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Science and Technology K–6 · Years 1–2

Seedlings lean towards the light

Living World (NSW 2017); Science understanding, Biological sciences (ACARA v9)

PracticalLow risk

The idea

Plants grow towards the light they need, so a seedling lit from one side bends that way.

What you need

  • Two punnets of bean seedlings 5 cm tall, in punnets about 6 cm deep
  • Two identical cardboard cartons at least 30 cm tall inside, open at the base so each stands over a punnet: one with a 3 cm hole cut in one side 10 cm above the base, the other with no hole. A shoebox is too shallow for this: 5 cm seedlings in a 6 cm punnet already stand as tall as a shoebox, and seedlings in the dark stretch several centimetres a day, so a stem pressed against the lid cannot be read for a lean angle
  • A sunny windowsill; a protractor card to read the lean angle from the vertical

How to do it

  1. Predict which way the seedlings in each carton will lean after five days.
  2. Stand each seedling upright and record its starting lean from the vertical in degrees.
  3. Stand the carton with the hole over one punnet, the hole facing the window. Stand the carton with no hole over the other punnet beside it.
  4. Each morning open the cartons for one minute, check that the tallest seedling still has at least 5 cm of clear space above it and move that punnet to a taller carton if it has not, record the lean angle of the tallest seedling from the vertical and the direction of the lean, then close them.
  5. After five school days compare the two punnets and turn the holed carton around so the hole faces away from the window.
  6. Keep recording for three more days, now noting the direction the growing tip points as well as the lean of the whole stem.

What you should see

Within the first few days the seedlings in the holed carton lean towards the hole, while the closed-carton seedlings grow straight, tall and pale. After the carton is turned, the tips begin to bend towards the new hole direction during the three extra days. The lean angle each day is the class's measurement. The lower stem keeps its old lean, so after the turn the tip direction, not the lean of the whole stem, is the reading to check. The learner knows it worked when the lean points towards the hole before the turn, and the growing tips point towards the new hole direction by the end of the three extra days.

What changes

What you change
direction of the only light source (hole position)
What you measure
lean angle from the vertical (degrees) and lean direction; after the turn, the direction the growing tip points
What you keep the same
  • same seedlings
  • cartons opened for the same minute
  • same windowsill
  • at least 5 cm of clear space above the tallest seedling every day

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

  • Plants cannot move.
  • The plant leans because the carton pushes it.

Safety card

Low riskLearners carry it out

Hazards

  • Soil on hands; potting mix and soil can carry Legionella bacteria (NSW Health)

Controls

  • The punnets come already planted and the mix is kept damp, so no dry potting mix is opened in class
  • Where potting mix is opened, NSW Health advises wetting it down and wearing gloves and a mask, if possible a P2 or N95 mask, and the adult does that away from faces; learners wear gloves when handling the punnets; hands washed after handling the punnets

Note

No chemicals or heat. Record the activity on the school's risk assessment (Primary School RiskAssess, Ecosolve Australia, riskassess.com.au).

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

  • Science and Technology K-6 Syllabus (2017), NESA. Current syllabus; NESA's timeline is 2026 plan and prepare, 2027 start teaching the 2024 syllabus. Code read from the official syllabus document on 2026-09-22.ST1-4LW-SST1-1WS-S
  • Science and Technology K-6 Syllabus (2024), NESA. Implementation from 2027, so this code describes the future syllabus. Code read from the outcomes page on 2026-09-22.ST1-SCI-01ST1-PQU-01
  • Australian Curriculum v9AC9S1U01AC9S1I01AC9S1I02AC9S1I03AC9S1I04

Sources

The pages the author read to write this activity.

  1. www.scootle.edu.au/ec/search?accContentId=AC9S1U01
  2. www.nsw.gov.au/education-and-training/nesa/curriculum/science/science-and-technology-k-6-2017
  3. primaryconnections.org.au/teaching-sequences/year-1/survive-thrive
  4. www.health.nsw.gov.au/Infectious/factsheets/Pages/legionnaires_disease.aspx

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