Download Investigating Plant Growth

Investigating Plant Growth & Mitosis
Background Information
Most plants continue to grow throughout their lives. Like other multicellular
organisms, plants grow through a combination of cell growth and cell division
(parts of the cell cycle). Cell growth increases cell size, while cell division (mitosis)
increases the number of cells. Meristematic tissue, made up of meristematic cells,
is responsible for plant growth. Meristematic cells have the same function in
plants as stem cells in animals—they divide themselves to create new cells. In
other words, meristematic tissue is undifferentiated tissue. Meristematic tissue
contains actively dividing cells that result in formation of other tissue types (e.g.
vascular, dermal or ground tissue) found in plants.
Most plants have several different zones where you’ll find these dividing cells –
these zones are called meristems.
Where Are The Meristems Located?
Meristematic tissue is found in the plant’s stem, roots, shoots, and buds. Mitosis
occurs in all of these meristems.
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Apical meristematic tissue is found in buds and root tips of plants.
Lateral meristematic tissue make the plant grow thicker. Examples of
lateral meristematic tissue include the cambium or 'bark' found in trees.
Lateral meristems occur in woody trees and plants.
The diagrams below show meristematic tissue found in the root tip of an onion.
Objectives:
 SWBAT relate a plant’s structure to its function—in this case the root tip
and growth (mitosis).
 SWBAT identify the stages of mitosis on a prepared slide and in
photographs of onion root tips.
 SWBAT calculate the percentage of time spent in the various phases of the
cell cycle.
1. Your teacher has set up compound light microscopes with prepared slides of
onion root tips. After bringing the specimen into your field of view, sketch
what you see at 40x, 100x, and 400x in the table below.
40 x
100x
400x
2. Obtain a onion root tip photograph from your teacher. As you review your
photograph, tally the number of cells in each phase of mitosis in the table
below.
Interphase
Prophase
Metaphase
Anaphase
Telophase
Onion Root Tip
# Cells in Phase:
% in Each
Phase=
# Cells in Phase
Total # Cells
x 100
Does an onion root tip (meristematic tissue) spend the same amount of time
in each stage of the cell cycle?
3. Use the template below to (a) make a claim, (b) cite evidence, and (c) provide
scientific justification for your findings.
The diagram below shows mitosis in the root tips of a plant that was exposed to
a compound that is known to be insecticidal (kills insects—acts as a pesticide)
(a) Metaphase with lagging chromosome, after 12 h
(b) Metaphase with macro nucleus after 6 h
(c) A sticky metaphase after 24 h
(d) Anaphase with bridge and macro nuclei after 12 h
(e) Anaphase with lagging chromosome after 6
(f) Disturbed metaphase after 6 h
(g) Interphase with two micro nuclei after 12 h
(h) Sticky anaphase and lagging chromosome after 12 h
(i) Anaphase with bridge after 6 h
A student claims that root tip exposure to this insecticide has no impact on
mitosis or the cell cycle of plants. Evaluate the student’s claim to determine if
you agree or disagree with his/her claim and why. Cite evidence to substantiate
your response.