B2.2 Challenges of Size - Plant Transport

Question 1

<p>State the function of the xylem</p>

Answer 1

<p>Transports water and mineral ions from the roots to the stem, leaves and flowers</p>

Question 2

<p>State the function of the phloem</p>

Answer 2

<p>Transports dissolves sugars from photosynthesis, and other soluble food molecules from the leaves to all other areas of the plant</p>

Question 3

<p>Name the structure formed by xylem and phloem within the plant</p>

Answer 3

<p>Vascular bundle</p>

Question 4

<p>What tissue makes up the bulk of the plant in woody plants like trees</p>

Answer 4

<p>Xylem</p>

Question 5

<p>Describe an experiment that can be done to easily visualise the xylem in plant tissue</p>

Answer 5

<ul> <li>Place celery in a jug of water containing food colouring</li> <li>Leave for 24 hours</li> <li>Cut slice of celery and veiw using magnifiying glass or light microscope.</li></ul>

Question 6

<p>Describe the structure of xylem</p>

Answer 6

<ul> <li>Made from dead cells</li> <li>No cell walls at the ends of cells</li> <li>Dead cells form tubes for water and mineral ions to flow</li> <li>Xylem cellulose cell wall is thickened and stiffened with lignin to provide support</li></ul>

Question 7

<p>Destribe the structure of phloem.</p>

Answer 7

<ul> <li>Made of living cells</li> <li>Cell walls connecting these cells do not completely breakdown creating sieve plates</li> <li>Sieve plates allow dissolved sugars to pass</li> <li>Connected cells form a tube allowing dissolved sugers to be transported</li></ul>

Question 8

<p>State the direction of flow in the xylem</p>

Answer 8

<p>One-way - Roots to leaves</p>

Question 9

<p>State the direction of flow in the phloem</p>

Answer 9

<p>Two-way</p>

Question 10

<p>State which tissue in a plant would transport glucose</p>

Answer 10

<p>Phloem</p>

Question 11

<p>If a cross section was taken through the plant in the stem, where would you expect the vascular bundle to be found?</p>

Answer 11

<ul> <li>Bundles organised spherically in the cortex</li> <li>Larger phloem at top of the bundle with smaller xylem tubes underneath.</li></ul>

Question 12

<p>If a cross section was taken through the plant in the root, where would you expect the vascular bundle to be found?</p>

Answer 12

<ul> <li>Bundle in the centre ofthe root</li> <li>Xylem in the centre of the bundle</li> <li>Phloem around the outside of the xylem</li> <li>Surrounded by ground tissue</li></ul>

Question 13

<p>If a cross section was taken through the plant in the leaf, where would you expect the vascular bundle to be found?</p>

Answer 13

<ul> <li>Bundles found in the spongy mesophyll layer</li> <li>Xylem closest to palisade mesophyll layer (towards top of the leaf).</li> <li>Phloem closest to the lower epidermis</li></ul>

Question 14

<p>How do vascular bundles provide support?</p>

Answer 14

<ul> <li>In the leaf they form a network that supports softer tissue</li> <li>In the stem they are loacted around the outer edge providing the stem with strength to resit bending</li> <li>In the root they are found in the centre to enable the root to act as an anchor</li></ul>

Question 15

<p>What is transpiration?</p>

Answer 15

<p>The movement of water through the xylem.</p>

Question 16

<p>Explain the transpiration stream.</p>

Answer 16

<ul> <li>The stream of water though the plants xylem caused by the loss of water through the plants stomata in the wind.</li> <li>Water evaporates through stomata</li> <li>Water potential gradient between leaves and stem - water moves into leaves by osmosis</li> <li>Water potential gradient between stem and roots - water moves into stem by osmosis</li> <li>Water potential gradient between roots and soil - water moves into root hair cells by osmosis</li></ul>

Question 17

<p>Explain what makes water vapour diffuse from the inside of the a cell into the air?</p>

Answer 17

<ul> <li>Water evaporates from inside the leaf into the leaf's air spaces</li> <li>Concentration gradient between the air inside leaf and the air outside the leaf</li> <li>Water vapour diffuses from the area of high concrentration or the air inside the leaf, to the area of low concentration of the air outside the leaf</li></ul>

Question 18

<p>Explain the structure of the stomata and how they open and close to control gaseous exchange.</p>

Answer 18

<ul> <li>Stomata are made up of two guard cells,</li> <li>When there is plenty of light and water the guard cells take up water by osmosis and become turgid,</li> <li>The inner wall of the guard cell is thickened so the cell curves as it becomes turgid creating a gap between the two guard cells,</li> <li>This gap is known as the stomata,</li> <li>If conditions for photosynthesis are poor then the guardcells lose water and become flacid,</li> <li>When the cells are flacid the gap between them closes.</li></ul>

Question 19

<p>Explain why the upper surface of many leaves is covered in a thick, waxy cuticle?</p>

Answer 19

<ul> <li>To prevent uncontrolled water loss</li> <li>In hot environemnts this layer is very think and shiny</li></ul>

Question 20

<p>How can the rate of transpiration be calculated?</p>

Answer 20

<ul> <li>Calculate the rate of movement of an air bubble using a potometer</li> <li>rate of movement = distance (mm)÷ time (s)</li></ul>

Question 21

<p>Why does the plants need for CO₂ increase the rate of transpiration in a plant.</p>

Answer 21

<ul> <li>Plants need glucose for respiration</li> <li>Glucose is product of photosynthesis</li> <li>Photosynthesis requires carbon dioxide and water</li> <li>Plant must open stomata to enable the diffusion of carbon dioxide into the leaf</li> <li>Open stomata allows water vapour to leave the leaf via diffusion</li> <li>Lose of water from leaf increases rate of transpiration</li></ul>

Question 22

<p>State the factors affecting the rate of transpiration</p>

Answer 22

<ul> <li>Light intensity = increase light, increase transpiration</li> <li>Temperature= increase temperature, increase transpiration</li> <li>Air movement =increase air movement, increase transpiration</li> <li>Humidity =increase humidty, decrease transpiration</li></ul>

Question 23

<p>Explain what the ringing experiment shows.</p>

Answer 23

<ul> <li>IA ring of bark is scraped away that also removes the phloem, exposing the xylem.</li> <li>Sugar then attempts to move down the stem but is stopped by the ring.</li> <li>This is demonstrated by abulgeof sugar forms above the ring.</li> <li>Suggesting that sugar moves down the stem in the phloem and sugar transported by the phloem.</li></ul>

Question 24

<p>Expalin how the potometer experiment can be used to measure the rate of transpiration</p>

Answer 24

<ul> <li>Set up potometer making sure the stem is cut under water to ensure no air bubble</li> <li>Release an air bubble into the capillary tube</li> <li>As the water evaporates form the leaves and moves into the stem the bubble moves towards the plant</li> <li>Measure how fast the air bubble travels</li> <li>Refil and repeat the experiment</li></ul>