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Tissues and the Primary Growth of Stems (External Organization of Stems…
Tissues and the Primary Growth of Stems
Basic types of Cells and Tissues
Parenchyma cells
only have primary walls that remain thin
Chlorenchyma cells
parenchyma cell involved in photosynthesis
numerous chloroplast
Glandular cells
contain few chloroplast
transport sugars& minerals
produces parenchyma cells
transfer cells
mediate short distances
increase surface area with knots, ridges, & other ingrowths
Parenchyma Tissue
Mass of Parenchyma cells
most common type of cell/tissue
Constituting all soft parts of the plant
example: leaves, pedals, fruits, and seeds
Active metabolically
Usually remain alive after they mature
Collenchyma Cells
primary wall- thin in spots thick in others
present in elongating tips
long and flexible (grape vine )
requires glucose
Sclerenchyma Cells
has a primary and secondary wall
can be deformed and will go back to there shape
has two types
Conducting
tracheids
dead @ maturity
long/narrow with tapered end
vessel elements
dead @ maturity
found in flowering plants
mechanical
scleriod
dead @ maturity
fibers
long, dead, involve storage
External Organization of Stems
stem is an axis
Flowing plants
nodes
Where leaves are attached
Internodes
regions between nodes
leaf axil
stem area just above point where leaf attaches
axillary bud
miniature shoot
bud scales
protect delicate organs
small, corky, waxy
terminal bud
extreme tip of each stem
phyllotaxy
arrangement of leaves on stem
stolons
aka runners
bulbs
short stems with fleshy leaves
Corms
vertical think stems, thin papery leaves
Rhizomes
Fleshy horizontal stems allow to spread underground
tubers
horizontal stems grow for short period mainly for storage
Internal Organization of Stems: Arrangement of Primary Tissues
Epidermis
outermost surface
encrusted with cutin
makes walls impermeable to water
cutin builds up a layer called cuticle
Cortex
interior to the epidermis
cortex cells fit together compactly
Vascular tissue
has two types:
Xylem
Phloem
Diffusion throughout the body
Xylem
two types:
tracheids
refered to as tracheary element
vessel elements
must stop dividing
secondary wall reinforces primary wall
cell dies
annular thickening
rings for movement of water
vessel elements
entire stack of bundles
Phloem
two types
sieve cells
refered to as sieve elements
sieve tube membrane
must remain alive to conduct
has pores
Vascular bundles
Xylem and Phloem occur together as vascular bundle
surround pith
vascular bundles always collateral
has both xylem and phloem
Stem Growth and Differentiation
apical meristem
creating new cells and their tips
subapical meristem
just below apical meristem
cells dividing and growing
protoxylem
cells from subapical meristem
constitute first xylem
metaxylem
largest tracheary elements
protoderm
epidermal cells in early stages of differention
provascular tissue
young cells of xylem and phloem
ground meristem
stages of pith and cortex
primary tissues
tissues produced by apical meristem
primary growth
growth and tissue formation
