← Back to course
Cells and Systems 6-8 / Week 04 / Wednesday
3/6
Week 04 · Plant Cells Have More

Wednesday

Windowsill Lab: Celery and colored water
// Cell walls, chloroplasts and the color green
⏱ about 20 min

Wednesday: Windowsill Lab: Celery and Colored Water

Rocket squeezes food coloring into a jar of water until it is deep blue. "Now the celery drinks it. We watch the color climb."

Raven checks the clock. "It will take hours, not minutes. Predict where the color goes first."

"Straight up the pipes," Rocket says. "The xylem. Then into the leaves at the top."

A grown-up trims the base of the stalk and stands it in the jar. Nova hovers over the leafy top. "What will you measure?"

"How high the color climbs, every hour," Raven says. "In millimeters." Rocket grabs the ruler and the hand lens.

"And at the end," Nova says, "a grown-up slices it across. Then you will see exactly where the water went."

Your mission

Today you make water movement visible. Tinted water climbs the xylem of a celery stalk, and the color shows you the path.

You will measure how high the color climbs over several hours. Then a grown-up cuts the stalk across to show the colored xylem bundles.

While you wait, you study leaf veins with the hand lens. Both tasks go in the data table and your Windowsill Log.

  • One fresh celery stalk with leaves, if possible, trimmed at the base by a grown-up
  • A clear jar or cup, water, and blue or red food coloring
  • A ruler, a hand lens or phone camera zoom, and a kitchen timer
  • Two or three leaves from outside or from a houseplant, with a grown-up's permission
  • Paper towels and your Windowsill Log
Safety first
A grown-up does all cutting: trimming the base and slicing the stalk across at the end.
Celery is a lab material. It is not eaten after the lab. Nothing is tasted. Keep hands away from your face.
Food coloring stains. Work over a tray and wipe spills right away.
Wash your hands after handling the celery, the leaves or the colored water.
  1. Fill the jar one third with water. Add food coloring until the water is deeply colored.
  2. Ask the grown-up to trim about one centimeter from the base of the celery stalk.
  3. Stand the stalk in the jar, cut end down. Note the time as hour zero.
  4. Hold the ruler beside the stalk. Record the height of any visible color above the water line. At the start it is zero.
  5. Every hour, measure how high the color has climbed. Record it in the table.
  6. While you wait, look at a leaf with the hand lens. Find the midrib and the veins. Sketch the pattern.
  7. After at least four hours, ask the grown-up to slice the stalk across, high above the water line.
  8. Look at the cut face with the hand lens. Count the colored dots and record the number.
PREDICT BEFORE YOU WATCH
  • Read the question.
  • Tap your answer.
Where will the color appear first?
When the stalk is sliced across, what will the colored parts look like?
TimeColor height above water (mm)What the leaves look likeNotes
Hour 00
Hour 1
Hour 2
Hour 3
Hour 4 or later
Cross sectionnumber of colored dots:

Reading the result

The colored lines climbing the stalk are xylem bundles. Water travels up through them toward the leaves.

The colored dots in the cross section are the same bundles seen end on. Xylem and phloem run the length of the stem in these strands.

The pull comes from the top. Water evaporating from the leaf surface, transpiration, draws water up from below.

If the color climbed slowly, the air may be humid, so less water evaporated. Fewer leaves also means less pull.

The leaf you studied shows veins branching from a midrib. Those veins are the leaf's share of the same vascular tissue.

What the lab showsTrue or false?
The colored lines in the celery are xylem bundles carrying water.?
The color spread evenly through every cell of the stalk.?
Water evaporating from the leaves helps pull water up the stalk.?
The dots in the cross section are the vascular bundles seen end on.?
WHY THIS EXERCISEThe lab turns an invisible process, water moving through tissue, into something you can measure.
Which tissue carried the colored water up the celery stalk? Type one word.
WHY THIS EXERCISENaming the tissue connects your celery to every tree that lifts water to its top.
Sketch the celery cross section with its colored dots. Beside it, sketch the leaf veins you saw through the hand lens.

Patient measuring. Tomorrow you read the biology text's own table comparing animal and plant cells.

← Tuesday