6transpiration

Transpiration and the Function of Stomata

Transpiration and the Function of Stomata

A plant may close its stomata on a hot day to reduce the loss of water by transpiration

The Role of Transpiration

Factors Affecting the Rate of Transpiration

1. LIGHT2. TEMPERATURE3. WIND4. HUMIDITY


1. Same Type 2. Same Size 3. Same time


CONTROLLED VARIABLESMANIPULATED VARIABLES

PROCEDURE

1. Take the initial reading of the electronic balance.

2. Take the final reading of the electronic balance after 2 hours (120 minutes).

Assumed that the Rate of transpiration = The rate of water loss

Rate of transpiration = Initial mass - final mass 120 minutes

= X g/min

RESULT ( AFTER 2 hours/120 min )

Initial mass (g)

X

Final mass (g)

Y

Amount of water loss

X – Y (g)

Rate of transpiration

(g/min)

Potometer K

300 180 120

120/120

1

Potometer L

300 120 180

180/120

1.5


Manipulated variables

Responding variables

Fixed variables Wind, Temperature, Humidity, timesize and type of plant

Presence of light

Rate of transpiration / difference in weight of the apparatus





Fixed variables Wind, Temperature, Humidity, timesize and type of plant

Presence of light


Inference

Rate of transpiration depends on the presence of light

HypothesisLight increases the rate of

transpiration

Observation The water loss is more for the

potometer that is subjected to light.

Difference The water loss in Potometer K is

more than the water loss in Potometer L.

Conclusion The rate of transpiration is faster when there is light because light stimulates

the opening of the stomata.


Manipulated variables TEMPERATURE

Responding variablesRate of transpiration / difference in weight of the apparatus

Fixed variables


Light, Humidity, Wind, time, size and type of plant


Manipulated variables TEMPERATURE


Fixed variables Light, Humidity, Wind, time, size and type of plant

Inference

Rate of transpiration depends on the temperature

HypothesisThe higher the temperature, the faster the rate of transpiration


potometer that is subjected to direct sunlight.

Difference The water loss in Potometer R is

more than the water loss in Potometer Q.

Conclusion The rate of transpiration is faster at a higher

temperature because waterevaporates at a higher temperature.




Fixed variables

1. LIGHT2. TEMPERATURE3. WIND

Light, Temperature, Humidity, timesize and type of plant

Presence of wind


4. HUMIDITY




Fixed variables Light, Temperature, Humidity, timesize and type of plant

Presence of wind


Inference

Rate of transpiration depends on the presence of wind

Hypothesis Windy condition increases

the rate of transpiration


potometer that is subjected to wind.

Difference The water loss in Potometer L is

more than the water loss in Potometer K.

Conclusion

The rate of transpiration is faster if wind is present.


Manipulated variables HUMIDITY


Fixed variables


Light, Temperature, Wind, time, size and type of plant


Manipulated variables HUMIDITY


Fixed variables Light, Temperature, Wind, time, size and type of plant

Inference

Rate of transpiration depends on the humidity

Hypothesis The lower the humidity, the

faster the rate of transpiration


potometer that is subjected to room condition.

Difference The water loss in Potometer M is

more than the water loss in Potometer N.

Conclusion The rate of transpiration is faster at a lower humidity because water evaporates faster if the humidity of the surrounding is lower.

12

T

H

O

R

N

Stoma

Wilting occurs

By opening and closing their stomata

Light, temperature, wind and humidity

To cool the plants and to transport water and minerals

6transpiration

Documents