Plant Stress Ecophysiology 

As sessile organisms, plants cannot migrate in search of more favorable environments for their development. Therefore, plants must exhibit mechanisms to deal with stressful conditions, such as water, saline, light and thermal stresses. In this course, students are exposed to an interdisciplinary (molecular biology, physiology and ecology) and practical (greenhouse experiments) approach to understand the main responses of plants (from molecular to ecosystem level) to those abiotic stressors. 

OBJECTIVES: 

• Understand the concept of 'stress' in the context of plant ecophysiology;

• Investigate the main mechanisms/strategies that plants can exhibit to deal with  abiotic stressors;

• Explore the effects of climate change on plants' physiology; 

• Learn how to plan and execute a greenhouse experiment  to evaluate the effects of distinct abiotic stressors on seedlings' morpho-physiology.

THE CONCEPT OF STRESS IN PLANT BIOLOGY

• What is ecophysiology?

• What is stress?

• Ecological and Physiological optimum;

• Limitation & stress;

• Abiotic & biotic stressors;

• Acclimatization, adaptation, modification;

• Do plants have memory?

MOLECULAR TO CELLULAR PLANT STRESS RESPONSE

• Signal perception (sensors);

• Signal transduction (secondary messengers and hormones);

• Regulation of genetic expression;

• Metabolic changes (proteins of stress response);

• Resistance (protection and repair).

CELLULAR TO WHOLE-PLANT STRESS RESPONSE

• Light stress (evaporative cooling, leaf size, leaf movement, trichomes, chloroplast movement);

• Shade (etiolation, pigments);

• Water stress (stomatal closure, cuticular thickness, leaf area, succulence, root:shoot ratio, resistance to cavitation);

• Flooding (vertical growth, lenticels, air parenchyma, epinasty, pneumatophores);

• High salinity (ultrafiltration, salt glands, succulence).

PLANT STRESS RESPONSE AT POPULATION LEVEL

• Disturbances;

• Density-dependent stress (constant productivity, self-thinning);

• Density-independent stress;

• Intraspecific variation (phenotypic plasticity, genotypic variation, environmental heterogeneity);

• Adaptive evolution.

PLANT STRESS RESPONSE AT COMMUNITY LEVEL

• Positive interactions (mutualism, comensalism);

• Negative interactions (competition, predation, amensalism);

• Indirect interactions;

• Intensification and buffering effects;

• Biotic stress (pathogens, herbivory);

• Acquired systemic response versus hypersensitive response.

PLANT STRESS RESPONSE AT ECOSYSTEM LEVEL

• Ecosystem processes;

• Ecosystem services (provision, regulation, cultural);

• Climate and land-use changes;

• Dynamic vegetation models (applications and limitations);

• Meta-analysis of climate change drivers.

EXPERIMENTAL PLANNING

• The scientific method;

• Theoretical and operational variables; 

• Hypothesis versus expected results; 

• Categorical versus continuous variables;

• Dependent versus independent variables; 

• Basic principles of experimentation (replication, randomization, and local control).

STARTING A SCIENTIFIC EXPERIMENT

• Formulating questions, hypothesis and expected results;

• Defining experimental unit, treatment, factors, and levels; 

• Distribution of experimental units to treatments.

[Practical class report]

DATA COLLECTION

• Seedling survival rates;

•  Seedling growth (stem height and diameter); 

• Stomatal conductance; 

• Leaf water potential; 

• Leaf area;

•  Root:shoot ratio;

[Practical class report]

DATA ANALYSIS (PART 1)

• Kaplan-Meier survival analysis;  

• Calculating relative growth rate; 

• Statistical tests (assumptions, transformations, corrections, effects of outliers); 

• Principles of data management.

[Practical class report]

DATA ANALYSIS (PART 2)

• Temporal scales of plant response to stress (physiological regulation, acclimatization, modification, genetic adaptation);

• Leaf area - functional meaning;

• Leaf area - methods of measurement;

[Practical class report]

DATA ANALYSIS 

• Data management and curation;

• Test assumptions and data transformation;

• Tukey test;

• Analysis of variance – ANOVA.

[Practcical class report]

PRESENTATION AND INTERPRETATION OF RESULTS

• Graphical elements;

• Table formatting;

• Presenting results of Tukey and ANOVA tests;

• Objectivity, clarity and language accuracy;

• Bibliographic referencing.