Jan. 11, 2011 Bot4730/5730 Plant Physiological Ecology Course Overview and Introduction

Syllabus overview Goals Readings Laboratory relation to Lecture Grading and expectations Undergraduate vs. Graduate Requirements

My Biases Most of my work has been at whole plant and larger scales Most of my work has focused on field projects 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 process Observations Analysis Mechanistic model Prediction Hypotheses/Theories

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?

Woodward New Phyt Ecophysiology Publications Span Large Temporal and Spatial Scales

Conceptual Idea of Ecology Hereditary potentialEnvironmental Factors Physiological Processes Growth and Reproduction Ecological Expression Theory 1.Individuals in a population are not identical 2.Some of this variation is heritable 3.All populations have the potential to populate the whole earth 4.Different individuals leave different numbers of descendants 5.Number of descendents depends on interaction between physiology and environment Potential Species Historical Filter Physiological Filter Biotic Filter

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 pathway Anabolic pathways consume energy to synthesize complex molecules from simple ones –Photosynthesis free energy requiring anabolic pathway

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 stressed 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 acclimation

Macromolecules Carbohydrates –Energy and C currency Lipids –Storage –Membranes Nucleic acids –RNA, DNA Polypeptides –3-D structure

Enzymes 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 E A, 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 reactions –Competitive or noncompetitive Feedback inhibition switches off of a metabolic pathway by its end product