1. Horticultural Biology for Landscape
Horticulture
These are broad topics covered under Horticultural Biology:
- Classification and Nomenclature of plants
- Structure of plants
- Growth and Metabolism of plants
- Development of plants
- Plant Reproduction
Classification and Nomeclature
- Why classify and name plants?
- -To help identify them
- -To organize knowledge into a logical system
- -To store and summarize useful information
Read the article on The Language of
Horticulture by Denise Adams to get a good sense of the issue of
plant names.
Plants and names
- All plants have one scientific (botanical) name and one or
more common names
- Quercus nigra (Black oak)
- -it is a tree (woody, perennial)
- -it has deep green, glossy leaves
- -the leaves have pointy lobes
- -the buds and midveins are fuzzy
- -it produces catkins and acorns
- -it drops its leaves in winter
Systems for Plant Classification
- Botanical - based on biological (i.e., genetic,
evolutionary) relationships
- Horticultural - based on use
Example of broad horticultural classification
- Edible plants
- Vegetables
- Fruits &Nuts
- Beverage, herbs, spices
- Ornamental plants
- Flower, bedding, and foliage
- Landscape (nursery)
- Industrial plants
- perfumes, oil, medicine
Example of narrower horticultural classification: Ornamental
crops
- Flower, bedding, and foliage plants
- -annuals, biennials, perennials (mostly herbaceous
plants)
- Landscape (or nursery) plants
- -lawn and turf
- -ground covers and vines
- -evergreen shrubs and trees
- -deciduous shrubs and trees
Botanical Classification
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- Focuses on evolutionary relationships between
plants
- Uses reproductive structures (e.g. flowers) and their
component parts (numbers) as a basis to group plants
- Binomial system (2 names, both in latin)
- -Genus + specific epithet = species
- -Dianthus caryophyllus (Carnation)
- Developed by Linnaeus (the guy at left) and published
in 1753 'Species Plantarum'
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The problem with Common Names of plants
- Question: What are water beech, blue beech, ironwood,
musclewood?
- Answer: American Hornbeam, Carpinus caroliniana Walt.
- A Mayflower may be:
- -also called mayapple (Podophyllum) in the
Midwest
- -Epigaea repens in New England
- -a legume (bean) in the West Indies
Botanical names permit unequivocal identification of plants.
To assess the impact Linnaeus had on the classification and naming
of all living things, let's look at a well-known plant: The common
Carnation.
- Native to the Mediterranean Sea area; grown by greeks and
romans
- Theophrastus named it 'flower of the gods' (Dios Anthos)
- May have been used in coronation ceremonies
Before Linnaeus
- By the Middle Ages, the carnation was known as: Dianthus
floribus solitariis, squamis calycinis subovalis brevissimus,
corollis crenatis
- Linnaeus called it Dianthus caryophyllus
After Linnaeus' seminal work
- All plants got two names (in fact, this pattern applies to all
living organisms)
- Genus - e.g.
- Quercus (oaks)
- Acer (maples)
- Pelargonium (geraniums)
- Brassica (cole crops)
- Genus + specific epithet = Species - e.g.
- Quercus alba (white oak)
- Acer rubrum (red maple)
- Pelargonium xhortorum (common geranium)
- Brassica oleracea (cabbage, broccoli, etc)
What is a species?
'...a kind of plant...that is distinct from other kinds in marked
or essential features and that has good characteristics of
indentification and may be assumed to represent a continuing
succession of individuals from generation to generation...'
Horticultural Nomenclature
- Landscape Horticulturists deal with naming plants by
variety
- Botanical varieties (natural variants)
- Juniperus communis var depressa (prostrate
common juniper)
- Juniperus communis var communis (common
juniper)
- Cornus florida var rubra (pink flowering
dogwood)
- Cornus florida var alba (white flowering
dogwood)
- Cultivated varieties (developed for cultivation) =
CULTIVAR
- A cultivar is a group of cultivated plants that is
distinguishable by a character or a group of characters and
that maintains its identity when propagated
- Examples of cultivars
- Malus pumila 'Jonathan'
- Malus pumila cv Jonathan (not cv 'Jonathan')
- Brassica oleracea ssp capitata 'Danish
Ballhead' ('Danish Ballhead' cabbage)
Plant structure
- External characteristics (Basic plant morphology)
- Overall growth habit
- Leaf shape, stem characteristics, etc
- Floral structures
- Fruits
- Generalized Plant Structure
- Growth Habit - tree, shrub, herbaceous; upright, prostrate,
climbing, trailing, etc
- Leaf Morphology
- - Simple, compound
- - Leaf margins (entire, serrate, lobed, etc)
- - Shape (linear, oblong, ovate, peltate, etc)
- Flower Morphology
- - Simple (perfect, monoecious, dioecious)
- - Inflorescence (spike, raceme, panicle, etc)
- Fruit Morphology
- - Simple
- * dry (pod, silique, follicle, capsule, samara,
acorn)
- * fleshy (berry, pepo, hesperidium, stone, pome)
- - Aggregate (strawberry)
- - Multiple (pineapple)
- Anatomical Features
- - Organization of plant tissues
- leaves
- roots
- stems
- flowers
- fruits
- - Meristems
- Shoot apex
- Root apex
Growth and Metabolism
- Cellular structure and processes
- Chemical Reactions & Enzymes
- Movement of Water - diffusion, osmosis
- Photosynthesis - the path of energy
- Chemical constituents of plants
- - Carbohydrates: glucose, fructose, sucrose, starch,
cellulose
- - Lipids: various oils (for cooking, for cosmetics)
- - Proteins: seed proteins, individual amino acids
- - Assorted secondary compounds
- *vanillin, methyl salicylate
- *flavonoids & carotenoids (flower colors)
- *alkaloids (caffeine, cocaine, morphine, nicotine,
quinine, etc)
- *various cancer-fighting compounds (e.g. Taxol)
Plant Growth and Development
- Seeds
- Types of seeds
- Seed viability and quality
- Seed Germination and establishment of plants
- Effects of moisture and temperature on germination
- Plant Development
- Life cycles: Seed >> Seedling >> Vegetative
Period >> Reproductive Period >> Senescence
- Transition from juvenile to mature
- Growth Regulation
- Control of plant growth by internal chemical signals
- auxins, cytokinins, gibberellins, abscisic acid,
ethylene
- elongation and dwarfing by external regulators
- Control of organ formation in tissue culture
- Control of plant growth by external signals
- Light - Duration, Quality and Direction
- Gravity
Flowering and Plant Reproduction
- Light
- role in photosynthesis
- role in flowering (Induction of flowering by light/dark
duration = photoperiod)
- Plant Reproduction
- Sexual reproduction = by seed
- - Begins with flowering
- - Involves pollination, production of fruit, and seed
- - Associated with inheritance of characteristics
- - Discipline of genetics
- Asexual reproduction = by vegetative parts (important in
the technology of propagation)
- Genetics
- Practiced since antiquity
- Principles deduced by Gregor Mendel (dude at
right) in 1850's
- Elucidated patterns of inheritance of various
characteristics in peas
- Laid the foundation for breeding and plant
improvement that provides great horticultural
riches
- Example: Inheritance of flower color
- Modern Genetics = Molecular aspects of cellular
reproduction
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Modern Genetics addresses the mechanistic processes controlled by
key molecules, such as DNA and RNA, that are eventually expressed at
the level of the whole organism:
Continue with Environment in Landscape
Horticulture or return to Science in
Landscape Horticulture.
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