Stomata and Transpiration in Plants
Name
Part 1: Study of Distribution of Stomata on Leaves
http://amrita.olabs.edu.in/?sub=79&brch=7&sim=128&cnt=1
Read the background information provided in the “Theory” section for thislab and
answer the following pre-lab questions:
1. What are stomata? Stomata are minute pores found on the
epidermis of leaves and young shoots of plants .
2. What is the function of stomata? They control the exchange of gases
3. What regulates the size of the stomata opening? The pore is surrounded by a pair of specialized
cells called the guard cells that are responsible in regulating the size of theopening.
4. What gases exit the plant through stomata? Oxygen and water are released through thestomata.
5. What gas enters the plant through the stomata? Carbon dioxide enters through thestomata.
6. Under what conditions would a plant surface have more stomata? Stomata are found more on
plant surfaces thriving under higher light, lower atmospheric carbon dioxide concentrations and
in moist environments.
7. What is the formula for Stomatal index?
Select “Simulator” to begin virtual part of the lab
You may need this image as a reference for
the Simulator part of this activity
To complete Table 1:
a. Select the type of view from the “Select
view” drop-down list. To viewthe leaf
epidermis, select the “Binocular view”.
1
, b. Select the slide containing the leaf from the “Select sample” drop-down list.
c. The power of the lens can be changed by selecting the required lens power from thedrop-down
list “Select objective lens”. KEEP THE OBJECTIVE LENS ON 40X
d. To coarse focus on the tissue, move the tube up and down by clicking on the “Coarse
adjustment” right and left arrow.
e. To achieve a fine and sharp focus, move the tube very slowly by clicking on the “Fine
adjustment” right and left arrow.
f. Move the slide to observe each part of the sample by clicking on the directional arrow of the
“Slide adjustment”. YOU WILL COUNT ALL OF THE STOMATA ON THE SAMPLE (not
just in the first view) – I suggest you use the slide adjustment to move the view to one end of slide
to start your count and count the stomata first and then the epidermiscells.
g. Count the number of stomata and epidermal cells in the specimen and enter thevalues in
Table 2 below.
Table 1: Study of Distribution of Stomata in the Upper and Lower Surface of Leaves
Plant
Petunia Lilly
Upper
Lower Epidermis Upper Epidermis Lower Epidermis
Epidermis
Number of
6 11 56 56
Stomata
Number of
epidermal 63 55 51 51
cells
Stomata
Index
(6/ (11/ (56/ (56/
(show the
(6+63))x100 (11+55))x100=16 (56+51))x100=52. (56+51))x100=52.
calculation
= 8.7 .7 34 34
and the
answer)
Select “Video” to watch a video recording of the lab to review the lab prior to completingthe analysis
Analysis of Part 1: Study of Distribution of Stomata on Leaves
1. Assuming that environmental conditions are ideal, predict where on a tree you would expect to see
more stomata. Explain why. The stomata must be open during the daylighthours to let oxygen and
carbon dioxide pass through. While they are open, water vapor escapes into the atmosphere
(transpiration). ............................................................... Transpiration is the loss of water
through stomata, so, more stomata are found on the lower surface to prevent excessiveloss of water.
2
Name
Part 1: Study of Distribution of Stomata on Leaves
http://amrita.olabs.edu.in/?sub=79&brch=7&sim=128&cnt=1
Read the background information provided in the “Theory” section for thislab and
answer the following pre-lab questions:
1. What are stomata? Stomata are minute pores found on the
epidermis of leaves and young shoots of plants .
2. What is the function of stomata? They control the exchange of gases
3. What regulates the size of the stomata opening? The pore is surrounded by a pair of specialized
cells called the guard cells that are responsible in regulating the size of theopening.
4. What gases exit the plant through stomata? Oxygen and water are released through thestomata.
5. What gas enters the plant through the stomata? Carbon dioxide enters through thestomata.
6. Under what conditions would a plant surface have more stomata? Stomata are found more on
plant surfaces thriving under higher light, lower atmospheric carbon dioxide concentrations and
in moist environments.
7. What is the formula for Stomatal index?
Select “Simulator” to begin virtual part of the lab
You may need this image as a reference for
the Simulator part of this activity
To complete Table 1:
a. Select the type of view from the “Select
view” drop-down list. To viewthe leaf
epidermis, select the “Binocular view”.
1
, b. Select the slide containing the leaf from the “Select sample” drop-down list.
c. The power of the lens can be changed by selecting the required lens power from thedrop-down
list “Select objective lens”. KEEP THE OBJECTIVE LENS ON 40X
d. To coarse focus on the tissue, move the tube up and down by clicking on the “Coarse
adjustment” right and left arrow.
e. To achieve a fine and sharp focus, move the tube very slowly by clicking on the “Fine
adjustment” right and left arrow.
f. Move the slide to observe each part of the sample by clicking on the directional arrow of the
“Slide adjustment”. YOU WILL COUNT ALL OF THE STOMATA ON THE SAMPLE (not
just in the first view) – I suggest you use the slide adjustment to move the view to one end of slide
to start your count and count the stomata first and then the epidermiscells.
g. Count the number of stomata and epidermal cells in the specimen and enter thevalues in
Table 2 below.
Table 1: Study of Distribution of Stomata in the Upper and Lower Surface of Leaves
Plant
Petunia Lilly
Upper
Lower Epidermis Upper Epidermis Lower Epidermis
Epidermis
Number of
6 11 56 56
Stomata
Number of
epidermal 63 55 51 51
cells
Stomata
Index
(6/ (11/ (56/ (56/
(show the
(6+63))x100 (11+55))x100=16 (56+51))x100=52. (56+51))x100=52.
calculation
= 8.7 .7 34 34
and the
answer)
Select “Video” to watch a video recording of the lab to review the lab prior to completingthe analysis
Analysis of Part 1: Study of Distribution of Stomata on Leaves
1. Assuming that environmental conditions are ideal, predict where on a tree you would expect to see
more stomata. Explain why. The stomata must be open during the daylighthours to let oxygen and
carbon dioxide pass through. While they are open, water vapor escapes into the atmosphere
(transpiration). ............................................................... Transpiration is the loss of water
through stomata, so, more stomata are found on the lower surface to prevent excessiveloss of water.
2
