Roots, Stems, and Leaves Ms. Moore 9/6/2012

1. Roots, Stems, and LeavesMs. Moore9/6/2012

2. Floral bud surrounded by leaves Small stem surrounded by leaves • What part of the plant do we eat? • Label the stems, roots, and leaves of each vegetable. Stem with eyes that grow into branches

3. Principal Organs of Seed Plants • Roots • Absorb water • Anchor plants into ground • Hold plants upright through weather • Stems • Support system • Transport system • Defense against predators and disease • Leaves • Photosynthesis • Protect against water loss

4. Tissue Systems • Dermal • Epidermal cells: surround outer covering of a plant • Waxy layer protects against water loss and injury (cuticle) • Vascular • Xylem • Phloem • Ground • Between dermal and vascular tissues • Meristematic • Produces new cells by mitosis

6. Dermal Tissue • Single layer of closely packed cells • Covers and protects the plant; acts as “skin” • Thick waxy layer, known as cuticle

7. Vascular Tissue • Xylem • Tracheid • Vessel element • Phloem • Sieve tube elements • Companion cells

8. Ground Tissue • Parenchyma • Packed with chloroplasts; site of photosynthesis • Collenchyma • Celery “strings”; flexible walls for support • Sclerenchyma • Rigid; strength and support

9. Meristematic Tissue • Meristems: clusters of tissue responsible for continuing growth • Meristematic tissue: undifferentialted cells produced by mitosis • Apical meristem: group of cells near the end or top of plant that divide to produce increased length of stems and roots

11. Mastery • What are the three main organs of seed plants? • List the three tissue systems of plants. • What two cell types make up xylem? Phloem? • What is the function of meristematic tissue in a plant?

12. Types of Roots • Taproots • Primary root grows long and thick • Mainly in dicots • Fibrous roots • No single root grows larger than the rest • Mainly in monocots

13. Structure and Growth • Root hair: water enters plant at tiny projections • Cortex: spongy layer of ground tissue • Endodermis: encloses vascular subsystem • Vascular cylinder: contains xylem and phloem • Root cap: protects root as it grows through soil • Casparian strip: waterproofs endodermis

14. Uptake of Nutrients

15. Mastery • Compare a taproot and a fibrous root. • How are tissues distributed in a plant root? • What are the two main functions of roots?

16. Stem Structure and Function • Produce leaves, branches, and flowers • Hold leaves up to sunlight • Transport substances between roots and leaves • Primary Growth: cell divisions in apical meristem • Secondary Growth: growth in lateral meristems in conifers and dicots

18. Stem Structure • Nodes: where leaves are attached • Internodes: region between two nodes • Buds: contain undeveloped tissue that can produce new stems, leaves, flowers • Pith: parenchyma cells inside ring of vascular tissue (outside cells = cortex) in stem

19. Monocot vs. Dicot

20. Growth • Primary: apical meristem; all seed plants • Secondary: lateral meristem; dicots • Vascular cambium: increases the thickness of stems over time • Cork cambium: produces outer covering of stems

21. Formation of Wood • Heartwood: older xylem near center no longer conducts water; darker in color • Sapwood: active in fluid transport; surrounds heartwood; lighter in color • Bark: tissues outside the vascular cambium

22. Mastery • How do the functions of a stem relate to the roots and leaves of a plant? • Describe how the arrangement of vascular bundles differs between monocot and dicot stems. • What is primary and secondary growth? • How do heartwood and sapwood differ?

23. Leaf Structure • Structure is optimized for absorbing light and carrying out photosynthesis and gas exchange. • Blades: collect sunlight • Petiole: attachment • Vascular tissues are connected directly to stem’s vascular tissues. • Xylem and phloem tissues are gathered together into bundles that run from the stem into the petiole to the leaf blade. • In the leaf blade, vascular bundles are surrounded by parenchyma and sclerenchyma cells.

25. Leaf Function: Photosynthesis • Photosynthesis: 6CO2 + 6H2O  C6H12O6 + 6O2 • Mesophyll: specialized ground tissue where most photosynthesis occurs • Palisade mesophyll: closely packed cells that absorb light; located under the epidermis • Spongy mesophyll: loose tissue with many air spaces (gas exchange) • Stomata: porelike openings in the underside of the leaf that allow CO2 and O2 to diffuse in and out of leaf • Guard cells: specialized cells in the epidermis that control the opening and closing of stomata (due to changes in water pressure)

26. Why is photosynthesis important to all life?

27. Leaf Function: Transpiration • The surfaces of spongy mesophyllare kept moist so that gases can enter and leave the cells easily. • Transpiration: the loss of water through the leaves

28. Leaf Functions: Gas Exchange • Leaves take in CO2 and give off O2 during photosynthesis. • Do leaves ever take in O2? • Gas exchange takes place in the stomata. • Plants keep stomata open just long enough to allow photosynthesis to occur. • Why don’t they keep stomata open at all times? • What cells regulate the opening and closing of stomata?

30. Mastery • How is the structure of a leaf optimized for light absorption? • What factors regulate the opening and closing of guard cells? • Are stomata more likely to be open or closed on a hot day? • Describe transport of water and nutrients in a leaf.

31. Transport in Plants • Combination of root pressure, capillary action, and transpiration (loss of water through leaves) provides enough force to move water through the xylem tissue. Up next…Transpiration Lab!

32. Water Transport • How is water transported throughout the plant? • Water molecules are attracted to one another by a force called cohesion; they are attracted to other molecules by adhesion. • The tendency of water to rise in a thin tube (xylem) is called capillary action. • Water is attracted to the walls of the tube and they are also attracted to one another.

33. Nutrient Transport • Phloem carries out the seasonal movement of sugars within a plant. • Pressure-flow hypothesis: When nutrients are pumped into or removed from the phloem system, the change in concentration causes a movement of fluid in that same direction. • Source: an area rich in nutrients • Sink: an area that needs nutrients

34. Review • Vocabulary • Study Guide • Any Questions?