plant organ system

what is transpiration?

loss of water of water vapour from leaves and stems of plant

what is transpiration a consequence of?

gaseous exchange

how can transpiration occur? (x3)

water evaporates from the open stomata

water molecules are attracted to each other so others are pulled out of xylem

causing more water to be pulled out of soil so a transpiration stream occurs

is transpiration affected by the same factors of the rate of evaporation?

yes

how does increase of temperature affect the rate of transpiration?

molecules move faster, resulting in evaporation happening at a faster rate

rate of photosynthesis increases, so more stomata are open for gaseous exchange, more water evaporates so transpiration increases

how does increase of relative humidity affect the rate of transpiration?

if relative humidity is high, there would be a reduced conc gradient between inside and outside of the leaf = slower rate of diffusion, slower rate of transpiration

how does increase of air movement affect the rate of transpiration?

if more air is moving away from the leaf, the conc of water vapour surrounding the leaf is low

steeper conc gradient so diffusion happens faster, increasing the rate of transpiration

how does increase of light intensity affect the rate of transpiration?

increase rate of photosynthesis, so more stomata need to be open for gaseous exchange, more water can evaporate so more transpiration

what does measuring the uptake of water indicate?

rate of transpiration

what is a potometer used for?

measuring the uptake of water

what do guard cells do?

open and close the stomata

what are the features of the guard cells? (x4)

kidney shaped

thin outer walls

thick inner walls

light sensitive