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Plant Structures Roots, Stems, and Leaves

Plant Structures Roots, Stems, and Leaves. Chapter 23. 23-1 Specialized Tissues in Plants. Plants are as successful if not more successful than animals Seed plants have three main structures: Roots Stems Leaves Linked together by various means. 23-1 Specialized Tissues in Plants. Roots

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Plant Structures Roots, Stems, and Leaves

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  1. Plant StructuresRoots, Stems, and Leaves Chapter 23

  2. 23-1 Specialized Tissues in Plants • Plants are as successful if not more successful than animals • Seed plants have three main structures: • Roots • Stems • Leaves • Linked together by various means

  3. 23-1 Specialized Tissues in Plants • Roots • Absorbs water and nutrients • Anchor plant to the ground • Hold soil in place and prevent erosion • Protect from soil bacteria • Transport water and nutrients • Provide upright support

  4. 23-1 Specialized Tissues in Plants • Stems • Support for the plant body • Carries nutrients throughout plant • Defense system to protect against predators and infection • Few millimeters to 100 meters

  5. 23-1 Specialized Tissues in Plants • Leaves • Main photosynthetic systems • Suseptable to extreme drying • Sight of oxygen/carbon dioxide intake and release

  6. 23-1 Specialized Tissues in Plants • Plant tissue systems • Exist within the root, stems, and leaves • Dermal tissue • Vascular tissue • Ground tissue

  7. 23-1 Specialized Tissues in Plants • Dermal Tissue • Outer covering • Single layer of cells • Cuticle – waxy coating • Trichomes – Spiny projections on the leaf • Roots have dermal tissue • Root hairs • Guard Cells

  8. 23-1 Specialized Tissues in Plants • Vascular Tissue • Transport System • Subsystems • Xylem • Phloem • Subsystems are used to carry fluids throughout plant

  9. 23-1 Specialized Tissues in Plants • Xylem • Two types • Seed plants • Angiosperms • Tracheid – long narrow cells • Walls are connected to neighboring cells • Will eventually die • Vessel Element – wider that trachieds

  10. 23-1 Specialized Tissues in Plants • Phloem • Sieve Tube Elements • Cells arranged end to end • Pump sugars and other foods • Companion Cells • Surround sieve tube elements • Support phloem cells

  11. 23-1 Specialized Tissues in Plants • Ground Tissue • Cells between dermal and vascular tissue • Parenchyma • Thin cell walls, large vacuoules • Collenchyma • Strong, flexible cell walls • Sclerenchyma • Extremely thick, rigid cell walls

  12. 23-1 Specialized Tissues in Plants • Plant Growth • Meristems – tissues responsible for growth • Undifferentiated cells • Apical Meristem • Produce growth increased length • Differentiation • Cells will assume roles in the plant • Flower Development • Starts in the meristem

  13. 23-2 Roots • Types of Roots • Taproots • Found in dicots • Long, thick root • Hickory and oak trees • Fibrous roots • Found in monocots • No single root larger than any other • Many thin roots

  14. 23-2 Roots • Root Structure • Outside layer • Epidermis • Root hairs • Cortex • Central cylinder – vascular system • Root Cap – cellular production • Key role in water/mineral transport

  15. 23-2 Roots • Root Functions • Anchor plant • Absorb water • Absorb nutrients

  16. 23-2 Roots • Plant Nutrient Uptake • Soil type determines plant type • Plant requirements • Oxygen, CO2 • Nitrogen • Phosphorus • Postassium • Magnesium • Calcium • Trace elements

  17. 23-2 Roots • Active Transport in Plants • Root hairs use ATP • Pump minerals from soil • Causes water molecules to follow by osmosis • Vascular Cylinder • Casparian Strip – water retention • Root Pressure • Forces water up into the plant

  18. 23-3 Stems • Stem Structure • Produce leaves, branches, and flowers • Hold leaves up • Transport substance between roots and leaves • Essential part of transport system • Function in storage and photosynthesis

  19. 23-3 Stems • Xylem and phloem – major tubule systems • Transport water and nutrients • Composed of three tissue layers • Contain nodes – attachment for leaves • Internodes – regions between the nodes • Buds – undeveloped tissue

  20. 23-3 Stems • Stem Types • Monocot – vascular bundles are scattered throughout • Distinct epidermis • Dicot – vascular tissue arranged in a cylinder • Pith – parenchyma cells inside the ring

  21. 23-3 Stems • Stem Growth • Primary growth – new cells produced at the root tips and shoots • Increases the length • Secondary growth – increase in stem width • Vascular cambium – produces tissue and increases thickness • Cork cambium – produces outer covering of stems

  22. 23-3 Stems • Formation of Vascular Cambium • Xylem and phloem bundles present intially • Secondary growth initiates production of a thin layer • The vascular cambium divides • Produces new xylem and phloem

  23. 23-3 Stems • Formation of wood • Wood – layers of exlem • Produced year after year • Results from the older xylem not conducting water – heartwood • Becomes darker with age • Sapwood – surrounds heartwood

  24. 23-3 Roots • Formation of Bark • All the tissues outside the vascular cambium • Consists of outermost layers of dead cork • Water proof

  25. 23-4 Leaves • Main sight of photosynthesis • Consist of: • Blade – thin flattened section • Petiole – stalk that attaches stem to blade • Covered by epidermis and cuticle • Create water proof barrier

  26. 23-4 Leaves • Leaf Functions • Photosynthesis – occurs in the mesophyll • Palisade mesophyll – absorb light • Spongy mesophyll – beneath palisede level • Stomata – pores in the underside of the leaf • Guard Cells – Surround the stomata

  27. 23-4 Leaves • Transpiration • Loss of water through its leaves • Replaced by water drawn into the leaf

  28. 23-4 Leaves • Gas Exchange • Take in CO2 and release O2 • Can also do the opposite – How? • Gas exchange takes place at the stomata • Not open all the time • Stomata is controlled by water pressure in guard cells

  29. 23-5 Transport in Plants • Water Transport • Active transport and root pressure • Cause water to move from soil to roots • Capillary action • Combined with active transport and root pressure, moves materials throughout the plant

  30. 23-5 Transport in Plants • Capillary Transport • Capillary transport results from both cohesive and adhesive forces • Water molecules attracted to one another • Water is also attracted to the xylem tubes in the plant • Causes water to move from roots to the stem and upward

  31. 23-5 Transport in Plants • Transpiration • Evaporation is the major moving force • As water is lost, osmotic pressure moves water out of vascular tissue • This pulls water up from the stem to the leaves • Affected by heat, humidity, and wind

  32. 23-5 Transport in Plants • Controlling Transpiration • Open the stomata – increase water loss • Close the stomata – decrease water loss

  33. 23-5 Transport in Plants • Transpiration and Wilting • Osmotic pressure – keeps plants semi-rigid • Wilting is a result of high transpiration rates • Loss of water causes a drop in osmotic pressure • Loss of rigidity • Conserves water

  34. 23-5 Transport in Plants • Nutrient Transport • Most nutrients are pushed through plant • Nutrient movement takes place in phloem • Source to Sink • Source – any cell that produces sugars • Sink – any cell where sugars are used • Pressure-flow Hypothesis

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