Botany II - Applied Plant Physiology

Course CodeBSC204
Fee CodeS3
Duration (approx)100 hours
QualificationStatement of Attainment


Study the principles and practices of plant physiology in this advanced botany course. Learn in depth how plants grow, which factors promote their development and which factors hinder their growth. This course is for people who work or wish to work in the horticulture industry or as a scientist, for nursery personnel, technicians and researchers and science students wishing to further their knowledge in plant physiology.  

Lessons include: Flower physiology; photoperiodism; control of flower bud initiation and development; dormancy; effects of plant associations and competition; respiration and post harvest physiology; post harvest storage, transport, retailing and shelf life; endogenous and synthetic growth regulators; risks involved with plant growth manipulation.botany II.

ACS Student comment: "I find the course quite interesting! At first glance the reading material and questions look so simple, but they actually require quite a bit of thinking and probing.  The course is very well designed!" - Joanne McLeod, Australia - Botany II course.

Lesson Structure

There are 10 lessons in this course:

  1. Flower physiology
    • Introduction
    • The flowering response
    • Genes control flowering
    • Physiological age
    • Minimum leaf number
    • Photoperiodism
    • Terminology
  2. Phytochrome
    • Light sensing systems
    • Blue light responses
    • Red light responses
    • Other light responses
    • Phytochrome
    • Photoreceptor forms: Pr, Pfr
    • How molelcules change
    • Relevance to commercial horticulture
    • Controlling light
    • Terminology
  3. Photoperiodism
    • Light
    • Measuring light
    • What wavelengths do plants need
    • Typical photoperiod responses
    • Photoperiodic responses in seasonal flowering plants
    • Photoperiodic classification of plants: short day plants, long day plants, day neutral plants
    • Detection of photoperiod
    • Critical photoperiod and flowering
    • Research facts
    • Other photoperiodic effects
    • Terminology
  4. Control of flower bud initiation and development
    • Stages in flower bud growth
    • What can affect flower bud initiation
    • Differentiation
    • Development
    • Anthesis
    • Effect of temperature on growth and flowering
    • Vernalisation
    • Thermoperiodism
    • Research reports or reviews of specific plants
    • Terminology
  5. Dormancy
    • Dormancy in plants
    • Abscisic acid and dormancy
    • Breaking dormancy
    • Dormancy in seeds
    • Factors affecting seed dormancy
    • Breaking seed dormancy
    • Terminology
  6. Effects of plant associations and competition
    • Introduction
    • Competition
    • Parasitism
    • Coevolution
    • Mutualism
    • Plant herbivore and pathogen interactions
    • Crop spacing and crop yields
    • Crop canopy and plant density
    • Impact of weeds
    • Protected environments
    • Greenhouses
    • Shadehouses
  7. Respiration and post harvest physiology
    • Respiration
    • Glycolysis
    • Aerobic respiration
    • Anaerobic respiration
    • Bioluminescence and Fluorescence
    • Post harvest respiration
    • Terminology
  8. Post harvest storage, transport, retailing and shelf life
    • Effect of growing conditions on post harvest life
    • Controlled storage conditions: temperature, atmosphere, humidity
    • Normal atmospheric conditions
    • Controlled and modified atmospheres
    • Effect of oxygen levels Effect of carbon dioxide levels
    • Ethylene
    • Controlling ethylene levels
    • Modified Atmosphere Packaging
    • Commodity transport
    • Retailing and shelf life
  9. Endogenous and synthetic growth regulators
    • Nature of plant hormones
    • Auxins: IAA, IBA, NAA
    • Gibberellins: natural and synthetic
    • Cytokinins: over 130 different types
    • Abscisic acid
    • Ethylene
    • Other hormones: anti auxins, growth inhibitors, growth retardants, defoliants, growth Stimulators, non standard hormones
    • Controlled ripening and degreening
    • Waxing
  10. Risks involved with plant growth manipulation
    • Commercial risks
    • Human health and safety risks
    • Plant pathology risks
    • Ecological risks
    • Genetic modification
    • Benefits
    • environmental hazards
    • Human hazards
    • Terminology


  • Investigate the physiology of growth development and flowering.
  • Examine the nature of phytochrome and its effect on flowering in the phytochrome reaction.
  • Examine the photoperiodic responses of flowering plants to differing dark and light periods.
  • Examine the effect of temperature on the onset of flowering and flower development.
  • Understand and describe the causes of dormancy in seeds and plants and describe the methods of breaking dormancy.
  • Understand plant associations and competition and their effects on quality and marketable yield.
  • Explain the process of respiration in plant cells and its effect on post-harvest storage and transportation of crops.
  • Describe physiological processes in post-harvest crops in relation to the storage conditions.
  • Investigate the effect on plants of endogenous and synthetic growth regulators.
  • Understand risk assessments relevant to plant growth manipulation.

What are Enzymes?

An enzyme is a protein that encourages a chemical reaction to take place. Enzymes have three major properties:

  1. They can bring about chemical change in other substances without themselves being changed in the process (i.e. it is a catalyst).

  2. They can also achieve those changes inside the cell in conditions of mild heat and comparatively mild acidity or alkalinity. In a laboratory, such changes would require conditions of great heat and the use of strong acids or alkalis.

  3. It takes only a very small amount of an enzyme to achieve big changes.

Enzymes are therefore very powerful chemicals indeed and they are specific to certain tasks. One particular enzyme will carry out one job and no other. Some enzymes can break down only some carbohydrates while others only act on protein.

Most reactions in living things will not occur without an enzyme being present. The enzyme combines with a chemical, thus activating it to react with another chemical. As this chemical reaction takes place the enzyme is released and/or reconstituted, returning to its original condition.

Enzymes posses an active centre where the substrates to react bind, and where prosthetic groups and co-factors link when they are needed in the reaction. The active or catalytic centre is made up of a few amino acids, that are usually organized spatially in a cave-like shape that is non polar (excludes water). 

Co-factors may be small non-protein organic molecules (coenzymes) such as CoA or they may be metal ions. These are usually derived from vitamins and are only transiently bound to the enzyme. An example is NAD+, which catalyzes oxidation-reduction reactions where alcohols are converted into ketones or aldehydes. Inorganic cofactors are many minerals (Iron, magnesium, iodine).  Prosthetic groups are cofactors that bound tightly to the enzyme activating it. Hence we have two groups of co-factors; coenzymes which are organic, non protein and loose binding; and prosthetic groups which may organic or inorganic and bind tight to the enzyme

Without the cofactors enzymes are in their inactive form. When enzymes bind to the cofactor, their (spatial) conformation changes thus being able to bind to the substrates.   

Co factors are changed by the enzymatic reactions that they are part of. Co-factors must be returned back their original form for the cycle to complete.  Prosthetics groups need a separate phase in the reaction pathway, coenzymes may however need a different enzyme to start the regeneration.

An inactive protein is termed an apoenzyme, while a complete active enzyme (with a co-factor) is called a holoenzyme.

Most reactions in living beings will not occur without an enzyme being present.


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