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Ch 5: Tissues and the Primary Growth of Stems (Externall Organization of…
Ch 5: Tissues and the Primary Growth of Stems
Types of cells & Tissues
Parenchyma Cells
thin primary walls
most common type
soft leaves, petals are composed
examples include
Glandular cells
transfer cells
chlorenchyma cells
Parenchyma Tissue
mass of parenchyma cells
most common type
collect nutrients for long
are called Phloem
Collenchyma Cells
primary wall thin/thick certain places
exhibits plasticity
Collenchyma & Parenchyma work together
present where flexibility is needed
extra glucose for production
Scleremchyma Cells
Primary wall
elastic
Secondary wall
thick
lignified & elastic
develop from Parenchyma
supports plant by strength alone
two types of Sclerenchyma
Conducting
divided into
long, narrow tracheids
short, wide vessel elements
has elastic secondary wall
mechanical
divided into
short sclereids
long fibers
has elastic secondary wall
cannot expand due to rigidity
Externall Organization of stems
stem
is an axis
shoot
is stem w/leaves, buds etc.
flowering plants have
nodes/connecting points
internodes/region between nodes
leaf axil
area above where leaf attaches
axillary bud
a mini shoot
can produce fowers
can be vegetative
phyllotaxy
arrangement of leaves on stem
stolons/runners
long/thin internodes
leaves do not expand
good microhabitat means
new roots
growth
new plant
bulbs
short roots w/ thick leaves
ex: garlic, onion, etc.
corms
thick stems w/thin leaves
ex: crocus, gladiolus
Rhizomes
fleshy horizontal stems
allow plants to spread underground
Tubers
grow for short time
mainly nutritional storage
ex:potatoes
Internal Organization of stems
epidermas
outer most layer of stem
cutin
fatty substance
allows for water impermeability
cuticle
cutin build up
severe conditions may cause
wax outside the cuticle
provides defense against pathogens
serves as a barrier from bacteria
stromata
made up of
gaurd cells
cell that surrounds stromata
swell by absorbing water
stromatal pore
open during daytime
allow CO2 to enter
do ot extend
trichomes/hairs
elongation of epidermal cells
act like a barrier from insects
Cortex
outer layer tissue after epidermas
most plant
composed of
photosynthetic parenchyma
sometimes collenchyma
other species
can be more complex
contains cells that secrete latex, resin and mucilage
can contain calcium oxalate crystals
can also contain deposits of silica
Vascular tissues
Two types
Xylem
Conducts water and minerals
Phloem
Distributes sugar and minerals
Occurs in plants
Xylem
2 types conducting cells
Tracheids
Vessel elements
has secondary impermeable wall
Has primary permeable wall
Phloem
2 types of conducting cells
Sieve cells
Long and tapered
Small sieve areas over surface
Sieve tube members
Has only primary wall
Sieve pores
Permit movement of phloem sap
The holes in primary walls
Sieve areas
Sieve pore clustered together
Sieve tube
In angiosperm
Sieve Columns connected to sieve areas
Vascular Bundles
Occurrence of xylem and phloem together
Located interior of cortex
Pith
Region of parenchyma
Located in center of shoots and roots
Are collateral
Contains xylem /phloem strands
Primary xylen
Part of primary plant body
Primary phloem
Part of primary body
Forms in leaves, flowers, fruits
Stem Growth/Differentiation
Stem growth
Can occur from
Creation of new cells
Mitosis and cytokinesis
Produces cells for whole stem
In region of apocalypse meristems
Differentiation
Cells stop dividing
Cells elongate
Affects cells around it eventualy
