Hands-On Lab
Race to the Top
In this investigation, students will investigate various plant organs. They will use microsopes to observe
the structure of roots, stems, and leaves of different plants. Students will examine the structure of the
specialized cells that make up these plant organs and relate their structure to function.
Timing: one 90-minute class session
Objective(s):
Students will observe plant structures and form a hypothesis about the way in which different plants
move water through their bodies.
Safety Precautions:
Remind students to wear gloves, aprons, and closed-toe shoes, and not to eat or drink anything in the
lab. Tell students to report any broken glass and not to try and clean it up by themselves.
Materials:
Per student group:
• unlabeled full plant samples with roots, stems, and leaves intact: one moss; one monocot, one
fruit-bearing dicot; and one root vegetable dicot,
• numbered and labeled slides, with cover slips, of the following cross sections: moss leaf-like
organ, stem-like organ, and rhizoids, monocot root, stem and leaf, fruit dicot root stem and leaf,
and root vegetable dicot root, stem, and leaf, 12
• covered container with a wet paper towel on the bottom for slide storage
• small beaker of water
• pipette
• sheets of notebook paper, 4
• compound microscope
• dissecting microscope
• hand lens
Per class:
• one of each plant type used in lab in a small pot with soil
• red food coloring
• 250 mL beaker or graduated cylinder, 4
• projected image Monocot-Dicot
• projected image [monocot stem and dicot stem with xylem, phloem identified or labeled]
Teacher Preparation:
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Grow plants well in advance so they are seedlings with leaves by the time of the lab, or buy
appropriate seedlings close to the time of the lab. Each lab group will need moss, one monocot
plant (such as a green onion), two dicot plants: one a fruit-bearing plant (such as a bean plant
with or without fruit on it) and one a root vegetable (such as a radish).
Collect moss samples the day before the lab, keeping them moist in a closed container with a
wet paper towel.
The whole plant samples will need to be removed from the soil on the day of the lab (so roots
are visible and clean) and placed in separate beakers with about 1.5 centimeters of water
covering the bottom of the beaker. Number each plant sample and remember which sample
was labeled with which number.
To make plant wet mount slides for use by students:
o With wet hands and a razor blade, cut thin cross sections of the plants’ root, stem, and
leaf tissues. Moss leaves can be placed flat, directly on a slide.
o Place each sample on a slide that is numbered according to which plant sample it is and
labeled as to what structure it is. Example: “#3 root” or “#4 leaf.”
o Add a drop of iodine to each cross section once it is on the slide to make structures
more visible (optional).
o A drop of water may be needed to keep sample moist.
o Cover with cover slips and press out air bubbles.
Prepare a covered container for each set of slides with a wet paper towel in the bottom to store
slide samples and keep them moist when not in use.
Prepare copies of the Student Investigation Sheets for students.
Procedure:
The Hands-On Labs include both Directed and Guided Inquiry approaches. If your students are new
to the investigational methods being used in the Hands-On Lab, it is recommended that the Directed
Inquiry approach be used to provide scaffolding that will ensure student safety and support the success
of their investigations. Often, the Directed Inquiry approach involves modeling the basic laboratory
techniques and methods to be used in the activity. A discussion of each step in the investigative
process will also be included. In some cases, students may then be asked to create a procedure based
on the one modeled for them. This may involve changing specific variables or adjusting the procedure
to determine the effect on the outcome.
You may choose to use the Guided Inquiry path on its own or after completing the Directed Inquiry
activity. During Guided Inquiry, students are allowed to conduct the investigations more independently.
They will be given opportunities to formulate their own questions, develop their own procedures, and/or
manipulate variables of their own choosing. It may be necessary to provide additional materials and
supplies for students using Guided Inquiry. It will also be important to set clear limits on students’
activities to ensure their safety and the relevance of their inquiry experience to the content you are
teaching.
Directed Inquiry
Tell students that, as a class, they will be observing a set of unknown plants over several days to
determine how each plant moves water through the body of the plant. These plants will receive the
same amount of sunlight and will be potted in the same size pot/cup with the same amount of soil.
Explain that the plants will be watered with 30 mL of water mixed with 5 drops of red food coloring.
Ask four different students to measure the correct amount of water and food coloring for one of the
plants. Set the plants near a light source. The class will check on the plants at the end of class and for
the next several days.
Tell students that they will now take a closer look at the same four plants in their lab groups. They will
be developing hypotheses about whether the plants are nonvascular, monocots, or dicots. Provide
them with some background information on monocots and dicots by projecting the image MonocotDicot. Explain to students that monocots have more stomata on their broad leaves than do dicots on
their relatively narrow leaves. Explain that a cotyledon is a leaf-like structure that originates in the seed
as part of the embryo. Have students make sketches of the differences between monocots and dicots
as shown in the image.
Next, review the following procedure with the class:
1. Fold four pieces of notebook paper into four equal sections. Number the papers Plant 1, Plant 2,
Plant 3, Plant 4.
2. Label each section on each paper as follows: whole plant, roots, stem, leaf. Note that mosses
do not have “true” leaves, stems, or roots and that in many mosses, the roots are referred to as
rhizoids.
3. Observe the whole plants first. Hand lenses or dissecting microscopes may be used to carefully
inspect and observe each visible structure.
4. Record observations in the appropriate section on each piece of notebook paper. Include
descriptions and drawings/diagrams.
Instruct students to work in their lab groups to complete the procedure. After groups are finished,
discuss their observations as a class. Be sure to discuss whether or not they noticed different
arrangements of the veins on the leaves.
Have students develop a hypothesis about each plant type. Is each plant a nonvascular plant, a
monocot, or a dicot? Students should write their hypotheses the back of each numbered paper in this
format: Hypothesis #1: I think plant # ____ is a ___________ because ______________.
Instruct students to look at each slide sample, following the same observation techniques they used
when observing the whole plants. If the samples on the slides seem dry, students can add a drop of
water to the slide. Provide them with some background information on vascular bundles and xylem and
phloem by projecting the images [monocot stem with xylem and phloem labeled and dicot stem with
xylem and phloem labeled]. Point out the differences between the appearance of vascular bundles in
monocots and dicots.
Students should identify and label the xylem and phloem where appropriate.
Students should compare their drawings to their sketches of monocot and dicot structures and decide
whether or not to revise their hypotheses.
Come together as a class and ask the question:
“Which of these plants has the ability to grow tall?”
Students should realize that all of the plants except the moss have the ability to grow tall because,
other than the moss, they all have vascular systems.
Reveal the correct category of each plant.
End the lab session by checking on the plants treated with food coloring. Do any of the stems and
leaves have any visible food coloring in them? Have students record their observations. Continue to
allow students to observe the plants at the beginning of each class for several days. You may need to
water them each day, so be sure to add equal amounts of water to each plant. At the end of the
observation period, have students record whether their hypotheses about water transport were
supported or refuted. Ask if they could have made better hypotheses if they had known the categories
of the plants prior to forming their hypotheses.
Guided Inquiry
Show students the supplies for the classroom experiment (four plants, red food coloring, beakers) and
ask them what steps they could take to test how the different plants transport water.
As a class, decide on a procedure and ask four different students to measure the correct amount of
water and food coloring for one of the plants. Set the plants near a light source. The class will check on
the plants at the end of class and for the next several days.
Students can develop their own protocols for observing the plant structures and recording their
observations, based on their knowledge of the materials used. Tell them they will be observing the
external and internal structures of four different plants and will hypothesize whether each plant is a
nonvascular plant, a monocot, or a dicot.
Allow students to work in their lab groups to research the meaning of monocot and dicot. Once they are
finished their research, they may begin their observations of the four plants. Make sure students write
their hypotheses before you reveal the correct category of each plant. Ask the students some guiding
questions to help them focus their inquiry:
• What external features will help you categorize the plants?
• What internal features will help you categorize the plants?
Reveal the correct category of each plant.
End the lab session by checking on the plants treated with food coloring. Do any of the stems and
leaves have any visible food coloring in them? Have students record their observations. Continue to
allow students to observe the plants at the beginning of each class for several days. You may need to
water them each day, so be sure to add equal amounts of water to each plant. At the end of the
observation period, have students record whether their hypotheses about water transport were
supported or refuted. Ask if they could have made better hypotheses if they had known the categories
of the plants prior to forming their hypotheses.
Analysis and Conclusions:
In order to help students analyze and interpret their results, consider discussing some or all of the
following questions, or assigning them as homework:
1. For what functions are the cells in the stems of plants specialized? The cells in the stems of vascular
plants are specialized for the internal transport of fluids, such as water, and nutrients. To achieve this
function, the cells that are aligned to form a system tubes known as xylem and phloem, which run from
the roots, through the stems, and to the leaves, and back. Another function these cells have is to
provide support for the plant. For this reason, stem cells have a rigid cell wall.
2. Describe four major differences between monocots and dicots. Monocots have a single cotyledon,
while dicots have two; the vascular bundles in monocots are scattered throughout the stem, while in
dicots, they are arranged in a definite ring; monocots display parallel leaf vein patterns and the leaf
veins of dicots are displayed as a net pattern. Monocots have more stomata on their leaves than do
dicots.
3. Was your hypothesis about the method and speed of water transport in the four plants supported or
refuted? If it was refuted, what are some possible explanations? Answers will vary. Possible errors
could have occurred during the observations or the plants may have been disturbed during the
observation period.
4. Based on the results of this lab alone, can you make a broad judgment about the differences in
transpiration in monocots and dicots? Why or why not? The sample size: two dicots and a monocot are
too small to make a valid generalization about the speed of water uptake in monocots opposed to
dicots. We could have been looking at an unusually fast (or slow) monocot or dicot—one that is not
representative of monocots or dicots in general.
5. Predict the results of this experiment if a plant’s stomata were blocked. Which plants used in this
experiment would be most affected, and why? Blocking the stomata likely will slow the pace of
transpiration of dye. This would affect the dicots more than they monocot, because dicots have more
stomata.
6. Early plants lived in water before they colonized land. How have plants adapted to be able to survive
on dry land? Sample answer: Plants have evolved to have roots that absorb water and vascular
systems to transport water and nutrients throughout the plant. Land plants have waxy coverings that
slow evaporation from their bodies. They have also adapted by making flowers for reproduction and
seeds.
Inquiry and Nature of Science Skills in this Lab:
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Identify Questions
o Develop a question that:
 asks a question about a specific science concept or process
o Recognize and develop testable questions that:
 Specify a cause-effect relationship
 Require the changing of one variable at a time
 Can be answered with a science investigation or observational study
o Develop predictions/hypotheses that:
 State what may happen in an investigation based on prior knowledge or
experience (prediction)
 State the expected cause and effect (if-then statement) in an investigation based
on prior knowledge and experience (hypothesis)
Design Investigations
o Design and conduct field studies using:
 Observational Study - compares changes in data points over time
o Design and conduct investigations using:
 Fair test - changing only one variable at a time makes comparisons valid
 Independent variable - the one variable the investigator chooses to change
 Dependent variables - what changes as a result of, or in response to, the change
in the independent variable
 Constant- identify variables that must remain unchanged
 Multiple trials - repeated tests with the same variables to check for variability of
results
o Explain the investigative processes by:
 Describing the logical sequence that was used to conduct the investigation
 Properly citing all equipment and materials
 Describing it so that it can be easily repeated by a fellow scientist
o Practice lab safety by:
 Following lab safety procedures
 Recognizing safety equipment and materials and knowing their proper use
 Incorporating laboratory safety practices into the investigation design
Gather Data
o Choose appropriate tools to conduct an investigation:
 Magnifying Glass
 Microscope
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 Lenses
 Pipette
 Slides and cover slips
 Other Laboratory equipment
o Use senses to observe:
 Seeing (color, shape, size, texture, motion)
o Use the appropriate format to record data:
 Writing (journal, worksheet, electronic text)
 Sketch
 Diagram
Interpret Data
o Sort and classify using scientific reasoning by:
 Sorting objects, substances and organisms by characteristic
 Applying a classification scheme to objects, substances or organisms
 Developing a classification scheme for objects, substances or organisms
Evaluate Evidence
o Draw and support a conclusion by:
 Using data to determine the cause-effect relationship observed in the
investigation
 Reporting trends and patterns in the data
 Comparing results to hypothesis
 Answering the testable question
Communication in Science
o Report results using:
 Scientific illustration with proper labeling
 Images or video
Analyze Scientific Results
o Participate in critiquing/peer review by:
 Evaluating an investigative design
 Evaluating data for accuracy
 Evaluating a conclusion
Patterns and Systems
o Systems:
 A system, such as the human body, is composed of subsystems.
 Some systems (such as heating or cooling systems) have feedback mechanisms
that serve to keep changes within specified limits.
 Physical and biological systems tend to change until they reach equilibrium and
remain that way unless their surroundings change.
A system usually has some properties that are different from those of its parts but
appear because of the interaction of those parts.
Scientific Investigation
o Scientific Investigation:
 Science investigation begins with a testable question.
 New observations should be made when there is disagreement among initial
observations.
 Hypotheses are valuable, even if they turn out not to be true, because they lead
to further investigation.
 Scientific investigations lead to the development of scientific explanations.
o Scientific Data and Outcomes:
 People are more likely to believe ideas if good reasons are given for them.
 Scientific claims are based on data and reliable scientific sources.
 Collecting and analyzing data is the best way to understand a changing pattern.
Scientific Endeavor
o Characteristics of Science:
 Science is based on factual knowledge.
 Scientists are curious about wanting to know how things work.
 Scientific claims can be substantiated using data and observation.
 Scientific theories are based on accumulated evidence.
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