Transport In Plants

Question 1

Why do plants need a transport system?

Answer 1

Plants need a transport system because large plants have a smaller surface area to volume ratio, requiring a specialised gas exchange surface and a transport system. They also need to move water and minerals from roots to leaves and sugars from leaves to the rest of the plant.

Question 2

What is the transport system in plants composed of?

Answer 2

The transport system in plants consists of specialised vascular tissue.

Question 3

What does xylem carry?

Answer 3

Xylem carries water and mineral ions.

Question 4

What does phloem carry?

Answer 4

Phloem carries sugars.

Question 5

Where are xylem and phloem found?

Answer 5

Xylem and phloem are found in vascular bundles.

Question 6

What other types of tissues are found in vascular bundles?

Answer 6

Vascular bundles contain other types of tissues such as collenchyma and sclerenchyma, which provide strength and help support the plant.

Question 7

What is the structure of xylem and phloem in the root?

Answer 7

In the root, xylem and phloem are found in the endodermis and medulla.

Question 8

What is the structure of xylem and phloem in the stem?

Answer 8

In the stem, xylem and phloem are found in the medulla, along with collenchyma and sclerenchyma.

Question 9

Function of the xylem

Answer 9

Transports water and dissolved mineral around the plant

Question 10

Structure of xylem

Answer 10

-walls are lignified- waterproof
-made of dead cells
-parenchyma cells acts as packing tissue to separate and support vessels

Question 11

Structural ADAPTATIONS of the xylem

Answer 11

-Lignified makes it waterproof and gives it strength
-Bordered pits so water and minerals can move into other vessels
-Narrow tubes so water column doesn’t break

Question 12

Function of phloem

Answer 12

-transports assimilates around plant

Question 13

What is a structure and the adaptation for phloem

Answer 13

-Sieve tube elements- no nucleus and other organelles to free up space for mass flow
-companion cells which have mitochondria to produce atp for the active processes
-has sieve plates - which allows movement of sap from one element to the next

Question 14

What is the plasmodesmata

Answer 14

Gap in the cell wall containing cytoplasm that connects 2 cells

Question 15

What are the pathways taken by water

Answer 15

Apoplast
Symplast
Vacuolar

Question 16

What is the apoplast pathway

Answer 16

Water travels through spaces in the cell wall between cells

Question 17

What is the symplast pathway

Answer 17

Water travels through the cytoplasm

Question 18

What is the vacuolar pathway

Answer 18

-water moves similar to symplast but also through the vacuole

Question 19

What is transpiration

Answer 19

The evaporation of water from the leaf

Question 20

How is water loss limited from transpiration

Answer 20

Waxy cuticle limits it

Question 21

When does majority of water loss happen and why

Answer 21

During the day when the stomata is open

Question 22

What is the pathway of water loss

Answer 22

-water moves into leaf by xylem and moves by osmosis to the spongy mesophyll
-it then evaporates from the cell wall
-and leaves by the stomata by diffusion

Question 23

What is the importance of transpiration

Answer 23

-maintains cell turgidity
-keeps plant cool on a hot day
-transports minerals up the plant

Question 24

How does light intensity affect transpiration

Answer 24

-stomata opens to allow gas exchanges higher light intensity= higher transpiration

Question 25

How does temperature affect transpiration

Answer 25

-increases rate of evaporation form cell surface -increases diffusion through stomata

Question 26

How does humidity affect transpiration

Answer 26

-high humidity in air DECREASES transpiration as more moisture in air so small water potential between air outside and leaf

Question 27

How does wind affect transpiration

Answer 27

-it carries the water vapour away -which maintains a high water potential

Question 28

Describe water movement across the root

Answer 28

-root hair cell increases surface area of the root -water moves across root cortex down a water potential to the endodermis -water travels through the apoplast pathway but is blocked by the casparian strip so has to take the symplast Pathway

Question 29

What is mass flow

Answer 29

Water travelling upwards through the xylem

Question 30

What is rhe 3 processes that help water travel up the stem

Answer 30

Root pressure Transpiration pull (cohesion-tension theory) Capillary action

Question 31

Explain the process of root pressure

Answer 31

-pressure in the root medulla pushes water into xylem -water moves up xylem -this pushes water a few meters up the stem

Question 32

Explain the process of the cohesion tension theory (transpiration pull)

Answer 32

-water is loss from top part of the plant -so must be replaced -water molecules stick together by cohesion -this holds the water in a column -when water is lost from top the whole column is pulled upwards creating tension

Question 33

Why do xylem need to be lignified

Answer 33

To make them stronger Because of cohesion tension colum is pulled up creating tension

Question 34

Explain the process of capillary action

Answer 34

-adhesion makes the water molecules stick to the walls of the xylem -so forces of attraction can pull the water up the sides of the column

Question 35

What is a terrestrial plant and how do they reduce water loss

Answer 35

-plants that live on land -have waxy cuticle which reduces evaporation -stomata is closed at night - when there no light for photosynthesis to stop gas exchange -stomata under leaves- to reduce evaporation because of direct sunlight

Question 36

What is a xerophyte and give examples

Answer 36

A plant that is adapted to live in dry conditions E.g cactus and marram grass

Question 37

give the adaptations of marram grass

Answer 37

-leaf is rolled - to trap air inside making it humid to reduce water loss -thick waxy cuticle on outer side - to reduce evaporation -stomata in pits in lower epidermis- covered with hair to reduce air movement -stomata on inner side of rolled leaf- protected by enclosed air space

Question 38

Give adaptations of catcti

Answer 38

-green stem for photosynthesis -succulents- so store water in stems -stems are ribbed so can expand when water is available -leaves reduced to spines which reduce surface area to reduce water loss -roots are widespread - gets any available water from underground

Question 39

What is a hydrophyte and give and example

Answer 39

-plant that is adapted to live in water E.g water lily

Question 40

Give adaptation of water lily

Answer 40

-stomata on upper side of epidermis - allows it to be exposed to air for gas exchange -large air spaces to keep it afloat and can absorb sunlight

Question 41

What is translocation and where does it occur

Answer 41

-movement of assimilates -happens in phloem

Question 42

What is the source

Answer 42

Where assimilates are produced

Question 43

What is the sink

Answer 43

Where the assimilates are used or stored

Question 44

What is the first step of translocation and explain it

Answer 44

Loading - H+ ions are actively pumped out of the companion cells - H+ ions flow back into the companion cells down the conc gradient through a co transporter protein with sucrose -water potential is low bc sucrose conc is high -water ,moves into companion cell -water and sucrose them diffuse into the sieve tube through the plasmodesmata

Question 45

What is the second step of translocation

Answer 45

-pressure flow -since water and sucrose have moved in sieve tubes the hydrostatic pressure is increased near the source -cells in the sink are using water and sucrose, removing them from the phloem tubes creating a low pressure at the sink -sugars move down the phloem by mass flow

Question 46

What’s the last step of translocation

Answer 46

Unloading - as sucrose conc is higher in the phloem it diffuses into the respiring sink cells -water follows by osmosis lowering through hydrostatic pressure and increasing mass flow In some cases sucrose is actively pumped against its conc gradient into the sink

Question 47

What is used to measure transpiration in plants

Answer 47

Potometer

Question 48

Explain the investigation into transpiration

Answer 48

Set up pototmeter and pick 2 species to compare Make sure shoots are cut under water Measure the distance of the bubble moved at regular intervals Find mean and plot it on a graph Make sure the size of the leaf is the same for both species Make sure temperature is the same when experiment is carried out as it can affect transpiration if not controlled, same with light intensity, keep lamp at the same distance throughout experiment

Question 50

What are precautions needed for setting up the potometer

Answer 50

Shoot should be cut under water No extra air bubbles Leaf should be dry otherwise stomata is blocked