Transport in Plants - Xylem 3B

Question 1

Xylem function

Answer 1

transports water and mineral ions in solution

Question 2

Xylem structure

Answer 2

very long, tube like and they have no end walls

Question 3

Describe the Cohesion tension theory in plants

Answer 3

Water evaporates from the leaves at the top of the xylem

This creates tension which pulls more water into the leaf

Water molecules are cohesive (they stick together) so when some are pulled into the leaf others follow this means that the whole column of water in the xylem from the leaves down to the roots moves upwards

Water enters the stem through the roots

Question 4

Describe transpiration

Answer 4

Water evaporates from the moist cell walls and accumulates in the spaces between cells in the leaf

When the stomata open it moves out of the leaf down the concentration gradient

Question 5

Factors which affect the transpiration rate

Answer 5

light - more light faster transpiration rate (positive correlation) stomata open when its light to let in CO2 for photosynthesis . Dark they are closed meaning little photosynthesis

Temperature - higher temp faster transpiration rate warmer water more energy evaporates from leaf faster increases concentration gradient, increasing diffusion gradient

Humidity - lower the humidity faster the transpiration rate negative correlation. Dry air increases concentration gradient which increases transpiration

Wind - more wind faster transpiration lots of air blows away water molecules from around the stomata this increases the concentration gradient, increasing the transpiration rate

Question 6

Transpiration rate practical

Answer 6

1.