Reproduction in Plants

1. Reproduction in Plants

2. Asexual Reproduction / Vegetative Propagation • the production of offspring from a single parent; the genetic makeup of the offspring is identical to that of the parent • Plants use a number of structures to reproduce asexually.

3. Plants Can Use Modified Stems To Reproduce Asexually rhizomes corms “eyes” on tubers

4. Plants Use Modified Stems To Reproduce Asexually Stolons or “runners”

5. Plants Use Modified Leaves To Reproduce Asexually New plants Kalanchoe plant

6. Plants Use Roots To Reproduce Asexually suckers Root fragments

7. Costs And Benefits Of Asexual Reproduction COSTS • Genetically identical population lacks the variation needed if the environment changes significantly. E.g. deadly plant virus, climate change • All individuals could die if their traits no longer help them survive and reproduce. BENEFITS • All offspring will inherit traits that allow a plant to survive in a particular environment. • The plant does not have to produce specialized reproductive structures so less energy is required and individuals are produced faster. • Only one plant is needed. • Plantlets are generally more robust than young seedlings produced by sexual reproduction so they have a higher survival rate.

8. Human Uses Of Asexual Plant Propagation • Cloning of desirable plants for commercial nurseries • E.g. stem cuttings put in water; transferred to soil once roots grow • Stem cuttings can also be dipped into rooting hormone and planted directly into soil

9. Human Uses Of Asexual Plant Propagation • Grafting: involves cutting a young branch from a plant that has desirable characteristics and attaching it to the stem of another plant • Usually both plants are of the same or closely-related species • The cambium of the scion (branch) and the cambium of the stock (plant that provides the stem and root system) grow together so that the vascular tissues of both fuse together • Able to combine desirable traits of the two plants

10. Grafting Roses, Fruit Trees and Vines • Scions from a single tree or grape vine that produced desirable fruit are grafted onto all the plants in the orchard or vineyard. • Genetic diversity tends to be very low which can render the plants vulnerable to disease, pests, or changes in environmental conditions.

11. Tissue Culturing • Some plants cannot reproduce asexually or only with difficulty. • Clones can be produced by culturing particular tissues in a series of culture media where the plant tissue can grow into a complete plant.

12. Sexual Reproduction In Seed Plants • Seeds are the critical structures that allow the introduction of an individual to a new area. • A seed has two main functions: • to protect and nourish the enclosed embryo • to carry the embryo to a new location • In angiosperms, seeds are contained in fruits.

13. Flower Parts GizmoPollination: Flower To Fruit (Activity A)

14. Parts Of A Representative Flower

15. Insect-pollinated flowers are showy Wind-pollinated flowers are plain (e.g. wheat, maple tree) Some plants produce male flowers and female flowers on the same plant (e.g. corn) Some species have individual plants that only produce either male or female flowers (e.g. willows, gingko) Flower Adaptations

16. Angiosperms are pollinated by wind or animals – usually insects. EXAMPLES ?????? Most species cross-pollinate. Some can also self-pollinate. (e.g. tomato plants, wheat, peas) Gizmo:Pollination: Flower to Fruit Activity B; refer to text re: double fertilization Pollination And Fertilization

17. Life Cycle of an Angiosperm

18. Angiosperm Seed Structure • Refer to your handout comparing monocots and dicots.

19. Fruit Formation • The cotyledons and/or endosperm provide nutrition to the developing fruit. • A fruit helps to protect and disperse the seed. • A fruit is a mature ovary and develops once the ovule is fertilized by a haploid sperm nucleus. • The ovary wall develops into the fruit wall or pericarp and may be fleshy (e.g. plums, peppers) or dry (e.g. walnuts, wheat).

20. Seed dispersal by Animals

21. Seed Dispersal Mechanisms: Seeds have a wide range of structures and mechanisms to help them disperse.

22. Seed dispersal by Wind

23. Seed dispersal by Water

24. Seed dispersal by Water

25. Costs And Benefits Of Sexual Reproduction COSTS • Energy and resources must be devoted to the production and maintenance of structures and cells that are devoted entirely to this process. • When resources are scarce, sexual reproduction can lower the chances than an individual organism will survive. BENEFITS • outweigh the costs • high level of genetic diversity; if the environmental conditions change, there is a higher chance that some individuals will have traits that are suited to the new environment and will survive and reproduce • Products of sexual reproduction are seeds; Seeds can be dispersed away from the parent plant = less competition for resources or better growing conditions • Seeds can remain dormant for long periods then germinate when conditions are favourable