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 eatures: Angiosperms have 3 unique Features: 1. F 1. Flowers 2. F 2. Fruits F 3. double Fertilization

Alternation of Generations 1. Sporophyte (mature plant) produces spores 2. 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

NameStructureFunction Sepals Little green leaflets attached to receptacle Protect the buds PetalsBrightly colored, 2 nd whorlAttract insects & other pollinators StamenAnther + filament ♂ Reproductive organ FilamentThin stalkSupport anther AntherTerminal end of filament Contains chambers to develop male gametophyte (pollen) CarpelStigma + style + ovary ♀ Reproductive organ StigmaSticky end of style“landing platform” for pollen Style Slender neck supporting stigma, leads to ovary Support stigma and pollen tubes OvariesSwollen lower portion of carpelDevelopment of ovules

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 GametophyteFemale Gametophyte = Pollen Sac= Embryo Sac Produced in antherProduced 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 2 nd 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 SimpleAggregateMultiple Single ovary of one flower Many ovaries of one flower Many ovaries of many flowers CherryRaspberryPineapple

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 H 2 O ◦ 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 1. Radicle  Root 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

Dicot and Monocot Seed Germination

SexualAsexual Both ways to reproduce Flower  seeds Runners, bulb, root, graft, vegetative (grass), fragmentation Genetic diversityClone More complex & hazardous for plant Simpler & safer for plant Monoculture - cultivate w/ 1 plant Reduces competition Benefits farmers Plant Reproduction