Download Mitosis in Plant Cells Lab

page 1
Mitosis in Plant Cells Lab
Introduction
There are two major differences in mitosis between plant and animal cells. First, plant cells do not
contain centrioles, therefore their centrosomes are different. The mitotic spindles that separate the
sister chromatids are created from the cell’s cytoskeleton. The second difference occurs during
cytokinesis. Since plant cells have a cell wall as well as a membrane, it can not divide by simply
pinching the cell membrane together. Instead a plate forms between the new nuclei, dividing the cell
in two. The plate forms from the aggregation of vesicles containing cell wall components.
To investigate plant cell mitosis we will look at onion root tips under the microscope. The tip of the
root is where growth occurs to reach nutrients and water for the plants. As discussed previously, a
multicelluar organism grow through an increase in the number of cells, thus cells at the tip of the
onion root go through mitosis at a high rate. Below is a picture of an onion root tip.
Source: http://www.life.uiuc.edu/ib/202/labs/structure/plant_transpiration/onion50.html
The part of the root tip that grows, and thus the area of a high rate of cell division, is the apical
meristem (D). The apical meristem is protected by a root cap (E). In this laboratory, you will view
the apical meristem onion root tip and identify cells in various stages of the cell cycle. Based on the
number of cells in each stage you will determine the approximate time a cell spends in each stage
during its life.
Objectives
• You will find and identify cells in various stages of the cell cycle in the apical meristem region of
an onion root.
• You will determine the amount of time a cell spends in each phase of the cell cycle.
Procedure
1. Look at the image of the onion root tip on the screen. 2. Find at least one cell in each stage of the cell cycle and draw the images on page 2.
KC 4 Science
© 2008 Kent ISD
page 2
Mitosis in Plant Cells Lab (continued)
Procedure
1. Look at the image of the onion root tip on the screen. 2. Find at least one cell in each stage of the cell cycle and draw the images below.
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
3. Due to the preparation of the slide, the nucleus of every cell is not visible. Choose 50 cells at
random whose nucleus or chromosomes are visible. Record how many cells of the 50 are in each
stage in the table below. (it may be difficult to determine the difference between telophase and
cytokinesis)
Stage of cell cycle
Interphase
Mitosis
Number of cells:
Proportion of time in each
stage of the cell cycle (%)
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
4. The proportion of time spent in each stage will be equivalent to the percentage of cells in each
stage. Put the percentage in the last column of the table.
KC 4 Science
© 2008 Kent ISD
page 3
Mitosis in Plant Cells Lab (continued)
Questions and Analysis
1. Which phase requires the majority of time in the cell cycle? What happens during this phase that
might require a large amount of time?
2. What are two differences between mitosis in a plant cell and mitosis in an animal cell.
3. Do you think the proportion of time spent in mitosis would be greater or smaller in more mature
regions of the root? Why?
4. What evidence shows that mitosis is a continuous process, not a series of separate events?
KC 4 Science
© 2008 Kent ISD