Download classification of horticultural crops

PRINCIPLES OF HORTICULTURE/INTRODUCTION TO HORTICULTURE
(NRM103/ HORT103)
OBJECTIVE OF THE MODULE
COURSE OUTLINE
1.0 DEFINITION OF HORTICULTURE
1.1 Divisions of Horticulture
1.2 Characteristics of horticultural crops
1.3 Classification criteria
1.4 Classification of horticultural crops
2.0 TAXONOMY OF PLANTS
2.1 Hierarchy
2.2 Classification process
2.3 Natural and artificial classification
3.0 LIGHT AND PLANT FLOWERING
3.1 Photoperiodism
3.2 Mechanism of photoperiodism
4.0 PLANT GROWTH REGULATORS (PGRs)
4.1 Auxins
4.2 Gibberellins
4.3 Cytokinins
4.4 Abscisins
4.5 Ethylene
4.6 Hormonal control of the whole plant
4.7 Use of PRGs in horticulture
5.0 VEGETATIVE PROPAGATION
5.1 Cloning in horticulture
5.2 Propagation by layering
5.3 Propagation by Grafting and Budding
1
5.3 Graft incompatibility
5.4 Propagation from cuttings
5.5 External and internal factors affecting rooting of cuttings
6.0 TISSUE CULTURE
6.1 Micropropagation (Its applications, advantages and disadvantages)
6.2 Embryo culture
6.3 Somatic embryogenesis
6.4 Meristem tip culture
6.5 Anther culture
6.6 Protoplast culture
6.7 Somaclonal variation
6.8 Invitro selection
7.0 PROPAGATION STRUCTURES
7.1 Greenhouses
7.2 Lathhouses
7.3 Hotbeds
7.4 Cold beds
8.0 IRRIGATION AND NUTRITION MANAGEMENT IN HORTICULTURE
8.1 Soil Moisture and its measurement
8.2 Irrigation methods
8.3 Essential element for plant growth
9.0 POSTHARVEST TECHNOLOGY
9.1 Deterioration of produce
9.2 Ethylene production
9.3 Compositional changes
9.4 Physiological breakdown
9.5 Effects of temperature, RH, atmospheric gases, ethylene and light
9.6 Harvesting
9.7 Storage
2
Reference texts
Hartman, H. T., Kester, D. E., Davies, F. T. and Geneve, R. L. (2002) Plant
propagation principles and practices(6th Edition) Eastern Economic Edition
Janick, J. (1986) Horticultural Science (4th Edition) Freeman and Company
Jeffrey, C. (1982) An introduction to plant taxonomy (2nd Ed) Cambridge University
Press
3
1.0 ORIGINS OF HORTICULTURE

The concept of horticulture is part of agriculture.

The word agriculture (agri- field; culture- tillage) means tillage of the soil leading to
the production of crops.

Agriculture can be traced back to the Neolithic Age (9 000-7000BC), when man
changed from being a hunter and a gatherer to managing or manipulating individual
species of plant and animal.

Horticulture is a concept that later started in the 17th Century. In literature, the term
first appeared in 1631 by Peter Lauremberg as ‘horticultura’.

In English, horticulture was first mentioned in “The New World of English Words”
by Phillips E. in 1678.

The word is derived from the Latin names ‘hortus’, which means garden; and ‘colere’
meaning to cultivate.

Horticulture is part of agriculture concerned with garden crops, as contrasted with
agronomy (field crops, mainly grains and forages) and forestry (forest trees and
products)

Garden is derived from Anglo-Saxon term ‘gyrdan’ which means to enclose.

Garden crops traditionally include fruits, vegetables, and all plants grown for
ornamental purposes, as well as spices and medicinal plants.

Horticulture deals with intensively cultivated crops, which are of high value to
warrant high input of labour and capital.

Crops have also been separated using custom e.g. tobacco and potatoes may be
classified as agronomic crops despite their characteristics.
DEFINITION OF HORTICULTURE

The division of agriculture which relates to the culture of those plants commonly
known as fruits, vegetables and ornamental plants [Schilleter and Ritchley,
(1940)Textbook of general horticulture. McGraw-Hill Book Company, New York
and London]

The intensive cultivation of plants [Halfacre R. G. and Barden, J. A. (1979),
Horticulture. McGraw-Hill, USA]
4

The branch of agriculture concerned with intensively cultivated plants, directly used
by people for food, for medicinal purposes, or for aesthetic gratification [Janick, J.
(1986) Horticultural Science (4th Ed.). W. H. Freeman and Company, USA]

It is part of plant agriculture that is concerned with so-called garden crops [Hartman
H. T., Kester, D. E. and Davies, F. T. (1990)]
RELATIONSHIPS OF HORTICULTURE TO AGRICULTURAL BRANCHES
AGRICULTURE
PLANTS
AGRONOMY
AGROFORESTRY
ANIMALS
FORESTRY
HORTICULTURE
FLORICULTURE OLERICULTURE POMOLOGY LANDSCAPE
NURSERY
BRANCHES OF HORTICULTURE
Floriculture: It is the division of horticulture concerned with the science and art of
growing flowers and foliage plants
Olericulture: It is the division of horticulture concerned with the science and art of
vegetable production
Pomology: It is the division of horticulture concerned with the science of fruit
production.
Nursery culture: It is the branch of horticulture that is concerned with production of
young fruit trees, ornamentals and vegetable seedlings
Landscape design: It is the branch of horticulture that deals with the planning and
planting of outdoor environment to produce the most desirable relationships between
landforms, buildings and plants to best meet people’s objectives for function and beauty.
5
IMPORTANCE OF HORTICULTURE
SOURCE OF FOOD

Society depends on horticulture for a substantial amount of its food. This is
sourced from vegetables, fruits and nuts.

They supply carbohydrates, vitamins and minerals
ORNAMENTALS

Landscaping has become an important component of construction. Plants in
landscape include shrubs, trees, bedding plants and grasses.

Public malls, playgrounds and cemeteries are places where plants are displayed
for specific purposes.

Flowers are important on special occasions such as roses for Valentines Day,
Mothers Day, Graduations, Reconciliation; poinsentias for Christmas and lilies
for Easter.
JOBS

Directly provides jobs to the society. These include nurserymen, florists,
greenhouse managers, extension officers, sales or marketing officers, teachers,
lecturers, farm managers

Indirectly provides jobs in the following areas
Research, Chemical industry (extraction of pigments e.g. oleoresin), Machinery
(engineers and designers of tools for planting, weeding, harvesting). Distribution
(freight forwarders, transporters, drivers)
EXPORT MARKETS

Horticulture provides foreign currency through exports. Floriculture exports of
1985 totalled Z$3.1 million and continued to grow rapidly to $500 million for
1995/96 season.
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CHARACTERISTICS OF HORTICULTURAL CROPS

Many have high water content, hence they are utilised mostly in their living state

Highly perishable

Constituent water is essential to their quality

Generally grown more intensively and returns per unit area are normally higher
than with agronomic or forestry crops

Mainly consumed for the supply of micronutrients and vitamins and for their
contribution to flavour (spices) and interest of food (garnishing)

They are generally not staple crops

Consumption levels depend on the selling price and the buyer’s income

Crops are normally traded in relatively small quantities, in free marketing systems
where both supply and demand determine the price.
CLASSIFICATION OF HORTICULTURAL CROPS
Why classifying horticultural plants?

There are many horticultural plants in the world. A lot of knowledge has been
gathered on the plants. Classification makes summarisation of information on the
plants possible hence serves time in information sharing.

It is a means of identification and communication on horticultural plants

It facilitates prediction
TYPES OF CLASSIFICATION

There are two types of classification, which are natural and artificial.

Scientific plant classification falls under natural classification
Natural Classification

Classifies objects together on the basis of the sum total of all their characters
(features which exist in the group of objects in two or more distinguishable
different states e.g. hair colour, eye colour in human)

It puts together those that are more alike in most respects
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Artificial Classification

Classifies objects together on the basis of only one or a very few specially
selected characters and ignores all the characters that the objects might have.

It does not take into account the natural relations of plants.

However, it is useful in horticulture. Plants can be classified on the basis of their
ability to withstand drought e.g. drought tolerant, drought prone etc., which is
useful information for crop husbandry.
COMPARISON OF ARTIFICIAL AND NATURAL CLASSIFICATION
NATURAL
ARTIFICIAL
Basis of classification
Basis of classification
It utilises the sum-total of all the characters
It utilises one or very few characters of its
of its members
members that are especially selected
Advantages
Disadvantages
Groups together plants most alike in their
May not group plants that are most closely
hereditary constitution
related phylogenetically
Generally groups together plants most
May fail to group plants that are closely
closely related phylogenetically
related phylogenetically
Contains a lot of information about
Contains limited information about its
members of the group
members
Additional information of its members can
More information about its members
easily be incorporated
cannot be easily incorporated
Has a high predictive value
Low predictive value
Disadvantages
Advantages
Identification of members may be difficult
Identification of members is made easy
Placing of poorly known plants may be
Poorly known members may be definitely
uncertain or impossible
placed
It is liable to change as more information is
Does not change with increase in our
gathered on the plants
knowledge
Adapted from Jeffrey (1982)
8
SCIENTIFIC AND BOTANICAL (NATURAL) CLASSIFICATION SYSTEMS
HORTICULTURAL CROPS

Scientific systems of classification go beyond the superficial or natural system by
employing a number of criteria that include morphological, anatomical, ultrastructural
physiological, phytochemical, cytological and evolutionary (phylogenetical) criteria.

Individual members are assigned to a descending series of related plants based on
their known common characteristics.

The binomial nomenclature was introduced by Carolus Linnaeus, which used 2 Latin
names for naming a plant, which are the genus and the specific epiphet.

Taxonomic hierarchy:
1. KINGDOM
2. DIVISION/PHYLUM
3. CLASS
4. ORDER
5. FAMILY
6. GENUS
7. SPECIES
8. FORM/VARIETY
9. CULTIVAR
Common terms
KINGDOM –It is the highest taxonomic category
DIVISION
CLASS –
ORDER – a category of taxonomic classification ranking above the family and below
the class
5. FAMILY – a group of related plants or animals forming a category ranking above a
genus and below an order and usually comprising several to many genera
6. GENUS- a class , kind, or group marked by common characteristics or by one
common characteristic
7. GENUS – a kind, class or group marked by common characteristics or by one common
characteristic
8.SPECIES –a category of individuals ranking immediately below the genus or subgenus.
1.
2.
3.
4.
9
TAXON
KINGDOM
PHYLUM
CLASS
ORDER
FAMILY
GENUS
SPECIES
EXAMPLE
Plantae
Magnoliophyta
Liliopsida
Liliales
Liliaceae
Allium
Allium cepa
COMMON NAME
Plant
Flowering plant
Monocot
Lily order
Lily family
onion
Rules of classification
1. The binary name should be underlined or written in italics (to indicate that they
are non-English names)
2. Genus starts with a capital letter and the species is written in lowercase
throughout. The term species is both singular and plural. It can be shortened as
spp. for plural “species”.
OPERATIONAL (ARTIFICIAL) CLASSIFICATION SYSTEMS
1. CLASSIFICATION BASED ON SEASONAL GROWTH CYCLE

Plants can be classified into three general groups based on growth cycle. These
are: annuals, biennials, perennials (evergreen, deciduous) and mononcarp.
SEED
DEATH
ANNUAL
VEGETATIVE
GROWTH
REPRODUCTIVE
ANNUAL: The plant lives through only one growing season, completing its life cycle
(seed, flowering, fruiting and death). Examples are tomato (Lycopersicon esculentum)
sugarbeans (Phaseolus vulgaris).
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SEED
DEATH
PERENNIAL
AL
VEGETATIVE
GROWTH
DORMANCY
REPRODUCTIVE GROWTH
PERENNIAL: These are herbaceous or woody plants that persist year-round through
unfavourable conditions (winter or drought) and then flower and fruit after a variable
number of years of vegetative growth. Perennials survive harsh conditions as dormant
underground organs. Examples are irises (Iris spp.) & fruit trees.
SEED
DEATH
VEGETATIVE
GROWTH 1
BIENNIAL
DORMANCY
VEGETATIVE
GROWTH 2
REPRODUCTIVE
BIENNIAL: These are plants that complete a life cycle in two growing seasons. The
first season is for vegetative growth and the second season the plant produces a stem
and flowers. Examples are onions (Allium cepa).
11
SEED
DEATH
MONOCARP
REPRODUCTIVE
VEGETATIVE
GROWTH
DORMANCY
Monocarp: These are characterised by
2. CLASSIFICATION BASED ON THE KINDS OF STEMS
Herbs: plants with soft non-woody stems. They have primary vegetative
parts. Examples include Zea mays
Shrubs: A shrub has no main trunk. It is woody and has secondary tissue.
Shrubs are perennial and usually smaller than the trees. Examples are azalea
(Rhododendron spp.), Bougainvillea
Trees: Trees are large plants characterised by one main trunk. They branch
on the upper part of the plant are woody and have secondary tissue.
3. CLASSIFICATION BASED ON COMMON STEM GROWTH FORMS
Erect: A stem is erect if it can stand upright (at an angle 900 to ground level)
without artificial support.
12
Decumbent: The stems of decumbent plants are extremely inclined with the
tips raised. A good example is Arachis hypogea(groundnuts).
Declined/Climbing: These are vines that without additional support, will
creep on the ground. There are three general modes of climbing. Thesea are
1. Twiners – they simply wrap their stringy stems around the support e.g.
sweet potatoes
2. Tendrils – these coil around support on physical contact. An example is
Pisum sativum
3. Climbimg by adventitious roots:
4. CLASSIFICATION BASED ON FRUITS
5. CLASSIFICATION BASED ON OTHER OPERATIONAL ATRIBUTES
OVERALL CLASSIFICATION OF HORTICULTURAL PLANTS
13
EDIBLES
1. VEGETABLES
1.1 Plants Grown for aerial portions
1) Cole Crops (broccoli, cabbage, cauliflower)
2) Legumes or pulse crops (bean, pea)
3) Solonaceous fruit crops (Capsicum pepper, eggplant, tomato)
4) Vine crops or curcubits (cucumber, melon, squash and pumpkin)
5) Pot Herbs or Greens (chard, dandelion, spinach)
6) Mushrooms (Agaricus, Oyster, Lentinus)
7) Other vegetables (asparagus, okra, sweet corn)
1.2 Plants grown for underground portions
1) Root crops

Temperate (beet, carrot, radish and turnip)

Tropical (cassava, sweetpotato, taro and yam)
2) Tuber crops (Jerusalem artichoke, potato)
3) Bulb and corm crops (garlic, onion, shallot)
2.0 FRUITS
2.1 Temperate (Deciduous)
1) Small fruits

Berries (blueberry, cranberry, strawberry)

Brambles (blackberry, raspberry)

Vines (grape, kiwifruit)
2) Tree fruits

Pome fruits (apple, pear, quince)

Stone fruits (apricot, cherry, peach and plum)
2.2 Subtropical and tropical (Evergreen)
14
1) Herbaceous and vine fruits (banana, papaya, passion fruit, pineapple)
2) Tree fruits

Citrus (grapefruit, orange, lime, lemon, naartjies, mandarin)

Non citrus (avocado, date, fig, mango, mangosteen)
3.0 NUTS
1) Temperate (almond, chestnut, filbert, pecan, pistachio)
2) Tropical (Brazil nut, cashew, macadamia)
4.0 BEVERAGE CROPS
1) Seed (cacao, coffee)
2) Leaf (maté, tea)
5.0 HERBS AND SPICES
1) Culinary herbs (dill, rosemary, sage)
2) Flavourings (peppermint, spearmint)
3) Tropical spices (cinnamon, clove, nutmeg and pepper)
ORNAMENTALS
1.0 FLOWERS , BEDDING AND FOLIAGE PLANTS
1) Annuals (marigold, petunia, zinnia)
2) Biennials (English daisy, foxglove)
3) Perennials (daylily, rose, delphinium, iris, peony)

Bulbs and corms (crocus, gladiolus, narcissus, tulip)
2.0 LANDSCAPE (NURSERY)
1) Lawn and turf (bermudagrass, bluegrass, fescue, perennial ryegrass)
2) Ground covers and vines (English ivy, Japanese spurge, myrtle)
3) Evergreen shrubs and trees

Broadleaf (holly, rhododendron)

Narrowleaf (fir, juniper and yew)
4) Deciduous shrubs (dogwood, forsythia, lilac, viburnum)
15
5) Deciduous trees (ash, crabapple, magnolia, sugar marple)
3.0 INDUSTRIAL
1) Drugs and medicinals (digitalis, quinine)
2) Oil seeds (jojoba, oilpalm, tung)
3) Extractives and resins (Scotch pine, Pará rubber tree)
2.0 TAXONOMY OF PLANTS
2.1 Hierarchy
2.2 Classification process
2.3 Natural and artificial classification
3.0 LIGHT AND PLANT FLOWERING
3.1 Photoperiodism
3.2 Mechanism of photoperiodism
4.0 PLANT GROWTH REGULATORS (PGRs)
4.1 Auxins
4.2 Gibberellins
4.3 Cytokinins
4.4 Abscisins
4.5 Ethylene
4.6 Hormonal control of the whole plant
4.7 Use of PRGs in horticulture
5.0 VEGETATIVE PROPAGATION
5.1 Cloning in horticulture
5.2 Propagation by layering
5.3 Propagation by Grafting and Budding
5.3 Graft incompatibility
5.4 Propagation from cuttings
5.5 External and internal factors affecting rooting of cuttings
16
6.0 TISSUE CULTURE
6.1 Micropropagation (Its applications, advantages and disadvantages)
6.2 Embryo culture
6.3 Somatic embryogenesis
6.4 Meristem tip culture
6.5 Anther culture
6.6 Protoplast culture
6.7 Somaclonal variation
6.8 Invitro selection
7.0 PROPAGATION STRUCTURES
7.1 Greenhouses
7.2 Lathhouses
7.3 Hotbeds
7.4 Cold beds
8.0 IRRIGATION AND NUTRITION MANAGEMENT IN HORTICULTURE
8.1 Soil Moisture and its measurement
8.2 Irrigation methods
8.3 Essential element for plant growth
9.0 POSTHARVEST TECHNOLOGY
9.1 Deterioration of produce
9.2 Ethylene production
9.3 Compositional changes
9.4 Physiological breakdown
9.5 Effects of temperature, RH, atmospheric gases, ethylene and light
9.6 Harvesting
9.7 Storage
17
CHAPTER 2.0 TAXONOMY OF PLANTS
SCIENTIFIC CLASSIFICATION OF PLANTS
18
1) PRACTICAL 1: IDENTIFICATION OF COMMON HORTICULTURAL
CROPS
Full Name
: …………………………………………………
Registration Number
:…………………………………………………...
SAMPLE
NAME OF CROP
FAMILY OF CROP
CODE
A
B
C
D
E
F
G
H
I
J
19
Assignment
1. Advise smallholder farmers of the challenges or hardships they are likely to face
in commercial horticultural production [10]
2. Write a short essay on the importance of classifying horticultural crops [10]
20
CHAPTER 4.0 Plant Hormones (Plant Growth Regulators)
Introduction
As a plant grows its physical traits, or phenotype, are the outcome of a complex
interaction between its genetic instructions, or genotype, and the external environment.
The growth and differentiation of cells in different parts of the plant are coordinated in
response to these inputs.
There has to be communication between these levels. How does the plant receive and
respond to environmental inputs or "signals"? What communication is inside the plant to
adjust growth and development in response to the environment? The answer lies in an
understanding of plant hormones.
Definition:
Plant hormones are small organic compounds that influence physiological responses to
environmental stimuli at very low concentrations (generally less that 10-7 M). Hormones
are not directly involved in metabolic or developmental processes but they act at low
concentrations to modify those processes.
Plant hormones are used extensively in agriculture, horticulture, and biotechnology to
modify plant growth and development.
Hormones regulate or influence a range of cellular and physiological processes, including
o
Cell Division
o
Cell Enlargement
o
Cell Differentiation
o
Flowering
o
Fruit Ripening
21
o
Movement (tropisms)
o
Seed Dormancy
o
Seed Germination
o
Senescence
o
Leaf Abscission
o
Stomatal Conductance
Not all researchers agree that the term "hormone" should be applied to plants. Plants do
not have a circulatory system and therefore hormone action in plants is fundamentally
different from hormone action in animals. Many plant biologists use the term "plant
growth regulator" instead of "hormone" to indicate this fact. The table below summarizes
some of the differences between plant and animal hormones.
Plant Hormones
1. Small molecules only
2. Produced throughout the plant
3. Mainly local targets (nearby cells and
tissues)
4. Effects vary depending on interaction
with other hormones
5. "Decentralized" regulation
Animal Hormones
1. Peptides/proteins and/or small
molecules
2. Produced in specialized "glands"
3. Distant targets ("action at a
distance")
4. Specific effects
5. Regulation by central nervous
system
Broadly speaking, the mechanism by which hormones act at the cellular level is similar in
plants and animals. In both cases, the hormone must first bind to a protein receptor,
either on the cell surface or inside the cell. This activates a signal transduction
pathway, which amplifies the signal and leads to changes in enzyme activities, ion
gradients, gene expression, and other physiological responses.
Five classes of plant hormones are recognized.
22
1. Auxins
2. Cytokinins
3. Gibberellins
4. Abscisic Acid
5. Ethylene
Other "hormone-like" substances produced by plants include
o
Polyamines
o
Jasmonates
o
Salicylic acid
o
Brassinosteroids
o
Florigens
o
Phytochrome (photoreceptor)
o
Nitric oxide?
Auxins

Name from the Greek work auxein which means to "increase" or "augment"

First plant hormone discovered
1. Phototropism experiments of Charles and Francis Darwin using oat
coleoptiles
2. Auxin eventually isolated by Frits Went

Auxins are produced primarily in shoot tips (shoot apical meristem) and growing
leaves and fruits.

Auxins regulate two important processes in plant growth: phototropism
(response to light) and gravitropism (response to gravity)

Auxins promote stem growth by stimulating cell elongation

Auxins control vascular differentiation of xylem and phloem
23

Auxins stimulate lateral root growth and root initiation on stem cuttings

Auxins move through the plant by "polar transport"
- Unidirectional movement down the stem through parenchyma cells
- Auxin apparently does not travel through the vascular tissue

Auxins inhibit lateral bud sprouting. This is called apical dominance

Indole-3-acetic acid (IAA) is the natural auxin

IAA is derived from the amino acid tryptophan

Several synthetic auxins have related structures
1. napthalene acetic acid (NAA) (controls fruit set and sucker growth)
2. indole butyric acid (Rootone)
3. 2,4-D (herbicide, causes uncoordinated growth in broad-leaved weeds)
Cytokinins

Produced mainly in roots; travels through the xylem

Derived from the nucleotide adenine
1. Synthetic cytokinins include benzyladenine and kinetin
2. These growth stimulators are used extensively in plant tissue culture and
are therefore important in biotechnology applications

Promote cell division ("cytokinesis")

Stimulate lateral bud growth
- determined by relative concentrations of auxin and cytokinin
24
Gibberellins

Largest group of hormones, over 70 known gibberellins

First isolated from a fungus (Gibberella fujikori)
- cause of "foolish seedling"

Derived from the terpenoid pathway

Produced in embryonic tissues (meristems)

Promotes stem elongation
o
Many "dwarf" plants are genetic mutants deficient in gibberellin synthesis

Enhances the effects of auxin

Stimulates germination in buds and seeds

Used commercially to break dormancy

Example: Germination in wheat seeds
1. Seed takes up water
2. Embryo produces GA
3. GA diffuses to aleurone layer (surrounding endosperm)
4. Aleurone produces amylase
5. Amylase diffuses to endosperm and breaks down starch to glucose
6. Glucose feeds growing embyro
Abscisic Acid

Synthesized in plastids from carotenoids
25
- Derived from terpenoid pathway

Produced in leaves, stems, and green fruits

Causes stomatal closure during water stress

Promotes dormancy in seeds and buds
Ethylene

Gaseous Hormone

Formed from the amino acid methione
- reaction involves cyclized intermediate 1-aminocyclopropane-1carboxylic acid (ACC)

Promotes leaf abscission

Promotes fruit ripening

Used commercially for fruit ripening
Ethephon is a commercial fruit ripener that breaks down to ethylene inside plant tissues
26