xylem;
-water under tension is pulled in a continuous column;
-cohesion between water molecules;
-adhesion of water molecules to xylem;
-capillary action;
-water moves up xylem via mass flow;
-from higher hydrostatic pressure to a lower hydrostatic pressure, down a pressure gradient;
what substances are transported in the xylem
mineral ions, slats (water)
what are steps that the student should take to ensure that the potometer is set up correctly?
-ensure shoot is healthy;
-assemble apparatus/ cut shoot underwater;
-cut shoot at an angle;
-check there are no air bubbles in apparatus;
-apparatus is water tight/no leaks;
-leaves dry;
why would a student carry out three replicates of an experiment
- to ensure that the data is more reliable
-it reduces the effect of an outlier or anomaly
apart form light and temperature why is transpiration lower in the afternoon than midday
in the afternoon;
-plant dying/less healthy;
-stomatal closure;
-less air movement/ wind;
explain why a potometer gives an estimate of the rate of transpiration.
-potometer measures water uptake;
-not all water taken up is lost;
-some water used for photosynthesis/ making cells turgid;
explain why water loss from leave is unavoidable.
-stomata is open during the day for gas exchange;
-co2 moves in and o2 moves out
-gas exchange is used for photosynthesis;
-photosynthesis is essential for the plant to gain energy/ make sugars
-some lost through the cuticle
state adaptation of leaves which reduce evaporation
-hairy leaves. trap water vapor
-stomata in pits/sunken. Trap water vapor/moisture
-rolled leaves/ presence of hinge cells. Reduces SA OR rolled leaves trap water vapour/ moisture.
-high solute content in cells. reduces water potential inside leaf cells
-thicker cuticle. which is waterproof/ relatively impermable
-few stommata. reduces diffusion
-smaller leaves/ needles. smaller SA
-stomata close during the day. reduces diffusion
-most stomata on lower surface. less exposure to sun OR cooler OR reduces diffusion
