Plants

1. Plants Diversity, Structure, and Function

2. Introduction Plants are the most dominant life forms on this earth. Without them no life would exist, they are the basis of all life. 280,000 species of plants inhabit Earth today. Most plants live in terrestrial environments, including deserts, grasslands, and forests. Some species, such as sea grasses, have returned to aquatic habitats. Land plants (including the sea grasses) evolved from a green algae four main groups of land plants: bryophytes, pteridophytes, gymnosperms, and angiosperms.

3. Cont� most common bryophytes are mosses. The pteridophytes include ferns. The gymnosperms include pines and other conifers. The angiosperms are the flowering plants

4. Vascular and Non-Vascular Mosses and other bryophytes have evolved several adaptations. For example, the offspring develop from multicellular embryos that remain attached to the �mother� plant which protects and nourished the embryos. The other major groups of land plants evolved vascular tissue and are known as the vascular plants. In vascular tissues, cells join into tubes that transport water and nutrients throughout the plant body. Most bryophytes lack water-conducting tubes and are sometimes referred to as �nonvascular plants Ferns and other pteridiophytes are sometimes called seedless plants because there is no seed stage in their life cycles.

5. Seed Development evolution of the seed in an ancestor common to gymnosperms and angiosperms facilitated reproduction on land. A seed consists of a plant embryo packaged along with a food supply within a protective coat. The first seed plants evolved about 360 million years ago, near the end of the Devonian. The early seed plants gave rise to the diversity of present-day gymnosperms, including conifers majority of modern-day plant species are flowering plants, or angiosperms. Flowers evolved in the early Cretaceous period, about 130 million years ago. A flower is a complex reproductive structure that bears seeds within protective chambers called ovaries

6. Evolution four great episodes in the evolution of land plants: the origin of bryophytes from algal ancestors the origin and diversification of vascular plants the origin of seeds the evolution of flowers

7. The Green Algae Connection Plants are multicellular, eukaryotic, photosynthetic autrotrophs. But red and brown seaweeds also fit this description. Land plants have cells walls made of cellulose and chlorophyll a and b in chloroplasts. However, several algal groups have cellulose cell walls and others have both chlorophylls. Land plants connected to green algae in 2 ways 1. Both possess rosette cellulose-synthesizing complexes that synthesize the cellulose microfibrils of the cell wall. 2. presence of peroxisomes, help minimize the loss of organic products due to photorespiration.

8. Separation From Green Algae 1. apical meristems 2. multicellular embryos dependent on the parent plant 3. alternation of generations 4. sporangia that produce walled spores 5. gametangia that produce gametes resources that a photosynthetic organism requires are found in 2 diff. places. Light and carbon dioxide are mainly aboveground. Water and mineral resources are found mainly in the soil. The elongation and branching of the shoots and roots maximize their exposure to environmental resources. This growth is sustained by apical meristems, localized regions of cell division at the tips of shoots and roots.

9. Cont� Multicellular plant embryos develop from zygotes that are retained within tissues of the female parent. parent provides nutrients, such as sugars and amino acids, to the embryo.

10. Cont�. All land plants show alternation of generations in which two multicellular body forms alternate One of the multicellular bodies is called the gametophyte with haploid cells. Gametophytes produce gametes, egg and sperm. Fusion of egg andsperm duringfertilizationform a diploidzygote.

11. Cont� Mitotic division of the diploid zygote produces the other multicellular body, the sporophyte. Meiosis in a mature sporophyte produces haploid reproductive cells called spores. A spore is a reproductive cell that can develop into a new organism without fusing with another cell. Mitotic division of a plant spore produces a new multicellular gametophyte. humans do not have alternation of generations because the only haploid stage in the life cycle is the gamete, which is single-celled.

12. Cont� Multicellular organs, called sporangia, are found on the sporophyte and produce these spores. Within a sporangia, diploid spore mother cells undergo meiosis and generate haploid spores. The outer tissues of the sporangium protect the developing spores until they are ready to be released into the air

13. Cont� gametophytes of bryophytes, pteridophytes, and gymnosperms produce their gametes within multicellular organs, called gametangia. A female gametangium, called an archegonium, produces a single egg cell in a vase-shaped organ

14. Other Adaptations adaptations for acquiring, transporting, and conserving water, adaptations for reducing the harmful effect of UV radiation, adaptations for repelling terrestrial herbivores and resisting pathogens. epidermis of leaves and other aerial parts is coated with a cuticle of polyesters and waxes. The cuticle protects the plant from microbial attack. The wax acts as waterproofing to prevent excessive water loss.

15. Cont� Pores, called stomata, in the epidermis of leaves and other photosynthetic organs allow the exchange of carbon dioxide and oxygen between the outside air and the leaf interior. Stomata are also the major sites for water to exit from leaves via evaporation. Changes in the shape of the cells, guard cells, bordering the stomata can close the pores to minimize water loss in hot, dry conditions.

16. Cont� Except for bryophytes, land plants have true roots, stems, and leaves, which are defined by the presence of vascular tissues. Vascular tissue transports materials among these organs. Tube-shaped cells, called xylem, carry water and minerals up from roots. When functioning, these cells are dead, with only their walls providing a system of microscopic water pipes. Phloem is a living tissue in which nutrient-conducting cells arranged into tubes distribute sugars, amino acids, and other organic products

17. Xylem and Phloem

18. Cont� Land plants produce many unique molecules called secondary compounds Examples of secondary compounds in plants include alkaloids, terpenes, tannins, and phenolics such as Flavonoids. Various secondary compounds have bitter tastes, strong odors, or toxic effects that help defend land plants against herbivorous animals or microbial attack. Flavonoids absorb harmful UV radiation. Lignin, a phenolic polymer, hardens the cell walls of �woody� tissues in vascular plants, providing support for even the tallest of trees

19. Those Smart Humans Humans have found many applications, including medicinal applications, for secondary compounds extracted from plants. For example, the alkaloid quinine helps prevent malaria. Other Chemicals used in perfumes ect�. Up to 40% of medications are plant derived Ex. Asprin from the bark of a Willow tree

20. Origin and Evolution of Plants Several lines of evidence support the phylogenetic connection between land plants and green algae, especially the charophyceans, including: homologous chloroplasts, homologous cell walls, homologous peroxisomes, phragmoplasts, homologous sperm, and molecular systematics. Homologous chloroplasts - The chloroplasts of land plants are most similar to the plastids of green algae and of eulgenoids which acquired green algae as secondary endosymbionts. Similarities include the presence of chlorophyll b and beta-carotene and thylakoids stacked as grana. Comparisons of chloroplast DNA with that of algal plastids place the charophyceans as most closely related to land plants.

21. Cont� Homologous cellulose walls - In both land plants and charophycean algae, cellulose comprises 20-26% of the cell wall. Also, both share cellulose-manufacturing rosettes. Homologous peroxisomes - Both land plants and charophycean algae package enzymes that minimize the costs of photorespiration in peroxisomes. Phagmoplasts - These plate-like structures occur during cell division only in land plants and charopyceans. Many plants have flagellated sperm, which match charophycean sperm closely in ultrastructure.

22. Cont� Molecular systematics - similarities derived from comparing chloroplast genes, analyses of several nuclear genes also provide evidence of a charophycean ancestry of plants. In fact, the most complex charophyceans appear to be the algae most closely related to land plants. All available evidence upholds the hypothesis that modern charophyceans and land plants evolved from a common ancestor. oldest known traces of land plants are found in mid-Cambrian rocks from about 550 million years ago.

23. Look

24. Bryophytes represented by 3 phyla: Hepatophyta � liverworts, Anthocerophyta � hornworts, Bryophyta � mosses diverse bryophytes are not a monophyletic group. Several lines of evidence indicate that these three phyla diverged independently early in plant evolution

25. Cont.. gametophyte is the dominant generation in the life cycles of bryophytes Bryophytes are anchored by tubular cells or filaments of cells, called rhizoids. Rhizoids are not composed of tissues. They lack specialized conducting cells. do not play a primary role in water and mineral absorption. Most bryophytes lack conducting tissues to distribute water and organic compounds within the gametophyte. Those with specialized conducting tissues lack the lignin coating found in the xylem of vascular plants. Lacking support tissues, most bryophytes are only a few centimeters tall.

26. Cont� gametophytes of mosses and some liverworts are more �leafy� because they have stemlike structures that bear leaflike appendages. They are not true stems or leaves because they lack lignin-coated vascular cells. The �leaves� of most mosses lack a cuticle and are only once cell thick, features that enhance water and mineral absorption from the moist environment. Some mosses have more complex �leaves� with ridges to enhance absorption of sunlight. ridges are coated with cuticle. Some mosses have conducting tissues in their stems and can grow as tall as 2m. See Pic Next Slide

27. Cont�

28. Life Cycle

29. Cont�. Moss sporophytes consist of a foot, an elongated stalk (the seta), and a sporangium (the capsule). The foot gathers nutrients and water from the parent gametophyte via transfer cells. The moss capsule (sporangium) is the site of meiosis and spore production. One capsule can generate over 50 million spores Wind dispersal of lightweight spores has distributed bryophytes around the world. They are common and diverse in moist forests and wetlands. Some even inhabit extreme environments like mountaintops, tundra, and deserts. Mosses can loose most of their body water and then rehydrate and reactivate their cells when moisture again becomes available.

30. Cont� Sphagnum, a wetland moss, is especially abundant and widespread Sphagnum has been used in the past as diapers and a natural antiseptic material for wounds Bryophytes were probably Earth�s only plants for the first 100 million years that terrestrial communities existed. Then vegetation began to take on a taller profile with the evolution of vascular plants.

31. Vascular Plants Modern vascular plants (pteridophytes, gymnosperms, and angiosperms) have food transport tissues (phloem) and water conducting tissues (xylem) with lignified cells The first vascular plants, pteridophytes, were seedless. Cooksonia, an extinct plant over 400 million years old, is the earliest known vascular plant. Its fossils are found in Europe and North America. The branched sporophytes were up to 50cm tall with small lignified cells, much like the xylem cells of modern pteridophytes.

32. Pteridophytes Are seedless vascular plants consists of two modern phyla:Lycophyta � lycophytes, Pterophyta - ferns, whisk ferns, and horsetails probably evolved from different ancestors among the early vascular plants have true roots with lignified vascular tissue. uncertain if the roots of seed plants arose independently or are homologous to pteridophyte roots.

33. Cont.. the sporophyte generation is the larger and more complex plant. the leafy fern plants that you are familiar with are sporophytes. The gametophytes are tiny plants that grow on or just below the soil surface. reduction in the size of the gametophytes is even more extreme in seed plants. Ferns also demonstrate a key variation among vascular plants: the distinction between homosporous and heterosporous plants. A homosporous sporophyte produces a single type of spore.

34. Cont� This spore develops into a bisexual gametophyte with both archegonia (female sex organs) and antheridia (male sex organs). A heterosporous sporophyte produces two kinds of spores. Megaspores develop into females gametophytes. Microspores develop into male gametophytes. Regardless of origin, the flagellated sperm cells of ferns, other seedless vascular plants, and even some seed plants must swim in a film of water to reach eggs. Because of this, seedless vascular plants are most common in relatively damp habitats.

35. Life Cycle

36. Lycophyta Phylum Lycophyta - Modern lycophytes are relicts of past. By the Carboniferous period, lycophytes existed as either small, herbaceous plants or as giant woody trees with diameters of over 2m and heights over 40m. The giant lycophytes thrived in warm, moist swamps, but became extinct when the climate became cooler and drier. The smaller lycophytes survived and are represented by about 1,000 species today. Modern lycophytes include tropical species that grow on trees as epiphytes, using the trees as substrates, not as hosts. Others grow on the forest floor in temperate regions.

37. Pterophyta phylum Pterophyta consists of ferns and their relatives. Psilophytes, the whisk ferns, used to be considered a �living fossil, but comparisons of DNA sequences and ultrastructural details, indicate that the lack of true roots and leaves evolved secondarily. Sphenophytes are commonly called horsetails because of their often brushy appearance. During the Carboniferous, sphenophytes grew to 15m, but today they survive as about 15 species in a single wide-spread genus, Equisetum. Horsetails are often found in marshy habitats and along streams and sandy roadways

38. Wisk Fern�Horsetail

39. Ferns first appeared in the Devonian and have radiated extensively until there are over 12,000 species today. Ferns are most diverse in the tropics but are also found in temperate forests and even arid habitats. Fern leaves or fronds may be divided into many leaflets.

40. Dead Plant Energy Lycophyta and Pterophyta formed forests during the Carboniferous period about 290-360 million years ago. These plants left not only living represent-atives and fossils, but also fossil fuel in the form of coal.

41. Plants With Seeds The evolution of plants is highlighted by two important landmarks: (1) the evolution of seeds, which lead to the gymnosperms and angiosperms, the plants that dominate most modern landscapes (2) the emergence of the importance of seed plants to animals, specifically to humans. Agriculture, the cultivation and harvest of plants (primarily seed plants), began approximately 10,000 years ago in Asia, Europe, and the Americas. This was the single most important cultural change in the history of humanity, for it made possible the transition from hunter-gather societies to permanent settlements.

42. Cont�. Seed plants are vascular plants that produce seeds. 3 important reproductive adaptations: continued reduction of the gametophyte the advent of the seed the evolution of pollen. gametophytes of seed plants are even more reduced than those of seedless vascular plants such as ferns. delicate female gametophyte and young embryos are protected from many environmental stresses because they are retained within the moist sporangia of the parental sporophyte.

43. Small Gametophytes

44. Seed Development Spores were the main way that plants spread over Earth for the first 200 millions years of life on land seed represents a different solution to resisting harsh environments and dispersing offspring. seed consists of a sporophyte embryo packaged along with a food supply within a protective coat All seed plants are heterosporous, producing 2 different types of sporangia that produce two types of spores. Megasporangia produce megaspores, which give rise to female (egg-containing) gametophytes. Microsporangia produce microspores, which give rise to male (sperm-containing) gametophytes.

45. Seed Cont.. seed�s protective coat is derived from the integuments of the ovule. Within this seed coat, a seed may remain dormant for days, months, or even years until favorable conditions trigger germination. When the seed is eventually released from the parent plant, it may be close to the parent, or be carried off by wind or animals.

46. Pollen: No More Water microspores, released from the microsporangium, develop into pollen grains. These are covered with a tough coat They are carried away by wind or animals until pollination occurs when they land in the vicinity of an ovule. The pollen grain will elongate a tube into the ovule and deliver one or two sperm into the female gametophyte In bryophytes and pteridophytes, flagellated sperm must swim through a film of water to reach eggs cells The evolution of pollen in seed plants led to even greater success and diversity of plants on land.

47. 2 Types of Seed Plants gymnosperms and angiosperms most familiar gymnosperms are the conifers, the cone-bearing plants such as pines. The ovules and seeds of gymnosperms (�naked seeds�) develop on the surfaces of specialized leaves called sporophylls. In contrast, ovules and seeds of angiosperms develop in enclosed chambers (ovaries). Gymnosperms appears in the fossil record much earlier than angiosperms descended from progymnosperms, a group of Devonian plants. earliest progymnosperms lacked seeds, by the end of the Devonian, some species had evolved seeds.

48. Gymnosperms Cont� Adaptive radiation during the Carboniferous and early Permian produced the various phyla of gymnosperms. flora and fauna of Earth changed during the formation of the supercontinent Pangaea in the Permian. This likely led to major environmental changes, including drier and warmer continental interiors. Many groups of organisms disappeared and others emerged as their successors.Ex. amphibians decreased in diversity while reptiles increased. lycophytes, horsetails, and ferns that dominated in Carboniferous swamps were largely replaced by gymnosperms, which were more suited to the drier climate.

49. Cont� 4 phyla of extant gymnosperms are ginko, cycads, gnetophytes, and conifers

50. Phylum Ginkgophyta consists of only a single extant species, Ginkgo biloba. popular ornamental species has fanlike leaves that turn gold before they fall off in the autumn. Landscapers usually only plant male trees because the seed coats on female plants decay, they produce a repulsive odor (to humans, at least).

51. Phylum Cycadophyta Have palm like leaves, but are not palms

52. Phylum Gnetophyta Phylum Gnetophyta consists of three very different genera. Weltwitschia plants, from deserts in southwestern Africa, have straplike leaves. Gentum species are tropical trees or vines. Ephedra (Mormon tea) is a shrub of the American deserts.

53. Phylum Coniferophyta The term conifer comes from the reproductive structure, the cone. about 550 species of conifers include pines, firs, spruces, larches, yews, junipers, cedars, cypresses, and redwoods, up to and over 100 meters tall. 1994 the Wollemi pine was found in the rain forest of Sydney, Australia. It was thought extinct for over 100 million years The bristlecone pines in the Rockies are about 5000 years old. Most conifers are evergreen, retaining their leaves and photosynthesizing throughout the year

54. Conifer Pics

55. Pine Tree

56. Angiosperms better known as flowering plants, are vascular seed plants that produce flowers and fruits. They are by far the most diverse and geographically widespread of all plants. There are abut 250,000 known species of angiosperms. placed in a single phylum, the phylum Anthophyta. As late as the 1990s, most plant taxonomists divided the angiosperms into two main classes, the monocots and the dicots. Cotyledon-seed leaf Most monocots have leaves with parallel veins, while most dicots have netlike venation

57. Monocot and Dicot

58. Cont�

59. Why So Much Better Then Gymnosperms Refinements in vascular tissue, especially xylem, probably played a role in the enormous success of angiosperms in diverse terrestrial habitats. reproductive adaptations associated with flowers and fruits contributed the most. Flowers- reproductive structures that produce pollen and seeds. 1st appeared 130 mya they made reproduction much more efficient now it is not just the random chance of wind now plants could attract many different animals and get them to pollinate for them. Pretty smart!!!! And Done Many Different Ways!!!!!!!! Some relationships are specific Ex. Darwin

60. Parts Of A Flower

61. Fruit fruit is a mature ovary. As seeds develop from ovules after fertilization, the wall of the ovary thickens to form the fruit. Fruits protect dormant seeds and aids in their dispersal Pass through an animals digestive tract unharmed and conveniently land in a pile of fertilizer some time later Various modifications in fruits help disperse seeds. In some plants, such as dandelions and maples, the fruit functions like a kite or propeller, enhancing wind dispersal. Many angiosperms use animals to carry seeds. Fruits may be modified as burrs that cling to animal fur. Edible fruits are eaten by animals

62. Fruits

63. Fruit Classification

64. We Still Rely on Fruit selectively breeding plants, humans have capitalized on the production of edible fruits. Apples, oranges, and other fruits in grocery stores are exaggerated versions of much smaller natural varieties of fleshy fruits. The staple foods for humans are the dry, wind-dispersed fruits of grasses. These are harvested while still on the parent plant. The cereal grains of wheat, rice, corn, and other grasses are actually fruits with a dry pericarp that adheres tightly to the seed coat of the single seed inside

66. Angiosperms Coevolved With Animals Ever since they colonized the land, animals have influenced the evolution of terrestrial plants and vice versa. The fact that animals must eat affects the natural selection of both animals and plants. Natural selection must have favored plants that kept their spores and gametophytes far above the ground, rather than dropping them within the reach of hungry ground animals. In turn, this may have been a selective factor in the evolution of flying insects

67. Cont� some herbivores may have become beneficial to plants by carrying the pollen and seeds of plants that they used as food. Natural selection reinforced these interactions, for they improved the reproductive success of both partners. Pollinator-plant relationships are partly responsible for the diversity of flowers

68. Dependence Flowering plants provide nearly all our food. All of our fruit and vegetable crops are angiosperms. Corn, rice, wheat, and other grain are grass fruits grow angiosperms for fiber, medications, perfumes, and decoration. Agriculture allowed us to stay in one place and move from a hunter-gather society Building Materials---at a cost---As the forests disappear, thousand of plants species and the animals that depend on these plants also go extinct.

69. Destruction

70. Medicines We have explored the potential uses for only a tiny fraction of the 250,000 known plant species

71. Structures and Functions plant body consists of organs that are composed of different tissues, and these tissues are teams of different cell types 3 basic organs: roots, stems, and leaves Plants must simultaneously inhabit and draw resources from two very different environments So a subterranean root system and an aerial shoot system of stems and leaves are the answer Both systems depend on the other-- Lacking chloroplasts and living in the dark, roots would starve without the sugar and other organic nutrients imported from the photosynthetic tissues of the shoot system. Conversely, the shoot system depends on water and minerals absorbed from the soil by the roots

72. Monocot---Dicot

74. 3 Tissue System dermal, vascular, and ground tissue systems dermal tissue, or epidermis, is generally a single layer of tightly packed cells that covers and protects has other specialized characteristics consistent with the function the roots hairs are extensions of epidermal cells The epidermis of leaves and most stems secretes a waxy coating, the cuticle, that helps the plant retain water.

75. Cont�. Vascular tissue, continuous throughout the plant, is involved in the transport of materials water conducting elements of xylem, the tracheids and vessel elements, are elongated cells that are dead at functional maturity Tracheids are long, thin cells with tapered ends. Water moves from cell to cell mainly through pits. walls are hardened with lignin, tracheids function in support as well as transport. Vessel elements are aligned end to end, forming long micropipes, xylem vessels phloem, sucrose, other organic compounds, and some mineral ions move through tubes formed by chains of cells, sieve-tube members

76. Cont.. Ground tissue is tissue that is neither dermal tissue nor vascular tissue divided into pith, internal to vascular tissue, and cortex, external to the vascular tissue functions of ground tissue include photosynthesis, storage, and support

78. Phloem

79. Plant Tissue---3Cell Types parenchyma, collenchyma, and sclerenchyma distinguishing characteristics may be present in the protoplast, the cell contents exclusive of the cell wall. parenchyma cells have primary walls that are relatively thin and flexible, and most lack secondary walls they generally are the least specialized, but there are exceptions sieve-tube members of the phloem are parenchyma cells. perform most of the metabolic functions of the plant, synthesizing and storing various organic products fleshy tissue of most fruit is composed of parenchyma cells

80. Cont� parenchyma cells do not generally undergo cell division. Most retain the ability to divide and differentiate into other cell types under special conditions - during the repair and replacement of organs after injury to the plant. In the laboratory, it is possible to regenerate an entire plant from a single parenchyma cell Collenchyma cells have thicker primary walls than parenchyma cells Grouped into strands or cylinders, collenchyma cells help support young parts of the plant shoot cells are living and flexible and elongate with the stems and leaves they support

81. Cont� Sclerenchyma cells also function as supporting elements of the plant, with thick secondary walls usually strengthened by lignin cannot elongate and occur in plant regions that have stopped lengthening Many sclerenchyma cells are dead at functional maturity Vessel elements and tracheids in the xylem are sclerenchyma cells fibers and sclereids, are specialized entirely in support. Fibers are long, slender and tapered, and usually occur in groups. Those from hemp fibers are used for making rope and those from flax for weaving into linen. Sclereids, shorter than fibers and irregular in shape, impart the hardness to nutshells and seed coats

82. Growth and Development has perpetually embryonic tissues called meristems in its regions of growth Apical meristems, located at the tips of roots and in the buds of shoots, supply cells for the plant to grow in length. elongation, primary growth--- secondary growth, progressive thickening of roots and shoots Secondary growth is the product of lateral meristems extending along the length of roots and shoots. root tip is covered by a thimble-like root cap, which protects the meristem as the root pushes through the abrasive soil

84. Cont.. primary meristems: the protoderm, procambium, and ground meristem will produce the three primary tissue systems of the root: dermal, vascular, and ground tissues epidermis develops from the dermal tissues. ground tissue produces the endodermis and cortex. The vascular tissue produces the stele, the pericycle, pith, xylem, and phloem. stele, which in roots is a central cylinder of vascular tissue where both xylem and phloem develop ground tissue between the protoderm and procambium gives rise to the ground tissue system They store food and are active in the uptake of minerals innermost layer of the cortex, the endodermis

85. root may sprout lateral roots from the outermost layer of stele, the pericycle

86. Cont� secondary plant body consists of the tissues produced during this secondary growth in diameter. The vascular cambium acts as a meristem for the production of secondary xylem and secondary phloem. The cork cambium acts as a meristem for a tough thick covering for stems and roots that replaces the epidermis like bark on a tree

88. References Jack Brown M.S. Biology Microsoft Encarta Encyclopedia 2004 Starr and Taggart: The Unity and Diversity of Life 10th edition: 2004: Thomson Brookes/Cole Campbell and Reece: Biology 6th edition: 2002: Benjamin Cummings. Raven and Johnson: Holt Biology: 2004: Holt, Rinehart and Winston.