29 plants ii text

The evolutionary view of origin of plants! ,[object Object],[object Object],[object Object],[object Object],[object Object]

Genetic Evidence ,[object Object],[object Object],Chara , a pond organism (a) 10 mm Coleochaete orbicularis , a disk- shaped charophycean (LM) (b) 40 µm Figure 29.3a, b

Defining the Plant Kingdom ,[object Object],[object Object],Plantae Streptophyta Viridiplantae Red algae Chlorophytes Charophyceans Embryophytes Ancestral alga Figure 29.4

Derived Traits of Plants ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],APICAL MERISTEMS Apical meristem of shoot Developing leaves 100 µm Apical meristems of plant shoots and roots . The light micrographs are longitudinal sections at the tips of a shoot and root. Apical meristem of root Root 100 µm Shoot Figure 29.5 Haploid multicellular organism (gametophyte) Mitosis Mitosis Gametes Zygote Diploid multicellular organism (sporophyte) Alternation of generations: a generalized scheme MEIOSIS FERTILIZATION 2 n 2 n n n n n n Spores Mitosis ALTERNATION OF GENERATIONS

[object Object],WALLED SPORES PRODUCED IN SPORANGIA MULTICELLULAR GAMETANGIA MULTICELLULAR, DEPENDENT EMBRYOS Spores Sporangium Longitudinal section of Sphagnum sporangium (LM) Sporophyte Gametophyte Sporophyte and sporangium of Sphagnum (a moss) Female gametophyte Archegonium with egg Antheridium with sperm Male gametophyte Archegonia and antheridia of Marchantia (a liverwort) Embryo Maternal tissue 2 µm Wall ingrowths Placental transfer cell 10 µm Embryo and placental transfer cell of Marchantia Figure 29.5

[object Object],[object Object],Fossilized spores. Unlike the spores of most living plants, which are single grains, these spores found in Oman are in groups of four (left; one hidden) and two (right). (a) Fossilized sporophyte tissue. The spores were embedded in tissue that appears to be from plants. (b) Figure 29.6 a, b

[object Object],[object Object],An overview of land plant evolution Land plants can be informally grouped based on the presence or absence of vascular Table 29.1

Bryophytes (nonvascular plants) Seedless vascular plants Seed plants Vascular plants Land plants Origin of seed plants (about 360 mya) Origin of vascular plants (about 420 mya) Origin of land plants (about 475 mya) Ancestral green alga Charophyceans Liverworts Hornworts Mosses Lycophytes (club mosses, spike mosses, quillworts) Pterophyte (ferns, horsetails, whisk fern) Gymnosperms Angiosperms

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[object Object],Mature sporophytes Young sporophyte Male gametophyte Raindrop Sperm Key Haploid ( n ) Diploid (2 n ) Antheridia Female gametophyte Egg Archegonia FERTILIZATION (within archegonium) Zygote Archegonium Embryo Female gametophytes Gametophore Foot Capsule (sporangium) Seta Peristome Spores Protonemata “ Bud” “ Bud” MEIOSIS Sporangium Calyptra Capsule with peristome (LM) Rhizoid Mature sporophytes Spores develop into threadlike protonemata. 1 The haploid protonemata produce “buds” that grow into gametophytes. 2 Most mosses have separate male and female gametophytes, with antheridia and archegonia, respectively. 3 A sperm swims through a film of moisture to an archegonium and fertilizes the egg. 4 Meiosis occurs and haploid spores develop in the sporangium of the sporophyte. When the sporangium lid pops off, the peristome “teeth” regulate gradual release of the spores. 8 The sporophyte grows a long stalk, or seta, that emerges from the archegonium. 6 The diploid zygote develops into a sporophyte embryo within the archegonium. 5 Attached by its foot, the sporophyte remains nutritionally dependent on the gametophyte. 7 Figure 29.8

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Bryophyte Sporophytes ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],LIVERWORTS (PHYLUM HEPATOPHYTA) HORNWORTS (PHYLUM ANTHOCEROPHYTA) MOSSES (PHYLUM BRYOPHYTA) Gametophore of female gametophyte Marchantia polymorpha , a “thalloid” liverwort Foot Sporangium Seta 500 µm Marchantia sporophyte (LM) Plagiochila deltoidea , a “leafy” liverwort An Anthoceros hornwort species Sporophyte Gametophyte Polytrichum commune , hairy-cap moss Sporophyte Gametophyte Figure 29.9

Ecological and Economic Importance of Mosses ,[object Object],[object Object],[object Object],“ Tolland Man,” a bog mummy dating from 405–100 B.C. The acidic, oxygen-poor conditions produced by Sphagnum canpreserve human or other animal bodies for thousands of years. Gametophyte Sporangium at tip of sporophyte Living photosynthetic cells Dead water- storing cells 100 µm Closeup of Sphagnum . Note the “leafy” gametophytes and their offspring, the sporophytes. (b) Sphagnum “leaf” (LM). The combination of living photosynthetic cells and dead water-storing cells gives the moss its spongy quality. (c) Peat being harvested from a peat bog (a) Figure 29.10 a–d (d)

Life Cycles with Dominant Sporophytes ,[object Object],[object Object],[object Object]

Sporophyte dominance ,[object Object],Fern sperm use flagella to swim from the antheridia to eggs in the archegonia. 4 Sporangia release spores. Most fern species produce a single type of spore that gives rise to a bisexual gametophyte. The fern spore develops into a small, photosynthetic gametophyte. 2 Although this illustration shows an egg and sperm from the same gametophyte, a variety of mechanisms promote cross-fertilization between gametophytes. 3 On the underside of the sporophyte‘s reproductive leaves are spots called sori. Each sorus is a cluster of sporangia. 6 A zygote develops into a new sporophyte, and the young plant grows out from an archegonium of its parent, the gametophyte. 5 MEIOSIS Sporangium Sporangium Mature sporophyte New sporophyte Zygote FERTILIZATION Archegonium Egg Haploid ( n ) Diploid (2 n ) Spore Young gametophyte Fiddlehead Antheridium Sperm Gametophyte Key Sorus Figure 29.12 1

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Evolution of Roots ,[object Object],[object Object],[object Object],[object Object]

Evolution of Leaves ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],Vascular tissue Microphylls, such as those of lycophytes, may have originated as small stem outgrowths supported by single, unbranched strands of vascular tissue. (a) Megaphylls, which have branched vascular systems, may have evolved by the fusion of branched stems. (b) Figure 29.13a, b

Sporophylls and Spore Variations ,[object Object],[object Object],[object Object],[object Object]

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Classification of Seedless Vascular Plants ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],LYCOPHYTES (PHYLUM LYCOPHYTA) PTEROPHYTES (PHYLUM PTEROPHYTA) WHISK FERNS AND RELATIVES HORSETAILS FERNS Isoetes gunnii , a quillwort Selaginella apoda , a spike moss Diphasiastrum tristachyum , a club moss Strobili (clusters of sporophylls) Psilotum nudum, a whisk fern Equisetum arvense, field horsetail Vegetative stem Strobilus on fertile stem Athyrium filix-femina , lady fern Figure 29.14

The Significance of Seedless Vascular Plants ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],Figure 30.1

Advantages of Reduced Gametophytes ,[object Object],[object Object]

[object Object],Figure 30.2a–c Microscopic female gametophytes ( n ) in ovulate cones (dependent) Sporophyte (2 n ), the flowering plant (independent) Microscopic male gametophytes ( n ) inside these parts of flowers (dependent) Microscopic male gametophytes ( n ) in pollen cones (dependent) Sporophyte (2 n ) (independent) Microscopic female gametophytes ( n ) inside these parts of flowers (dependent) Gametophyte ( n ) Gametophyte ( n ) Sporophyte (2 n ) Sporophyte (2 n ) Sporophyte dependent on gametophyte (mosses and other bryophytes). (a) Large sporophyte and small, independent gametophyte (ferns and other seedless vascular plants). (b) Reduced gametophyte dependent on sporophyte (seed plants: gymnosperms and angiosperms). (c)

Heterospory: The Rule Among Seed Plants ,[object Object],[object Object],[object Object],[object Object]

Ovules and Production of Eggs ,[object Object],[object Object],Figure 30.3a (a) Unfertilized ovule. In this sectional view through the ovule of a pine (a gymnosperm), a fleshy megasporangium is surrounded by a protective layer of tissue called an integument. (Angiosperms have two integuments.) Integument Spore wall Megasporangium (2 n ) Megaspore ( n )

Pollen and Production of Sperm ,[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],Figure 30.3b (b) Fertilized ovule. A megaspore develops into a multicellular female gametophyte. The micropyle, the only opening through the integument, allows entry of a pollen grain. The pollen grain contains a male gametophyte, which develops a pollen tube that discharges sperm. Spore wall Male gametophyte (within germinating pollen grain) ( n ) Female gametophyte ( n ) Egg nucleus ( n ) Discharged sperm nucleus ( n ) Pollen grain ( n ) Micropyle

The Evolutionary Advantage of Seeds ,[object Object],[object Object],[object Object],Figure 30.3c Gymnosperm seed. Fertilization initiates the transformation of the ovule into a seed, which consists of a sporophyte embryo, a food supply, and a protective seed coat derived from the integument. (c) Seed coat (derived from Integument) Food supply (female gametophyte tissue) ( n ) Embryo (2 n ) (new sporophyte)

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[object Object],Figure 30.4 Gnetum Ephedra Ovulate cones Welwitschia PHYLUM GNETOPHYTA PHYLUM CYCADOPHYTA PHYLUM GINKGOPHYTA Cycas revoluta

[object Object],Figure 30.4 PHYLUM CYCADOPHYTA Douglas fir Pacific yew Common juniper Wollemia pine Bristlecone pine Sequoia

Gymnosperm Evolution ,[object Object],[object Object],Figure 30.5

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A Closer Look at the Life Cycle of a Pine ,[object Object],[object Object],[object Object],[object Object]

[object Object],Figure 30.6 Ovule Megasporocyte (2 n ) Integument Longitudinal section of ovulate cone Ovulate cone Pollen cone Mature sporophyte (2 n ) Longitudinal section of pollen cone Microsporocytes (2 n ) Pollen grains ( n ) (containing male gametophytes) MEIOSIS Micropyle Germinating pollen grain Megasporangium MEIOSIS Sporophyll Microsporangium Surviving megaspore ( n ) Germinating pollen grain Archegonium Integument Egg ( n ) Female gametophyte Germinating pollen grain ( n ) Discharged sperm nucleus ( n ) Pollen tube Egg nucleus ( n ) FERTILIZATION Seed coat (derived from parent sporophyte) (2 n ) Food reserves (gametophyte tissue) ( n ) Embryo (new sporophyte) (2 n ) Seeds on surface of ovulate scale Seedling Key Diploid (2 n ) Haploid ( n ) A pollen cone contains many microsporangia held in sporophylls. Each microsporangium contains microsporocytes (microspore mother cells). These undergo meiosis, giving rise to haploid microspores that develop into pollen grains. 3 In most conifer species, each tree has both ovulate and pollen cones. 1 A pollen grain enters through the micropyle and germinates, forming a pollen tube that slowly digests through the megasporangium. 4 While the pollen tube develops, the megasporocyte (megaspore mother cell) undergoes meiosis, producing four haploid cells. One survives as a megaspore. 5 The female gametophyte develops within the megaspore and contains two or three archegonia, each with an egg. 6 By the time the eggs are mature, two sperm cells have developed in the pollen tube, which extends to the female gametophyte. Fertilization occurs when sperm and egg nuclei unite. 7 Fertilization usually occurs more than a year after pollination. All eggs may be fertilized, but usually only one zygote develops into an embryo. The ovule becomes a seed, consisting of an embryo, food supply, and seed coat. 8 An ovulate cone scale has two ovules, each containing a megasporangium. Only one ovule is shown. 2

Characteristics of Angiosperms ,[object Object],[object Object]

Flowers ,[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],Figure 30.7 Anther Filament Stigma Style Ovary Carpel Petal Receptacle Ovule Sepal Stamen

Fruits ,[object Object],[object Object],Figure 30.8a–e (b) Ruby grapefruit, a fleshy fruit with a hard outer layer and soft inner layer of pericarp (a) Tomato, a fleshy fruit with soft outer and inner layers of pericarp (c) Nectarine, a fleshy fruit with a soft outer layer and hard inner layer (pit) of pericarp (e) Walnut, a dry fruit that remains closed at maturity (d) Milkweed, a dry fruit that splits open at maturity

[object Object],Figure 30.9a–c Wings enable maple fruits to be easily carried by the wind. (a) Seeds within berries and other edible fruits are often dispersed in animal feces. (b) The barbs of cockleburs facilitate seed dispersal by allowing the fruits to “ hitchhike” on animals. (c)

The Angiosperm Life Cycle ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],Figure 30.10 Key Mature flower on sporophyte plant (2 n ) Ovule with megasporangium (2 n ) Female gametophyte (embryo sac) Nucleus of developing endosperm (3 n ) Discharged sperm nuclei ( n ) Pollen tube Male gametophyte (in pollen grain) Pollen tube Sperm Surviving megaspore ( n ) Microspore ( n ) Generative cell Tube cell Stigma Ovary MEIOSIS MEIOSIS Megasporangium ( n ) Pollen grains Egg Nucleus ( n ) Zygote (2 n ) Antipodal cells Polar nuclei Synergids Egg ( n ) Embryo (2 n ) Endosperm (food Supply) (3 n ) Seed coat (2 n ) Seed FERTILIZATION Haploid ( n ) Diploid (2 n ) Anther Sperm ( n ) Pollen tube Style Microsporangium Microsporocytes (2 n ) Germinating Seed Anthers contain microsporangia. Each microsporangium contains microsporocytes (microspore mother cells) that divide by meiosis, producing microspores. 1 Microspores form pollen grains (containing male gametophytes). The generative cell will divide to form two sperm. The tube cell will produce the pollen tube. 2 In the megasporangium of each ovule, the megasporocyte divides by meiosis and produces four megaspores. The surviving megaspore in each ovule forms a female gametophyte (embryo sac). 3 After pollination, eventually two sperm nuclei are discharged in each ovule. 4 Double fertilization occurs. One sperm fertilizes the egg, forming a zygote. The other sperm combines with the two polar nuclei to form the nucleus of the endosperm, which is triploid in this example. 5 The zygote develops into an embryo that is packaged along with food into a seed. (The fruit tissues surround- ing the seed are not shown). 6 When a seed germinates, the embryo develops into a mature sporophyte. 7

Angiosperm Evolution ,[object Object],[object Object],[object Object],[object Object]

Fossil Angiosperms ,[object Object],[object Object],Figure 30.11a, b Carpel Stamen Archaefructus sinensis, a 125-million-year- old fossil. (a) Artist’s reconstruction of Archaefructus sinensis (b) 5 cm

An “Evo-Devo” Hypothesis of Flower Origins ,[object Object],[object Object]

Angiosperm Diversity ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],Figure 30.12 Amborella trichopoda Water lily (Nymphaea “ Rene Gerard”) Star anise (Illicium floridanum) BASAL ANGIOSPERMS HYPOTHETICAL TREE OF FLOWERING PLANTS MAGNOLIIDS Amborella Water lilies Star anise and relatives Magnoliids Monocots Eudicots Southern magnolia ( Magnolia grandiflora )

[object Object],Figure 30.12 Orchid ( Lemboglossum fossii ) Monocot Characteristics Embryos Leaf venation Stems Roots Pollen Flowers Pollen grain with one opening Root system Usually fibrous (no main root) Vascular tissue scattered Veins usually parallel One cotyledon Two cotyledons Veins usually netlike Vascular tissue usually arranged in ring Taproot (main root) usually present Pollen grain with three openings Zucchini ( Cucurbita Pepo ) , female (left) and male flowers Pea ( Lathyrus nervosus, Lord Anson’s blue pea), a legume Dog rose ( Rosa canina ), a wild rose Pygmy date palm ( Phoenix roebelenii ) Lily ( Lilium “ Enchant- ment” ) Barley ( Hordeum vulgare ), a grass Anther Stigma California poppy ( Eschscholzia californica ) Pyrenean oak ( Quercus pyrenaica ) Floral organs usually in multiples of three Floral organs usually in multiples of four or five Filament Ovary Eudicot Characteristics MONOCOTS EUDICOTS

Evolutionary Links Between Angiosperms and Animals ,[object Object],[object Object],Figure 30.13a–c (a) A flower pollinated by honeybees. This honeybee is harvesting pollen and nectar (a sugary solution secreted by flower glands) from a Scottish broom flower. The flower has a tripping mechanism that arches the stamens over the bee and dusts it with pollen, some of which will rub off onto the stigma of the next flower the bee visits. (c) A flower pollinated by nocturnal animals. Some angiosperms, such as this cactus, depend mainly on nocturnal pollinators, including bats. Common adaptations of such plants include large, light-colored, highly fragrant flowers that nighttime pollinators can locate. (b) A flower pollinated by hummingbirds. The long, thin beak and tongue of this rufous hummingbird enable the animal to probe flowers that secrete nectar deep within floral tubes. Before the hummer leaves, anthers will dust its beak and head feathers with pollen. Many flowers that are pollinated by birds are red or pink, colors to which bird eyes are especially sensitive.

Products from Seed Plants ,[object Object],[object Object],[object Object],[object Object],Table 30.1

Threats to Plant Diversity ,[object Object],[object Object]

29 plants ii text

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