unit 7 plants
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Unit 7 Plants
Part 2: Tissues, Roots, Stems & Leaves
Plant Tissues – 1. Dermal Tissue
• Outer covering
• Made of epidermal cells
• Waxy coating: cuticle
• Accessories: – Trichomes (“fuzz”)– Root hairs (absorption)– Guard cells (regulate water/gas
movement at surface)
Plant Tissues – 2. Vascular Tissue
• Transport system – Moves water/nutrients
• Xylem: water-conducting tissue– Tracheids– Vessel elements
• Phloem: food-conducting tissue– Sieve tube elements– Companion cells
Plant Tissues – 3. Ground Tissue
• Everything else• Three types– Parenchyma (majority) Thin cell walls; functions
include storage & photosynthesis
– Collenchyma Strong, flexible cell walls; functions include support
– Sclerenchyma Extremely thick/rigid; extra support/toughness
Plant Growth• Indeterminate (never stop)
• Meristem Tissue clusters where new growth occurs via mitosis
• Cells produced in meristem = undifferentiated (not yet specialized)
• Apical meristem = at end of root or stem; responsible for increased length
• Cells gradually differentiate
Plant Roots: 1. Types
• Taproots Long, thick primary root; mainly in dicots
• Fibrous roots Branching system, no primary; mainly in monocots
Plant Roots: 2.
Structure/Growth
Plant Roots: 3. Functions• Anchor
• Uptake nutrients from soil (N, P, K, Mg, Ca)
• Active transport of mineral ions Leads to osmosis of water
• One-way movement into vascular cylinder and up (capillary action)
• Generates root pressure to move water/nutrients from roots all the way up plant
Stems: 1. Structure/Function
• Three functions:– Produce
leaves/branches/flowers– Hold leaves up to sun– Transport substances
between roots + leaves
Stems: 2. Primary Growth
• Primary growth: New cells only produced at root + shoot tips (ends)
• Cell division in apical meristem
Stems: 3. Secondary Growth
• Stems grow thicker/wider• Dicots and conifers• Division of the vascular cambium (a different
kind of meristem)– Produces more xylem + phloem
• Grows from inside - outward• Protected by cork cambium
Stems: 3. Secondary Growth
• Leads to formation of wood• Wood = layers of xylem• Center = oldest, eventually non-functional
xylem (heartwood)• Exterior layer = sapwood (active)
Leaves: 1. Structure
• Blades: flattened; collect sunlight
• Petiole: stem
Leaves: 2. Function
• A. Photosynthesis– Special ground tissue: mesophyll palisade +
spongy)– Stomata (pores; gas movement)– Guard cells (regulation)
Leaves: 2. Function
• B. Transpiration– Loss of water– Replaced by water drawn up from roots
• C. Gas exchange– Take in CO2, give off O2
– Guard cells regulate movement in response to environment
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