Transpiration

Question 1

transpiration

Answer 1

release of water vapour into air from aerial organs
2 functions:
- cool leaves from sunlight
- pulls water and minerals up

Question 2

stomata

Answer 2

90% transpiration
- occur at highest density on leaf udnerside
- >1% leaf surface area
- can be found on all aerial organs

Question 3

regulation of transpiration: stomata

Answer 3

opening and closing of stomata controlled through turgor pressure of guard cells
- turgid guard cells: open
- flaccid guard cells: close

while mechanism controlled by K+ and water potential, signal to open and close varies: water status, CO2 levels, light intensity, humidity, temp, hormones

Question 4

transpiration: lenticels

Answer 4

• lenticels are pores and cannot regulate to open/close
• typically not as high up in water column (stem/trunks) as leaves
• only 0.1% transpiration
• in fruit like apple, lenticels form from stomata: lenticels in these fruits can account for 20% of transpiration

Question 5

transpiration: cuticle

Answer 5

• allow very little water loss (~5%)
• plants in arid environments will try to reduce water loss:
• thicker cuticle
• mesophyll packed close, no air spaces
• sunken stomata
• increases layers of epidermis
• only open stomata at night