Angiosperm Reproduction Chapter 38 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: Flowers Fruits double Fertilization

Alternation of Generations 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: Sepal – leaflike, protect flower bud Petal – modified leaves, attract pollinators Stamen – ♂ reproductive organ anther + filament Carpel – ♀ reproductive organ stigma + style + ovary Flower attached to stem at receptacle Pollination by wind, insects, birds

Name Structure Function Sepals Little green leaflets attached to receptacle Protect the buds Petals Brightly colored, 2nd whorl Attract insects & other pollinators Stamen Anther + filament ♂ Reproductive organ Filament Thin stalk Support anther Anther Terminal end of filament Contains chambers to develop male gametophyte (pollen) Carpel Stigma + style + ovary ♀ Reproductive organ Stigma Sticky end of style “landing platform” for pollen Style Slender neck supporting stigma, leads to ovary Support stigma and pollen tubes Ovaries Swollen lower portion of carpel Development 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)

SYMMETRY OVARY LOCATION FLORAL DISTRIBUTION Bilateral symmetry (orchid) Lupine inflorescence Superior ovary Radial symmetry (daffodil) Sunflower inflorescence Semi-inferior ovary Inferior ovary Sepal Fused petals

REPRODUCTIVE VARIATIONS Maize, a monoecious species Dioecious Sagittaria latifolia (common arrowhead)

Male Gametophyte Female Gametophyte = Pollen Sac = Embryo Sac Produced in anther Produced in ovule (in ovary) Has 2 haploid nuclei: Tube nucleus (forms pollen tube) Generative nucleus (divides to form 2 sperm cells) Has 3 important haploid nuclei: Egg (fuses with sperm) 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 One sperm + egg  zygote (2n) One sperm + 2 polar bodies  endosperm (triploid 3n) Endosperm = nutrition for embryo plant Ovule develops into seed; ovary develops into fruit Seed = embryo + endosperm

“Pin” and “thrum” flower types reduce self-fertilization Self-incompatibility: prevent reject own pollen or closely related individual Stigma Pin flower Anther with pollen Thrum flower “Pin” and “thrum” flower types reduce self-fertilization

The development of a eudicot plant embryo

Fruit Protects enclosed seed(s) Aids in dispersal by water, wind, or animals Simple Aggregate Multiple Single ovary of one flower Many ovaries of one flower Many ovaries of many flowers Cherry Raspberry Pineapple

Developmental origins of fruit

Seeds Adaptations: Dormancy = “resting” Dispersal: variety of methods Low metabolic rate, not growing or developing Increases chances of germination in most advantageous time & place Dispersal: variety of methods 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 Stimulated by light 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

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.

Check your understanding Compare and contrast: What does each of the following develop into? Zygote Integument Ovule Ovary Pollination Fertilization Germination