BIO 1510: Lecture Exam 3-2: 35
Terms
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- Meristems
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Small clumps of undifferentiated cells from which new cells arise
Analagous to stem cells in animals - 2 types of meristems for growth
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Apical meristems: primary growth at tip of stem or root
Lateral meristems: secondary growth to increase girth - 3 types of Plant Tissue
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Dermal
Ground
Vascular - Plant Tissue: Dermal
- Specialized cells for protection & absorption
- Plant Tissue: Dermal: Cells
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epidermal cells- outer covering of entire plant body
guard cells – open & close the stomata
trichomes – hairlike outgrowths that cool plant surfaces, reduce evaporation, & sometimes secrete toxins
root hairs – increased surface area for absorption - Plant Tissue: Ground
- most of plant body
- Plant Tissue: Ground: Cells
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Parenchyma cells: living protoplasts, food & water storage, photosynthesis, & secretion
Long-lived (up to 100 years)
Collenchyma cells: living protoplasts, provide flexible support
Sclerenchyma cells: nonliving protoplasts at maturity, strengthen plant tissues - Plant Tissue: Vascular: 2 Types
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Xylem: transports water & solutes from roots
Phloem: transports food (sugars) from photosynthetic sites - Plant Tissue: Vascular: Xylem
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Vessels: continuous tubes formed from dead, hollow cells
Tracheids: dead, tapered cells that overlap - Plant Tissue: Vascular: Phloem
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Sieve-tube members: elongated cells with clusters of pores for food transport, each with a (companion cell)
Companion cell: parenchyma cell that performs metabolic
functions for specialized sieve-tube members - 3 Plant Organs
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Roots
Stems
Leaves - Roots
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Root cap – composed of columella cells
Protect meristem as root grows through soil and act as gravity sensors
Zone of cell division – mitotic divisions
Zone of elongation – cells elongate (which lengthens the root) and vacuoles swell
Zone of maturation – cells differentiate (epidermis, xylem, phloem, etc.) - Modified Roots
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Pneumatophores – outgrowths of underwater roots that acquire oxygen
Prop roots – for support against the wind
Contractile roots – spiral into the soil to pull plant deeper for temperature control
Food storage – sweet potatoes, carrots, beets, radishes, etc.
Parasitic roots – penetrate & feed off other plants
Water storage – in arid regions
Buttress roots – support in tropical trees - Stem Structures
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Apical meristems at tip of stem
Apical meristems at junction of leaf & stem
Form buds which can:
Repeat the growth pattern of the terminal meristem
Make flowers directly
Lenticels – for gas exchange into stem tissue - External Leaf Structure
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Simple leaves – undivided blades
Compound leaves – 2 or more leaflets
- Pinnately – leaflets in pairs along an axis
- Palmately – leaflets radiate from a common point - Leaf Arrangements
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Alternate (spiral)
Opposite – 2 leaves per node
Whorl – circle of leaves at same node - Internal Leaf Structure: Epidermis
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Transparent epidermis around entire surface
Upper surface has a waxy cuticle
Lower surface has many stomata (for gas & water exchange) - Internal Leaf Structure: Mesophyll
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Mesophyll –between upper & lower epiderm.
Palisade: tightly packed cells with chlorophyll
Spongy: loosely packed cells with extracellular spaces for gas & water exchange - Internal Leaf Structure: Vascular Tissue
- xylem & phloem
- Modified Leaves
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Bracts: colored leaves that mimic flower petals
Spines: cacti
Reproductive leaves: produce tiny “plantlets†which can grow into new plants (Kalanchoe)
Window leaves: transparent leaves that allow light to penetrate & reach chloroplasts underground
Shade leaves: more surface area but thinner than those leaves on the same plant in direct sunlight
Insectivorous leaves: secrete enzyme to digest insects