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Jan. 11, 2011
Plant Physiological Ecology
Course Overview and Introduction
Syllabus overview
Laboratory relation to Lecture
Grading and expectations
Undergraduate vs. Graduate
My Biases
• Most of my work has been at whole plant
and larger scales
• Most of my work has focused on field
• Most of my work on woody plants
• Focus of my work has been flux ecology
Science and models
• Science is observation, interpretation and
application to test predictions
• Science can also be called a modeling
Mechanistic model
What is Ecophysiology or
Physiological Ecology?
• Field was developed to answer
mechanistic questions posed at a higher
level of integration with answers at a lower
level of integration
• Physiological ecology is the science of
determining the physiological controls on
ecological phenomena or the study of
environmental controls on plant physiology
• what are some of the questions?
Ecophysiology Publications Span
Large Temporal and Spatial Scales
Woodward New Phyt. 2007
Conceptual Idea of Ecology
Hereditary potential
Environmental Factors
Physiological Processes
Growth and Reproduction
Potential Species
Historical Filter
Physiological Filter
Biotic Filter
Ecological Expression
Individuals in a population are not identical
Some of this variation is heritable
All populations have the potential to populate the whole earth
Different individuals leave different numbers of descendants
Number of descendents depends on interaction between physiology
and environment
Conceptual Idea of Ecology cont.
• Individuals will leave descendents in some
environments but not others
• If some individuals leave more
descendants than others causing change
in population characteristics then evolution
occurs by natural selection
– Differential success of different physiologies
changes ecosystem properties
– Other types of evolutionary mechanisms?
Free Energy
• Changes in free energy (ΔG) occur between the
start and the end of a process
– ΔG = Δ H –T Δ S
– For a system to be spontaneous ΔG must be negative
– More negative ΔG indicates a greater amount of work
that a spontaneous system can perform
– Simply stated “nature runs downhill”
• Equilibrium ΔG = 0
• Exergonic reactions ΔG < 0; release free energy
• Endergonic reactions ΔG > 0; require free energy
Overview of physiology
• Metabolism is the totality of an organism’s
chemical reactions
– Metabolism manages the energy and material
resources of an organism
• Catabolic pathways yield energy and break
down complex molecules to simpler ones
– Cellular respiration free energy yielding catabolic
• Anabolic pathways consume energy to
synthesize complex molecules from simple
– Photosynthesis free energy requiring anabolic
General Environmental Responses
• Stress – any environmental or biotic factor that reduces
the rate of a physiological process below its maximum
• This definition results in most plants being continuously
• Three time scale responses to stress
– Stress Response – immediate reduction in
physiological rate
– Acclimation – morphological and physiological
adjustment by individuals to compensate for stress
– Adaptation – evolutionary response resulting from
genetic changes in populations as a result of
• Carbohydrates
– Energy and C currency
• Lipids
– Storage
– Membranes
• Nucleic acids
• Polypeptides
– 3-D structure
• Enzymes are biological catalysts
– All enzymes are proteins except for ribozymes
• In exergonic reactions, activation energy
released back to the surroundings and more
energy released with new bonds
• Enzymes speed reactions by lowering EA,
but do not change ΔG
– Hasten reactions that would occur eventually
– Enzymes selective; determine which reactions
will occur at any given time
Enzyme Controls
• Cofactors inorganic enzyme helpers that
promote catalytic activity
• Coenzymes are organic enzyme helpers
that promote catalytic activity
• Inhibitors prevent enzymes from catalyzing
– Competitive or noncompetitive
• Feedback inhibition switches off of a
metabolic pathway by its end product