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Tissues and the Primary Growth of Stems (Arrangements of primary tissues…
Tissues and the Primary Growth of Stems
Types of Tissues and Cells
Collenchyma cells
Image
prevalent in shoot tips and petioles
Primary cell wall
Thick in other, especially in corner
exhibits plasticity
present in shoots tips of vining plants
layer under epidermis or band next to vascular bundles
Parenchyma cells in inner tissue provide support
Parenchyma Cells
mass forms parenchyma tissues
Chlorenchyma Cells
numerous amount of chloroplast
Thin cell walls
allows light and CO2 to pass through readily
Involve in photosynthesis
Glandular Cells and secretion includes
Contain large amount of dictysomes and ER
Secretions Includes
Nectar
Fragnance
Oil
resins
Mucilage
Metabolize Sugar and minerals
Large extensive plasma membrane
Used for short distance transport
contains numerous molecular pumps
Some Dies of maturity to function
May Create openings to release pollen and seeds
Form spaces to allow diffusion of gases within leaves
Transfer Cells
increases surface Area
Thin primary cell wall
inexpensive metabolically
mechanical Sclerenchyma
Long Fibers
found in areas where strength and flexibility is required
prevalent in wood of the most flowering plants
more flexible
Short sclereids
isodiometric
brtittle and inflexible
mass forms
shells walnuts and coconuts
"pits" or "stone" of cherries and peaches
Arrangements of primary tissues
Epidermis
outermost surface of an herbaceous stem
single layer of parenchyma cells
It work as a barrier against invasion by bacteria
it is also water proofing
Phloem
sieve cells and sieve tube members
have only primary walls
Has two conducting cells
their plasmodesmata enlarge to a diameter
Vascular Tissue
Has xylem and Phloem
It is not a circulatory system
Thin sheet of cell
Diffusion is adequate of the distribution of sugar
Cortex
it is quit simple and homogeous
interior to the epidermis is cortex
most of the plants fit together compact
Xylem
Has two types of cell tracheid and vessel elements
It is initially a small parenchyma cell
Has only a thin primary wall
Vascular Bundles
xylem and phloem occurs together
arranged in one ring surrounding the pith
all are collateral
Fibers
long many types are dead
others type remain alive and are involved in storage
Steam growth and differentiation
produce progenitor cells for the rest time
stems grow longer by creating new cells at their tips
cells divide by mitosis and cytokinesis
Vessel elements
found almost exclusively in flowering plant
short and wide with rather perpendicular end wall
dead at maturity
Sclereids
more or less isodiametric
often dead at maturity
External organization of Stems
In this stem is an axis
shoot is the stem plus any leaves, flowers or buds that may be present
Internal Organization of stem
It is an arrangement of primary tissue
