Plant Ecophysiology Lab
Purpose
The purpose of this lab investigation is to explore how plants manage the tradeoff between
light capture and water loss. The balance between these two physiological needs can be
studied through examination of plant morphology. During this session you should think
about how you might chose to present and organize this lab investigation and your students’
possible responses to participation.
Instructors
Brad Oberle
Graduate Teaching/Research Assistant
[email protected]
314.935.7230
Taina Matheson Price
Graduate Teaching/Research Assistant
[email protected]
314.935.7230
Presentation Connections
Dr. Barbara Schaal: Plants and Food, Day 1; Plants and the Environment, Day 5
Inquiry
Lessons illustrating scientific inquiry as the process(es) utilized by scientists in
research
Lab activities that either (1) support the conceptual framework of the lecture
presentations and/or (2) support the transfer of concepts into inquiry-based
activities for high school students
Related Reading
• Simpson and Ogorzaly, “Economic Botany” 3rd edition, 2001
Application to Global Community
Photosynthesis requires water, air and light in the same place. Water and light are readily
available in some global locations, and severely limited in others. Agricultural activities will
be successful or unsuccessful in certain regions depending upon availability of the
photosynthetic reagents.
Application to Inquiry-Based Teaching at the Secondary Level
• The effect of local climate on plant morphology.
• The effect of global climate change on plant morphology.
U29 Bio 523 Plants and People
Lab Investigation Preface
Plant Ecophysiology Lab
Plants are Primary Producers. In this activity we will explore the meaning of this phrase and
its importance for understanding plant form and function.
Background
What does ‘producer’ mean biologically? Plants are autotrophs. Autotrophs derive the
energy they need to grow and reproduce directly from the environment. Specifically plants
are photosynthetic. They are organisms that convert light energy to chemical potential
energy by reducing inorganic carbon.
How does this reaction work? In plants this occurs in the chloroplast. Chlorophyll, a
pigment, absorbs both red and blue light (it reflects green). Once it absorbs enough energy it
loses an electron. Electrons from many pigment systems are shuttled among a series of
molecules. Ultimately this energy is used to create simple sugars from carbon dioxide and
water, producing oxygen as a waste product.
The entire process can be summarized by this reaction:
6 CO2 + 12 H2O + light → C6H12O6 + 6 O2 + 6 H2O
So producer has two meanings biologically:
A. Plants produce compounds that store energy for other biological processes.
B. Plants produce solid material structures from a liquid and a gas.
Plants are Primary Producers because collectively they drive the energy and material
dynamics of the Biosphere.
What are the consequences of being primary producers for individual plants? How is this
relevant to understanding plant form? Photosynthesis requires water, air and light in the
same place. Think about where these reagents are available and where they are limiting.
Two of these reagents are most abundant above ground: leaves have evolved to conduct
photosynthesis there. Light penetrates leaf surface to photosynthetic tissues. Roots and
stems have evolved for mechanical support and to deliver water through evapo-transpiration.
Water sweats out of pores in the leaf pulling water up from the roots.
Atmospheric carbon dioxide concentration does not vary much across environments where
photosynthesis occurs, but light and water do. Either water or light can limit photosynthesis,
and excessive light can lead to water stress. For this activity we will investigate how plants
manage the tradeoff between light capture and water loss.
U29 Bio 523 Plants and People
Lab Investigation
1
Investigation questions
1. What are water limited environments?
2. What are light limited environments?
These different conditions have different effects on the shape of leaves.
3. What would be an appropriate shape for a leaf in a water-limited environment?
4. What would be an appropriate leaf shape in a light-limited environment?
5. Based on these concepts, develop a hypothesis for how leaf shape would differ between
high light and low light environments:
6. Develop a hypothesis for how the density of stomata might differ between high light and
low light environments:
In order to test your hypotheses we will collect leaves from different environments and
measure their shapes.
Materials
Clipper pole
Scale
Graph paper, pencils, scissors
Fingernail polish
Dissecting microscope
U29 Bio 523 Plants and People
Lab Investigation
2
Data Sheet
Leaf Shape:
High Light
Leaf Area
Leaf Weight
Ratio
Mean:________________
Low Light
Leaf Area
Leaf Weight
Ratio
Mean:________________
Stomata density
High Light:_______________
U29 Bio 523 Plants and People
Lab Investigation
Low Light:___________________
3