Given below is an apparatus which was set up to investigate a physiological process in plants. The setup (a potted plant under a bell jar, the pot sealed in a rubber sheet, standing on a glass plate with vaseline) was placed in bright sunlight. Answer the questions that follow: Given below is an apparatus which was set up to investigate a physiological process in plants. The setup (a potted plant under a bell jar, the pot sealed in a rubber sheet, standing on a glass plate with vaseline) was placed in bright sunlight. Answer the questions that follow:
Mention two external factors which can accelerate the above process.
Topic: Factors accelerating transpiration
Answer
- HIGH TEMPERATURE — more heat energy for evaporation, so water changes into vapour faster.
- BRIGHT LIGHT — the stomata open wider in light, so more vapour escapes.
(Also acceptable: WIND, which carries the vapour away and keeps the air outside the leaf dry; and LOW HUMIDITY, for the same reason.)
Two factors, and for each state the direction AND the reason.
The four external factors, and note that HUMIDITY works in the OPPOSITE direction to the other three: TEMPERATURE up — transpiration UP LIGHT up — transpiration UP WIND up — transpiration UP HUMIDITY up — transpiration DOWN
THE UNDERLYING PRINCIPLE that makes all four derivable: evaporation depends on the DIFFERENCE in water-vapour concentration between the inside of the leaf and the air outside. Anything that WIDENS that gap speeds transpiration; anything that narrows it slows transpiration.