Angiosperm Reproduction 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: Flowers Fruits Double Fertilization

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)

Pollination: transfer pollen from anther to stigma Pollen tube grows down into ovary for 2 sperm to travel to egg

“Pin” and “thrum” flower types reduce self-fertilization Some plants are self-pollinated Cross-pollinated plants: Self-incompatibility: plant rejects own pollen or closely related plant Maximize genetic variation Stigma Pin flower Anther with pollen 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 Root develops Shoot tip emerges above ground Stimulated by light Foliage leaves expand & turn green  photosynthesis Very hazardous for plants due to vulnerability Predators, parasites, wind

Seed Germination

(Vegetative Reproduction) 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 beta-carotene (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