Plant Parts and their Functions

1. Plant Parts and their Functions

2. Leaves-Internal

3. Leaves-Internal • Upper and lower epidermis-skin of the leaf that prevents the loss of too much moisture • Cuticle: waxy protective coating on outer surface • Stomas-small openings under the leaf for breathing or transpiration • Guard Cells-open and close stomas

4. Leaves-Internal Air Space: CO2 & O2 Vein: Movement of Fluid Xylem: transport water up Phloem: transport glucose

5. Leaves-Internal • Chloroplasts-small green particles that contain chlorophyll • gives leaves their green color • necessary for photosynthesis

6. Leaves-Internal

7. Functions of Leaves • Photosynthesis-manufactures food in green plants which is the beginning of the food chain for all living things • Photosynthesis is the process by which carbon dioxide and water in the presence of light are converted to sugar and oxygen

9. Functions of Whole Plant • Respiration – the process through which plant leaves, stems and roots consume oxygen and give off carbon dioxide. • Plants produce much more oxygen through photosynthesis than they use through respiration.

10. Respiration • At night photosynthesis cannot occur. • The guard cells lose water. This causes the guard cells to become limp, closing the stomata. • With the stoma closed, CO2 does not enter the leaf, and H2O does not leave. • Since photosynthesis does not occur at night, there is no need for CO2.

12. Functions of Leaves • Transpiration – loss of water through the leaves or stems of plants • Transpiration exchange gases as oxygen and carbon dioxide

13. Transpiration • occurs as the sun warms the water inside the blade. • The warming changes much of the water into vapor. • This gas can then escape through the stomata.

14. Transpiration • Transpiration helps cool the inside of the leaf because the escaping vapor has absorbed heat. • Simply, transpiration is the plant giving off moisture and an exchange of gas.

15. Transpiration • Transpiration also helps keep water flowing up the stem from the roots. • Water forms a continuous column as it flows up the roots, through the stem, and into the leaves. • Increases turgid pressure in the plant. • As water molecules are lost through transpiration, the entire column of water is pulled upward.

16. Transpiration

17. Stems • Movement of Materials • Support of the leaves and reproductive structures • Food storages • Reproduction with stem cuttings or grafting

18. Stems-Internal (dicot)

19. Stems-Internal • Pith-dead center of stem for support • Heartwood-old inactive xylem • Sapwood-new active xylem • Cambium-thin, green, actively growing tissue located between bark and wood and produces all new stem cells • Phloem-active • Bark-old inactive phloem

20. The outer bark is the tree’s protection from the outside world. Continually renewed from within, it helps keep out moisture in the rain, and prevents the tree from losing moisture when the air is dry. It insulates against cold and heat and wards off insect enemies. • The inner bark, or “phloem”, is pipeline through which food is passed to the rest of the tree. It lives for only a short time, then dies and turns to cork to become part of the protective outer bark. • The cambium cell layer is the growing part of the trunk. It annually produces new bark and new wood in response to hormones that pass down through the phloem with food from the leaves. These hormones, called “auxins”, stimulate growth in cells. Auxins are produced by leaf buds at the ends of branches as soon as they start growing in spring. • Sapwood is the tree’s pipeline for water moving up to the leaves. Sapwood is new wood. As newer rings of sapwood are laid down, inner cells lose their vitality and turn to heartwood. “xylem” • Heartwood is the central, supporting pillar of the tree. Although dead, it will not decay or lose strength while the outer layers are intact. A composite of hollow, needlelike cellulose fibers bound together by a chemical glue called lignin, it is in many ways as strong as steel. A piece 12" long and 1" by 2" in cross section set vertically can support a weight of twenty tons!

21. Stems-Internal (Translocation) • Xylem-tissue that transports water and nutrients up from the roots to stems and leaves • Phloem-tissue that transports food down from leaves to roots Phloem Phloem Xylem

22. Stems-Internal • Monocot : examples: corn, grasses • Dicot: example: trees

23. Functions of Stems • Translocation – move water and minerals from roots up to leaves & move food from leaves down to the roots • Xylem and phloem cells help with this process.

24. Roots-Internal • Much like stems in that they have a phloem, cambium, and xylem layer • Phloem-the outer layer that carries food down the root • Xylem-the inner layer that carries water and minerals up to the stem

25. Layers of Roots • Fibrous-many branched shallow roots • are easier to transplant • Tap-long root with few branched ones • more difficult to transplant

26. Functions of Roots • Absorption-take water and nutrients from the soil and conduct them to the stem • Anchor the plant and hold it upright • Store food for plant use • Asexual reproduction in some plants