Alevel biology practical question help!

why are the effects of photosynthesis and respiration ignored when taking potometer readings

(edited 6 years ago)

Potometers tend to be used to measure the rate of transpiration in a plant, and this is done by looking at the rate of water uptake. However, this presumes that all the water the plant takes up evaporates from the surface of its leaves and ignores the fact that some of it is used during processes in the plant such as photosynthesis.

Reply 2

mk_cbc

Original post by xxKristenxx

but why would you ignore them when taking readings.

Reply 3

xxKristenxx

Original post by mk_cbc

but why would you ignore them when taking readings.

The question doesn't mean why would you choose to ignore them I am pretty sure it means why do they accidentally get ignored when taking the readings, and that's an error in the methodology of the potometer. I am currently doing the same topic in my bio lessons and we had to discuss the fact potometers fail to include respiration and photosynthesis in the equation.

Otherwise, the answer would just be because we want the rate of transpiration, not overall water uptake.

Hope this helped :smile:

Reply 4

username2151383

Original post by mk_cbc

but why would you ignore them when taking readings.

because like 95% of it evaporates again
so you just ignore the 5% that gets used by photosynthesis and respiration

Reply 5

Mathumie

Because the purpose of using a potometers is to measure the rate transpiration which is basically just asking you to look at the uptake of water. It doesn't take into account where the water ends up.

Original post by mk_cbc

but why would you ignore them when taking readings.