This new resource supports the use of practicals across various A-level biology 2015 specifications for England (OCR, AQA, Edexcel and Eduqas).
In this practical, students will prepare and observe dividing cells from the meristems of actively growing garlic root tips.
This is an improved and simplified protocol from the well-known version using acetic orcein. Toluidine blue is used to stain the DNA in the meristem cells, giving a simpler and less hazardous process for the students, and producing an excellent level of contrast within the cells (see image above).
In plants, cell division by mitosis is restricted to specific tissues, called meristems, that are found at the growing root and shoot tips and in the cambium between the xylem and phloem of the vascular bundle. The cells in the meristems are undifferentiated. By following this protocol, students will be able to observe the dividing cells clearly, and calculate the mitotic index.
We recommend using garlic for the standard practical. Students may also wish to carry out further investigations using plants such as hyacinth, onion and broad bean: details for producing root tip squashes for these are also given.
- Tested materials to support the A-level practical endorsement (CPAC)
- Support materials for teachers and technicians
- Student worksheet to help provide evidence for meeting the practical skills requirements
- Student revision materials to help prepare for exams
Support materials for other key practicals in A-level specifications can be found on the A-level set practicals main page.