Botany I - Plant Physiology And Taxonomy

LEARN ABOUT THE WORLD OF BOTANY

The study of botany is not only relevant to botanists but also to horticulturists and anyone working with plants, from plant breeders through to nursery growers or agriculturists. If you understand how plants grow and flower, you can better grow and maintain them.

This course contains the basis of plant science, and is an introduction to plant physiology and taxonomy, covering general botany including morphology and anatomy.

Lessons cover: taxonomic classification of plants; cells and tissues; specific vegetative parts of a plant; flowers and fruit; seed and the developing embryo; photosynthesis and growing plants; respiration; the role of water; movement of water and assimilates through a plant; the effects of growth movements.

"It has been an eye opener!!  I am now living in a different world, my whole perspective to life and nature has changed and now I cherish it more.  It has broadened my mind and advanced my level of looking at things in my every day work as well. [My tutor] encourages me a lot and that kept me going.  She would give more positive constructive correction where necessary as if it was not that bad at all.  She has been supportive and understanding" Lucia Masuku, South Africa - Botany I course

Lesson Structure

There are 10 lessons in this course:

1. Taxonomic Plant Classification
   • History of taxonomy.
   • Binomial system.
   • Levels of classification.
   • Families.
   • Principle of priority.
   • Name changes.
   • Hybrids.
   • Varieties.
   • Cultivars.
   • Abbreviations.
   • Botanical keys.
   • Key to Phyla.
2. Cells and Tissues
   • Types of Plant Cells.
   • Plant Tissue.
   • Primary and Secondary Growth.
3. Vegetative Parts of a Plant
   • Stem Formation.
   • Leaf Structure and Leaf Arrangement.
   • Root Structure.
4. Flowers and Fruit
   • The Flower.
   • Inflorescence (panicle, umbel, composite head).
   • Fruits (simple, aggregate, multiple).
   • Reproductive Growth and Development.
5. Seed and the Developing Embryo
   • Seed Structure.
   • Food Storage Organs
   • Seed Coats.
   • Embryo.
   • Seed Germination.
   • Requirements.
   • Stimulants.
   • Inhibitors.
6. Photosynthesis and Growing Plants
   • Photosynthetic Apparatus.
   • Process.
   • Gas Exchange.
   • Light transformation to Energy.
7. Respiration
   • Stages of Respiration.
   • The Krebs Cycle.
   • Electron Transport Chain.
   • Rate of Respiration.
   • Control of ATP Production in Respiration.
8. The Role of Water
   • Osmosis.
   • Water Movement from Soil to Root.
   • The Transpiration Stream.
9. Movement of Water and Assimilates
   • Mechanisms of Nutrient Uptake.
   • Absorption and Transport of Mineral Nutrients.
   • Translocation of Sugars.
   • Adaptations for Water Storage.
   • Food and Water Storage Organs.
10. Effects of Tropisms and Other Growth Movements
    • Plant Hormones.
    • Tropisms.
    • Chemical Growth Modifications.

Aims

• Understand the relationship between the scientific principles of this unit and horticultural practices
• Demonstrate a knowledge of the Plant Kingdom and understanding of the taxonomic hierarchy
• Identify and describe the different types of plant cells and tissues, their structure and function
• Determine the role and function of specific vegetative parts of the plant
• Determine the role and function of the reproductive parts of the plant
• Demonstrate an understanding of the role and function of the seed in the life cycle of the plant
• Explain the mechanism and the role of photosynthesis in the metabolism of plants and relate to plant growth in controlled environments
• Explain the mechanism and the role of respiration in the metabolism of plants
• Demonstrate an understanding of the role of water in the plant
• Review the movement of water, solutes and assimilates through the plant
• Understand the effects of tropisms and other plant movements on growth and development
• Undertake risk assessments relevant to the learning outcomes in this unit

What You Will Do

• Prepare a collection of forty pressed, dried, labelled plants
• Learn how to key out plants using a Botanical Key
• Identify the phyla, family, genus and species of ten unknown plants
• Identify modified plant parts on live plants
• Describe in botanical terms leaf shapes from a range of different plants
• Dissect and draw labelled diagrams of several flowers
• Collect fruits and categorise them by type (pome, drupe, etc)
• Germinate seeds and describe changes that occur to the seeds over time
• Observe changes in potted plants under varying levels of sunlight and relate this to photosynthesis
• Observe transpiration in live plants and relate this to theoretical knowledge
• Observe and record osmosis in an experimental situation
• Observe and record phototropism in plants

Why Study Botany?

Our ability to manage plants in horticulture, agriculture, forestry and for a better environment; are all dependent upon our knowledge of botany. An understanding of botany essentially underpins our society, and human well-being. Without botanical knowledge, we could not be a productive in growing crops; we could not feed animals on our farms nearly as well, and carbon pollution could be far worse that it already is.

People study this course so that they can be better farmers, gardeners, environmental managers and foresters; not to mention scientists, teachers and journalists. Botany is useful in ways that most people do not recognise; and perhaps in ways we have not yet discovered.

For example; if we understand how plants flower better; we can better manage flower production for gardens and the cut flower industry; and better manage fruit production in orchards and vineyards.

Understanding Flowering

For plants to flower they must first go through a vegetative phase, during which the main processes are elongation of the stem and roots and increase in stem girth. The end of the vegetative phase is marked by flower initiation, whereby the vegetative shoot apex undergoes a sequence of physiological and structural changes to become a reproductive apex (reproductive apical meristem – that which develops into a flower or an inflorescence). The transition from a vegetative to a floral apex is often preceded by an elongation of the internodes and the early development of lateral buds below the shoot apex. The apex undergoes a marked increase in mitotic activity, accompanied by changes in dimensions and organisation. The development of the flower or inflorescence terminates the meristematic activity of the vegetative shoot apex. When these flowers are formed, the plant is prepared for sexual reproduction.

In as much as the reproductive apex exhibits a determinate growth pattern, flowering in annuals indicates that the plant is approaching completion of its life cycle. By contrast, flowering in perennials may be repeated again and again.

The period from germination to the time the seedling becomes established as an independent organism constitutes the most crucial phase in the life history of the plant. During this period, the plant is susceptible to injury by insect pests and parasitic fungi, and water stress can very rapidly result in death.

The stimuli for flower induction includes hormonal changes and environmental changes, such as day length (photoperiod) and temperature.

Genes Control Flowering
One of these pathways has been studied and understood in the genus Arabidopsis, a Brassicaceae plant, related to mustard.
We know that many different genes are involved in controlling the time at which a plant produces flowers. These genes cause and control certain biochemical pathways (i.e. sequences of chemical reactions). These pathways are not fully understood; however we do know that control of flowering time involves the integration of not one, but a number of biochemical signals.

Example: 
In this plant, the flowering time is affected by at least two different processes:

• Vernalisation (i.e. Environmental conditions stimulate flower initiation), and
• Non-environmental genetic characteristics (i.e. Genes cause biochemical processes that can suppress the initiation of flowering) 

More specifically, two different proteins (FCA and FY) interact to control the location at which a sequence of polyadenylic acid is spliced onto an RNA molecule in a gene (called the polyadenylation site).

Physiological Age
The plant’s physiological age may be a determining factor in whether a plant is able to form flowers. Physiological age refers to the plant’s stage of development. The stages are embryonic growth, juvenility, transition stage, maturity, senescence and death:

• Embryonic growth – the growth and development of the seed within the parent plant.
• Juvenility – following germination the plant increases in size as the cells enlarge and differentiate to form stems, leaves and roots. In some woody plants, this stage is characterised by the plant’s inability to form flowers, or the loss or reduction in the ability of cuttings to form adventitious roots.
• Maturity – this phase is marked by the formation and development of the sexual organs (the flower buds, flowers, fruit and seed).

• Senescence – the decline of the plant due to physiological change (due to the decline of cell division and reproduction) or environmental stress or pathogenic attack.

Many perennial species have two phases with distinctive morphological and physiological characteristics. The juvenile phase in such plants has the following characteristics:

• The leaves may be morphologically different to those of the adult or mature phase
• Flowering cannot be induced
• There is an increased ability of stem cuttings to form adventitious roots.

The adult or mature phase has the following characteristics:

• The leaves may be morphologically different to those of the juvenile phase
• Flowering and reproduction can occur
• Rooting ability is diminished or lost

The juvenile phase may last from one year up to 40 or more years, but commonly in trees lasts for 5 to 10 years.

The English Ivy (Hedera helix) is a well known example of a plant showing distinct juvenile and mature phases. In the juvenile phase it grows as a creeping vine, with palmate, lobed leaves. In the mature phase Hedera becomes shrub-like and forms flowers and berry fruits. The leaves are entire and ovate. Frequent pruning prevents the formation of flowers and keeps the plant in a prolonged juvenile (vegetative) phase, hence ivy is most commonly seen in gardens as a creeper. (For this reason, propagators frequently prune mother stock plants, keeping them in a juvenile, vegetative stage which ensures high rooting ability in the cuttings taken from those plants).

Juvenility may be induced in mature plants by treating shoots that develop from lateral buds with GA3 (discussed later in the course).

A similar condition is known as ‘ripeness to respond’ or ‘ripeness to flower’, whereby some species can only commence flowering in response to their environment (particularly to day length and temperature) when the organs that detect the environmental change (usually leaves and meristems) have reached physiological maturity.