unit two Plant Structure, Chemistry, Growth, Development, Genetics, Biodiversity, and Processes

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 toTheophrastus (370–285 bce). • Naming plants began with simple names referringto the plant’s 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 earlythe 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 groups—hardwoods 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. Jeffrey pine (Pinus jeffreyi Grev. and Balf.) in the Sierra Nevada mountains of northern California. Coast redwoods (Sequoia sempervirens D. Don, Endl.) along Highway 101 on “The Avenue of the Giants” in northern California. Figure 10-1 Figure 10-2 Climatic and Related Classifications

9. Common and Botanical Names • Most plants are generally known by their common names—easier 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 discussed—most likely with persons from the same community & the plant name cannot be mistaken.

10. Common names have limitations for universal written or verbal communication. There are too many and they are too variable to serve most scientific purposes. 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 oneanother, and may not beclosely related botanically.

11. Development of Botanical Classifications • Theophrastus (370–285 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 (1707–1778), 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 groups—taxa—based 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 plants—divided 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 Latin—Linnaeus 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 phylla—usually 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; addthe 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 plant’s 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-word—binomial—Latin name, which is international, and understood universally. • The first name refers to the genus; the second, its species. Complete Linnaean names have a third element—authority—the 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; itis underlined if hand- or type-written, italicized in print. • The specific epithet usually begins with a lowercaseletter—but may be capitalized if it is a person’s 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 taxonomybooks 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 chanceof 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 species—wild 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 fromthe 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 cultivars—the 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 theheading 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 SOLANACEAEincludes: 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 shownin the similarities between a potato flower and a tomato flower.

27. OLD NAME NEW NAME asteraceae (compositae) brassicaceae (cruciferae) poaceae (graminae) clusiaceae (guttifereae) lamiaciace (labiate) fabaceae (leguminosae) arecaceae (palmae) apiaceae (umbelliferae) Family • Most families’ names end with -aceae (ace-ay-ee) attached to a genus name, • Eight families did not follow this standard rule, andnew 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 key—rejecting 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 season—when 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 identifysome commonly known seed-bearing plants (Spermatophyta). See the entire table on pages 203-204 of your textbook.

31. Fruits of Taxus baccata L. ‘Lutea’. The single seed (arrow) is within the cuplike fruit, whichis poisonous. Inflorescence of a cycad (Dioon edule Lindl.) native to Mexico. The inflorescence is about 9 in. tall. The pinnate leaves might erroneously lead one to call this plant a palm. Figure 10-7 Figure 10-8 Plant Identification Key Examples of hard-to-classify plants.

32. Figure 10-9 Cotton (Gossypium hirsutum L.) flower in a longitudinal section. Plant Identification Key Examples of hard-to-classify plants.

33. A strawberry flower in a longitudinal section. Also shown is an individual achene. Figure 10-10 Plant Identification Key Examples of hard-to-classify plants.

34. Origin of Cultivated Plants • Most crop plants important today were cultivatedin 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 Plants—translated 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 Turkey–Iran region; The Mediterranean area. • The Ethiopia–Somaliland area of east Africa. • Mexico and Central America • The Peru–Ecuador–Bolivia and Brazil–Paraguay 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 4000—farming 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 suchas 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 year’s crop. • In cereals, this procedure starts to separate the “shattering” types—the seed separates from the head—from 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 numbersand larger inflorescences. • Trends toward determinate growth.

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

43. Grains and Vegetable Crops • Wheat(Triticum aestivumand 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, whichcan 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 aestivumand 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 aestivum—used 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 tosave their seeds for future planting. • Wheat has perfect (bisexual) flowers, making crosspollination 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 plant—there isno wild form except, apparently, teosinte, a close relative. • Economic life of the ancient American civilizations—the Aztecs, Mayas, and Incas—depended on corn. • At the time of Columbus’s 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 underthe 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 ofthe outstanding achievements of modern agriculture. • In 1935, 1% of corn planted in the U.S. was of the hybridtype—by 1970, almost all corn produced was hybrid. • Hybrid cultivars, along with fertilizers, irrigation, and mechanization, dramatically improved production. • Corn is now one of the world’s chief food crops. • Specialty corns—such as white, waxy, hard endosperm food grade, high oil, nutritionally enhanced, high amylase and high extractable starch corn—are being developed. • Ethanol production from high-starch corn as a replacementfor some petroleum fuels has become a major use of corn.

48. The primitive type contains a valuable trait—multiple-aleurone layers in the grain—transferred by plant breeders to modern dent corn. This example illustrates the needfor maintaining the germplasm of seemingly worthless plant types. Grains and Vegetable Crops Improvement in corn A primitive type (left ) still growingon 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 world’s population. • One of the oldest cultivated crops—believed 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 world’s soybeans.