* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download and carpellate flower
Survey
Document related concepts
Plant use of endophytic fungi in defense wikipedia , lookup
Evolutionary history of plants wikipedia , lookup
Plant physiology wikipedia , lookup
Gartons Agricultural Plant Breeders wikipedia , lookup
Ecology of Banksia wikipedia , lookup
Plant morphology wikipedia , lookup
Ornamental bulbous plant wikipedia , lookup
Plant breeding wikipedia , lookup
Plant ecology wikipedia , lookup
Plant evolutionary developmental biology wikipedia , lookup
Ficus macrophylla wikipedia , lookup
Pollination wikipedia , lookup
Perovskia atriplicifolia wikipedia , lookup
Flowering plant wikipedia , lookup
Transcript
Overview: • Angiosperm flowers can attract pollinators using visual cues and volatile chemicals reproduce sexually and asexually Symbiotic relationships are common between plants and other species Since the beginning of agriculture, plant breeders have genetically manipulated traits of wild angiosperm species by artificial selection Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings A. Alternation of Generations (n 2nn2n) B. 2n = diploid sporophyte 1. Dominant generation (what we see!) 2. Produces haploid spores by meiosis (in the sporangia-review Ch. 30!) 3. Spores divide by mitosis forming gametophyte (n) C. n= haploid gamete 1. male or female 2. mitosis in gametophyte produces sperm or eggs Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 38-2b Germinated pollen grain (n) (male gametophyte) Anther Ovary Pollen tube Ovule Embryo sac (n) (female gametophyte) FERTILIZATION Egg (n) Sperm (n) Key Zygote (2n) Mature sporophyte plant (2n) Haploid (n) Diploid (2n) Germinating seed Seed Seed Embryo (2n) (sporophyte) (b) Simplified angiosperm life cycle Simple fruit A. Reproductive structures of the angiosperm sporophyte; they attach to a part of the stem called the receptacle B. Sepals-usually green, protect the flower C. Petals-generally brightly colored, attract pollinators Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings D. Stamen 1. Anther- with pollen sacs that produce pollen grains 2. Filament-supports the anther E. Carpels (pistil) 1. A carpel has a long stigma on which pollen may land a. Style b. Ovary containing embryo sacs within ovules Copyrigt © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 38-2a Stamen Anther Stigma Carpel (pistil) Style Filament Ovary Sepal Petal Receptacle (a) Structure of an idealized flower Ovule • Complete flowers contain all four floral organs • Incomplete flowers lack one or more floral organs, for example stamens or carpels • Many angiosperms have mechanisms that make it difficult or impossible for a flower to self-fertilize • Monoecious- both flowers on same plant (ex. corn) • Dioecious species have staminate and carpellate flowers on separate plants • Others have stamens and carpels that mature at different times or are arranged to prevent selfing Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 38-13 (a) Sagittaria latifolia staminate flower (left) and carpellate flower (right) Stamens Styles Thrum flower (b) Oxalis alpina flowers Styles Stamens Pin flower A. Pollination- pollen lands on the stigma a. Wind can be a pollinator b. Insects specific for plants they pollinate c. Some flowers self-pollinate, but most cannot. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 38-4a Abiotic Pollination by Wind Hazel staminate flowers (stamens only) Hazel carpellate flower (carpels only) Fig. 38-4c Pollination by Moths and Butterflies Anther Stigma Moth on yucca flower Fig. 38-4d Pollination by Flies Fly egg Blowfly on carrion flower Fig. 38-4e Pollination by Birds Hummingbird drinking nectar of poro flower Fig. 38-4f Pollination by Bats Long-nosed bat feeding on cactus flower at night B. Pollen Tube grows down the carpels and discharges 2 sperm a. Double fertilization Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 38-5b i. one sperm (n) fertilizes the egg (n) zygote (2n) formed embryo Ovule Polar nuclei Egg Synergid 2 sperm Fig. 38-5c ii. one sperm (n) combines with two polar nuclei (n)+ (n) endosperm (3n) = food-storing tissue Endosperm nucleus (3n) (2 polar nuclei plus sperm) Zygote (2n) (egg plus sperm) •After double fertilization, each ovule develops into a seed Structure of the Mature Seed • The embryo and its food supply are enclosed by a hard, protective seed coat • The seed enters a state of dormancy Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings C. Fruit Development (pollination triggers hormonal changes that cause the ovary to grow tremendously) a. 3n nucleus divides to form multinucleate “SUPER CELL” b. Cytokinesis forms membranes and walls between nuclei c. Rich in nutrients for developing embryo and seedling d. Fruit protects seeds and aids in dispersal (water, wind, animals) e. Other flower parts wither away as ovary grows. – If a flowers is not pollinated it will wither and fall Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 38-10 Carpels Stamen Flower Petal Stigma Style Ovary Stamen Stamen Sepal Stigma Pea flower Ovule Ovary (in receptacle) Ovule Raspberry flower Carpel (fruitlet) Seed Stigma Ovary Pineapple inflorescence Each segment develops from the carpel of one flower Apple flower Remains of stamens and styles Sepals Stamen Seed Receptacle Pea fruit (a) Simple fruit Raspberry fruit (b) Aggregate fruit Pineapple fruit (c) Multiple fruit Apple fruit (d) Accessory fruit Fig. 38-11a Dispersal by Water Coconut Fig. 38-11b Dispersal by Wind Winged seed of Asian climbing gourd Dandelion “parachute” Winged fruit of maple Tumbleweed Fig. 38-11c Dispersal by Animals Barbed fruit Seeds carried to ant nest Seeds in feces Seeds buried in caches D. Embryo Development a. zygote divides by mitosis b. cotyledons begin to form c. embryo elongates and embryonic root and meristem form. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 38-9a Foliage leaves Cotyledon Epicotyl Hypocotyl Cotyledon Cotyledon Hypocotyl Hypocotyl Radicle Seed coat (a) Common garden bean Fig. 38-9b Foliage leaves Coleoptile Coleoptile Radicle (b) Maize Concept 38.2: Plants reproduce sexually, asexually, or both • Many angiosperm species reproduce both asexually and sexually • Sexual reproduction results in offspring that are genetically different from their parents • Asexual reproduction results in a clone of genetically identical organisms Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Mechanisms of Asexual Reproduction • Fragmentation, separation of a parent plant into parts that develop into whole plants, is a very common type of asexual reproduction • In some species, a parent plant’s root system gives rise to adventitious shoots that become separate shoot systems Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Apomixis is the asexual production of seeds from a diploid cell Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Advantages and Disadvantages of Asexual Versus Sexual Reproduction • Asexual reproduction is also called vegetative reproduction • Asexual reproduction can be beneficial to a successful plant in a stable environment • However, a clone of plants is vulnerable to local extinction if there is an environmental change • Sexual reproduction generates genetic variation that makes evolutionary adaptation possible • However, only a fraction of seedlings survive Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Mechanisms That Prevent Self-Fertilization • Many angiosperms have mechanisms that make it difficult or impossible for a flower to self-fertilize • Dioecious species have staminate and carpellate flowers on separate plants Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Others have stamens and carpels that mature at different times or are arranged to prevent selfing Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • The most common is self-incompatibility, a plant’s ability to reject its own pollen • Researchers are unraveling the molecular mechanisms involved in self-incompatibility • Some plants reject pollen that has an S-gene matching an allele in the stigma cells • Recognition of self pollen triggers a signal transduction pathway leading to a block in growth of a pollen tube Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Clones from Cuttings • Many kinds of plants are asexually reproduced from plant fragments called cuttings • A callus is a mass of dividing undifferentiated cells that forms where a stem is cut and produces adventitious roots Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Test-Tube Cloning and Related Techniques • Plant biologists have adopted in vitro methods to create and clone novel plant varieties • Transgenic plants are genetically modified (GM) to express a gene from another organism Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Vegetative Propagation and Agriculture • Humans have devised methods for asexual propagation of angiosperms • 3 methods are based on the ability of plants to form adventitious roots or shoots 1. Many kinds of plants are asexually reproduced from plant fragments called cuttings 2. Grafting: A twig or bud can be grafted onto a plant of a closely related species or variety 3. Transgenic plants are genetically modified (GM) to express a gene from another organism • – Plant biologists have adopted in vitro methods to create and clone novel plant varieties Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 38.3: Humans modify crops by breeding and genetic engineering • Plant biotechnology has two meanings: – In a general sense, it refers to innovations in the use of plants to make useful products – In a specific sense, it refers to use of GM organisms in agriculture and industry • Modern plant biotechnology is not limited to transfer of genes between closely related species or varieties of the same species Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Reducing Fossil Fuel Dependency • Biofuels are made by the fermentation and distillation of plant materials such as cellulose • Biofuels can be produced by rapidly growing crops Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Reducing World Hunger and Malnutrition • Genetically modified plants may increase the quality and quantity of food worldwide • Transgenic crops have been developed that: – Produce proteins to defend them against insect pests – Tolerate herbicides – Resist specific diseases Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 38-18 “Golden Rice” Genetically modified rice Ordinary rice Issues: • One concern is that genetic engineering may transfer allergens from a gene source to a plant used for food • Many ecologists are concerned that the growing of GM crops might have unforeseen effects on nontarget organisms • Perhaps the most serious concern is the possibility of introduced genes escaping into related weeds through crop-to-weed hybridization Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Efforts are underway to prevent this by introducing: – Male sterility – Apomixis – Transgenes into chloroplast DNA (not transferred by pollen) – Strict self-pollination Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings