NGSS*2nd GradeLife Science

2-LS2-1: Do Plants Need Light and Water?

Also called NGSS 2-LS2-1 · Topic: Interdependent Relationships in Ecosystems · Life Science

Practice It All 14 2nd Grade Science Standards

The Official Wording

Plan and conduct an investigation to determine if plants need sunlight and water to grow.

Assessment boundary: Assessment is limited to testing one variable at a time.

NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026

What 2-LS2-1 Means in Plain English

Second graders plan and carry out a test to find out whether plants need light and water to grow well. They set up cups of young plants, give some light or water and hold it back from others, and track how each plant changes over a week or two.

Each test changes only one thing: light or water, never both at once. Students do not yet explain how plants make food. That comes in 5th grade, where they find that plants get what they need mostly from air and water (5-LS1-1).

2-LS2-1 I Can Statements

I can plan a plant test that changes only one thing.
I can measure and record how tall a plant grows.
I can tell what plants need from my test results.

2-LS2-1 Worked Example

A ten-day test with radish sprouts that checks light and water one at a time.

The Question

Do radish sprouts need light and water to keep growing well?

Set It Up: Three clear cups of soil with radish sprouts about 1 cm tall, a cardboard box to cover one cup, a teaspoon and a ruler.

Radish sprouts: light and water

What Students Do

Label the cups Light and Water, No Light, and No Water.Three cups, all sprouts 1 cm
Put the No Light cup under the box and keep the other two in a bright spot.Only light differs for the boxed cup
Give the first two cups two teaspoons of water each day and the No Water cup none.Only water differs for the dry cup
Measure the tallest sprout in each cup and note its color every other day.A height and color chart
Compare the cups after ten days.Light and Water: 5 cm, green. No Light: 7 cm, pale and floppy. No Water: wilted

What They Find

Only the sprouts with both light and water grew green and strong, so the plants need both.

Why it works: Plants use light to make their own food and need water to stay firm, so without light they stretch tall and weak, and without water they wilt.

Common Mistakes with 2-LS2-1

Changing light and water together

One cup in a sunny spot with water, the other in a dark closet with none

Try this: Set up one comparison for light and a separate one for water, so each result has only one possible cause.

Thinking taller always means healthier

“The box plant grew the most, so plants don’t need light!”

Try this: Look at color and strength too. Plants kept in the dark stretch tall but turn pale and floppy, a sign they are struggling.

Ending the test too soon

Checking after one day and deciding nothing happened

Try this: Plants change slowly, so measure every other day for about two weeks before deciding what the test shows.

Where 2-LS2-1 Fits

Comes BeforeK-LS1-1Notice what plants and animals need to live, the pattern this test checks with evidence.

Alongside2-LS2-2Model how animals move seeds and pollen, another way plants depend on their surroundings.2.MD.A.1Measure sprout heights in centimeters with a ruler.

Comes Next5-LS1-1Show that a growing plant builds its body mostly from air and water, not from soil.

Practice 2-LS2-1

Graph Paper GeneratorFree ToolStudents graph each cup's sprout height every other day and watch the three lines pull apart.1 cm gridLine graphLarge squares

Open

Quick Check

You want to test if plants need water. What must stay the same in both cups?
Everything except water, like the light, the soil and the kind of plant. Then water is the only cause.
A plant in a dark box grew tall but pale. Is it healthy?
No. Plants in the dark stretch toward any light they can find, but they turn pale and weak.
What happened to the sprouts that got no water?
They wilted and dried up, which shows plants need water to live and grow.

2-LS2-1: Other Names

2-LS2-1NGSS 2-LS2-1What plants need to growPlant growth experiment