CHAPTER 5 and 6 Flashcards
the first clearly visible layer of the cell wall and is located between the plasma membrane and the middle lamella or, in some cells, between the secondary wall and the middle lamella.
Primary Cell Wall
It is responsible for the initial shape and size of the plant cell, and determines its subsequent changes in shape and size.
Primary Cell Wall
this, plant cells create channels that cross the cell walls and allow direct communication between adjacent cytoplasms. These channels are called
Plasmodesta
Plasmodesmata can appear concentrated in certain areas of the cell wall
forming what are called
Primary pore fields
the main substance in the walls of plant cells, helping plants to remain stiff and upright
Cellulose
matrix substance of the cell wall composed of two types of sugar molecules:
xylans and glucomannans
Hemicellulose
made of intractable material which acts as the cementing substance of wood
Lignin
They are typically concentrated in the heartwood and are often produced by
the standing tree as defensive compounds to environmental stresses
Extractives
Type of extractives that is insoluble in water, synthesized by epithelial cells that protect plants and wood against pathogens. and produced mainly in conifers
Terpenes
A vast group of naturally occurring
compounds with medicinal potencies referred to as isoprenoids
Terpenoids
also known as non-aromatic compounds that serve as a source of energy for
the wood cells and can act as surfactants
limiting fungal adhesion on wood
surface abundant in cuticle of plants
Aliphatic compounds
found in the bark and heartwood that serve the purpose of protecting lignocellulose from fungal and microbial attack and can be washed out as “resin” from live trees
Aromatic Phenolic compounds
FOUR (4) CLASSIFICATIONS OF AROMATIC PHENOLIC COMPOUNDS
LIGNANS
STILBENES
FLAVONOIDS
TANNINS
found in the knots of soft wood trees, mainly in the form of hydroxymatairesinol and often more significant in the nodes of branches subject to mechanical stresses and loads due to environmental conditions.
Lignan
Occurs naturally in all plant families and serves as protection against ultraviolet radiation, pathogens, and herbivores
Flavonoids
protect heartwood against fungal
colonization by a dual function:
fungicidal activity and being
excellent free radical scavengers
(antioxidants)
Flavonoids
has antioxidant properties, antifungals, and pharmacological and therapeutic uses and is isolated from certain fruits such as grapes are widely used in cosmetology and other drugs
Stilbenes
found commonly in the bark of trees,
wood, leaves, buds, stems, fruits,
seeds, roots, and plant galls and act as protection from infection against bacteria and fungi
Tannins
source of nitrogen necessary for the development of the plant and protective agents against ultraviolet radiation
Alkaloids
perennials that create stiff structures above ground
woody plants
“backbone”
for support
wood
“skin” for
protection
bark
only part of
the trunk that is alive
cambial layer
transports water
and mineral salts from roots
xylem
transports sucrose and amino acids between the leaves and other parts of the plant
phloem
an aggregate of untold number of small
units called cells.
wood
Wood cells are separated by an intercellular substance called the
middle lamella
the living part of the cell, which comprises of different cellular organelles. It is a jelly-
like, colorless, transparent and viscous living substances present within the cell wall
protoplasm
The substance present between the cell
membrane and the nucleus. Contains cell organelles like Golgi bodies, endoplasmic reticulum, mitochondria, ribosomes, but no
nucleus. Jelly-like fluid containing water, proteins and metabolic wastes.
cytoplasm
made up of microfibrils
that are dispersed in a
loose, irregular interwoven
pattern
primary wall
intercellular material extending
between the cell walls of
adjacent wood cells
True middle lamella
refers to the true middle
lamella and the primary cell
walls of two adjacent wood
cells
compound middle lamella
the thickest layer in the 2ndary cell wall consist of dense network of lamellae aligned nearly parallel to each other
S2 Layer
the warty layer
S3 Layer
non-structural constituents of wood composed of low molecular weight organic compounds that composed only 10% in trees but are diverse. Can be extracted in wood through solvents (e.g.
acetone)
extractives
Most wood extractives are _______ and only a little part is water-soluble
lipopholic
3 MAIN GROUP OF EXTRACTIVES
Aliphatic compounds
Terpenes
Phenolic compounds
primitive element of xylem (fluid-conducting tissues)
Tracheids
consisting of a single elongated cell with pointed ends and a secondary, cellulosic wall thickened with lignin (a chemical binding substance) containing numerous pits but having no perforations in the primary cell wall
Tracheids
typically composed of living cells that are thin-walled, unspecialized in structure, and therefore adaptable, with differentiation, to various functions
parenchyma
are actively involved in photosynthesis, secretion, food storage, and other activities of plant life one of the three main types of ground, or fundamental, tissue in
plants
Parenchyma
Types of Parenchyma
Longitudinal Parenchyma
Radial (Ray) Parenchyma
Epithelial Cells
Orientation: parallel to the
long axis of the stem
Function: food storage
Longitudinal parenchyma
Orientation: perpendicular to the long axis of the stem
Seriation, uniseriate – present in all softwoods species multiseriate (with horizontal resin canal) – present only in softwoods with resin canals
Function: food storage, (water transport in radial direction)
Radial parenchyma
formed by parenchyma cells only
homocellular ray
formed by parenchyma cells (RP) and ray tracheids (RT)
heterocelullar ray
form the the periphery of a structure
called a resin canal (RC) AND excrete resin into the RC
Epithelial Cells
Intercellular spaces or cavities
surrounded by parenchyma cells
rESIN CANAL
Orientation: Parallel or perpendicular
to the long axis of the stem
Occurrence
- only in all species of 4 genus of Pinaceae
family:
Resin canals
may be formed in
wounded trees that don’t
have normal resin
canals
Traumatic resin canals
purposes of these ducts is to protect and seal up a wound by
exuding resin to cover the damaged area of the tree
Resin canals
technically not individual cells, but are actually open, tube-like
spaces bordered by special cells that have the ability to secrete pitch or
resin into the neighboring opening
Resin canals
group of non-structural components in woods that consists of both hydrophilic and lipophilic compounds
CRYSTALLIFEROUS WOOD ELEMENTS
consists of terpenes and terpenoids
protects the tree from microbic attack
exclusive for softwood and tropical
hardwoods with resin canals
Oleoresin
dominated by monoterpenoids and
diterpenoids (resin acids)
all built up by different amounts of
isoprene-units (C5H8)
oleoresin
Volatile components in softwood oleoresin, built up to two Isoprene units
Gives wood the characteristic odor
Can be divided into acylic, monocyclic, bicyclic and tricyclic
Monoterpenoids
One of the most important group of extractives in softwood
Diterpenoids
There are more than 2500 types
Occurs in small amounts in tropical wood species
Sesquiterpenoids
mixtures of several related
carboxylic acids, primarily
abietic acid, found in tree resins
are tacky, yellowish
gums that are water-insoluble.
They are used to produce soaps for
diverse applications
Resin acids
extremely plastic—the cells
can extend and thus adjust to
increased growth of the organ
Collenchyma
greatly elongated cells whose long, tapering ends interlock, thus providing
maximum support to a plant. They often
occur in bundles or strands and can be found almost anywhere in the plant body,
fiber
