Transcript Warm-Up
Angiosperm Reproduction What you need to know: The process of double fertilization, a unique feature of angiosperms. The relationship between seed and fruit. The structure and function of all parts of the flower. Angiosperms have 3 unique Features: 1. 2. 3. Flowers Fruits double Fertilization Alternation of Generations 1. 2. Sporophyte (mature plant) produces spores Spores develop into male (♂) gametophyte (pollen) and female (♀) gametophyte (embryo sac) Flower Structure Reproductive shoots of angiosperm sporophyte Flower organs: 1. Sepal – leaflike, protect flower bud 2. Petal – modified leaves, attract pollinators 3. Stamen – ♂ reproductive organ anther + filament 4. Carpel – ♀ reproductive organ stigma + style + ovary Flower attached to stem at receptacle Pollination by wind, insects, birds Floral Variations Complete: has petals, sepals, stamen, carpels Incomplete: lacks 1+ of the above Perfect: has both stamen + carpel Imperfect: has stamen or carpel, not both (grass no petals) Monoecious: plant species w/ both staminate and carpellate flowers on the same individual (corn) Dioecious: plant species w/ staminate flowers and carpellate flowers on different individual plants (date palm, arrowhead) Male Gametophyte Female Gametophyte = Pollen Sac = Embryo Sac Produced in anther Produced in ovule (in ovary) Has 2 haploid nuclei: 1. Tube nucleus (forms pollen tube) 2. Generative nucleus (divides to form 2 sperm cells) Has 3 important haploid nuclei: 1. Egg (fuses with sperm) 2. 2 polar nuclei (fuses with 2nd sperm to make 3n endosperm) Pollination: transfer pollen from anther to stigma Pollen tube grows down into ovary Double Fertilization Union of 2 sperm cells with different cells of embryo sac 1. One sperm + egg zygote (2n) 2. One sperm + 2 polar bodies endosperm (triploid 3n) ◦ Endosperm = nutrition for embryo plant 3. Ovule develops into seed; ovary develops into fruit ◦ Seed = embryo + endosperm The development of a plant embryo Fruit Protects enclosed seed(s) Aids in dispersal by water, wind, or animals Simple Aggregate Multiple Many ovaries Single ovary Many ovaries of many of one flower of one flower flowers Cherry Raspberry Pineapple Developmental origins of fruit Seeds Adaptations: 1. Dormancy = “resting” Low metabolic rate, not growing or developing Increases chances of germination in most advantageous time & place 2. Dispersal: variety of methods 3. Protection: well protected by fruit Seed Structure Germination Imbibition: uptake of H2O ◦ Seed expands and seed coat ruptures ◦ Trigger metabolic changes to begin growth ◦ Enzymes digest storage materials of endosperm (cotyledons) ◦ Nutrients transferred to growth regions of embryo Germination Radicle Root Shoot tip emerges above ground 1. 2. Stimulated by light 3. Foliage leaves expand & turn green photosynthesis Very hazardous for plants due to vulnerability ◦ Predators, parasites, wind Dicot and Monocot Seed Germination Plant Reproduction Sexual Asexual Both ways to reproduce Flower seeds Runners, bulb, root, graft, vegetative (grass), fragmentation Genetic diversity Clone More complex & hazardous for plant Simpler & safer for plant • Monoculture - cultivate w/ 1 plant • Reduces competition • Benefits farmers