transport in plants QP2 PMT Flashcards
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
