Presentation on theme: "Ch 23- Roots, Stems, and Leaves"— Presentation transcript:
1 Ch 23- Roots, Stems, and Leaves Cells of seed plant are organized into different tissues and organsPrincipal organs of seed plants- roots, stems, leavesRoots- absorb water and dissolved nutrients, anchor plants in groundStems- supports, transports, and protects plantLeaves- broad, flat surfaces where photosynthesis takes place
2 Plant Tissue Systems What are the principal tissues of seed plants? Dermal, vascular, groundDermal tissue- “skin” of plant, outermost layerConsist of epidermal cellsCuticle- thick waxy coating that protects against water lossTrichomes- tiny projections that protects the leaf, gives fuzzy appearanceRoot hair cells- provide large amount of surface area, aids in water absorptionGuard 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 plantWhat specialized cells make up vascular tissueXylem and phloem- made up of networks of hollow connected cells that carry fluids throughout plantXylem- made up of tracheids and vessel elements, transfers water throughout plantTracheids- long, narrow cells with walls that resist pressure, die when matureVessel element- cell that forms part of continuous tube in which water can move, die when maturePhloem- made up of sieve tube elements and companion cells, transfer nutrients throughout cellSieve tube elements- cell that is joined end to end to form sieve tubesCompanion 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 thicknessParenchyma- cell with thin cell wall and large central vacuoleCollenchyma-cell with strong, flexible cell wall, helps support larger plantsSclerenchyma- cell with extremely thick, rigid cell wall that makes ground tissue tough and strongWhat 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 lifeMeristematic tissue- found only in tips of shoots and roots, responsible for plant growthApical meristem- group of undifferentiated cells that divide to produce increased length of stems and rootsHow 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 smallMainly in dicotsCarrots, oak trees, dandelionsFibrous- branch of roots where no single root grows larger than restMainly in monocotsGrasses
10 Root Structure and Growth Roots contains dermal, vascular, and ground tissueRoot consists of central vascular cylinder surrounded by ground tissue and epidermisRoot hair- tiny projection from epidermisCortex- spongy layer of ground tissue just inside epidermisEndodermis- layer of cells that completely encloses vascular tissueVascular cylinder- central region of root that includes vascular tissueRoot cap- tough structure that protects a root as it forces its way through surfaceWhat 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 flowersHold leaves up to sunlight, transport substances between roots and leavesStems made up of dermal, vascular, and ground tissueSurrounded by epidermal cells with waxy protective coatingContains 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 stemDicots- vascular bundles arranged in ringPith- parenchyma cells inside ring of vascular tissueHow 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 meristemTakes place in all seed plantsSecondary growth- growth in which stems increase in widthTakes place in lateral meristematic tissue- vascular cambium and cork cambiumVascular cambium- produces vascular tissues and increases the thickness of stems over timeCork cambium- produces the outer covering of stems
15 Tree rings indicate weather conditions, and age Formation of woodHeartwood- older xylem near center of stem, no longer conducts water, usually darkens with ageSapwood- surrounds heartwood, active in fluid transport, lighter in colorTree rings indicate weather conditions, and ageBark- phloem, cork cambium, and corkProtects tree
16 Sec 4- LeavesLeaf structure- ideal for absorbing light and carrying out photosynthesisBlades- thin, flattened sections of leavesPetiole- thin stalk that attaches blade to stemLeaf function- carry out photosynthesisMesophyll- tissue that makes up most of leaf, performs most of plant’s photosynthesisPalisade mesophyll- layer of tall, column shaped mesophyll cells just under epidermis of leafSpongy mesophyll- loose tissue beneath the palisade layer of a leafStomata- openings on underside of leaf, allow carbon dioxide and oxygen to diffuse into and out of leafGuard 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
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