Stomata & Transpiration Lab

Transpiration The evaporation of water from a plant

out of it’s leaves. Plants LOSE water through transpiration

(as it leaves through their stomata).

Plants GAIN water through their roots

Plants LOSE water through stomata in their leaves

Stomata can open & close

When might stomata spend more time open?

When might stomata need to spend more time closed?

What factors might affect transpiration rate?

In other words… what might affect how quickly or slowly water evaporates from a plant?

Based on the following table, is there a relationship between the habitat (in terms of moisture) to which plants are adapted and the density of stomata in their leaves?Plant Upper

epidermisLower epidermis

Anacharis (water weed)

0 0

Black walnut 0 160

Corn 70 88

Water lily 460 0

Tomato 12 130

Transpiration Lab-Part 1 Determine a method for calculating leaf

surface area Make a wet-mount slide of a “nail polish

stomata peel” to view a leaf epidermis (do each side of the leaf).

Transpiration Lab-Part 1 Draw & label what you

observe Count all the stomata

in 1 microscopic field & record the #. Do this for at least 3

microscopic fields to determine the average # of stomata/field

Transpiration Lab-part 2Design your own investigation Design a question to determine the effect of an environmental

variable(s) on the rate of transpiration in plants. (Must be approved by me TODAY). See p. S142-S143 for basic setup. Remember:

What’s the question being addressed? What assumptions are being made & can those be verified? Will the measurements you collect provide the data necessary to

answer the question you are asking? Did you include a control?

Materials: Determine if all the materials you will need are available, or if lab

group members need to bring additional materials tomorrow. Be sure that at least 1 person from your group will be here tomorrow

to set up the lab & that at least 1 person can collect the plant mass each day the rest of the week (think about AP test schedule).

Make a hypothesis about which environmental factors you think will have the greatest effect on transpiration rates