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Simulating Threshold Effects of Soil pH on Hydrangea Plants

Kit #320

In this simulation activity, students model how hydrangea plants are affected by soil pH. Agricultural lime (mostly CaCO3) is often used to adjust soil pH. Soil pH is a factor that influences the color of hydrangea flowers and the health of the plant. Below a positive threshold pH, hydrangea flowers are blue, above this threshold dose flowers are pink, and higher doses, above the negative threshold amount, cause health problems. The use of a simulation allows students to add “agricultural lime” to each “plant” and then immediately observe the “plant’s reaction.” Students use the data obtained from the simulation to determine the positive and negative threshold doses for “agricultural lime.” They also reflect upon the results to decide whether they have sufficient data to make a recommendation for an optimal amount of lime to use if you want to produce healthy plants with pink flowers.

Details at a Glance

  • 1-2 Days | 1-2 ~50 minute class periods
  • 1 Activity
  • Accommodates 3 classes, each with 6 groups of 4 students
  • Consumables service 72 students
  • Meets our criteria for supporting literacy
  • Requires a water source

Complete Kit Equipment Package

Simulating Threshold Effects of Soil pH on Hydrangea Plants

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Scientific Concepts

Concepts, Processes, and Issues
• Laboratory testing is often used to help establish positive and negative (toxic) threshold levels for substances.
• Quantitative data derived from tests can be mathematically extrapolated.
• Several factors must be considered when extrapolating lab-derived data.
Relevant National Agriculture, Food, and Natural Resources (AFNR) Standards
• Prepare growing media for use in plant systems
• Formulate and prepare growing media for specific plants or crops
• Develop and implement a fertilization plan for specific plants or crops.
• Describe nutrient deficiency symptoms and recognize environmental causes
of nutrient deficiencies.
• Monitor plants for signs of nutrient deficiencies and prepare a scouting report.
• Discuss the influence of pH and cation exchange capacity on the availability
of nutrients.
• Adjust the pH of growing media.
• Develop and implement a plant management plan for crop production.
• Prepare soil for planting with the addition of amendments.
• Apply preplant treatments required of seeds and plants and evaluate the results.

Guides & Student Sheets

Our kits and modules provide you with everything you need so you can open, review, and teach the material confidently the next day.

  • Full downloadable Teacher Guide with background information, detailed instruction, example data and answers
  • Downloadable Student Sheets with age appropriate background information, full procedure(s), and analysis questions
  • All materials necessary to carry out the investigation
  • Safety Data Sheets

Kit Components

  • 12 Chemplates® with stir sticks
  • 12 red/blue pencils
  • 6 15-mL dropper bottles of “agricultural lime”
  • 3 30-mL dropper bottles of “plant mass”
  • 3 30-mL dropper bottles of “soil aluminum”
  • 3 30-mL dropper bottles of “plant nutrients”
  • 1 Material Data Safety Sheet (MSDS) booklet
  • available as downloads Teacher's Guide, Student Worksheet and Guide, MSDS booklet
  • Not included and needed for instruction: Safety goggles.

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