Glossary of BIO 1510: Lecture Exam 3-2: 35

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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
Apical meristems: primary growth at tip of stem or root

Lateral meristems: secondary growth to increase girth
3 types of Plant Tissue
Plant Tissue: Dermal
Specialized cells for protection & absorption
Plant Tissue: Dermal: Cells
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
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
Xylem: transports water & solutes from roots

Phloem: transports food (sugars) from photosynthetic sites
Plant Tissue: Vascular: Xylem
Vessels: continuous tubes formed from dead, hollow cells

Tracheids: dead, tapered cells that overlap
Plant Tissue: Vascular: Phloem
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
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
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
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
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
Alternate (spiral)

Opposite – 2 leaves per node

Whorl – circle of leaves at same node
Internal Leaf Structure: Epidermis
Transparent epidermis around entire surface

Upper surface has a waxy cuticle

Lower surface has many stomata (for gas & water exchange)
Internal Leaf Structure: Mesophyll
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
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

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