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Introduction to PlantsKingdom: Plantae
Plants: Cell wall Autotroph (photosynthesis) Multi-cellular
12 Divisions (Phyla) Anthophyta = Angiosperms (flowering plants)
Largest # of species (~250,000 - 90% plants) Seed plants: product seed w/in a fruit Key adaptations: flowers & fruits Sporophytes are trees, shrubs, herbs that flower 2 main groups: Monocots & Dicots
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Monocots vs. Dicots
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Monocot Dicot
• One cotyledon (seed leaf) •Two cotyledon
• Parallel veins in leaves •Netted veins in leaves
• Fibrous root system •Taproot
• Floral parts in multiples of 3 •Floral parts in multiple layers of 4 or 5
• Complex vascular arrangement •Ring vascular arrangement
• Eg. grass, corn, palm, onion, tulip, bamboo •Eg. bean, pea, rose, sunflower
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Concept 35.1 The plant body has a heirarchy of organs, tissues, and cells
Basic Organs
• Roots• Stems• Leaves
Types of Tissue
• Dermal• Vascular• Ground
Cell Types
• Parenchyma• Collenchyma• Sclerenchyma• Xylem• Phloem
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•Above ground•Stems, leaves
•Underground (usually)•Roots
Shootsystem
Rootsystem
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A. Roots Anchors plant, absorbs H2O & minerals, stores
sugars/starches Root hairs – tiny extensions of epidermal cells,
increase surface area for H2O and mineral absorption
Mycorrhizae: symbiosis with fungi
Root hairs
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Fibrous Roots Taproots•Mat of thin roots spread just below surface •One thick, vertical root
•Shallow •Many lateral (branch) roots
• Increased surface area •Firmly anchors
•Monocots •Stores food in root
•Dicots
Fibrous Root(scallion)
Taproot(carrot)
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B. Stems Alternating system of nodes (leaf
attachment) and internodes Function: display leaves
Terminal bud – growth concentrated at apex (tip)
Apical dominance: terminal bud prevents growth of axillary buds; growth directed upward, toward light
Axillary buds – located in V between leaf and stem; forms branches (lateral shoots)
Pinching/pruning – removing terminal bud
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Modified stems• Runner or stolin
– Aspen, strawberries, grass– Grow on surface– For asexual reproduction
• Rhizome– Iris, ginger, potato, onion– Grow underground– Store food & DNA for new plant– Tuber: end of rhizome
• Bulb – underground shoot– Onion – storage leaves
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C. Leaves◦ epidermis of underside interrupted by stomata
(pores)◦ Mesophyll: ground tissue between upper/lower
epidermis◦ Parenchyma: sites of photosynthesis◦ Cuticle: waxy layer
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Three Tissue Systems
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A. Dermal Tissue• Single layer, closely packed cells that cover
entire plant• Protect against water loss & invasion by
pathogens• Cuticle: waxy layer• Epidermis, periderm
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B. Vascular Tissue
• Continuous throughout plant• Transports materials between roots & shoots
1. Xylem: transport H2O and minerals up from root
2. Phloem: transports food from leaves to other parts of plantstele
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C. Ground Tissue
• Anything that isn’t dermal or vascular• Function: storage, photosynthesis, support• Pith: inside vascular tissue• Cortex: outside vascular tissue
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III. Cell TypesA. Parenchyma: most abundant
Perform metabolism, synthesizes & stores organic products
B. Collenchyma: grouped in cylinders, support growing parts of plant
C. Sclerenchyma: rigid support cellD. Xylem: water conduction
Tracheids, vessel elements – dead, tubular, elongated cells
E. Phloem: sugar, organic cmpd. conduction Sieve tubes, plates, companion cells – alive
cells which aid movement of sugar
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PARENCHYMA CELLS
Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm
80 µmCortical parenchyma cells
Collenchyma cells (in cortex of Sambucus, elderberry; cell walls stained red) (LM)
COLLENCHYMA CELLS
SCLERENCHYMA CELLS
SUGAR-CONDUCTING CELLS OF THE PHLOEM
WATER-CONDUCTING CELLS OF THE XYLEM
5 µm
Fiber cells (transverse section from ash tree) (LM)
25 µm
Sclereid cells in pear (LM)
Cell wall
Sieve-tube members:longitudinal view
30 µm
15 µm
Companioncell
Companioncell
Sieve-tubemember
Plasmodesma
Sieveplate
Sieve plate with pores (LM)
Nucleus
Cytoplasm
Sieve-tube members:longitudinal view(LM)
Vessel elements withperforated end walls
Vesselelement
Tracheids
Pits
Tracheids and vessels(colorized SEM)
TracheidsVessel 100 µm
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Primary and Secondary Growth(apical vs. lateral meristems)
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Concept 35.3 Primary growth lengthens roots and shoots
Root cap: protects meristem as it pushes through soil; also secretes polysaccharide lubricant
Zone of Cell Division: apical meristem; new cells produced
Zone of Elongation: cells elongate; push root tip ahead
Zone of Maturation: growth & differentiation complete; fully mature cells
Root Hairs
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Concept 35.4 Secondary growth adds girth to stems and roots in woody plants
• Involves lateral meristems– Vascular cambium: produces secondary xylem
(wood)– Cork cambium: produces tough covering that
replaces epidermis• Bark = all tissues outside vascular cambium