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Tissue and the Primary Growth of Stems (External and Internal Organization…
Tissue and the Primary Growth of Stems
Concepts
Magnoliophyta
Angiosperms
Basel angiosperms
Waterlilies
Magnolias
Laurels
Eudicots
Roses
Asters
Maples
Monocots
Grasses
Lilies
Cattails
Palms
Philodendrons
Bromeliads
Largest in the plant kingdom
Plants continue to evolved
Plant bodies
Primary plant body
Herbs
Secondary plant body
Basic Types of Cells and Tissues
Plant cell groups
Parenchyma
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Primary walls that remain thin
Parenchyma tissue
Mass of parenchyma cells
Most common type of cell and tissue
Soft leaves, petals, fruits and seeds
Active metabolically
Remain alive after they mature
Collenchyma
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Parenchyma cells involved in photosynthesis
Primary wall that remains thin
Becomes thickened in corners
Exhibits plasticity
Present as a layer under the epidermis
As bands located next to vascular bundles
Makes tips stronger
Sclerenchyma
Primary wall
Thick secondary wall
Almost always lignified
Pits
Pit-pair
Both walls are elastic
Maintains leafs shape
Remain upright and do not droop
Conducting sclerenchyma
Mechanical sclerenchyma
Fibers
Sclereids
Short, more or less isodiametric
Acts brittle and inflexible
External and Internal Organization of Stems
Flowering plants
Basic stem organizations
Nodes
Leaves are attached
Internodes
Regions between nodes
Stolons
Long and thin
Steam area where leave attaches
Leaf axil
Axillary bud
Mature shoot
Dormant apical meristem
Several young leaves
Vegetative bud
Grows into a branch
Floral bud
Grows into a flower
Covered by small, corky, waxy bud scales
Protects the delicate organs inside
Extreme tip of each stem
Terminal bud
Arrangement of leaves on the stem
Phyllotaxy
Important so leaves do not shade each other
Distichous
Arranged in di or stichies rows
Decussate
Arranged in four rows
Spiral
Form spirals up the stem
Shoots
Bulbs
Short shoots
Think, fleshy leaves
Onions, daffodils, garlic
Corms
Vertical, think stems
Think, papery leaves
Crocus, gladiolus
Rhizomes
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Bamboo, irises, canna lilies
Fleshy horizontal stems
Allows plants to spread underground
Tubers
Horizontal
Grow for a short period
Mainly a need for storing nutrients
Potatoes
All storage shoots are subterranean
Epidermis
Outermost surface of an herbaceous stem
Prevents water loss
Barrier against invasion of bacteria, fungi and insects
Pairs of cells
Guard cells
Stomatal pore
Constitute a stoma
Elongate outward
Trichomes
Hairs
Outer tangential walls
Encrusted with cutin
Makes the wall impermeable to water
Cuticle
Layer of wax may be present
Cortex
Interior to the epidermis
In many plants simple
Homogeneous
In some plants complex
Containing many specialized cells
Vascular Tissue
Small organisms whose bodies are unicellular or thin
Adequate for the distribution of sugars, minerals, oxygen, dioxide
Xylem
Conducts water and minerals
Conducting cells
Tracheids
Vessel elements
Sclerenchyma
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Tracheary element
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Phloem
Distributes sugars and minerals
Vascular bundles
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When xylem and phloem occur together
Interior to the cortex
Primary xylem
Primary phloem
Collateral
Stem Growth and Differentiation
Stems grow longer by creating new cells at tips
Shoot apical meristems
Subapical meristem
Just below the apical meristem
Protoxylem
Constitute the first xylem to appear
Metaxylem
Largest tracheary
Vascular bundle
Exterior cells mature as protophloem
Cells closest to the metaxylem become metephloem
Protoderm
Epidermal cells in early stages of differentiation
Young cells of xylem and phloem
Provascular tissue
Young pith and cortex
Ground meristem
