transport in plants

Question 1

What is the adhesion tension theory

Answer 1

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.

Question 2

what’s the caspirian strip and its significance

Answer 2

it is impermeable - forces water to travel via the symplast pathway ( through the cytoplasm) rather than the apoplast pathway( through the cell walls)

Question 3

state the process of translocation

Answer 3

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

Question 4

what are xerophytes and examples

Answer 4

plant adapted to live in dry conditions
cacti and marram grass

Question 5

hydrophytes and examples

Answer 5

Plants that live in wet conditions
water lilies

Question 6

Marram grass adaptations

Answer 6

stomata on inner side
thick waxy cuticle
few air spaces - less surface for evaporation

Question 7

Cacti adaptaions

Answer 7

store water
spines for leaves - smaller surface area
wide roots

Question 8

adaptations of water lilies

Answer 8

Large air spaces - keeps it afloat & allows oxygen to diffuse quickly
stomata on upper epidermis - allows for gaseous exchange

Question 9

How does an increase in light intensity affect transpiration

Answer 9

more transpiration if more light - more opening stomata for photosynthesis

Question 10

how does an increase in temperature affect transpiration

Answer 10

INCREASES TRANSPIRATION:
more kinetic energy - more diffusion through stomata
decreases water potential in the air - steeper water potential gradient

Question 11

how does more air movement affect transpiration

Answer 11

move away water vapour , steep water potential gradient between leaf and outside increases transpiration rate

Question 12

how does more water availability affect transpiration

Answer 12

the stomata wil open more to replenish water lost - incerases transpiration

Question 13

how does an increase in humidity affect transpiration

Answer 13

less steep water potential gradient - less transpiration

Question 14

what are dicotyledonous plants

Answer 14

plants with 2 seed leaves and branching patters of veins in the leaf

Question 15

differences between sieve tube element and companion cells

Answer 15

Companion cells have nucleus / mitochondria;

Companion cells have more cytoplasm;

Sieve tube elements have cross walls;

Sieve tube elements have thinner walls

Question 16

Compare and contrast the apoplast and symplast pathways

Answer 16

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

Question 17

Describe how xylem vessels adapt them for water transport.

Answer 17

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