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Plants as sources of nonfood products

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Title: Plants as sources of nonfood products


1
Plants as sources of non-food products Plant
products well consider here use fiber from plant
tissues. The fiber, however, comes from different
plant parts Fiber cells are elongate and have
thickened secondary cell walls. Most of those
cell walls are cellulose, but there may also be
lignin, and they may be impregnated with tannins,
gums, pectin, or other polysaccharides. Much of
the fiber we use comes from xylem tubes, and is
comprised of elongate strings of many fiber
cells. Cellulose is extremely strong in tensile
strength (how much force it takes to pull the
fiber apart lengthwise).

2
The basic structure of cellulose as linked
ß-glucose (2 units) is
What gives these strings of glucose great tensile
strength is hydrogen bonding (cross linking) of
hydroxyl groups from individual
strings. Cellulose is strongest when its white
and pure. The presence of lignin makes the
fiber weaker, as well as frequently giving it
color. Plant fiber can be classified by source
surface fibers come from coverings of seeds,
leaves or fruit bast fiber comes from phloem
from inner bark hard fiber comes from vascular
bundles (phloem xylem) of leaves.
3
We now understand the genetic control over
cellulose biosynthesis. Control comes from one
gene RSW1. Synthesis occurs at the cell membrane
at what are called rosette terminal complexes
(RTCs). Heres what happens when synthesis
is blocked in Arabidopsis
4
Table 18.1 lists a number of sources for fibers,
where they come from within the plant, and how
they are used. The general categories
are textile fiber (cotton cloth, linen, hemp
cloth, piña cloth, ramie cloth) cordage fiber
(rope, twine and matting from hemp, musa, and
sisal) filling fiber (coir, kapok) The methods
for extracting fiber from all these plants are
basically similar for each fiber source Surface
fiber is extracted by ginning. The most obvious
example is ginning of cotton.
5
Originally, ginning was done by hand.
Then, in 1793, James Whitney invented the cotton
gin. It increased the efficiency of ginning by
50x.
6
To understand why it made such a difference, we
need to look at the cotton plant and how cotton
is harvested. Cotton species (different ones)
originate in both New and Old World regions. All
are in the genus Gossypium. New World species are
G. hirsutum and G. barbadense. Both are
tetraploid and long staple, meaning the seed
hairs that are cotton are long, sometimes gt2 cm.
The tetraploid genetics may have resulted from
hybridization of the Old World species. However
it originated, it comes from southern Mexico and
Central America. G. hirsutum is now the most
commonly grown cotton. Old world species are G.
herbaceum and G. raimondii. Both are diploid and
produce shorter fibers, generally lt2 cm.
7
Today, the cotton grown in the American South is
largely mechanically harvested.
Cotton fiber has a basic microstructure that
includes a natural twist.
8
On the left are cotton bolls on a plant following
spraying of the plants with defoliants to make
harvesting easier. On the right is an opened boll
that indicates how hairy cotton seeds are. The
modern saw gin (much like Whitneys gin) grabs
and pulls fiber, while the seeds cannot get past
a screen.
9
Ginned fiber is packed in bales. There are a
number of black folk songs about loading bales of
cotton onto ships, about working in the mills,
and about the pest problems in producing cotton
Gonna jump down, turn around, pick a bale
ocotton Gonna jump dpwn, turn around, to
pick a bale a day
10
Now, the first time I seen the boll weevil
He was settin on the square The next
time I saw the boll weevil, Had his whole
family there Just a lookin for a home
11
The baled cotton was shipped to the mills, where
the fibers were straightened (called carding),
combed, and spun into yarn. The yarn is bleached.
Today, chlorine-based bleaching is used. In the
1700s in England, bleaching involved soaking in
sour milk and cow dung, then steeping the yarn in
lye. Finally, the yarn was bathed in buttermilk
and spread out in the sun to dry and bleach it.
That must have made for quite a smell. The next
stage for most cotton used for thread and some
cotton cloth is mercerization. Cotton is passed
through a bath of NaOH. The thread or cloth
fibers swell, become stronger and has greater
affinity for dyes.
12
Cotton yarn or cloth is dyed with many of the
different natural or synthetic dyes, of course
including indigo to colour jeans. The last point
to make about cotton is that most American cotton
is now a bioengineered product. It is called
Bollgard (Monsanto) (or Bt) cotton. A bacterial
toxin has been introduced that acts as an
insecticide against various bollworms. How much
cotton is Bt?
13
How much difference does Bt make? In the U.S.,
with heavy use of pesticides, the improvement in
yield is only about 10. However, in India, where
pesticide, due to expense, is much less heavily
used, the increase in yield is 50 60.
14
The second most important fiber for clothing
comes from flax (Linum usitatissimum). Flax is
grown both for the fiber and for oil from the
seeds. Linseed oil is used in paints, wood
finishes, linoleum and as a drying oil. Flax is
the oldest source of fiber for clothing. The bast
fiber from stem phloem has been found in
archaeological sites at least 10,000 years old.
Egyptian linen fragments 6500 years old are in
museums. Use was not limited to the Old World
there are also very old pieces of cloth from the
American southwest. Linen manufacture begins by
harvesting flax stems around 1m long, then
retting rotting those stems. Retting can be
done in a pond or stream, or in a non-metallic
container. At the end of retting, the fibers are
soft and easily separated from the wood.
15
The separation process is called dressing or
scutching. After scutching, the fiber is combed
(or hackled), then spun into yarn that can be
woven.
16
Linen is used both for fine fabrics (Lace and
tablecloths, as well as clothing), towels, and
rougher fiber is used in cordage.
17
There are many other bast fiber sources and
products Ramie derived from Boehmeria nivea, a
member of the nettle family. Ramie originated in
China and the Malay Peninsula (two different
forms), and has been cultivated for fiber for
6,000 years. Production of fiber requires first
de-barking the stems, then scraping the outer
bark, then separating bark from parenchyma,
washing, drying, and de-gumming the parenchyma
fiber to extract spinnable fiber. Ramie is
strong, but not particularly durable or dyeable.
It is used for industrial sewing thread, packing
materials, fishing nets, and filter cloths. It is
also made into fabrics for household furnishings
and clothing, frequently in blends with other
textile fibers
18
Ramie clothing
The plant
19
Jute made into burlap, ropes, upholstery,
carpet backing, and coarse clothing, comes from
Corchorus species (dominated by C. olitorius).
The plant family is the Tiliaceae, which we
encounter locally as linden trees. The jute plant
is an annual native to Asia, but was converted
into the sackcloth worn in medieval Europe.
20
Cannabis sativa, marijuana for one use, but hemp
for its fiber, is also used for both rope and
cloth. During WWII it was cultivated widely for
the strong rope that could be made. However, its
fiber is much like linen, and can be made into
strong, durable, fine clothing.
hemp stem
hemp fiber
21
The U.S. has prohibitions on growing hemp, but
does permit importation of finished clothing.
Canada is now allowing pilot plantations. The
plants must have lt3 THC. Hemp clothing is not
new. Levi Strauss jeans were originally made with
hemp cloth thats where the name denim came
from Serge de Nimes hemp cloth from Nimes
denim Other fibers Manila hemp from Musa
textilis, a congeneric relative of banana Sisal
from Agave sisalana leaf fibers, used to make
rope and mats, and from the surface fiber of this
plant, kapok used to make stuffing, including in
life vests.
22
Piña from pineapple plants, made into shirts in
the Philippines Coir seed fiber from coconuts,
used to make rope and mats Artificial
fiber? Rayon is sometimes called an artificial
fiber, but its really a reconstituted cellulose
fiber fabric. The first form of viscose fabric
was developed in 1855, and various alternatives
continued to be developed until 1910 the name
rayon was not attached until 1924. The same
basic process that produces rayon fiber also
produces cellophane.
23
There are many steps in the process of making
viscose (rayon) fiber from wood pulp. Heres the
full list (from Wikipedia) 1. Cellulose
Production begins with processed cellulose (wood
pulp) 2. Immersion The cellulose is dissolved
in caustic soda 3. Pressing The solution is
then pressed between rollers to remove excess
liquid 4. White Crumb The pressed sheets are
crumbled or shredded to produce what is known as
"white crumb" 5. Aging The "white crumb" aged
through exposure to oxygen 6. Xanthation The
aged "white crumb" is mixed with carbon disulfide
in a process known as Xanthation
24
7. Yellow Crumb Xanthation changes the chemical
makeup of the cellulose mixture and the resulting
product is now called "yellow crumb" 8. Viscose
The "yellow crumb" is dissolved in a caustic
solution to form viscose 9. Ripening The
viscose is set to stand for a period of time,
allowing it to ripen 10. Filtering After
ripening, the viscose is filtered to remove any
undissolved particles 11. Extruding The viscose
solution is extruded through a spinneret, which
resembles a shower head with many small holes
12. Acid Bath As the viscose exits the
spinneret, it lands in a bath of sulfuric acid
resulting in the formation of rayon filaments
25
13. Drawing The rayon filaments are stretched,
known as drawing, to straighten out the fibers
14. Washing The fibers are then washed to
remove any residual chemicals
26
Trees, Wood, and Wood Products Trees cover 25 of
land in the U.S., 40 in Canada, and 33 of the
Earths land surface. 60 of forests are in the
tropics. Use of forests has been so intense that
30 50 of forest land has been cleared for
lumber, fuelwood, or agriculture. In the tropics
2 of whats left is being destroyed
annually. Only 2 of forests are protected in
parks, reserves, etc. and only 13 is
managed. Reforesting land from which trees are
harvested is a logical answer, but
27
Even in Canada, reforestation is a legal
requirement only on Federally or Provincially
owned land. In tropical forests density is high
and light penetration low, so that a seedling
cannot simply be planted in the place of a
harvested tree. Instead, an area has to be cut
around the harvested tree, meaning loss of a
diverse group of trees to permit growth of one
new, valuable tree. Time is also a factor. It
takes 25-40 years for a softwood tree to reach
harvesting size for pulp. It takes 90-150 years
for a hardwood tree to reach harvesting size.
28
What do we mean by hardwood and softwood?
Hardwood generally refers to trees from
angiosperm species softwood to coniferous (or
gymnosperm) trees. Hardwoods occupy 65 of the
worlds forests, conifers 35. That does not
necessarily indicate wood properties. Poplar
(aspen) and Balsa wood are hardwoods that are
of low density and soft, while yellow pine is
harder and denser than many hardwoods. There is a
real meaning to hard in hardwoods Hardness is
determined by the thickness of cell walls and the
proportion of vessels, tracheids, and fibers.
29
The other distinction is between heartwood the
inner secondary xylem, dry and darker because
cells contain tannins, gums and resins (which act
as preservatives) and sapwood, which is the
active xylem lying outside the heartwood. It is
wet due to its function of water and mineral
transport.
sapwood
heartwood
There are differences in heartwood colour and
properties that are important in how species are
used
30
(No Transcript)
31
Wood, in general, is second only to food in
importance as a plant product. Wood is used in
various ways as lumber plainsawn or quartersawn,
as veneer, as plywood (thin layers glued with
wood grain at right angles on adjacent sheets),
as fiberboard (typically MDF) and as OSB
(oriented strand board)
32
The most important species of softwoods are Pine
(Pinus spp.), Douglas Fir (Pseudotsuga spp.), and
spruce (Picea spp.) The most important species of
hardwoods from North America are oak (Quercus
spp.), maple (Acer spp.), cherry (Prunus spp.
this genus also includes apricot, almond, peach
and plum), and walnut (Juglans spp.) In the less
developed countries the major use is as fuel. In
the industrialized countries, 50 of harvested
wood is used as pulp. Most of that is used in the
manufacture of paper. This use is relatively
recent before the middle of the 19th century
paper was made from straw, leaves, and rags. The
U.S. Declaration of Independence and Constitution
were originally written on hemp paper.
33
There are older ways of making paper. In ancient
Egypt paper was made from papyrus (Cyperus
papyrus), a wetland sedge (like a grass, but with
triangular stems) from the Nile delta. The same
plant was called bublos when used in other
products thats where words like bibliography
and bible come from. Papyrus paper was made by
stripping off outer layers of the stem, then
laying strips of the pith together, with
additional layers at right angles (usually when
wet to increase adherence), and pounding the
layers together between hard tablets and drying
the result.
34
Because papyrus (a cellulose paper) can be
sensitive to decay, it was replaced by paper
made from animal tissues. Parchment is a thin
sheet made from calf, goat or sheep skin. It is
produced by stretching a skin, then scraping and
drying it under tension. Vellum is a parchment
made from the skin of a young calf. When you get
your sheepskin at the end of your undergraduate
career, it will not be on parchment.
engraving of a parchmenter 1568
35
  • The steps in paper manufacturing using wood pulp
  • Pulping Chemically the Kraft process is used
    crushed wood is cooked in a liquor the liquor
    contains NaOH, sulphites or sulphates each of
    these as a waste product has environmental
    impact that dissolves out the lignin and
    separates the fiber. Mechanically, chipped wood
    is fed into a steam pressure cooker the
    oatmeal-like output is then pressed between
    rollers. Since the lignin remains, paper produced
    by mechanical pulping is cheaper, but is weaker
    and yellows with age.
  • The pulp may then be bleached using chlorine. In
    addition to bleaching, this treatment produces
    organochlorine compounds including dioxins.

36
2. Drying - prepared pulp is spread over a web,
then pressed to remove water. The remainder is
taken up by an absorbent felt. Then heating
completes the process. The wood pulp can also be
used to make cardboard, fiberboard, cellophane,
or cellulose acetate, which is then used to make
molded plastics. The last two products are made
by treating pulp with either acetic acid or
acetic anhydride (remember rayon). You probably
used a cellulose acetate product when you brushed
your teeth or combed your hair. There are a
number of other products made from trees Resins
resins are insoluble in water, and have
therefore been used in waterproofing (pine pitch
to seal lapboard construction of ships).
37
A simple distillation of conifer resin produces
turpentine. Whats left over is rosin, used by
string-playing musicians and baseball
players. Part of what makes Band-Aids stick to
your skin is resin! Another important product
from the periderm of the cork cambium is cork
(called phellem in describing plant structure
earlier). Cork is light, tough, and a good
insulator. We use it in flooring and, of course,
to seal wine bottles. Instead of natural cork
(largely from cork oaks), a significant fraction
of what is used today is synthetic.
38
What about wood products not from trees? Bamboo
(a generic name for products from the stems of
grasses within the subfamily Bambusoidea) is used
in hundreds of different products, from furniture
and flooring to the Japanese shakuhachi, a wood
flute. Bamboos do not have secondary growth (the
enlargement of stems over years). Instead, the
culm is an annual growth, approximately fixed in
diameter. Species with large diameters are used
in construction we use species with smaller
diameters as stakes to hold up plants.
39
Bamboo is also gt90 of the food for pandas, and
China has protected some bamboo forests for
pandas.
Finally, bamboo is the chief source of pulp for
papermaking in India.
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