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Tissues and the Primary Growth of Stems (External Organization of Stems…
Tissues and the Primary Growth of Stems
Concepts
Body of herb has 3 different parts
Leaves
Stems
Roots
First land plants basically algae
Washed up on shore
Left as lakes and ponds evaporated
Basic Types of Cells and Tissues
Parenchyma
Only primary walls
Walls remain thin
Parenchyma Tissues
Mass of parenchyma cells
Most common type of cell and tissue
Some cells die at maturity
Soft parts of plants
Secretory glandular cells
Secrete
Nectar
Fragrances
Mucilage
Resins
Oils
Collenchyma
Have primary wall
Thin in some areas, thickened in other areas
Require more glucose for production
Usually produced in
Shoot tips
Young petioles
Sclerenchyma
Third basic type of cell and tissue
Primary and secondary wall
Both elastic
Can be deformed but return to starting size
Develop from parenchyma cells
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Two types
Conducting
Mechanical
Pits
External Organization of Stems
Nodes where leaves are attached
Internodes
Regions between nodes
Leaf axil
stem area above point where a leaf attaches
Axillary bud
Miniature shoot with dormant apical meristem
Bud scales
Cover the bud
corky, waxy, small
Terminal bud
Extreme tip of stem
Internal Organization of Stems
Arrangement of Primary Tissues
Epidermis
Outermost surface of herbaceous stem
Single layer of living parenchyma
Encrusted with cutin
Builds up to make cuticle
Cortex
interior to the epidermis
Composed of photosynthetic parenchyma and collenchyma
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Vascular Tissues
Two types
Xylem
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Phloem
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Xylem
Two types
Tracheids
Vessel elements
Vascular tissue
Phloem
two types
Sieve tube members
Sieve tube cells
Vascular tissue
Vascular Bundles
Where xylems and phloems are together
Stem Growth and Differentiation
stems grow by creating new cells
Apical meristem
Cells divide by mitosis
Protoderm
epidermal cells in early development
