6.3 Identifying Mitosis in Plant Cells Flashcards
Where does growth in plants take place?
Growth in plants occurs in specific regions called meristems
Where is the meristem found?
The root tip meristem can be found just behind the protective root cap
What happens in the root-tip meristem?
In the root tip meristem, there is a zone of cell division that contains cells undergoing mitosis
What is the squash technique?
Root tips are stained and then gently squashed, spreading the cells out into a thin sheet and allowing individual cells undergoing mitosis to be clearly seen
What is the method of observing root-tip meristems with the squash technique?
Garlic or onion (Allium cepa) root tips are most commonly used (the bulbs can be encouraged to grow roots by suspending them over water for a week or two)
Remove the tips of the roots (about 1cm) and place in a suitable stain (eg. warm, acidified acetic orcein, which stains chromosomes a deep purple)
The stained root tip is gently squashed on a glass slide using a blunt instrument (eg. the handle of a mounting needle)
Cells undergoing mitosis (similar to those in the images below) can be seen and drawn
Annotations can then be added to these drawings to show the different stages of mitosis
What are the limitations of observing root-tip meristems with the squash technique?
It can be very difficult to distinguish between prophase and telophase in cells - looking at the number of nuclei within one cell can help to identify which stage is likely to be occurring. If there are multiple nuclei within one cell then telophase is occurring.
The size of cells or structures of tissues may appear inconsistent in different specimen slides
Optical microscopes do not have the same magnification power as other types of microscopes and so there are some structures that can not be seen
The treatment of specimens when preparing slides could alter the structure of cells
