Publication No. 10406
Student Laboratory Kit
Materials Included In Kit
Hydrochloric acid solution, 1 M, 30 mL
Additional Materials Required
Actively growing onion root tips are required for Part II of the activity. Allow at least 2–4 days for new roots to grow. You may grow the roots ahead of time or you may have students grow them as a group and complete Part II afterward.
As shown in Figure 2, push toothpicks into the sides of the bulb to support the bulb on the rim of the cup. Add water to the cup during the root growing time as needed to keep the root area under water. The roots should be about 2 cm in length when they are ready to harvest. Have students remove entire lengths of root when cutting the roots from the onion. Do not have them cut just partial roots. This will prevent other students from removing a root that doesn’t have a root tip! After removing the entire root only the 1-cm tip should be cut off and used in the exercise. Several onions (5–6) will be required to provide enough root tips for an entire class.
Hydrochloric acid solution is toxic by ingestion or inhalation and severely corrosive to skin and eyes. Toluidine blue stain is slightly toxic by ingestion and is a permanent stain on many objects. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Please review current Safety Data Sheets for additional safety, handling and disposal information.
Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. Toluidine blue solution can be disposed of according to Flinn Suggested Disposal Method #26b and hydrochloric acid according to method #24b.
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering PracticesDeveloping and using models
Planning and carrying out investigations
Analyzing and interpreting data
Constructing explanations and designing solutions
Disciplinary Core IdeasMS-LS1.A: Structure and Function
MS-LS1.B: Growth and Development of Organisms
HS-LS1.A: Structure and Function
HS-LS1.B: Growth and Development of Organisms
Scale, proportion, and quantity
Systems and system models
Structure and function
Stability and change
HS-LS1-4. Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.
Campbell, N. A.; Reece, J. B. Biology, 7th ed.; Pearson Education: San Francisco, 2005; Chapter 12.
Inside the Cell; U.S. Department of Health and Human Services. National Institutes of Health. National Institute of General Medical Sciences. NIH Publication No. 05–1051, September 2005 revision. 46–51.
Living cells are continually involved in complex reactions associated with being alive. One important sequence of events critical to the survival of a cell type is its reproductive cycle. How do cells produce more cells like themselves?
The life of a eukaryotic cell consists of a continuous sequence of events known as the cell cycle (see Figure 1).
Hydrochloric acid, HCl, 1 M, 2–drops
Toluidine blue stain is moderately toxic by ingestion and is a permanent stain on many objects. Hydrochloric acid solution is toxic by ingestion or inhalation and severely corrosive to skin and eyes. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Razor blades are extremely sharp. Use care when cutting with them. Wash hands thoroughly with soap and water before leaving the laboratory.
Part I. Picturing Mitosis
Part II. Onion Root Cells