transport in plants Flashcards
What is the adhesion tension theory
water in roots = high hydrostatic pressure . low hydrostatic pressure in leaves
as water evaporates through the stomata this creates tension in the xylem
water moves up the xylem along hydrostatic pressure gradient
by cohesion and adhesion
by mass flow - supported by capillary action.
what’s the caspirian strip and its significance
it is impermeable - forces water to travel via the symplast pathway ( through the cytoplasm) rather than the apoplast pathway( through the cell walls)
state the process of translocation
H+ ion pumped out by a protein pump using ATP
facilitated diffusion of H+ and sucrose molecules through a cotransporter
sucrose moves into sieve tube element via plasmodesmata by diffusion
water moved out down the water potential gradient ( sucrose lowers water potential creating high hydrostatic pressure)
moved down to the roots down the hydrostatic pressure gradient
diffuses into roots to be used for active transport of mineral ions
what are xerophytes and examples
plant adapted to live in dry conditions
cacti and marram grass
hydrophytes and examples
Plants that live in wet conditions
water lilies
Marram grass adaptations
stomata on inner side
thick waxy cuticle
few air spaces - less surface for evaporation
Cacti adaptaions
store water
spines for leaves - smaller surface area
wide roots
adaptations of water lilies
Large air spaces - keeps it afloat & allows oxygen to diffuse quickly
stomata on upper epidermis - allows for gaseous exchange
How does an increase in light intensity affect transpiration
more transpiration if more light - more opening stomata for photosynthesis
how does an increase in temperature affect transpiration
INCREASES TRANSPIRATION:
more kinetic energy - more diffusion through stomata
decreases water potential in the air - steeper water potential gradient
how does more air movement affect transpiration
move away water vapour , steep water potential gradient between leaf and outside increases transpiration rate
how does more water availability affect transpiration
the stomata wil open more to replenish water lost - incerases transpiration
how does an increase in humidity affect transpiration
less steep water potential gradient - less transpiration
what are dicotyledonous plants
plants with 2 seed leaves and branching patters of veins in the leaf
differences between sieve tube element and companion cells
Companion cells have nucleus / mitochondria;
Companion cells have more cytoplasm;
Sieve tube elements have cross walls;
Sieve tube elements have thinner walls
Compare and contrast the apoplast and symplast pathways
Apoplast – water passes through cell walls, symplast through cytoplasm;
Apoplast – water doesn’t pass through plasma membranes, symplast, water does;
Apoplast – water doesn’t pass through plasmodesmata, symplast, water does;
Apoplast – pathway blocked by casparian strip, symplast isn’t;
Both are methods of water movement through roots;
Both use osmosis from high ψ to low ψ
Describe how xylem vessels adapt them for water transport.
lignin / AW;
(allows) adhesion / waterproof / stops collapse (under tension);
A two functions
rings / spirals / thickening / AW; A thick wall / rigid sides
prevents collapse (under tension); R strong / support / stops bursting
no cytoplasm / lack of contents / hollow / (empty) lumen / AW;
R “dead” unqualified
less resistance to flow / ease of flow / AW / more space (linked to
lack of contents);
lack of end walls / continuous tube; A long tube idea
less resistance to flow / ease of flow; A continuous columns idea
pits / pores, inside walls; A holes R gaps
lateral movement / get round air bubbles / supplies(water) to cells or
tissues / water in or out; R “just let things in and out” unqualified
develop as a continuous water-filled column / AW;
allows tension to pull water up / AW;
narrow lumen / AW;
idea of more capillary rise
