Sweating Trees: Which Leaf Wins the Transpiration Race?

By Georgia Brown’s Fifth-Grade Students, Sanibel Elementary School, Florida

Editor’s Note: Originally published in Dragonfly Magazine in the late 1990s, this timeless and inspiring inquiry was created by young investigators on Sanibel Island, Florida. It remains a perfect example of how local landscapes spark big questions.

A square graphic with a cream-colored background framed by a thin white border and a thicker dark pink outer border. Centered in a dark purple, blocky font is the title "Sea Grape and Gumbo Limbo Leaf Transpiration".
A vintage-style black and white photo showing approximately 20 children seated in three tiers. Every child is holding up a square poster or booklet that displays a circular design, likely related to a science or art project.

Our Spark Our school is on Sanibel Island, a barrier island on the coast of Florida. Every person and every plant here gets warmed by the sun. We knew that people perspire and plants “transpire” (give off water). But looking around our schoolyard, we saw two very different types of trees, and we had a question.

We have Sea Grape trees, which have large, round leaves, and Gumbo Limbo trees, which have bunches of tiny leaflets. We wondered: Do the large Sea Grape leaves transpire more water than the smaller Gumbo Limbo leaves?. Our Prediction We predicted that larger leaves would pass more water into the air than smaller leaves.

An image of leaves
An image of leaves

How We Investigated We didn’t just guess; we designed a way to catch the water.

  • The Trap: We cut the corners off plastic bags and taped test tubes into the holes.
  • The Setup: We placed the bags over single Sea Grape leaves and over bunches of Gumbo Limbo leaves. We sealed the bags tightly with masking tape so no air could get in or out.

The Wait: We left the bags on the trees for 24 hours.

A black and white photograph framed with a magenta border. Two smiling young girls are shown in a classroom setting, holding up a clear plastic bag that contains a large leaf, demonstrating a plant transpiration experiment.

What We Found When we checked our bags the next day, we saw the difference immediately. The bags on the Sea Grape leaves had collected anywhere from 7 to 10 milliliters of water. But the Gumbo Limbo bags? They had only 2 milliliters or less.

A hand-drawn bar chart titled "LEAF TRANSPIRATION" compares the water loss of "Gumbo-limbo" and "Seagrape" leaves across four groups each. The y-axis measures "Milliliters of Water" from 0 to 10. For Gumbo-limbo, Groups 1 and 3 have 0 mL, while Groups 2 (red) and 4 (purple) both show 2 mL. For Seagrape, all groups show significantly higher transpiration: Group 1 (pink) is 7 mL, Group 2 (yellow) is 9 mL, Group 3 (green) is 10 mL, and Group 4 (blue) is 8 mL. The chart clearly indicates that Seagrape leaves transpired much more water than Gumbo-limbo leaves in this experiment.

We proved that Sea Grape leaves are the transpiration champions!.

GO WILD: YOUR TURN

  • The Challenge: Don’t take our word for it. Find a broad-leaf plant and a needle-leaf plant (like a pine) in your neighborhood.
  • The Method: Recreate our “bag trap” using Ziploc bags and tape.
  • The Question: Which local tree is the “champion sweater” in your town?

THE FIELD GUIDE (For Educators)

Subject: Plant Physiology / Environmental Science

Grade Level: 3–6 Inquiry Focus: Experimental Design, Variable Control, Measurement.

The Science Behind It: This inquiry demonstrates transpiration—the process where water travels from roots, up the stem, and out through stomata in the leaves. The students’ data confirms that leaf surface area (morphology) directly impacts water loss. This is a great entry point for discussing evolutionary adaptations (e.g., why desert plants have spines instead of wide leaves).

Standards Connection:

  • NGSS: Structure and Function (LS1.A), Matter and Energy Flow in Organisms (LS1.C).
  • Skill: Planning and Carrying Out Investigations.

Materials Needed: Clear plastic bags, masking tape, measuring spoons, or graduated cylinders.

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