Plants

1. Plants Elgqvist 2009

2. Evolution and Classification • The common ancestor of plants is green algae • Lived in water or moist environments • Reproduced asexually by • binary fission • Reproduced sexually by • conjugation

3. Charactersitics • Plants are all • Eukaryotic • Multicellular • Photoautotrophs (use light to produce food) • Have cellulose in their cell walls • Absorb nutrients through their roots or rhizoids (a major difference from algae) • Sessile (cannot move at base)

4. Evolution and Classification Order of major evolutionary advances from algae to flowering plants • Spores • Vascular tissue • Seeds • Flowers

5. Evolution and Classification • Since plants came from algae, the first giant evolutionary step was to move onto land • To do this, cuticles (waxy layer around leaves) had to evolve to allow plant to prevent water loss • Reproduction with spores over reproduction by binary fission • Seedless • Reproduce with spores • Need moisture • non-vascular • Stuck low to the ground • Use rhizoids – root like structures

6. Seedless, Nonvascular Plants • Mosses • Hornworts • Liverworts Sporophyte growing from gametophyte

7. Evolution and Classification • Next came evolution of vascular tissue – tubular tissue that transports water and nutrients. • Allowed roots to sink into ground to reach deeper water • Allowed plant to grow up and compete for sunlight • Allowed plant to have a much greater surface for photosynthesis compared to land area taken • Nutrients and water can travel much faster to all parts of the plant, allowing it to grow bigger.

8. Seedless vascular plants • Reproduce with spores (still need moisture for sperm to swim from male gametophyte to female gametophyte - egg producing part of plant) • Can grow tall and spread leaves out

9. Seedless vascular plants • ferns • horsetails Spores found on underside of leaves (p 660)

10. Seedless Vascular Plants • Club mosses

11. Evolution and Classification • Then came seeds! • Soooooooooooo many ways to disseminate! Disperse!Spread out! Scatter and otherwise get away from the parent plant!

12. Seeds - dispersal Maple seeds come down like little helicopters Dandelion seeds float off in the breeze Ever had a bur stuck in your sock?

13. Seeds - dispersal A coconut (seed for a palm tree) Floating on the currents to far away islands By animals – carried off and buried, or ingested and “dropped” somewhere else

14. seeds • Advantages • Dispersal – so many ways! • Not bound to moist ground for sperm to swim to female gametophyte – yeah – true dry ground! • Protected by durable seed coat that can stay dormant for long periods • Cotelydons provide nutrition until sporophyte produces green parts (germination is complete)

15. Seed germinatingnotice the cotlyedons

16. Vascular seed plants • Sporophyte is most prominent part of life cycle, producing gametophytes (opposite of seedless plants) • Two types: • Gymnosperms • “naked seeds” • Four main divisions • Angiosperms • Flowering plants • Ovary grows into fruit around seeds

17. Gymnosperms • ginkgos

18. Gymnosperms • Gnetophytes – neato! (p 618)

19. Gymnosperms • Cycads

20. Gymnosperms • Conifers – • cone bearing plants • Pinetrees • Leaves are long and narrow = needles • Adapted for cold and shaped not to break under weight of snow.

21. Evolution and Classification • Finally Flowers! • Advantages: • Seeds Dressed, not Naked! - surrounded by a “fruit” • Many ways to attract pollinators • Seeds protected (and dispersed) by fruit

22. Angiosperms – “fruit” aren’t just apples and oranges.There are sooooo many ways to disperse.Take on many shapes and sizes

23. Angiosperms – attracting pollinators • Symbiosis – mutualism • Pollinators get nectar & plant gets to reproduce • Pollen is male sex cell of plant • Pollen is carried by pollinator from male gametophyte (stamen) to female gametophyte (pistil)

24. Angiosperms – attracting pollinators

25. Plant parts • What are the main functions of: • Roots? • To take in nutrients and water • To store energy (as starch – as in potatoes) • To anchor the plant • Stem? • To transport nutrients and water around plant • To support plant • Leaves? • Produce food with photosynthesis • Flower? • reproduction

26. Stems - structure • Vascular tissue – some transport down, some up • What goes up? • Water with dissolved nutrients from roots • What goes down? • Food made by leaves to feed rest of plant, and to be stored in roots for winter. • What is exception? • Food goes up in spring – sap rises – to give energy for leaves to grow back

27. Stem – transport tissue • Up vascular tissue is called • Xylem • Down is • Phloem – think phoodphloes down botany.hawaii.edu

28. Leaves – structureSee text p. 644 for diagram • Main function is photosynthesis • Cells filled with chloroplasts are sandwiched between: • Top layer cuticle: prevent water loss • Bottom layer cuticle with embedded stomata • Stomata open to let in • CO2 (carbon dioxide), and let out • Oxygen (O2) • Stomata close at night to prevent • Loss of water vapor • Running through all this is the vascular tissue transporting water and nutrients in from roots (xylem), and transporting food out (phloem).

29. Flowering plant life cycle • Pollen is produced by stamen – (get it?) • Pollen lands on female pistil • Pollen travels down pollen tube – in the style • Pollen fertilizes eggs inside ovary to produce zygotes • Zygotes grow into seeds • Ovary grows into fruit around seeds • Seeds get dispersed, land and grow into new sporophyte (main plant) • Sporophyte produces new gametophytes (flowers), which produce pollen and eggs

30. Tropisms – see text p. 651 • Plant responses to stimulus • Stimulus = gravity • Response: • Gravitropism – • Roots grow down and shoots grow up

31. Tropisms • Stimulus = light • Response: • Phototropism • Plants grow toward the light, • With help of auxin – a hormone that increases growth on side of stem that’s away from light • – get it?

32. Tropisms • Stimulus – touch • Response: • Thigmotropism • Plants grow toward touch • This is for vines that climb or use other plants/objects to support them

33. Nastic Responsessee text p. 650 • Movement independent of direction of stimulus • Can be repeated many times • Examples: • Sun flowers move to always face the sun • sunflowers move to face sun • Venus fly traps snap shut when an insect triggers the response