Unit 4- Plants

1. Unit 4- Plants M. Lauria

2. Background on Plants • The Plant kingdom includes more than 270,000 species • Believed to have evolved from green algae (chlorophyta). http://homepage.smc.edu/gallogly_ethan/travel_photos/misc/sean_mom_giant_redwood_tree.JPG

3. Adaptations to Land • In order to prevent water loss on dry land, plants have a cuticle (waxy covering). • Some have roots, stems and leaves to help obtain, transport, and use water and nutrients efficiently. • Use spores and seeds to protect reproductive cells.

4. Adaptations to Land (cont.) • Some plants have vascular tissues called xylem and phloem to help transport water and nutrients throughout the different parts of the plant. • Some have stomates to prevent water loss and control gas exchange with the atmosphere.

5. Stomates • Stomates are small openings along the surface of a leaf that control gas exchange. • They close when the plant is beginning to lose to much water. • They open when the plant needs CO2 www.emc.maricopa.edu/.../ BIOBK/BioBookPS.html

6. Cross- Section of a Leaf http://www.emc.maricopa.edu/faculty/farabee/BIOBK/leafstru.gif

7. Xylem • Conducts water • Xylem cell is called a tracheid, its cell walls are impermeable to water • Vessel elements are xylem cells found in angiosperms • When these cells die, their cytoplasm disintegrates and they are able to conduct water.

8. Phloem • Conducts a variety of plant nutrients and products • Phloem cells are called sieve tube elements, are positioned end to end and have holes that connect their interiors. • Companion cells are located next to sieve tubes and help to control them.

9. Cross Section of a Stem: Xylem and Phloem cd.ed.gov.hk/.../ Root/Ranuculus%2011.jpg

10. Classifying Plants From Modern Biology: Holt, Rinehart, and Winston

11. Non-vascular Plants • Lack vascular tissue and do not form true roots, stems or leaves. • Are seedless, and need water to reproduce sexually. • Have an alternation of generations- sporophyte and gametophyte.

12. Seedless Vascular Plants • Vascular plants can grow larger and live longer. Why? • Include: Ferns, whisk ferns, club mosses, horsetails. http://www.ct-botanical-society.org/ferns/fernpics/phegopterishexa_frond.jpg

13. Alternation of Generations in a Fern staff.jccc.net/.../ celldivision/images/fern.gif

14. Vascular Seed Plants • Plants with seeds have a greater chance at reproductive success than seedless plants. Why? • Two main groups of seed-bearing plants: gymnosperms (“naked” seed) and angiosperms (seed protected in fruits).

15. Gymnosperms • Have specialized male and female reproductive structures called scales. • Larger structure is called a cone. http://www.pfc.forestry.ca/diseases/CTD/Group/Rust/lrg_images/fig30b.gif

16. Conifers (evergreens) include pines, spruce, fir, cedars, redwoods. Leaves are needle-shaped. Do not necessarily shed needles in the fall. Pollen from a pollen cone fertilizes egg within a seed cone. Seed within a seed cone is considered “naked.” Gymnosperms

17. Flowering plants are most widespread of all plants? Why? Reproduce using pollination of flowers Seeds are contained within a protective fruit. Some flowers have both male parts (stamen- pollen producing) and female parts (ovary- egg producing) Angiosperms

18. Flower Parts www.ncsu.edu/project/ agronauts/images/flower.gif

19. Alternation of Generations In Vascular Seed Plants • Sporophyte is the dominant form, and the gametophyte grows within the flowers or cones of the sporophyte. http://www.stevedibler.com/photos/Nature-Scenery/Dogwood_tree.jpg