8.9.2 Stomata COPY

Question 1

What is the pleural name for a single stoma?

Answer 1

Stomata

Question 2

Stomata is the name of a group of single what

Answer 2

Stoma

Question 3

What are stomata

Answer 3

• Small pores
• on the above ground parts of plants
• most commonly found on the lower surface of leaves
• bound by two guard cells
• through which gases and water vapour diffuse

Question 4

What types of cells surround a single stoma

Answer 4

2 guard cells

Question 5

What makes a guard cell unusual

The features?

Answer 5

• Guard cells are unusual because
  
  • They are the only epidermal cell which have chloroplasts
• The cell walls of a guard cell are also unusual in that
  
  • The Inner eperdemis (next to the pore) is thicker than outer eperdermis (in most cases)

Question 6

How do plants control the exchange of gasses between the atmosphere and the internal tissues of the leaf

Answer 6

The stomata can change the width of the pore, which controls the level of gas exchange.

Question 7

what is the purpose of the stomatal pores in gas exchange

Answer 7

opens and closes to allow gas exchange

Question 8

During the day….

What role does water play in whether a pore opens or closes

Answer 8

• If water enters the guard cells it becomes turgid and the stomatal pore opens
• If water leaves the guard cells it becomes flacid and the stomatal pore closes

Question 9

What factors are thought to control how a stomatal pore opens

Answer 9

1. Chloroplasts in guard cells generate ATP via photosynthesis
2. ATP provides the energy to allow K⁺ ions from the surrounding epidermal cells to pass into the guard cells
3. Stored starch is converted into malate
4. The K+ and malate ions lower the water potential in the guard cells
5. Water therefore enters the the guard cells by osmosis ( froma higher concentration to a lesser concentration)
6. Cell walls of guard cells are thinner in some places than others
   
   • Guard cells expand when they absorb water
   • More where the cell wall is thin
   • Less where the cell wall is thick
7. This reveals a pore known as the Stoma

The reverse happens at night,

Question 10

How do plants lose water

Answer 10

• Plants lose water by evaporation through their stomata in a process called transpiration

Question 11

what happens if plants lose too much water?

Answer 11

1. The plant wilts.

Question 12

What is the benefit of having the stomata only on the lower ground side of a leaf?

Answer 12

• If stomata were found on the upper surface of a leaf
• Sunlight would increase evaporation, increase water loss and the plant will wilt

Question 13

How is a leaf designed to prevent water loss

Answer 13

• Stomata are usually only found on the lower ground surface of a leaf which reduces the risk of increased evaporation if they were found on the upper surface of a lead
• There is also a waxy cuticle on the upper surface of the lead which helps to reduce water loss
• The stomata themselves balance the need for gaseous exchange and management of water loss.

Question 14

What are the 3 ways the stomata balance the conflicting needs of gas exchange and water loss through the same pore?

What are the 3 ways the stomata prevent water loss?

What are 3 reasons why stomata might close?

Answer 14

1. At night the pore closes to reduce water loss
   * When there is insufficient light for photosynthesis to occur
2. The stomata also close where there is very bright light, usually accompanied by heat, to stop waterloss via evaporation
3. They also close when there is high water loss from the plant for any otherreason

Question 15

How do you find the are of the field of view in an experiment

Answer 15

1. Convert the diameter measures in the eyepiece units to micro millimetres using the calibration value
2. Calculate the radius
   
   1. r = diameter divided by 2
3. Calculate the area pie r sqaured.