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Ch 23- Roots, Stems, and Leaves

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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 What specialized cells make up vascular tissue
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 What are the functions of the three types of cells?
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 Tree rings indicate weather conditions, and age
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

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