Transpiration

Question 1

what is it?

Answer 1

Its a consequence of gas exchange:

• a plant needs to open its stomata to let CO2 in so that it produces glucose
• But this also lets water out - higher conc of H2O moves out of the lead down the gradient

Question 2

How does light affect the transpiration rate?

Answer 2

• the lighter it is the faster the rate
• The stomata opens when it gets light so CO2 can diffuse into the head for photosynthesis. When its dark, the stomata is normally closed

Question 3

How does temperature affect the transpiration rate?

Answer 3

the higher the temp the faster the rate. Warmer water molecules have more energy so they evaporate from the cells inside the leaf faster. This increases the water potential gradient between the inside and outside of the leaf, making water diffuse out of the lead faster.

Question 4

How does humidity affect the transpiration rate?

Answer 4

the lower the humidity the faster the rate. Tf the air is dry, the gradient between the leaf and the air is increased, which increases transpiration

Question 5

How does wind affect the transpiration rate?

Answer 5

the windier it is, the faster the rate. Lots of air movement blows away water molecules from around the stomata this increases the gradient, which increases the rate

Question 6

How are xerophytic plants adapted to reduce water loss?

Answer 6

Marram grass has a stomata that are sunk in pits, so they’re sheltered from the wind. This helps to slow transpiration down.
It also has a layer of hairs on the epidermis - traps moist air round the stomata, which reduces the water potential gradient between the lead and the air, slowing t down
In hot or windy conditions marram grass plants roll their leaves -again this traps moist airs, slowing t down. Also reduces the exposed SA for losing water and protects the stomata from the wind
Both marram grass and cacti have a thick, waxy layer on the epidermic - this reduces water loss by evaporation because the layer is waterproof
Cacti have spines instead of leaves - this reduces the SA for water loss
Cacti also close their stomata at the hottest times of the day when transpiration rates are the highest

Question 7

How are Hydrophilic plants adapted to survive in water?

Answer 7

Air spaces in the tissue help plants to float and store O2 for use in respiration.
Stomata are usually only present on the upper surface of floating leaves. This helps max gas exchange
Hydrophytes often have flexible leaves and stems - these plants are supported by the water around them, so they don’t need rigid stems for support. Flexibility helps to prevent damage by water currents.