Plant tissues, organs and systems

Question 1

How does epidermal tissue carry out its function?

Answer 1

• covered in a waxy cuticle
• helps reduce water loss by evaporation

Question 2

How does palisade mesophyll tissue carry out its function?

Answer 2

• lots of chloroplasts means photosynthesis can happen rapidly
• positioned at top of the plant, so they receive lots of light

Question 3

How does spongy mesophyll tissue carry out its function?

Answer 3

• lots of air spaces which allows gas to diffuse in an out of cells

Question 4

How does xylem carry out its function?

Answer 4

• a continuos tube of dead cells - allows movement of water and mineral ions from the roots to the stem and leaves, where it evaporates and leaves the plant (the transpiration stream)
• substance called lignin which makes it strong and waterproof. It has holes in it called bordered pits which allow minerals to go to specific places in the plant

Question 5

What is translocation?

Answer 5

the movement of food substances made in the leaves up or down the phloem, for use immediately or storage

Question 6

What is transpiration?

Answer 6

the evaporation of water from the leaves and stems of the plant

Question 7

What factors affect transpiration?

Answer 7

increase in temperature - molecules move faster, resulting in evaporation at a faster rate

increase in relative humidity - results in reduced concentration gradient

wind - concentration of water surrounding leave will be lower - steeper concentration gradient

increase in light intensity - or rate of photosynthesis increases, meaning stomata open

Question 8

What do guard cells do?

Answer 8

• close and open stomata

Question 9

features of guard cells:

Answer 9

• thin outer walls, thick inner walls
• when lots of water available, the cells fill and change shape, opening stomata
• more stomata on bottom of leaf to allow gases to be exchanged while minimising water loss by evaporation as the lower surface is shaded and cooler.