Chapter 38 Angiosperm Reproduction What you need to know: The relationship between seed and fruit. How temperature and moisture determine seed germination. How different modes of plant reproduction affect their genetic diversity. Angiosperms have 3 unique Features: 1. 2. 3. Flowers Fruits Double Fertilization SYMMETRY OVARY LOCATION FLORAL DISTRIBUTION Bilateral symmetry (orchid) Lupine inflorescence Superior ovary Radial symmetry (daffodil) Sepal Fused petals Semi-inferior ovary Inferior ovary Sunflower inflorescence REPRODUCTIVE VARIATIONS Maize, a monoecious species Dioecious Sagittaria latifolia (common arrowhead) Pollination: transfer pollen from anther to stigma Pollen tube grows down into ovary for 2 sperm to travel to egg Some plants are self-pollinated Cross-pollinated plants: ◦ Self-incompatibility: plant rejects own pollen or closely related plant ◦ Maximize genetic variation Stigma Stigma Anther with pollen Pin flower Thrum flower “Pin” and “thrum” flower types reduce self-fertilization The development of a plant embryo Fruit Egg cell plant embryo Ovules inside ovary seeds Ripe ovary fruit Fruit protects enclosed seed(s) Aids in dispersal by water, wind, or animals Types of Fruit Seeds Mature seed dormancy (resting) Low metabolic rate Growth & development suspended Resumes growth when environmental conditions suitable for germination Seed Structure Germination Seed take up water (imbibition) trigger metabolic changes to begin growth 1. Root develops 2. Shoot tip emerges above ground Stimulated by light 3. Foliage leaves expand & turn green photosynthesis Very hazardous for plants due to vulnerability Predators, parasites, wind Seed Germination Plant Reproduction Sexual Asexual (Vegetative Reproduction) Flower Seeds Runners, bulbs, grafts, cuttings vegetative (grass), fragmentation, test-tube cloning Genetic diversity Clones More complex & hazardous for seedlings Simpler (no pollinator needed) Advantage in unstable environments Suited for stable environments Asexual reproduction in aspen trees Test-tube cloning of carrots Just a few parenchyma cells from a carrot gave rise to this callus, a mass of undifferentiated cells. The callus differentiates into an entire plant, with leaves, stems, and roots. Humans Modify Crops Artificial selection of plants for breeding Plant Biotechnology: ◦ Genetically modified organisms “Golden Rice”: engineered to produce betacarotene (Vit. A) Bt corn: transgenic – expresses Bt (bacteria) gene produces protein toxic to insects ◦ Biofuels – reduce CO2 emissions Biodiesel: vegetable oils Bioethanol: convert cellulose into ethanol