Plant Reproduction & Response to the Environment

1. Plant Reproduction & Response to the Environment

2. Seeds • These features enable seeds to survive harsh environmental conditions and then sprout when favorable conditions exist. • A plant structure that contains an embryo, contains nutrients for the embryo, and is covered with a protective coat

3. Seeds • Seeds have one or more cotyledons that store or help absorb food for the sporophyte. • Plants whose seeds are part of fruits are called angiosperms (flowing plants) • Plants whose seeds are not part of fruits are called gymnosperms (non-flowering plants)

4. Alternation of Generations • Gametophyte (haploid)generation produces gametes. • Sporophyte (diploid)generation produces spores that can grow to form the next gametophyte generation. Gametophyte generation—maple pollen Sporophyte generation—maple tree

5. Alternation of Generations • Diploid sporophyte generation alternates with a haploid gametophyte generation • Gametophyte of gymnosperms are in the cones, and in angiosperms they are in the flowers

6. Reproduction in Gymnosperms • Two types of cones: • Pollen cone (male cone) – produce pollen • Seed cone (female cone) – contains the ovules, where the eggs are held • Pollination – transfer of pollen from the male structure to the female structure • Fertilization and development then occur

7. Reproduction in Gymnosperms

8. Reproduction in Angiosperms • Occurs in the flower • Most angiosperms are pollinated by animals (insects, birds) • Double fertilization • One sperm fertilizes the egg and becomes the zygote • A second sperm fertilizes the embryo sac and becomes the food supply

9. Reproduction in Angiosperms

10. Reproduction in Angiosperms • The ovary becomes the fruit • Seeds are dispersed by animals, wind, and water • Germination – early growth of the plant

11. Germination

12. Structure of a Flower • Sepals – enclose the bud • Petals – attract pollinators • Stamen – male structure • Filament – long, thin stalk that supports the anther • Anther – produces pollen • Carpels(or pistils) – female structure • Ovary – contains the ovules • Style – stalk of the carpel • Stigma – sticky surface where pollen lands

13. Structure of a Flower

14. Asexual Reproduction • Vegetative reproduction– production of new plants from stems, leafs, and roots • Cutting – pieces of plant cut off and planted • Grafting & budding– a stem or bud is cut from one plant & attached to another

15. Plant Hormones • Auxins – stimulate cell elongation • Cytokinins – stimulate cell division • Gibberellins – produce increases in size • Ethylene – stimulates fruit to ripen

16. Plant Responses • Tropisms – responses of plants to environmental stimuli • Gravitropism – response to gravity • Phototropism – response to light • Thigmotropism – response to touch • Positive – in the direction of the stimulus • Negative – away from the stimulus

17. Plant Responses