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
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
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
1.0 ORIGINS OF HORTICULTURE
q The concept of horticulture is part of agriculture.
q The word agriculture (agri- field; culture- tillage) means tillage of the soil leading to the production of crops.
q 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.
q Horticulture is a concept that later started in the 17th Century. In literature, the term first appeared in 1631 by Peter Lauremberg as ‘horticultura’.
q In English, horticulture was first mentioned in “The New World of English Words” by Phillips E. in 1678.
q The word is derived from the Latin names ‘hortus’, which means garden; and ‘colere’ meaning to cultivate.
q 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)
q Garden is derived from Anglo-Saxon term ‘gyrdan’ which means to enclose.
q Garden crops traditionally include fruits, vegetables, and all plants grown for ornamental purposes, as well as spices and medicinal plants.
q Horticulture deals with intensively cultivated crops, which are of high value to warrant high input of labour and capital.
q Crops have also been separated using custom e.g. tobacco and potatoes may be classified as agronomic crops despite their characteristics.
DEFINITION OF HORTICULTURE
q 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]
q The intensive cultivation of plants [Halfacre R. G. and Barden, J. A. (1979), Horticulture. McGraw-Hill, USA]
q 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]
q 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 ANIMALS
AGRONOMY AGROFORESTRY 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.
IMPORTANCE OF HORTICULTURE
SOURCE OF FOOD
q Society depends on horticulture for a substantial amount of its food. This is sourced from vegetables, fruits and nuts.
q They supply carbohydrates, vitamins and minerals
ORNAMENTALS
q Landscaping has become an important component of construction. Plants in landscape include shrubs, trees, bedding plants and grasses.
q Public malls, playgrounds and cemeteries are places where plants are displayed for specific purposes.
q Flowers are important on special occasions such as roses for Valentines Day, Mothers Day, Graduations, Reconciliation; poinsentias for Christmas and lilies for Easter.
JOBS
q Directly provides jobs to the society. These include nurserymen, florists, greenhouse managers, extension officers, sales or marketing officers, teachers, lecturers, farm managers
q 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
q 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.
CHARACTERISTICS OF HORTICULTURAL CROPS
q Many have high water content, hence they are utilised mostly in their living state
q Highly perishable
q Constituent water is essential to their quality
q Generally grown more intensively and returns per unit area are normally higher than with agronomic or forestry crops
q Mainly consumed for the supply of micronutrients and vitamins and for their contribution to flavour (spices) and interest of food (garnishing)
q They are generally not staple crops
q Consumption levels depend on the selling price and the buyer’s income
q 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?
q 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.
q It is a means of identification and communication on horticultural plants
q 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
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 / ARTIFICIALBasis of classification
/ Basis of classificationIt utilises the sum-total of all the characters of its members / It utilises one or very few characters of its members that are especially selected
Advantages / Disadvantages
Groups together plants most alike in their hereditary constitution / May not group plants that are most closely related phylogenetically
Generally groups together plants most closely related phylogenetically / May fail to group plants that are closely related phylogenetically
Contains a lot of information about members of the group / Contains limited information about its members
Additional information of its members can easily be incorporated / More information about its members 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 easyPlacing of poorly known plants may be uncertain or impossible / Poorly known members may be definitely placed
It is liable to change as more information is gathered on the plants / Does not change with increase in our knowledge
Adapted from Jeffrey (1982)
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
1. KINGDOM –It is the highest taxonomic category
2. DIVISION
3. CLASS –
4. 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.
TAXON / EXAMPLE / COMMON NAMEKINGDOM / Plantae / Plant
PHYLUM / Magnoliophyta / Flowering plant
CLASS / Liliopsida / Monocot
ORDER / Liliales / Lily order
FAMILY / Liliaceae / Lily family
GENUS /
Allium
SPECIES /Allium cepa
/ onionRules 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
q Plants can be classified into three general groups based on growth cycle. These are: annuals, biennials, perennials (evergreen, deciduous) and mononcarp.
SEED
DEATH 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).
SEED
DEATH 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
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).
SEED
DEATH VEGETATIVE
GROWTH
REPRODUCTIVE 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.
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
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)