Two well-watered, identical plants were placed in brightly lit rooms at different temperatures — one at 15°C and the other at 38°C. The plant in the warmer room showed wilting by the end of the day.
Mention the factor of the phenomenon that is being tested.
Topic: Factors affecting transpiration — temperature
Answer
TEMPERATURE.
Read the experiment as a CONTROLLED EXPERIMENT and the answer falls out. Everything has been kept the same between the two plants — they are identical, both well-watered, both in brightly lit rooms. Only ONE thing differs: the temperature, 15°C against 38°C.
The variable that is deliberately changed is the factor being tested. That is the whole logic of a fair test, and examiners set these questions to see whether you can spot it.
THE FOUR EXTERNAL FACTORS affecting transpiration: TEMPERATURE — higher temperature, faster transpiration LIGHT — stomata open in light, so transpiration rises HUMIDITY — higher humidity, SLOWER transpiration WIND — wind carries vapour away, so transpiration rises Note that humidity works in the opposite direction to the other three.