Question

What is the main source of energy which causes water loss in plants?
A - Heat from Sun
B - Light in Chlorophyll

This came as a MCQ in my exam. I am in doubt. Light causes the guard cells to open and water to diffuse out. On the other hand, I have also learned that Heat causes evaporation. So, what is the answer?

Answer 1

A

Answer 2

Hai Sweet Friend, @waqasabbasi WelcoMe To OpeN studY !!


@BEATZDJ Hmm, why you say option A why not B ?

Answer 3

The process in which moisture (water) is carried through plants from roots to small pores on the underside of leaves is called transpiration.
Plants put down roots into the soil to draw water and nutrients up into the stems and leaves. Some of this water is returned to the air by transpiration. Transpiration rates vary widely depending on weather conditions, such as temperature, humidity, sunlight availability and intensity, precipitation, soil type and saturation, wind, land slope, and water use and diversion by people. During dry periods, transpiration can contribute to the loss of moisture in the upper soil zone.
If you summarise the whole thing, it is basically the heat of the sun that causes dry vegetation so that's why the plants lose its moisture.

Does this make sense, @Koikkara ?

Answer 4

@BEATZDJ is correct its A

Answer 5

@BEATZDJ Lol...I do have sense but the person who asked this didn't know why it is option A, so I wanted you to post your answer with explanations so that the person can understand it ! This is what OS asks to have from Its Users ! Hope You Understands !
Also, I used too answer almost questions in here, means I do know the basic stuffs too !

NEXT TIME TEACH YOUR FRIEND NOT HELP HIM HOW TO CHEAT !

@waqasabbasi Hope, if U Are Satisfied with @BEATZDJ answer, Please Close This Question !

Thank U !! Keep In Touch, with Open study !!

Answer 6

Oh, that's true @Koikkara . I almost forgot it was called open STUDY for a reason. Thanks

Answer 7

@BEATZDJ Nice to meet you, Have an awesome Day !

Answer 8

I think answer should be B because unless there is light the guard cells would not open. I have read on the internet that light is most important environment factor that affects transpiration rate. This is one such example: http://water.me.vccs.edu/courses/SCT112/lecture3_2b.htm

Heat does lead to evaporation but without guard cells open the water cannot be lost from leaf. Light energy causes guard cells to open. Am I right? If not, can you tell why not B?

Answer 9

@waqasabbasi This is a difficult question...both answers could be right. I'll explain why:
You're right about unless there is light, the guard cells would not open, but, temperature greatly influences the magnitude of the driving force for water movement out of a plant rather than having a direct effect on stomata. As temperature increases, the water holding capacity of that air increases sharply. The amount of water does not change, just the ability of that air to hold water. Because warmer air can hold more water, its relative humidity is less than the same air sample at a lower temperature, or it is ‘drier air’. Because cooler air holds less water, its relative humidity increases or it is ‘moister air’. Therefore, warmer air will increase the driving force for transpiration and cooler air will decrease the driving force for transpiration.

I would need time to think about this..