1997 WWLPT Biology Institute:
Life Cycles: Reproduction & Embryological Development
Lesson Title: Studying
Plant Development Through Metabolic Activity
Though I do not believe
that a plant will spring
up where no seed has been,
I have great faith in a
Convince me that you have a seed
there and I
to expect wonders.
----Henry David Thoreau
Jewel J. Reuter, &
Target Age or Ability Group Audience
Materials & Equipment Needs
The Student Lab
Method of Evaluation/Assessment
A common problem teachers confront when studying plant development
is making this often unfamiliar material readily accessible to students.
The traditional approach comparing tissue and organ morphology usually
lapses into a simple textbook analysis; while a real investigation of the
biochemistry of development involves equipment few schools can afford.
The model experimental protocol presented here is designed to equip teachers
to present plant development in a hands-on fashion that engages students'
minds and provides for a wide range of supplemental, quantitative investigations.
It employs testing rates of cellular respiration to demonstrate the relationship
between the metabolic rates of different parts of the developing plant
and their respective roles, and it can be performed in any classroom using
common lab equipment at relatively little cost.
Students will learn about the major stages of plant development in terms
of both their morphology and physiology.
Students will study the evolutionary history of plants by comparing their
Students will hypothesize reasons for differences in metabolic rates based
on structure, function, or developmental stage of the plant
Students will relate respiration rate to differentiation and development.
Students will engage in experimental problem solving, creating hypotheses,
designing protocols, and collecting and analysing data.
Students will measure the change in gas pressure or volume due to the uptake
of oxygen in a closed system and interpret the causes for the change.
Students will discover how to relate the concept of slope to the metabolic
Students will use calculator or computer based technology to solve a problem.
Students will describe function of respirometers in terms of the ideal
Students will test various plant structures to compare developmental levels.
Target Audience or Age Group
biology students (AP, honors, general)
traditional lab exercise recommended
for those unfamiliar with the material or who have little time in the curriculum
to spend on plant development
Notes to the Teacher:
The protocol for this activity uses the analysis
of cell respiration in different key organs of germinating and sprouting
seeds to demonstrate the relationship between each organ's metabolic rates
and its respective role in development. Since energy production is
greatest in those parts of the plant where differentiation and growth are
occurring the most, comparing the respiration rates from these locations
allows one to study the development and growth events in the early life
cycle of plants and, hence, to know what is occurring and where.
This information in turn provides an empirical foundation for discussing
why the different differentiation events occur when they do.
The experimental system for this model is an elementary
one, employing the fact that in self-contained systems there is a
measurable change in gas volume and pressure if the amount of gas or a
portion of that gas is removed. Normally, any carbon dioxide release
in such a situation by a living organism would basically replace the oxygen
being consumed, maintaining a constant volume and pressure. But when
the carbon dioxide is removed from the surrounding air, one creates a condition
where any oxygen respired causes a corresponding drop in both the volume
and the pressure of the contained gas. These respective drops, in
turn, are easily quantified using simple respirometers utilizing either
traditional water displacement methods or gas probes interfaced with a
For additional information:
Materials & Equipment
Needs to top
A. Per Group of 2-4 Students
3 125-ml respirometers (see
3 600-ml beakers
1 100-ml graduated cylinder
1 250-ml graduated cylinder
forceps or tweezers
TI-82 or TI-83 calculator with CBL unit
Vernier Bio-Software Package or equivalent
Vernier Biology Gas Pressure Sensor (0-10 kpasc) or equivalent
B. Per Classroom of 24
1-L 15% KOH
an assortment of germinating
great northern beans
alaskan snow peas
Student Lab to top
There are a wide range of possible experiments one
can perform when studying metabolic differences in developing plants.
Everything from examining differences in the respiration rates between
different plant species to studying the effects of hormones on radicles
by looking at changes in levels of oxygen consumption. The goal of
this instructional module is not to limit the creativity of either teachers
or students but rather to encourage a discovery approach to learning.
Specific options for student experiments are available with both the novice
and advanced teacher as well as the beginning and AP level student in mind,
but the only limits for studying plant development with the model provided
here are one's own. The authors would love to
hear anything new or exciting that gets tried.
For information on:
of Evaluation/Assessment to
No set method for evaluating the experimental model
is presented here. Because the focus is on students designing and
performing their own investigations, any rubric depends on what ideas or
concepts the individual teacher chooses to concentrate. Possible
items one might want to consider holding students responsible for could
be as basic as simple experimental protocol (e.g. did students have a control?)
or as complex as creating and testing further questions about development
(e.g. why does the apical radicle consume more oxygen than the proximal
For further information:
Ideas to top
Plants are not the only organisms to which a teacher
can apply the model experimental protocol presented here. Classes
could study invertebrate metamorphosis with this technique, comparing how
respiration rates change from one developmental form to another (the common
flour beetle is one such example). They could also study more than
one species of insects to compare respiration rates in order to examine
evolutionary relationships. The growth of molds on food could be
analysed to determine optimal conditions for their development without
having to wait for extended periods of time, and potentially, even certain
vertebrates could be studied with this system. Basically anything
which respires could technically be use with the model, and the only current
limitations are that the organisms studied must be terrestrial (the authors
are working on an aquatic system using dissolved oxygen probes, but it
has not yet been thoroughly field-tested).
Teachers are encouraged to think up an idea and
try it. If it works, drop one of the authors
a line at their e-mail address and let them know. It is the hope
that this lesson will be continue to develop itself and tested material
to add this web site is greatly welcome.
References Including Web Addresses
Bewley, J. and Black, M. Seeds: Physiology of Development
and Germination, 2nd ed. New York: Plenum Press,
Botha, F., Potegieter, G., and Botha, A. "Respiratory
Metabolism and Gene Expression During Seed Germination." Plant
Growth Regulation (11), 1992.
Come, D. and Carbineau, F. "Some Aspects of Metabolic
Regulation of Seed Germination and Dormancy." Recent Advances
in the Development and Germination of Seeds. New York:
Plenum Press, 1989.
Deltour, R. and De Barsy, T. "Nucleolar Activation
and Vacuolation in Embryo Radicle Cells During Early Germination."
Journal of Cell Science (76:67-83), 1985.
Hopkins, W. Introduction to Plant Physiology.
New York: John Wiley and Sons, 1995.
Palme, K. and Schell, J. "On Plant Growth Regulators
and Their Metabolism: A Changing Perspective." Seminars
in Cell Biology (4:2), 1993.