Ch 23- Roots, Stems, and Leaves

1. Ch 23- Roots, Stems, and Leaves • Cells of seed plant are organized into different tissues and organs • Principal organs of seed plants- roots, stems, leaves • Roots- absorb water and dissolved nutrients, anchor plants in ground • Stems- supports, transports, and protects plant • Leaves- broad, flat surfaces where photosynthesis takes place

2. Plant Tissue Systems • What are the principal tissues of seed plants? • Dermal, vascular, ground • Dermal tissue- “skin” of plant, outermost layer • Consist of epidermal cells • Cuticle- thick waxy coating that protects against water loss • Trichomes- tiny projections that protects the leaf, gives fuzzy appearance • Root hair cells- provide large amount of surface area, aids in water absorption • Guard cells- regulate water loss and gas exchange on underside of leaves

4. Vascular tissue- plants “bloodstream” that transports water and nutrients throughout plant • What specialized cells make up vascular tissue • Xylem and phloem- made up of networks of hollow connected cells that carry fluids throughout plant • Xylem- made up of tracheids and vessel elements, transfers water throughout plant • Tracheids- long, narrow cells with walls that resist pressure, die when mature • Vessel element- cell that forms part of continuous tube in which water can move, die when mature • Phloem- made up of sieve tube elements and companion cells, transfer nutrients throughout cell • Sieve tube elements- cell that is joined end to end to form sieve tubes • Companion cells- cell that surrounds sieve tube elements

5. Ground tissue- cells that lie between dermal and vascular tissue, cell walls vary in thickness • Parenchyma- cell with thin cell wall and large central vacuole • Collenchyma-cell with strong, flexible cell wall, helps support larger plants • Sclerenchyma- cell with extremely thick, rigid cell wall that makes ground tissue tough and strong • What are the functions of the three types of cells?

7. Plant Growth and Meristematic Tissue • Meristems- clusters of tissue, responsible for continuing growth throughout plant’s life • Meristematic tissue- found only in tips of shoots and roots, responsible for plant growth • Apical meristem- group of undifferentiated cells that divide to produce increased length of stems and roots • How does meristematic tissue differ from other plant tissue? • Only plant tissue that produces new cells by mitosis

8. Sec 2- Roots • 2 main types of roots- taproots and fibrous roots • Taproot- primary root grows long and thick, secondary root remains small • Mainly in dicots • Carrots, oak trees, dandelions • Fibrous- branch of roots where no single root grows larger than rest • Mainly in monocots • Grasses

10. Root Structure and Growth • Roots contains dermal, vascular, and ground tissue • Root consists of central vascular cylinder surrounded by ground tissue and epidermis • Root hair- tiny projection from epidermis • Cortex- spongy layer of ground tissue just inside epidermis • Endodermis- layer of cells that completely encloses vascular tissue • Vascular cylinder- central region of root that includes vascular tissue • Root cap- tough structure that protects a root as it forces its way through surface • What are the different functions of roots? • Anchor plant in ground, absorb water and nutrients

12. Sec 3- Stems • What are the main functions of stems? • Produce leaves, branches, and flowers • Hold leaves up to sunlight, transport substances between roots and leaves • Stems made up of dermal, vascular, and ground tissue • Surrounded by epidermal cells with waxy protective coating • Contains nodes- where leaves are attached, internodes- regions between nodes, and buds- undeveloped tissue that produces new stems and leaves

13. How do monocot and dicot stems differ? • Monocots- vascular bundles are scattered throughout stem • Dicots- vascular bundles arranged in ring • Pith- parenchyma cells inside ring of vascular tissue • How do primary growth and secondary growth occur in stems? • Primary growth- growth that occurs at end of plant, increases plant in length. • Produces by cell division in apical meristem • Takes place in all seed plants • Secondary growth- growth in which stems increase in width • Takes place in lateral meristematic tissue- vascular cambium and cork cambium • Vascular cambium- produces vascular tissues and increases the thickness of stems over time • Cork cambium- produces the outer covering of stems

15. Formation of wood • Heartwood- older xylem near center of stem, no longer conducts water, usually darkens with age • Sapwood- surrounds heartwood, active in fluid transport, lighter in color • Tree rings indicate weather conditions, and age • Bark- phloem, cork cambium, and cork • Protects tree

16. Sec 4- Leaves • Leaf structure- ideal for absorbing light and carrying out photosynthesis • Blades- thin, flattened sections of leaves • Petiole- thin stalk that attaches blade to stem • Leaf function- carry out photosynthesis • Mesophyll- tissue that makes up most of leaf, performs most of plant’s photosynthesis • Palisade mesophyll- layer of tall, column shaped mesophyll cells just under epidermis of leaf • Spongy mesophyll- loose tissue beneath the palisade layer of a leaf • Stomata- openings on underside of leaf, allow carbon dioxide and oxygen to diffuse into and out of leaf • Guard cells- controls opening and closing of stomata

19. Transpiration- loss of water through its leaves • How does gas exchange take place in a leaf? • Plants regulate the opening and closing of their stomata to balance water loss with rates of photosynthesis

20. Sec 5- Transport in Plants