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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.

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Presentation on theme: "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."— Presentation transcript:

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

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