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Tissues and the Primary Growth of Stems (Internal Organization of Stems…
Tissues and the Primary Growth of Stems
Basic Types of Cells and Tissues
Sclerenchyma
elastic but return to shape
Dead at maturity
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Double cell wall
normally lignified
Types
Conducting
Mechanical
Sclereids
Short, Isodiametric
Shells
Fibers
Flexible
Wood
Collenchyma
wilting cells
need parenchymal tire for support
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variable primary wall thickness
allows for plasticity
Parenchyma
Only have cell walls
Makes up soft leaves, petals, fruits, and seeds
Most common type of plant tissue
Parenchyma Subtypes
Glandular Cells
Transfer Cells
Chlorenchyma
Normally living at maturity
Stamens die at maturity
External Organization of Stems
Nodes
Leaves
Leaf axil
covered in bud scales
Internodes
Between leaves
vines and stolons have long internodes
Phylotaxy
Arrangement of leaves on the stem
So no inter-plant shading goes on
Internal Organization of Stems
Vascular Bundles
Collateral
Coagulated in the pith
Groups of both vascular tissue types
Vascular Tissues
Phloem
Sieve tube member
Companion cells
Xylem
tracheids
Thinner
vessel elements
Thicker
Cortex
homogenous
Interior and composed of photosynthetic cells
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Epidermis
Outermost layer
Single parenchymal cell layer
Covered in waxy cuticle
Stem Growth and Differentiation
First xylem is the proto xylem
Subapical region is location of differentiation
Apical meristems produce new cells
Needed for Structural Support
Dead when full grown
Collenchyma
