Transport in Plants

Question 1

Explain the need for a transport system i multicellular plants interns of size and surface area (spec)

Answer 1

The small sa : v means that the diffusion distance for exchange to take place is too slow for diffusion to be sufficient. Therefore to feed the plant with the necessary nutrients, water and minerals the plants must have a transport system in place. There are also multiple cells that are in to dark of an area to acquire the benefits of photosynthesis and the sun.

Question 2

Structure and function of the roots ( 3 marks)

Answer 2

Vascular bundle found in the centre
Large central core of xylem - X shaped
Phloem between arms of xylem

Question 3

Structure and function of the stem (4 marks)

Answer 3

Vascular bundles found near the outer edge
Xylem found towards the inside of each vascular bundles
Phloem found towards the outside of each vascular bundles
Cambium found between xylem and phloem

Question 4

Structure and function of the leaf (3 marks)

Answer 4

Vascular bundle forms the midrib and veins of a leaf - found in the centre
xylem found closer to the flatter edge
Phloem found closer to the bump

Question 5

Structure and function of the Xylem vessel (treat like 6 marker go into as much detail as possible)

Answer 5

This transports water and minerals up the plant from the roots. It does this with the use of pressure. The water from the leaves my have evaporated or been used and therefore the loss of tension in the leaves causes the water and minerals up the stem due to an increase in tension in the xylem, due to water molecules being cohesive they stick to each other pulling each other up the xylem walls. The xylem walls are dead to provide a clear pathway for the water and minerals to travel through. It is comprised of thick elongated cells that are impregnated with lignin for structural and waterproofing for the stem. There is also lateral movement that occurs due to the bordered pits in the xylem to allow for flow of water even if there is a blockage or to prevent transport of a pathogen that maybe in a particular part of the xylem.

Question 6

Structure and function of the Phloem

Answer 6

The phloem is used for the transport of dissolved substances such as sugars.
It is comprised of living cells.
They have a sieve tube element that are lined up end to end with sieve plates. There are also companion cells that used to produce ATP for active transport. There are many plasmadesmata for ease of flow.

Question 7

Explain why transpiration is a consequence of gaseous exchange

Answer 7

The stomata are open during the day so the the plant can produce glucose in photosynthesis. And during this water is lost as the water potential outside of the plant is less than that inside of the plant and therefore the water travels down the gradient and out of the plant.

Question 8

Describe the factors that affect transpiration rate

Answer 8

Temperature - The hotter it is the more water that escapes due to evaporation. This increases the water potential inside of the cell, intern increasing the transpiration rate.
The air movement surrounding the plant - Water molecules would normally leave the stomata and then stay on the plant to increase the water potential outside and making the transpiration rate decrease but with wind the water particles are blown off so this effect wont occur increasing transpiration
Humidity - The lower the humidity the faster the transpiration rate as the air becomes dry around the plant and therefore the conc gradient of water is stronger for water to go outside.
Light- the lighter the sky the more stomata are open and as a result the water is lost through these pores.

Question 9

How is a potometer used to estimate the rate of water loss

Answer 9

The root must be cut underwater to prevent air from entering the xylem, The root must be cut at a slant to increase the surface area available for water uptake, the leaves must be dry and non wilting shoots. There should be time allocated for the equilibrium to be reached and for it to acclimatise. The time period should be accounted for, for when the meniscus starts and ends.

Question 10

What are the pathways of which water can travel describe what they are

Answer 10

The apoplast pathways is in between the cells exterior walls. The simplast pathway is through the cells cytoplasm . The vacuolar pathway is movement through the vacuoles.

Question 11

In what way does water potential move

Answer 11

From a high to low the closer to water the higher the water potential.

Question 12

Why is transpiration important

Answer 12

Used for the transport of mineral ions up the plant
Maintains cell turgidity
provides water for growth and photosynthesis
Keep the plant cool on a hot day to reduce loss by evaporation.

Question 13

Comment on the significance of the data that shows the SA and V of a body aswell as the SA of the exchange system

Answer 13

To check the SA:V and to determine whether it is high or low. You could calculate the value from the figures given and comment on he SA of the lungs in comparison to the bodies SA:V .

Question 14

how does water travel across the root cortex treat like a 6 marker ( include the terms casparian trips , water potential gradient )

Answer 14

Water diffuses through the epidermis through osmosis. It is carried through the cells by the conc gradient of water potential. The water travels across the apoplast pathway up to the casparian strip which is water proof forcing the water and mineral ions to travel the simplast pathway. The water and mineral ions are actively transported into the xylem creating a water potential gradient in the cell. The water after this cannot return back to the cortex due to water proofing casparian strip.

Question 15

Explain the mechanism by which water is transported from the root cortex to the air surrounding the leaves, with reference to adhesion , cohesion and the transand the transpiration stream.

Answer 15

Minerals are actively transported into the xylem vessels this lowers the water potential forcing water to diffuse by osmosis . This creates a root pressure forcing the water upwards. Also due to transpiration there is a decrease in tension at the top of the plant and therefore there is a build p of tension in the xylem . The water begins to travel up the xylem and due to the cohesion and adhesive properties of water they al move up as one due to both mass flow and the tension from the lost water in the leaves. The adhesive properties are used for the water as they stick to the walls of the xylem capillary action causes the water to shoot up the stem.

Question 16

Sieve tube elements are used to form the phloem, but how is there structured used for there service.

Answer 16

They have no nucleus and very little cytoplasm to have less obstructing the flow. The sieve tube elements are stacked along each other and have a sieve plate at the end of each cell. This plate is perforated to allow for the movement of fluids up and down the plant for the phloem.

Question 17

Companion cells

Answer 17

Cells along the sieve tube elements with dense cytoplasm and organelles to produce ATP for active loading of assimilates into the sieve tube elements.

Question 18

How is water moved up the stem

Answer 18

Up the xylem by mass flow

Question 19

Describe and explain the term root pressure

Answer 19

The root transports water actively through to the medulla and xylem, this process due to the cohesion of water draws a build up of water in the xylem. This root pressure can force water up the stem a few meters

Question 20

What is the reason for tension in the leaves

Answer 20

The low hydro static pressure from transpiration forces water to be pulled up by the tension.

Question 21

Brief description of terrestrial plants

Answer 21

These are all plants and they have learned to adapt to their particular environments. They have a number of ways to reduce the water loss or to increase it depending on their environment. These are basic adaptations not specialised to the environment.

Question 22

Name the type of plant adapted to reduce water loss from its leaves

Answer 22

Xerophyte

Question 23

State and explain two adaptations of leaves the reduce evaporation

Answer 23

Having less leaves to reduce surface area of evaporation to take place and a thick waxy cuticle to prevent water escaping through the endodermis.

Question 24

Name 4 adaptations of xerophytes

Answer 24

Closing up of the leaves of the plant to prevent water escaping.
Hair on the leaves to trap water particles.
Sunken stomata so the water has further to travel before leaving the plant.
Fewer stomata

Question 25

Describe how cells are organised into tissues , using xylem and phloem as examples, including specialised cells and there purposes

Answer 25

The xylem is a vessel that has lingnified cell walls so that it can structuralist support the plant even when water movement is slow and the plant is flaccid. It is used for the movement of water during transpiration stream. The phloem is used for th e transport of sugars and other assimilates. It passes through sieve tube elements that have a companion cell containing dense cytoplasm and organelles that are used to produced ATP for active transport of sugars to be transported by the phloem.

Question 26

Name 2 adaptations of a hydrophyte.

Answer 26

There are large air spaces to provide buoyancy, and the stomata are placed on the upper epidermis of the leaf to release water as much as possible.

Question 27

Active loading process

Answer 27

ATP actively transports H+ outside of the cell and this creates a conc gradient from outside to inside. Therefore the sucrose is put into the cell by facilitated diffusion. As the sucrose is increasing in conc in the companion it is diffused out of the cell through the plasmodesmata and into the sieve tube elements.

Question 28

What is meant by the source

Answer 28

A source is a part of the plant that loads sucrose into the sieve tube.

Question 29

What is meant by the sink

Answer 29

This is anywhere tat removes sucrose from the phloem sieve tubes.