🟨 3.1.2 - Transport In Plants (set A - The Need For Transport Systems In Multicellular Plants)

Question 1

Explain why plants require transport systems?

Answer 1

Transport system ensures that all the cells of a plant receive a sufficient amount of nutrients (eg water,minerals and sugars)
- this is important as plants are fairly big and have relatively small SA:V ratios but high metabolic rates

Question 2

Explain what vascular plants are - why is a system needed?

Answer 2

Plants that have specialised transport systems are known as vascular plants

• important as plants have relatively small SA:V ratio and high metabolic rates - need a system that ensures the cells of the plant receive sufficient amount of nutrients

Question 3

Explain why large organisms require specialised mass transport systems - give three reasons?

Answer 3

– Increasing transport distances (due to size)
– Surface area: volume ratio
– Increasing levels of activity (metabolic rate)

Question 4

Explain why plants need a specialised mass transport system - mention transport distance?

Answer 4

Every cell requires water, glucose and mineral ions - the roots take in water and mineral ions, whilst the leaves produce glucose - molecules need to be transported all the way from the exchange site to other parts of the plant - large transport distance means simple diffusion is non-viable as it would no meet the high metabolic requirements of the cells

Question 5

Explain how glucose is transported and why?

Answer 5

When glucose is made by photosynthesis it is combined with fructose and transported as sucrose which is a more efficient transport medium - if it was transported as glucose it would be taken in by surrounding cells

Question 6

Explain why plants need a specialised mass transport system - mention SA:V?

Answer 6

As the size of a plant increases, its surface area to volume ratio decreases - this is because volume increases much more rapidly than surface area

• has relatively less SA available for substances to diffuse through - rate of diffusion will not be fast enough to meet cells demands (supply of substances and removal of waste) so diffusion alone can not be relied on

Question 7

Explain why plants need a specialised mass transport system - mention metabolic rate?

Answer 7

Larger organisms are more physically active and contain more cells than smaller organisms - this means they have a higher level of metabolic activity, therefore their is a greater demand for oxygen and nutrients as well as production of waste products

• however plant cells and tissues have a lower metabolic rate than animials cells - therefore their demand for oxygen for aerobic respiration is reduced

Question 8

Define cotyledon?

Answer 8

are organs that act as food stores for the developing embryo plants and for the first leaves when the seed germinates

Question 9

Explain how plants are adapted to increase SA:V?

Answer 9

• plants have a branching body shape
• leaves are flat and thin
• roots have root hairs

Question 10

Explain what dicot plants are, give the name of the 2 main groups?

Answer 10

Plants that make seeds that contain 2 cotyledons

there are two main groups of dicots
- herbaceous dicots (non-woody stem)
- woody dicots (eg oak)

Question 11

Explain the vascular system of a dicot plant, explain what herbaceous consists of?

Answer 11

A plant has a series of transport vessels running through the roots,stems and leaves - the system is known as the vascular system

• Herbaceous dicots vascular systems are made up of 2 types of transport vessels; Xylem and Phloem arranged together in vascular bundles in the stem, roots and leaves

Question 12

Explain the transpiration system in plants, what it includes and what type of process it is?

Answer 12

• The movement of water molecules and dissolved minerals ions
• Xylem vessels
• Passive process

Question 13

Explain the translocation system in plants, what it includes and what type of process it is?

Answer 13

• The movement of sugars (Sucrose) & amino acids
• Phloem vessel – sieve & companion cells
• Active process

Question 14

Explain what a vascular bundle is, explain what the cambium is and its fucntion?

Answer 14

• Xylem and Phloem are arranged in vascular bundles in the roots, stems and leaves - arrangement is different in different organs
• There is a layer of cambium in between xylem and phloem, that is meristem cells which are involved in production of new xylem and phloem tissue

Question 15

Explain the distribution of the vascular bundle with focus on the xylem in the roots, why is this the case?

Answer 15

vascular bundle is found in the centre and the centre core of this is xylem tissue - this helps the roots withstand the pulling strains they are
subjected to as the plant transports water upwards and grows

Question 16

Explain the distribution of the vascular bundle with focus on the xylem in the stems, why is this the case?

Answer 16

vascular bundles are located around the outside and the xylem tissue is found on the inside (closest to the centre of the stem) to help support the plant

Question 17

Explain the distribution of the vascular bundle with focus on the xylem in the leaves, why is this the case?
- give the direction they spread from and the location of xylem tissue

Answer 17

vascular bundles form the midrib and veins and therefore spread from the centre of the leaf in a parallel line

• The xylem tissue is found on
  the upper side of the bundles (closest to the upper epidermis).

Question 18

Explain the distribution of the vascular bundle with focus on the phloem in the roots, why is this the case?

Answer 18

In the roots the vascular bundle is found in the centre and on the edges of the centre core is the phloem tissue.

Question 19

Explain the distribution of the vascular bundle with focus on the phloem in the stems, why is this the case?

Answer 19

In the stems, the vascular bundles are located around the outside and the phloem tissue is found on the outside (closest to the epidermis)

Question 20

Explain the distribution of the vascular bundle with focus on the phloem in the leaves, why is this the case?

• Explain the location of the phloem

Answer 20

In the leaves, the vascular bundles form the midrib and veins and therefore spread from the centre of the leaf in a parallel line

• The phloem tissue is found on the lower side of the bundles (closest to the lower epidermis).

Question 21

Describe the importance of vascular bundles in roots, explain the location and function of the pericyclic?

Answer 21

• Provides a ‘drill’ like structure which enables the plant to push down into the soil
• xylem tissues is the strongest so its in the centre (X structure)
• phloem in four separate sections

In the endodermis around the vascular bundle of the root there is a a layer of meristem cells that form the pericyclic

Question 22

Describe the importance of vascular bundles in leaves, explain the location and function of the pericyclic?

Answer 22

• Xylem is located on top of the phloem

Only applies to dicotyledonous plants

Question 23

Describe the importance of vascular bundles in stems, explain the location and function of the pericyclic?

Answer 23

• Xylem is located on the inside – in non wooded plants
• This provides additional support to the stem
• The cambium layer contains meristem cells

Question 24

Explain the structure of xylem - give 4 structural features?

Answer 24

• a dead tissue (there is no cytoplasm and no nuclei in xylem tissue)
• hollow tubes
• cell wall contains spiralised lignin that gives the tissue high strength
• pits in the wall, result of regions with non-lignin

Question 25

Explain the function of xylem?

Answer 25

Transports water and dissolved minerals upwards from the root hair cells to the leaves

Question 26

Explain the adaptions of xylem tissue?

Answer 26

• very long, tube like structure which are joined end to end - with no end walls on these cells - makes an uninterrupted tube, allowing water to pass up through them
• the walls are thickened with a woody substances (lignin) which helps support the xylem vessels, stopping them collapsing inwards, can be deposited in a spiral or as distinct rings - amount of lignin increases with cells age
• small pits in the walls where there is no lignin allow water and ions to move into and out of the vessels

Question 27

Explain the function of lignified cell walls in the xylem?

Answer 27

Adds strength to withstand the hydrostatic pressure so the vessels do not collapse, impermeable to water

Question 28

Explain the function of no end plates in the xylem?

Answer 28

Allows that mass flow of water and dissolved solutes as cohesive (between water molecules) and adhesive (between water and the walls) forces are not impeded

Question 29

Explain the function of no protoplasm (dead cells) in the xylem?

Answer 29

Doesn’t impeded the mass flow of water and dissolved solutes (transpiration stream)

Question 30

Explain the function of pits in the walls of the xylem?

Answer 30

Non-lignified sections allow the lateral continuous movement of water, in case of air bubbles forming in the vessels

Question 31

Explain the function of small diameter of vessels in the xylem?

Answer 31

Helps prevent the water column from breaking and assists with capillary action

Question 32

Structure of phloem