unit two Plant Structure, Chemistry, Growth, Development - PowerPoint PPT Presentation

Loading...

PPT – unit two Plant Structure, Chemistry, Growth, Development PowerPoint presentation | free to download - id: 3b48b0-YzY0Y



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

unit two Plant Structure, Chemistry, Growth, Development

Description:

unit two Plant Structure, Chemistry, Growth, Development, Genetics, Biodiversity, and Processes 6 Structure of Higher Plants 7 Plant Growth & Development – PowerPoint PPT presentation

Number of Views:533
Avg rating:3.0/5.0
Slides: 68
Provided by: virtualMj
Learn more at: http://virtual.mjc.edu
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: unit two Plant Structure, Chemistry, Growth, Development


1
unit two Plant Structure, Chemistry, Growth,
Development, Genetics, Biodiversity, and Processes
6 Structure of Higher Plants  7 Plant Growth
Development   8 Plant Chemistry Metabolism 9
Genetics Propagation 10 Cultivated Plants
Naming, Classifying, Origin, Improvement
Germplasm Diversity and Preservation  11
Photosynthesis Respiration   12 Water
Relations   13 Mineral Nutrition  
2
KEY LEARNING CONCEPTS
After reading this chapter, you should be able to
  • Explain how plants are named and classified.
  • Use the nomenclature and system of taxonomic
    classification to identify plants and their
    relationship to each other.
  • Explain how several crops originated and where
    they were domesticated.
  • Discuss the importance of saving germplasm from
    extinction and the global system created to
    preserve germplasm.

3
  • There are over 500,000 different kinds of plants.
  • The first recorded names were attributed
    to Theophrastus (370285 bce).
  • Naming plants began with simple names
    referring to the plants use, growing habit, or
    other attribute.
  • A difficulty is that often names are only used
    locally.
  • Any system of classifying plants depends on how
    the classification is to be used.

4
Climatic and Related Classifications
  • Farmers and others who grow plants commercially
    have to be able to identify and name crops.
  • And distinguish which crops and plants suit their
    climate.
  • Plants can be classified into distinct groups by
    climate.
  • The USDA has divided the U.S into several
    different cold hardiness zones many plants are
    classified by their ability to grow in the
    different zones.
  • Some annuals have specific climatic requirements,
    and are distinguished as winter or summer
    annuals.
  • Winter annuals are planted in the fall, and bloom
    early the following spring.
  • Summer annuals are planted in the spring, and
    bloom through the summer and fall.

5
Climatic and Related Classifications
  • Some crops grow best in certain seasons.
  • Warm-season plants grow best where monthly
    temperatures average 65- 80 F.
  • Corn, beans, tomatoes, peppers,, petunias,
    marigolds, zinnias.
  • Cool-season crops grow best at average monthly
    temperatures average 60-65 F.
  • Broccoli, cabbage, peas, flowering bulbous
    plants, cyclamen.
  • Numerous flower and vegetable cultivars can be
    classified as early, midseason, or late maturing.
  • Plants can be classified by the seasons in which
    they are most likely to flower and fruit.
  • Or when product quality can be expected to be
    maximum.
  • Many can be classed early, midseason, or late
    maturing

6
Climatic and Related Classifications
  • Vegetables are classified into groups according
    to their edible parts.
  • Ornamentals are sometimes classified by use, as
    are plants outside the home.
  • Houseplants are often classified according to
    their foliage, flowers, or growth habits.

7
Climatic and Related Classifications
  • Foresters classify trees into two broad
    groupshardwoods and softwoods.
  • Some hardwood types are oaks (Quercus), maples
    (Acer), birch (Betula), and beech (Fagus).
  • Some softwood trees are pines (Pinus), cedars
    (Cedrus), redwood (Sequoia), and spruce (Picea).
  • Trees are also classified according to the
    hardiness zones in which they can survive.

8
Climatic and Related Classifications
9
Common and Botanical Names
  • Most plants are generally known by their common
    nameseasier to remember, pronounce use.
  • Names often evolve due to certain plant
    characteristics.
  • A common name has value in conversation only if
    both persons know exactly what plant is being
    discussedmost likely with persons from the same
    community the plant name cannot be mistaken.

10
Common and Botanical Names
  • JASMINE - AN EXAMPLE

Star jasmine (Jasminum gracillimum) Star
jasmine (Trachelospermum jasminoides) Blue
jasmine (Clematis crispa) Cape jasmine (Gardenia
jasminoides) Crape jasmine (Tabernaemontana
divaricata) Night jasmine (Cestrum
nocturnum) Night jasmine (Nyctanthes
arbor-tristis)
Many common plant names contain the word
jasmine, but do not resemble one another, and may
not be closely related botanically.
11
Development of Botanical Classifications
  • Theophrastus (370285 bce), a student of
    Aristotle, classified plants by their texture or
    form.
  • He classified many as herbs, shrubs trees,
    noted annual, biennial perennial growth, and
    described differences in flower parts.
  • Carl von Linné (17071778), devised a system of
    categorizing plants that led to the modern
    taxonomy or nomenclature of plants.

12
Scientific Classification
  • The scientific system classifies living things by
    groupstaxabased on physical characteristics.
  • The first taxon, Domain, divides living things
    into
  • Prokaryotes (cells having no separate subcellular
    units).
  • Eukaryotes (cells having subcellular units).
  • The Eukaryote Domain is divided into the
    Kingdoms
  • Fungi, Protista, Plantae, and Animalia.
  • The Plantae Kingdom is divided into
  • Bryophytes (includes mosses and liverworts)
  • Vascular plantsdivided by seedless and seeded.

13
Scientific Classification
  • Seedless seeded plants are classed by Phyla.
  • Seedless phyla include the Pterophyta (ferns).
  • Seeded phyla include Cycadophyta (cycads),
    Ginkgophyta (ginkgo), Coniferophyta (conifers),
    and Anthophyta (angiosperms).
  • After phylum, plants are classified in descending
    rank by class, order, family, genus, and species.
  • Each descending rank more closely defines the
    physical characteristics common to members of
    that rank.

14
Plant Identification and Nomenclature
  • The family is usually the highest taxon commonly
    included in plant identification or study.
  • Students are usually required to learn family,
    genus, and species of some plants, as well as
    their common names.
  • Since the early Christian era, naturalists wrote
    their books in LatinLinnaeus used names of Latin
    form.
  • Most names he gave are phonetic,and give a clue
    to plant characteristics, native habitat, or for
    whom it is named.

15
Plant Identification and Nomenclature
  • Names that refer to leaves include folius,
    phyllon, or phyllausually as suffixes.
  • Names can also have prefixes, such as macro or
    micro.
  • Words are created
  • macrophylla (large leaf).
  • microfolius or microphylla (small leaf)
  • illicifolius (holly leaf) salicifolius (willow
    leaf).

The Latin for flower is flora add the prefix
grand, and it becomes grandiflora (large flower),
as in Magnolia grandiflora L. The southern
magnolia
16
Plant Identification and Nomenclature
  • Shapes or growing habits of plants are described
  • altus or alta (tall), arboreus (treelike),
    compactus (dense).
  • nanus or pumilus (dwarf), repens or reptans
    (creeping).
  • scandens (climbing).
  • Names based on flower or foliage color
  • albus or leuco (white), argentus (silver).
  • aureus or chryso (gold), rubra, rubens, or
    coccineus (red)
  • croceus, flavus, or luteus (yellow).

17
Plant Identification and Nomenclature
  • Species names sometimes reflect the plants place
    of origin.
  • australis (southern), borealis (northern).
  • campestris (field), insularis (island), montanus
    (mountain).
  • canadensis (from Canada).
  • chinensis or sinensis (from China).
  • chilensis or chileonsis (from Chile).
  • japonica, nipponica, or nipponicus (from Japan).

18
Plant Identification and Nomenclature
  • Each plant has a two-wordbinomialLatin name,
    which is international, and understood
    universally.
  • The first name refers to the genus the second,
    its species.
  • Complete Linnaean names have a third
    elementauthoritythe abbreviated name of the
    scientist who named the species.
  • Wild or naturally occurring plants are named
    under the International Code of Botanical
    Nomenclature.
  • Cultivated plants are covered by the
    International Code of Nomenclature for Cultivated
    Plants.

19
Plant Identification and Nomenclature
  • Basic rules of nomenclature
  • The generic name always begins with a capital
    letter it is underlined if hand- or
    type-written, italicized in print.
  • The specific epithet usually begins with a
    lowercase letterbut may be capitalized if it is
    a persons name.
  • To complete the binomial name, authority for
    describing and naming the plant is given after
    the genus and species.
  • Authority names are often abbreviated and
    taxonomy books have a list of the full names of
    these authorities.
  • When several plants in the same genus are listed,
    the genus name is given in full for the first,
    then shortened to the first initial (capitalized)
    for the other plants in the list.
  • This procedure should not be used if there is any
    chance of confusion with another genus with the
    same first initial.

20
Plant Identification and Nomenclature
  • Occasionally the genus is known but the exact
    species is not.
  • In such a case, the genus is given, followed by
    lowercase letters sp. for species (singular)
    and spp. (plural).
  • The singular and plural spelling of species is
    the same.
  • The sp. or spp. is never underlined or
    italicized.

21
Subspecific Categories
  • Sometimes a botanical binomial is not sufficient
    to identify a specieswild or cultivated.
  • Botanists and horticulturists may form
    subspecific categories, such as botanical
    variety, cultivar, and group.

22
Botanical Variety
  • A plant group can be so different in the wild
    from the general species it warrants a botanical
    variety classification below that of species.
  • An example is Buxus microphylla Sieb. and Zucc.
    var. japonica Rehd. and Wils.
  • The var. stands for varietas, Latin for
    variety.
  • When a varietas epithet is formed from a
    surname, it may or may not be capitalized
    depending on the personal preference of the
    author.
  • The trend is to not capitalize them, as
    recommended by the International Codes.

23
Cultivar
  • There are two main categories of cultivarsthe
    clones and the lines.
  • The word cultivar is abbreviated cv. the
    plural is cvs.
  • A cultivar is often a distinct variant selected
    because it was uniquely different from any plant
    in cultivation.
  • The cultivar name is always capitalized but never
    underlined or italicized.
  • Either single quotes or the term cv. is used,
    but never both.
  • Tables or lists usually use cultivar or cv.
    in the heading to avoid single quotes around each
    name.

24
Group
  • The group category is used for some vegetables
    some ornamentals like lilies, orchids, roses
    tulips.
  • Below species, not used as frequently as the
    cultivar.
  • A group includes more than one cultivar of a
    particular kind of plant.
  • When a species has many cultivars, cultivars that
    are similar are categorized into groups.

25
Family
  • The family is a group of closely related genera.
  • Relationship can be based on plant structures or
    chemical characteristics, but flower structure is
    the usual basis.
  • The first letter of family names is always
    capitalized and names are sometimes underlined or
    italicized.
  • Family names may be written entirely in capital
    letters.

26
Family
  • The nightshade family SOLANACEAE includes

Potato flower
Solanum (potato) Lycopersicon (tomato) Capsicum
(pepper) Nicotiana (tobacco) Datura (deadly
nightshade) Petunia, and many others.
Tomato flower
All species in this family have similar flower
structures, as shown in the similarities between
a potato flower and a tomato flower.
27
Family
  • Most families names end with -aceae (ace-ay-ee)
    attached to a genus name,
  • Eight families did not follow this standard rule,
    and new names have been adopted for these
    families.

28
Plant Identification Key
  • Keying plants is a process of elimination by
    making yes or no decisions to characteristics
    offered in the keyrejecting those that do not
    apply (dichotomy).
  • To use a key you need to know the vocabulary of
    plant structure.
  • To use a key, eliminate the alternative that does
    not pertain to the plant in question proceed to
    the next pair of numbers directly under the
    proper choice.
  • This procedure is followed until the plant to be
    identified fits a given set of plant
    characteristics.

29
Plant Identification Key
  • Certain plant parts might not be available
    because of seasonwhen needed to identify the
    plant.
  • It might be necessary to preserve flowers for
    future examination or describe them thoroughly
    when abundant.
  • Then wait for the fruit to develop to accurately
    determine its characteristics.
  • Family characteristics are determined by
    observing and studying certain flower
    characteristics.
  • Once the family is known, species are
    identified by referring to taxonomic books with
    detailed keys.

30
Plant Identification Key
  • Simplified dichotomous key used to identify some
    commonly known seed-bearing plants
    (Spermatophyta).

See the entire table on pages 203-204 of your
textbook.
31
Plant Identification Key
  • Examples of hard-to-classify plants.

32
Plant Identification Key
  • Examples of hard-to-classify plants.

33
Plant Identification Key
  • Examples of hard-to-classify plants.

34
Origin of Cultivated Plants
  • Most crop plants important today were
    cultivated in a primitive way long before
    recorded history.
  • Most are still cultivated, but in much improved
    forms.
  • Others unknown to early humans have been added to
    make our present-day selection of food plants.
  • Much later, people became more concerned about
    aesthetics added shade trees, shrubs, flowering
    plants lawn grasses to the list of cultivated
    plants.
  • Swiss botanist Alphonse DeCandolle wrote Origin
    of Cultivated Plants, first published in 1833.
  • Russian plant geneticist Nikolai Vavilov
    published The Origin, Variation, Immunity, and
    Breeding of Cultivated Plantstranslated from
    Russian in 1951.

35
Origin of Cultivated Plants
  • Vavilov concluded that various cultivated plants
    originated in eight independent centers.
  • Central China India Indochina and Malay
    Archipelago.
  • The TurkeyIran region The Mediterranean area.
  • The EthiopiaSomaliland area of east Africa.
  • Mexico and Central America
  • The PeruEcuadorBolivia and BrazilParaguay
    area.

36
Domestication of Plants
  • There is evidence that agricultural villages
    existed about 8000 to 9000 bce in the Fertile
    Crescent.
  • Radiocarbon dating suggests animals were being
    domesticated in this area by at least 5000 to
    6000 bce.
  • An indigenous savanna type agriculture was
    developing from domesticated native plants about
    4000 bce in a belt across central Africa.
  • The first home of the human race, as we know it
    now.
  • The Chinese center of agricultural origins became
    important about 4000farming culture in southeast
    Asia Indonesia domesticated rice about 6000 bce.

37
Domestication of Plants
  • In the New World, evidence from archeological
    sites shows agricultural beginnings in two areas.
  • One is present-day southern Mexico and Central
    America.
  • Where plant cultivation began about 5000 to 7000
    bce.
  • The second is a broad noncenter stretching from
    Chile northward to the Atlantic Ocean and
    eastward into Brazil.
  • No major cultivated crop originated in the area
    of the present-day U.S.agriculture here relies
    in a large measure on introduced crops.
  • The only food crop to originate in the continent
    of Australia was the macadamia, or Queensland nut.

38
Domestication of Plants
39
Vegetative or Asexual Propagation Methods
  • Some of the oldest cultivated woody plants are
    the easiest to propagate by vegetative methods
    such as hardwood cuttings.
  • Grape, fig, olive, mulberry, pomegranate, and
    quince.
  • Many types of ancient plants brought domesticated
    by early people were easily maintained
    increased by unsophisticated vegetative methods.

40
Seed or Sexual Propagation Methods
  • Domestication of seed-propagated plants probably
    began as purposeful harvesting of wild grass
    seeds.
  • Some of which were sown to produce the next
    years crop.
  • In cereals, this procedure starts to separate the
    shattering typesthe seed separates from the
    headfrom the nonshattering types.
  • Most of the seeds that shatter fall to the
    ground, while nonshattering seeds are harvested
    and can be resown.
  • Planting harvested seeds closely in a cultivated
    plot kept free of competing weeds automatically
    selects for the stronger, more vigorous plants.

41
Seed or Sexual Propagation Methods
  • Desirable characteristics arising from selection
  • Loss of seed dormancy, increased flower
    numbers and larger inflorescences.
  • Trends toward determinate growth.

42
Improvement in Some Important Crop Plants
  • Present, improved cultivars of important
    crops have been so adapted to conform to
    human cultural practices that they all now
    completely depend on our care for their continued
    existence.

43
Grains and Vegetable Crops
  • Wheat (Triticum aestivum and T. turgidum Durum
    group)
  • The most widely cultivated plant in the world
    today, the chief cereal, and is used worldwide
    for making bread.
  • Evolved from wild wheatlike grass found and
    cultivated by ancient humans in the Near East
    region about 7000 bce.
  • Probably improved by spontaneous hybridizations,
    by chromosome doubling mutations to increase
    fertility.
  • Species occur in a series with increasing
    chromosome numbers.
  • Breeders have developed dwarf forms of wheat,
    which can produce high seed yields without
    falling over (lodging).
  • From the Near East, early wheat forms were taken
    into ancient Egypt, the Balkans, and central
    Europe.
  • The Spanish brought wheat to the Americas.

44
Grains and Vegetable Crops
  • Wheat (Triticum aestivum and T. turgidum Durum
    group)
  • Introduction of Turkey Red wheat by Russian
    immigrants established the U.S. hard red winter
    wheat industry.
  • The two major wheat species today are
  • Triticum aestivumused for flour in making breads
    and pastries
  • T. turgidum (Durum group)for macaroni, spaghetti
    noodles.
  • Wheat cultivars resistant to the devastating stem
    rust disease must continually be developed to
    cope with the mutating stem rust pathogen.
  • Wheat plants are self-pollinated, allowing
    farmers to save their seeds for future planting.
  • Wheat has perfect (bisexual) flowers, making
    cross pollination difficult.

45
Grains and Vegetable Crops
  • Corn (Zea mays)
  • Originated in the New World about 5000 to 6000
    bce.
  • Probably in several places in both Mexico and
    South America.
  • Maize is known only as a domesticated plantthere
    is no wild form except, apparently, teosinte, a
    close relative.
  • Economic life of the ancient American
    civilizationsthe Aztecs, Mayas, and
    Incasdepended on corn.
  • At the time of Columbuss expeditions to the New
    World, corn was being grown by Indian tribes from
    Canada to Chile.
  • Corn mutates easily, forming new types.
  • Even today, it is an extremely variable species,
    from grain color, to the size shape of the
    grains ears.

46
Grains and Vegetable Crops
Hypotheses advanced to explain the origin of corn
  • It developed from pod corn, a type in which
    each individual kernel is enclosed in floral
    bracts.
  • It originated from teosinte, by gradual selection
    under the influence of harvesting by humans
  • Corn, teosinte Tripsacum (a perennial grass)
    descended along independent lines directly from a
    common ancestor.
  • A tripartite theory that
  • (a) cultivated corn originated from pod corn.
  • (b) teosinte is a derivative of a hybrid of corn
    and Tripsacum.
  • (c) the majority of modern corn cultivars are the
    product of an admixture with teosinte or
    Tripsacum, or both.

47
Grains and Vegetable Crops
  • Corn (Zea mays)
  • The development of hybrid corn in the 1930s is
    one of the outstanding achievements of modern
    agriculture.
  • In 1935, 1 of corn planted in the U.S. was of
    the hybrid typeby 1970, almost all corn produced
    was hybrid.
  • Hybrid cultivars, along with fertilizers,
    irrigation, and mechanization, dramatically
    improved production.
  • Corn is now one of the worlds chief food crops.
  • Specialty cornssuch as white, waxy, hard
    endosperm food grade, high oil, nutritionally
    enhanced, high amylase and high extractable
    starch cornare being developed.
  • Ethanol production from high-starch corn as a
    replacement for some petroleum fuels has become a
    major use of corn.

48
Grains and Vegetable Crops
Improvement in corn
A primitive type (left ) still growing on the
eastern slope of the Andes mountains in South
America, Modern hybrid corn (right ).
49
Grains and Vegetable Crops
  • Rice (Oryza sativa)  
  • The basic food for more than half the worlds
    population.
  • One of the oldest cultivated cropsbelieved to
    have originated in southeast Asia about 5,000
    years ago, or even earlier.
  • There are about twenty-five species, but O.
    perennis, is likely the one from which cultivated
    rice was developed.
  • During cultivation, mutations and hybridization
    with other species probably occurred, leading to
    improved forms.
  • Rice was first cultivated in America about 1685.
  • Experiment stations were established by the U.S.
    in the 1900s, and have resulted in many superior
    cultivars being introduced.
  • Hybrid rice is now common in China Southeast
    Asia.
  • A genetically engineered rice has been developed
    that produces beta-carotene increasing the
    nutritional value.

50
Grains and Vegetable Crops
  • Soybean (Glycine max)
  • U.S. soybean production has risen from 5 million
    bushels in 1925 to about 3 billion bushels in
    2008.
  • Partly due to more productive, disease-resistant
    cultivars.
  • From 1910 to 1950, many new strains seed lots
    were brought to the U.S. from the Orient, largely
    by the USDA.
  • Hybridization developed many superior cultivars.
  • High yields, proper bean maturity for the
    particular area.
  • Strong, erect plants that hold their seeds until
    harvest.
  • High disease resistance and bean quality.
  • The soybean is particularly well adapted to the
    U.S. Midwest corn belt and the southeastern
    states.
  • Which together account for about 40 of the
    worlds soybeans.

51
Grains and Vegetable Crops
  • Sugar Beet (Beta vulgaris)
  • The modern sugar beet was developed entirely by
    human efforts in plant breedingour only major
    food crop not grown in some primitive form in
    ancient times.
  • Developed about 250 years ago in Europe to
    compete with very expensive cane sugar.
  • Sugar beets and sugar cane contain the same kind
    of sugar.
  • Breeding and selection increased the sugar
    content in the root from about 2 to about 16 -
    20.
  • By the end of the nineteenth century, sugar beets
    were being grown in North America.
  • They are an important temperate zone crop in many
    areas of the U.S. southern Canadamore so in
    other parts of the world.

52
Grains and Vegetable Crops
  • Potato (Solanum tuberosum) 
  • One of the big four crops that feed the worlds
    population.
  • Wild species are widespread in South America, and
    were likely cultivated in this area more than
    4,000 years ago
  • About 1575, Spanish explorers carried it back to
    Europe, where today 90 worlds potatoes are
    grown.
  • The potato plant produces pink, white, or blue
    flowers that develop into small green berries
    containing seeds.
  • The seeds produce new types of potato plants much
    different from the parent plant and from each
    other in many respects.
  • In early potato culture, the South American
    Indians likely selected superior plant types
    from natural crosses.
  • A single superior plant could be perpetuated and
    increased in great numbers as a clone by tuber
    division.

53
Grains and Vegetable Crops
  • Potato (Solanum tuberosum)
  • Some superior selections propagated by vegetative
    methods became commercially successful cultivars.
  • Certain of these cultivars would degenerate after
    many generations yield only weak unproductive
    plants.
  • These clonal cultivars had become infected with
    viruses that passed along to generation after
    generation.
  • Such viruses do not pass through seed to new
    plantsgrowth is not inhibited by the virus in
    potatoes propogated by seed.
  • In modern commercial potato growing, seed tubers
    or seed potatoes are planted to maintain clonal
    uniformity.
  • Certified seed potatoes are produced by
    commercial growers and strictly inspected by
    state government agencies.

54
Grains and Vegetable Crops
  • Tomato (Lycopersicon esculentum)
  • The cultivated tomato originated from wild forms
    in the PeruEcuadorBolivia area of the Andes
    Mountains.
  • Explorers introduced the tomato to Europe about
    1550.
  • It was brought back west, to the Carolinas, about
    1710.
  • Most people considered the tomato poisonous.
  • U.S. acceptance of it as a food plant began about
    1825.
  • In the early 1900s, USDA state experiment
    stations began breeding cultivars to include
    specific characteristics.
  • Recently introduced cultivars are resistant to
    fusarium wilt, verticillium wilt, and
    nematodesthose developed for machine harvesting
    have firm-fleshed fruits that all ripen at one
    time
  • Vigorous, highly productive F1 hybrids, marketed
    both as seeds bedding plants, are recent
    developments by seed companies.

55
Grains and Vegetable Crops
  • Apple (Malus pumila) 
  • Early colonists likely planted many seedlings
    because it was easier to bring seeds rather than
    material for grafting.
  • They continued to increase their orchards by
    planting seedlings.
  • Certain individual seedling trees were much
    superior to the others formed the starting
    point for many hundreds of cultivars grown in the
    U.S.
  • These numbers dwindled until the 1980s, when 15
    cultivars accounted for over 90 of the apples
    produced in the U.S.
  • All the major apple cultivars now being grown
    originated as chance seedlings many years ago.
  • The McIntosh apple was found growing as a
    seedling tree near Dundela, Ontario, Canada by
    John McIntosh in 1796.
  • The Delicious started as a chance seedling near
    Peru, Iowa.

56
Grains and Vegetable Crops
  • Pear (Pyrus communis)  
  • Cultivars originating as chance seedlings have
    dominated.
  • Te Bartlett originated in England as a chance
    seedling in 1796.
  • No pear cultivar from a controlled breeding
    program in the United States has become
    commercially important.

57
Fruit Crops
  • Peach and Nectarine (Prunis persica)  
  • Important peach and nectarine cultivars grown
    today are the products of public private plant
    breeding programs.

58
Fruit Crops
  • Strawberry (Fragaria x Ananassa)
  • Todays strawberry originated in France about
    1720 as a natural hybrid between two American
    Fragaria species.
  • A number of cultivar selections were made and
    maintained vegetatively by runners in the early
    days of strawberry culture.
  • Early cultivars were susceptible to viruses,
    verticillium wilt, and other diseases and were
    low in productivity.
  • Since World War II, many new cultivars have
    replaced older ones, from USDA state breeding
    programs.
  • New cultivars have been developed for
  • Specific climatic regions.
  • Adaptability of fruits to for freezing or for
    fresh shipping.
  • Resistance to viruses, fungi and to winter cold.
  • Fruit appearance flavor, and extended
    fruit-producing period.

59
Evolution and Darwinism
  • Charles Darwin provided scientific
    explanations of how evolution occurred, published
    in 1859.
  • In Darwins time, nothing was known about
    heredity.
  • Gregor Mendel, in the 1860s, demonstrated the
    genetic mode of plant inheritance.
  • The foundation for the science of genetics.
  • Integration of Darwinian selection and Mendelian
    genetics are now generally accepted as the proper
    explanation of evolution.
  • Many crop scientists have discovered patterns of
    evolution in various crop genera.
  • Breeders have made useful application of this
    knowledge in terms of collecting utilizing
    germplasm resources

60
Evolution and Darwinism
  • Modern breeding programs have produced an array
    of new cultivars for many cropsin what has been
    called directed and accelerated evolution.
  • Since the start of the 20th century, breeding
    programs have had a tremendous beneficial impact
    on our food supply and range of ornamental
    plants.
  • The USDA most state agricultural experiment
    stations in the United States maintain such
    programs.
  • Most new vegetable flower lines are far
    superior in vigor and insect disease
    resistance.
  • New vegetable cultivars are also superior in
    flavor, appearance, and productivity.

61
Evolution and Darwinism
  • By developing plants that show strong resistance
    to insects and disease, plant breeders are
    reducing the need for insecticides and
    fungicides.
  • Plant breeders have a useful procedure for
    obtaining improved plant forms by spontaneous or
    induced mutations from chromosome or gene
    changes.
  • Induced by chemical treatment with colchicine or
    by irradiation with gamma or X-rays.
  • Breeders created a new human-made cereal,
    triticale, by hybridizing, wheat and rye.
  • The name triticale derives from the generic names
    of these two grains Tritium and Secale.

62
Evolution and Darwinism
  • Germplasm is the protoplasm of reproductive cells
    containing the units of heredity.
  • Chromosomes genes.
  • Plant explorers continue their searches for
    germplasm containing useful genes.
  • They have found many plants that have
    subsequently made a major impact on the worlds
    agriculture.
  • Plants moved into a new region often perform much
    better than they did in their original home.

63
Evolution and Darwinism
  • Many early plant collecting trips were
    unsuccessful because the plants did not survive
    the long trip back.
  • Nathanial Ward, invented the Wardian casea small
    glass-enclosed box with soil in the bottom.
  • Plants in a Wardian case could survive long sea
    voyages, allowing importation of species never
    before received alive.
  • Many plant explorers from the U.S. brought back
    plants that would be the foundation for several
    crops.
  • Plant-collecting trips to the native homes of
    certain desirable plant types are still being
    made.

64
Evolution and Darwinism
  • Two international conventions relate to
    promotion of conservation protection of
    biological diversity.
  • The Convention on International Trade in
    Endangered Species of Wild Fauna and Flora
    (CITES).
  • The Convention on Biological Diversity (CBD).
  • Annually, an estimated 500 - 800 billion of
    genetic resources derived products is traded
    globally.
  • Moving plant materials about the world can
    introduce devastating insect or disease pests
    into a country where they have never before
    appeared.
  • To guard against the introduction of such pests,
    most countries have set up elaborate inspection,
    fumigation, and quarantine procedures.

65
Evolution and Darwinism
  • A concerted worldwide effort is needed to ensure
    the survival of the earths endangered plant
    species and thus preserve genetic diversity.
  • In 1998, FAO estimated that 6.1 million
    accessions of food, forage industrial crops had
    been conserved.
  • Genetic diversity of plants, animals and
    microbes, is of fundamental importance to our
    survival.
  • Food and other agricultural crops are derived
    from the genetic diversity of natural plant
    populations.
  • As many as one in ten plant species is now
    extinct or endangered.
  • Such endangered germplasm can be saved stored
    for future use as seeds or living plants in
    protected locations.

66
Broadening the Base of Agricultural Production
  • The worlds peoples are largely fed today by only
    about twenty crops.
  • Reliance on so few crops could lead to a
    catastrophic famine if but a few of them were
    obliterated by insect or disease attacks or by
    climatic changes.
  • Since 1990, crop scientists have met regularly in
    the United States to share information on new
    crops and the potential for new crop development.
  • Looking for solutions to problems like hunger,
    malnutrition, deforestation, desertization, and
    agricultural sustainability.

67
(No Transcript)
About PowerShow.com