Transcript seed plants
Seed Plants Gymnosperms & Angiosperms 1 Evolution Of Land Plants REMEMBER: • Terrestrial plants evolved from a green algal ancestor • The earliest land plants were nonvascular, spore producers (bryophytes) • Ferns were the 1st vascular, spore producing plants • Gymnosperms & angiosperms were the 1st vascular, seed plants 2 3 Characteristics of Seed Plants • Multicellular • Autotrophic • Alternation of Generations • Reproduce by Seeds • Vascular tissue for transport • Heterosporous – make female megaspores & male microspores 4 Dandelion dispersing seeds Reasons for Success on Land • Waxy cuticle • Stomata with guard cells to open & close • Gametes protected in tissue called Gametangia • Pollen tube to transfer sperm to the egg instead of water • Seeds protect developing embryo & contain food 5 Seeds and Fruits 6 Seeds • Seeds contain a young, developing plant embryo • Seeds are covered with a protective seed coat (testa) • Inside is stored food or endosperm that the young plant uses as it begins to sprout or germinate • Seeds form from ripened ovules after fertilization 7 Parts of a Seed Embryo • Primary root or Radicle • One or two embryonic leaves called Cotyledons • Plumule becomes the shoot • Stem like portion below cotyledons called Hypocotyl • Stem like portion above cotyledons called Epicotyl 8 Parts of a Seed 9 10 Endosperm (3n) Seed Coat Cotyledon Plumule Epicotyl Hypocotyl Radicle 11 Seed Dispersal • Seeds must be scattered (dispersed) away from the parent plant • Testa (seed coats) may last thousands of years • Seeds eaten by animals aren’t digested but pass out with wastes 12 Seed Dispersal • Seeds may have adaptations such as stickers, hooks, or fuzz to adhere to animals 13 Seed Dispersal • Both water and wind can scatter seeds Wind Dispersal Water Dispersal 14 Seed Germination • Early growth of plant embryo • Begins when seed absorbs water & breaks seed coat (testa) • Embryo uses stored food of cotyledons to begin growing 15 Fruits • Form when ovary with ovules (eggs) ripens • May be dry and hardened (nuts) • May be enlarged and fleshy (berries, apples, tomatoes) • Used to help disperse seeds 16 Types of Fruits • Simple fruits – form from a single ovary (apple) • Aggregate fruits – forms from several ovaries of the same flower (blackberry) • Multiple fruit – forms from several ovaries of different flowers (inflorescence) 17 18 Plants with Vascular Tissue 19 Taxonomy of Vascular Seed Plants • Phylum Gnetophyta: Ephedra, Gnetum • Phylum Cycadophyta: Cycads • Phylum Ginkgophyta: Ginkgo • Phylum Coniferophyta: Conifers • Phylum Anthophyta: Flowering plants gymnosperrms angiosperms 20 Sporophyte microsporangium megasporangiumx microspores megasporesx microgametophyte megagametophytex antheridium archegonium lsperm eggmm 21 Seed plants (Ch.30) Tiny gametophytes protected in ovules and pollen grains Advantages of seeds Gymnosperms have “naked seeds” Angiosperms have seeds in fruits Monocots Eudicots 22 12: Gymnosperms and Angiosperms • Gymnosperm – Intro and evolution – Life cycle and reproduction – Uses and significance • Angiosperms: Flowering plants – Intro and evolution – Life cycle and reproduction – Uses and significance – Monocots vs. dicots 23 Kingdom Plantae • Evolutionary tree of plants • From primitive more advanced traits Bryophytes _______ Gymnosperms __________ Flowers ________ Green alga ancestor Vascular Terrestrial 24 GYMNOSPERMS • Introduction – Gymnosperm means “naked seed” (From the Greek: gymnos = naked; sperm = seed) • More advanced than ferns – do not have spores, they have seeds. • The seeds of the gymnosperms lack a protective enclosure (unlike flowering plants which have flowers and fruit). • Examples of gymnosperms: • Conifers (pine trees), cycads, 25 ginkgo biloba Evolution of gymnosperms • Gymnosperms evolved from fern-like ancestors • Advancements of gymnosperms over ferns: • 1. Seed (plant embryo, food storage tissue, and seed coat) • 2. Gymnosperms do not depend on water for fertilization (have air-borne pollen) • 3. Have a more dominant sporophyte generation • 4. Have a more efficient vascular system 26 • Exhibits alternation of generations • Sporophyte generation (2n) is dominant • Gametophyte generation (1n) is contained in and dependent on the sporophyte generation Gymnosperm life cycle 27 Gymnosperm lifecycle 28 Sporophyte generation • Sporophyte produces two types of spores (heterosporous) • Megasporangium – undergoes meiosis to produce megaspores (female gametophyte) • sporangium – undergoes meiosis to produce haploid microspores, germinate to produce male gametophyte (pollen) • Many gymnosperms use wind 29 for pollination and seed dispersal Wood produced by gymnosperms • Gymnosperms have a very efficient and effective vascular system • Usually woody plants • Xylem wood of a tree • Phloem bark of the tree • Wood is formed from secondary growth 30 Primary vs. secondary growth • 1. Primary growth – occurs in apical meristems of shoots and roots • Results in increase in length • 2. Secondary growth – derived from secondary or lateral meristems • Results in increase in girth (width) • Common in trees (wood and bark) 31 Secondary growth • The cambium forms secondary xylem and secondary phloem • Wood – is secondary xylem; cells are dead at maturity and only cell wall remains • Bark – is secondary phloem (conducts food) 32 Annual rings • Annual rings – xylem formed by the vascular cambium during one growth season • Early Spring wood – vessel diameter is large, xylem walls are thinner • Late Summer wood – vessel diameter is small, walls are thicker • Tropical trees: have no annual rings, because seasons are so similar 33 Vascular tissue: Trees • Vascular tissue is located on the outer layers of the tree. bark _______ Vascular cambium wood ________ copyright cmassengale 34 Gymnosperms • Conifers are most important group of gymnosperms • Largest and most familiar group • Bare seeds in cones • Staminate cones – male cones • Ovulate cones – _________ cones • Seeds produced on an open scale • (Do not produce flowers or fruit) 35 Gymnosperms • Mainly woody plants that include • Oldest living trees: bristlecone pine, 5000 yrs old! • Most massive trees (giant sequoia): up to 375 ft. tall, 41 ft wide! • Tallest living trees (redwoods) 36 Conifers • Conifers adapted to temperate to cold regions • Narrow leaves (needles) help to conserve water • Covered by resins – for protection from predators, fire, etc. 37 Other gymnosperms • Cycads – short shrubs, native to tropical regions (look like palms) • Ginkgo biloba – a “living fossil”, male and female tree, used as a medicinal plant 38 Other gymnosperms • Welwitschia – a bizarre gymnosperm plant that grows in Namib desert (So. Africa). • Live up to 2000 years in these extreme conditions! • Only makes two leaves throughout its life. It takes water from sea mist 39 Significance of gymnosperms • • • • • • • • • Ecological importance: Provide food and habitat for wildlife Forests prevent soil erosion Reduce greenhouse-effect gasses Economic and commercial importance: Lumber for wood, paper, etc. Resins – wood, furniture, etc. Ornamental plants (trees, landscaping) Food – pine nuts (pesto, etc.) 40 ANGIOSPERMS • • • • Angiosperm means “covered seed” Have flowers Have fruits with seeds Live everywhere – dominant plants in the world • 260,000 species (88% of Plant Kingdom) • Angiosperms are the most successful and advanced plants on earth 41 Evolution of Angiosperms • Advancements over gymnosperms: • Angiosperms have flowers – many use pollinators • Fruits and seeds – adapted for dispersal • Double fertilization of the endosperm in the seed 42 Angiosperm life cycle • Flower has male and female sex organs 43 Flower structure • Male sex organs: Stamens, composed of anther – organ that produces pollen (male gametophyte) • Female sex organs: The carpel • Ovary is the enlarged basal portion of carpel that contains the ovules (female gametophyte) • The stigma is the receptive portion of the carpel for pollen grains to adhere 44 Flower structure • Non-reproductive parts: • Sepals (green) are the outermost whorl of leaf-like bracts • Petals (usually colored) are the inner whorl of leaf-like bracts • Both can have various shapes and colors • Tepals _______________ 45 Angiosperm life cycle • Heterosporous: forms two different types of spores (micro- and megaspores; male and female spores) • Male – pollen grains contain tube nucleus and generative cell (2 sperm nuclei) • Female – female gametophyte contains egg and 2 polar nuclei 46 Angiosper m lifecycle Flowering plants exhibit alternation of generations. The large, familiar flowering plant is the diploid sporophyte, while the haploid gametophyte stages are microscopic. The unique feature about the life cycle of flowering plants is a double fertilization that produces a diploid zygote and a triploid endosperm or nutritive tissue. 47 Double fertilization • Pollen grain germinates on stigma forming a pollen tube, which grows down style to the ovary • Pollen has 2 haploid sperm nuclei, which travel to the ovary • One sperm nucleus fertilizes the haploid egg forming the 2n zygote • Another sperm nucleus unites with the 2 polar nuclei, forming the triploid (3n) endosperm 48 Seeds • Fertilized egg grows into a ___________, which grows into plant embryo • Endosperm is stored food tissue – for the embryo to grow • Mature ovule becomes the seed coat and/or fruit 49 Monocot vs. dicot • Angiosperms are divided into monocots and dicots • As the zygote grows into the embryo, the first leaves of the young sporophyte develop and are called as cotyledons (seed leaves) • Monocots have one cotyledon (corn, lily, etc). • Dicots have two cotyledons (bean, oak, 50 etc). Comparing monocot vs. dicot plants FEATURE MONOCOTS DICOTS Cotyledons 1 2 Leaf venation parallel broad Root system Fibrous Tap Number of floral parts Vascular bundle position Woody or herbaceous In 3’s In 4’s or 5’s Scattered Arranged in a circle Herbaceous Either 51 Monocot vs. dicot • Number of cotyledons: one vs. two 52 Monocot vs. dicot • Leaf venation pattern: • Monocot is parallel • Dicot is net pattern 53 Monocot vs. dicot root • Monocot: Fibrous root • Dicot: Tap root 54 Monocot vs. dicot • Flower parts: • Monocot: in groups of three • Dicot: in groups of four or five copyright cmassengale 55 Monocot vs. dicot • Vascular bundle position: • Monocot: _____________ • Dicot: arranged in a circle 56 Monocot vs. dicot • Stem type: • Monocot: Herbaceous • Dicot: herbaceous or woody 57 Summary: Monocot vs. dicot 58 Seed plants (Ch.30) protected gametophytes advantages of seeds gymnosperms angiosperms monocots eudicots Fig. 30.2 Notice how the importance of the gametophypte dwindles as we move from mosses to ferns to seed plants. The gametophyte of a seed plant is microscopic and not green (does not carry out photosynthesis) 59 Seed plants (Ch.30) protected gametophytes advantages of seeds gymnosperms angiosperms monocots eudicots Lots of specialized terms are used to describe the life cycle of see plants. Here, we will use the fewest we can, and simply drastically. Fig. 30.3. This whole structure is a ovule (integument, the cells of the megasporangium, and the cells of the megaspore). The megaspore is formed by meiosis, so is a haploid gametophyte, the rest is diploid sporophyte. 60 Seed plants (Ch.30) protected gametophytes advantages of seeds gymnosperms angiosperms monocots eudicots Lots of specialized terms are used to describe the life cycle of see plants. Here, we will use the fewest we can, and simply drastically. Fig. 30.3. One of the female gametophyte cells becomes an egg (n). The rest divide to produce the rest of the cells of the female gametophyte. A male gametophyte (n), or pollen grain, enters the ovule, and the nucleus of one of its cells acts like a sperm, and fertilizes the egg (= zygote). 61 Seed plants (Ch.30) protected gametophytes advantages of seeds gymnosperms angiosperms monocots eudicots Lots of specialized terms are used to describe the life cycle of see plants. Here, we will use the fewest we can, and simply drastically. Fig. 30.3. The haploid female gametophyte (minus the cell that became the egg) becomes a mass of tissue that will provide a food supply for the new embryo developing from the zygote. The integument becomes a hard seed coat. Note that the embryo stops developing until it germinates 62 thus the “baby plant” in a peanut! Seed plants (Ch.30) protected gametophytes advantages of seeds gymnosperms angiosperms monocots eudicots The advantages of seeds are pretty obvious - there is no need for the gametophyte to live in a damp place so sperm can swim to the egg - seed plants can, and do, live everywhere. 63 Seed plants (Ch.30) protected gametophytes advantages of seeds gymnosperms angiosperms monocots eudicots Gymnosperms are seed plants that do not have a fruit around the seed, and thus have “naked seeds”. Most of us think of gymnosperms as just “pines” (or conifers), but there is quite a diversity. Ginkos live on campus - have you seen one? The “fruit” is not really a fruit, but part of the ovule.. pine gingko 64 Seed plants (Ch.30) protected gametophytes advantages of seeds gymnosperms angiosperms monocots eudicots Angiosperms do not have naked seeds, but seeds surrounded by a n extra layer of tissue that forms a fruit (which may be juicy or dry). Fig. 30.8, 30.9 65 Seed plants (Ch.30) protected gametophytes advantages of seeds gymnosperms angiosperms monocots eudicots But of course, angiosperms also have flowers! Fig. 30.7. You do not have to memorize all the parts, but know that that most flowers have both male, pollen producing parts, and female ovules. 66 Seed plants (Ch.30) protected gametophytes advantages of seeds gymnosperms angiosperms monocots eudicots Almost all angiosperms fall naturally into two groups, monocots (one cotyledon, or seed leaf) and dicots (two cotyledons). A few dicots don’t form a clade, but the huge majoroty that do are called true dicots, or eudicots. Fig. 30.12 (p. 603) 67 Seed plants (Ch.30) protected gametophytes advantages of seeds gymnosperms angiosperms monocots eudicots Fig. 30.13. Angiosperms and animals have evolved very intricate mutualistic interactions involving pollination - interactions that benefit both. 68 Learning goals: Lecture 3, Biological Diversity (Plants and Fungi) Readings: Chapters 29, 30, and 31 (read all of these, but the parts covered in lecture are most likely to be on a test ). Land plants II - Seed plants (Ch.30) Land Plants I- how land plants colonized land (Ch. 29) Tiny gametophytes protected in ovules and pollen; advantages of Land plants evolved from green seeds; Gymnosperms have “naked algae; terrestrial adaptations; seeds”; Angiosperms have seeds in alternation of generations; fruits; Monocots, Eudicots bryophytes dominated by gametophyte generation; ferns Fungi (Ch. 31) dominated by sporophyte Characteristics; fungi reproduce by spores; fungal origins and relationships; importance 69 Lecture 3 spe cific reading. The en tir e reading is Chap ters 29, 30, and 31 Fig. 28.3, p. 568 – read just figure legends – note that coml ex algae li ke Ulva seem ve ry “plant-like” Fig. 29.3. p. 574, Genetic Evidence Fig. 29.5, p. 576, (top), p. 576, (als o p. 574, Adaptations enabling the move to la nd. Fig. 29.5 (bottom) , p. 576, Alt ernation of gene rations Fig. 29.8, p. 581, als o p. 580, Bryophy te gametophtes Fig. 29.12, p. 585 Fig. 29.14, p. 587, take a look at the c lub moss and hor setail pho tos, simil ar to one shown in lecture Fig. 29.15, p. 588, read Sign ifi canc e of seedless vascu la r plants (even though not discuss ed in lecture) Fig. 30.2, p. 592 Fig. 30.3, p. 593, als o p. 592 Ovu les and Produc tion of Egg s, Poll en and Produc it on of sperm, p. 593, the Evo lutiona ry advan tages of seeds Fig. 30.7, p. 598, Flowers Fig. 30.8, p. 598, p. 598-599, Fruits Fig. 30.9, p. 599, more fruit s. Fig. 30.12, left side, p. 603, focus on co tyledons and leaf venation, but read all cha rcters that disti ngu ish monocots and dicots. Fig. 30.13, p. 604 Fig. 31.2, p. 609 Fig. 31.6, p. 611 Fig. 31.7, p. 611 Fig. 31.5, p. 611. If you want to unde rstand about the he terokaryotic stage , you may wan t to read p. 610-611, Sexua l r eprodu ction Fig. 31.23, p. 621-622, Lichens Fig. 31.25, p. 622-623, Pathogens Fig. 31.26, p. 623, Practical Uses of Fung i 70 Pine Life-Cycle 71 pollen cone male or pollen cone Female or ovulate cone ovulate cone 72 male cone microsporophyll microsporangium 73 female cone ovule .megasporangium scale “megasporophyll” 74 seeds scale 75 Coniferophyta Yew Juniper 76 Coniferophyta Bristlecone Pine 77 Coniferophyta Giant Redwood or Sequoia 78 Hemlock Coniferophyta Spruce 79 Coniferophyta Bald Cypress 80 Douglas Fir Coniferophyta Fi r 81 Cycadophyta : cycads 82 Ginkgophyta: Ginkgo biloba 83 Gnetophyta: Ephedra mormon tea 84 Gnetophyta: Gnetum 85 Gnetophyta: Welwitschia 86 Leaves: Many different sizes, shapes. (Pine needles, cabbage, oak, etc.) * Capture sun’s energy for photosynthesis * Structure of a leaf: - Upper surface cells - Chloroplasts - Veins with xylem and phloem - Underside surface cells - Stomata (“stoma” in Greek means “mouth”, opening) 87 The Structur e of a Leaf 88 Cuticle Upper Epidermis Palisade mesophyll Vascular Bundle Spongy mesophyll Lower Epidermis 89 90 VENATION 91 Transpiration = process of evaporation from leaves. * Too much evaporation and the plant shrivels and dies * Closing the stomata helps slow down transpiration. 92 Stems: support the plant and carry substances between the roots and leaves. * Some stems also store food (starches) like in asparagus. * They vary in size and shape: - Boabab tree has a huge stems. - Cabbage have short, hidden stems. 93 94 * Structure of stems: - Herbaceous (soft) [dandelions,tomato plants] - Woody (hard) like trees and rose bushes - Both have xylem and phloem, but woody stems have extra layers: Outer Bark Inner Bark (phloem) Cambium (to produce new phloem and xylem) Sapwood (active xylem - still transporting) Heartwood (inactive xylem); just gives strength 95 Pith (center storing food & water in young Parts of a Woody Stem 96 Annual Rings = xylem rings * Spring Xylem is wide & light brown (grows rapidly) * Summer Xylem is thin & darker (grow slower) * Each pair of light & dark rings = one year’s growth. 97 98 Roots: (Anchors. Absorbs water & nutrients from soil) * Two Types 1. Taproot = deep into soil 2. Fibrous Roots = several branching main roots * Root structure - Root Cap the rounded tip containing dead cells. - Root hairs increase surface absorption area - Cambium produces xylem and phloem tissues. 99 - Xylem transports substances up to the plant Fibrous Roots Tap Root 100 Root: Internal Structure 101 Roots do not absorb water and minerals through a smooth Epidermis. Tiny, hairlike projections called ROOT HAIRS on the epidermis absorb water and dissolved minerals from the soil. Root Hairs also INCREASE the Surface Area of the Plant Roots. 102 Epidermis Cortex Pith Xylem Phloem Endodermis Dicot Root Monocot Root 103 Gymnosperms Gymnosperm = seed plant that produces naked seeds. * Many have needlelike or scalelike leaves and deep root systems. * Note the book says fossils indicate there were many more gymnosperms in the past than today. This is because the global flood 4,000 years ago wiped out many plants. (The dates given by many books of millions of years are false guesses. See the booklet by Dr. 104 Humphreys.) Types of Gymnosperms: - Cycads (look like palm trees with large cones) - Ginkgo (only the Ginkgo biloba survives today) - Gnetophytes (found only in deserts - Conifers (largest & most common, pines, cedars, etc.) [Conifers are evergreens: keep needles all year] 105 Oldest living organism – Bristlecone Pine About 4,000 years old = just after Noah’s Flood. 106 Reproduction of Gymnosperms: * Cones – covered in scales, both male and female cones are produced. - Pollen is produced by male cones, and pollen are tiny cells that later become sperm cells. - Ovule is a structure containing an egg cell. Pollination = transfer of pollen from male structure to female part. (Pollen falls from a male cone to a female cone and fertilizes an ovule, which develops into a seed, with the zygote as the embryo part of the seed. It can take two years for seeds to mature, then the cones open & wind 107 carries the seeds off.) The Life Cycle Of a Gymnosperm 108 Angiosperms Angiosperms – Two characteristics: 1. flowers 2. fruit (To remember, think: “Angie” likes flowers, but “Gym” does not.) * They produce seeds inside a fruit. * Flower = angiosperm reproductive structure * Fruit starts as an Ovary = where the seeds develop 109 Flower Structure: Not all flowers have same parts. Some have only male parts. * Sepals = leaf-like structures covering a bud. * Petals = colorful structures of an open flower. * Stamens = male parts (stalks topped by knobs) * Pistils = the female parts in the center of the flower. - Stigma = sticky tip of the pistil - Style = tube connecting stigma to ovary. 110 111 112 The Structure of a Flower 113 Flower Structure Stigma Filament Style Anther Ovary Receptacle Petal Sepal Ovule 114 Life Cycle Of an Angiosperm 115 Reproduction of Angiosperms: * Pollination = Pollen falls on a stigma when wind, bees, or bats carry it. (Sugar-rich nectar in the flower attracts bees or bats.) * Fertilization = sperm & egg join together in the flower’s ovule. - The zygote develops into the embryo part of the seed. - The ovary around the seed develops into a fruit. (Apples, cherries, tomatoes, squash, etc. are all fruit.) * Dispersal – animals eat the fruit and the seeds come out the other end. 116 Two types of Angiosperms: 1. Monocots – have only one seed leaf (cotyledon) (grasses, corn, wheat, rice, lilies, tulips) (flowers have either 3 petals or a multiple of 3 petals) (long slender leaves with veins parallel like train rails) (vascular tissue scattered randomly in the stem) 2. Dicots – have two cotyledons (roses, violets, plus oak, maple, bean, and apple trees) (flowers have 4 or 5 petals or multiples of these numbers) (leaves are wide, with veins branches off one another) (vascular tissue bundles arranged in a circle) Angiosperms are used for food, clothing (cotton), Michael’s medicine (digoxin) 117 Seed Structure Examples: 118 Plant Responses and Growth 119 Tropism = a plant’s growth response toward or away from a stimulus. * Positive tropism is when it grows toward a stimulus. * Negative is when it grows away from it. * Stimuli can be light, touch, and even gravity. - Touch (thigmotropism) [vines coil around anything they touch.] - Light (phototropism) [leaves, stems, etc, grow toward light.] - Gravity (gravitropism) (Positive) roots grow toward gravity’s pull (Negative) stems grow away from its pull 120 Hormones = a chemical that affects how the plant grows and develops, & make tropism possible. * Hormones also control germination, formation of flowers, stems, and the shedding of leaves and ripening of fruit. * Auxin is an important hormone that speeds up plant cell growth rate. - If light shines on one side of a stem, auxin moves to the shaded side and causes that side to grow faster so the stem bends toward the light as it grows. 121 Life Spans of Angiosperms: * Annuals = complete a life cycle in one year. (pansies, wheat, tomatoes, cucumbers, etc) * Biennials = complete life cycle in two years. (Second year they produce flowers and seeds.) (Parsley, celery, etc) * Perennials = live for more than two years (Oak tree, honeysuckles, etc) (Roots and stems survive the winter) 122 123