3.4.2.1 Mass Transport In Plants - Xylem & Transpiration

Question 1

What does xylem transport

Answer 1

Water and mineral ions

Question 2

What does phloem transport

Answer 2

Sucrose and amino acids

Question 3

What are andeosperms

Answer 3

Flowering plants

Question 4

What are packing cells

Answer 4

Cells that fill up space

Question 5

What is the structure of xylem tissue

Answer 5

Tracheid, parenchyma cell, xylem vessel, fibre
Vessel elements are stacked end to end, end walls disintegrate forming hollow tubes, traceids are the same but have slanted end walls

Question 6

What is lignification in xylem

Answer 6

Lignin kills trachieds, xylem vessels, fibres. Is impermeable to anything. Lines xylem vessel elements, killing anything in the cell, cell is hollow for water to move through.
Gives strength preventing xylem vessel elements from collapsing when water is moving through, impermeable to water so provides hydrophilic lining

Question 7

What is the role of the vessel element and the tracheid

Answer 7

Transportation of water and mineral ions

Question 8

What is the role of the fibre in xylem

Answer 8

Provide mechanical support for tissue

Question 9

What is the role of the parenchyma cells in xylem

Answer 9

Packing cell between vessel elements

Question 10

Describe the movement of water in a leaf and the uptake of water

Answer 10

Water evaporates out of spongy mesophyll cells into air spaces, diffusion of water out of stomata
99% of water uptake is transpired - cooling effect, brings in mineral ions through roots. 1% is used for photosynthesis and maintaining turgor

Question 11

Describe movement of water through a plant

Answer 11

Transpiration stream - single continuous column of water from roots to the leaves, through xylem
Evaporation into water vapour and diffusion out stomata
Pull of water out of leaf causes tension on water

Question 12

Describe the location of the vascular bundles in stem and root

Answer 12

Stem - around the periphery (edge) of stem to provide strength and structure
Roots - are straight down the middle of root as gravity imposes strain on roots

Question 13

Name two parenchyma cells found in stem and/or root

Answer 13

Cortex, pith

Question 14

How does water move up the stem and explain the theory

Answer 14

Cohesion - tension theory
Cohesion between water molecules as they form hydrogen bonds with each other, surface tension of the water also creates cohesion. As water is lost through transpiration, pulls on water creating tension, therefore more can be drawn up stem

Question 15

How are mineral ions taken up by plant roots and how do you know

Answer 15

active transport
Ion concentration in roots is far greater than in soil so uptake is against gradient
Respiratory inhibitors added to root reduces uptake

Question 16

Describe the structure of a root hair cell and how its features are beneficial for uptake of mineral ions

Answer 16

Cell wall, cytoplasm, vacuole, nucleus
Large SA, lots of mitochondria, lots of carrier proteins, thin cell wall

Question 17

How do you measure transpiration rates

Answer 17

Potometer
Whole thing is set up underwater including cutting the leaf shoot and attaching it, leaves need to stay dry, cover joints with Vaseline to be airtight

Question 18

How do you calculate rate of water uptake by using a potometer

Answer 18

Speed of air bubble movement (mm/s) x cross sectional area of capillary tube (mm2) = rate of water uptake (mm3/s)

Question 19

What Factors affect transpiration rate

Answer 19

Light intensity, temperature, humidity, air movement

Question 20

How does increased light intensity affect rate of transpiration

Answer 20

Increased rate
stimulates stomata opening for gas exchange for photosynthesis, increased number of open stomata increases SA for diffusion of water vapour

Question 21

How does increased temperature affect rate of transpiration

Answer 21

Increase in rate
Increased evaporation out of mesophyll cells, air spaces in leaf become saturated with water vapour, increased diffusion gradient to outside of leaf

Question 22

How does increased humidity affect rate of transpiration

Answer 22

Decreases rate
Increased number of water molecules in air surrounding stomata openings, reduced diffusion gradient to outside of leaf

Question 23

How does increased air movement affect rate of transpiration

Answer 23

Increase in rate
Saturated air moved away from leaf surface, increasing diffusion gradient to outside of leaf