PLANT SECRETIONS/ EXUDATES
Plant secretions or exudates are substances
that ooze out form the pores of injured or
diseased plant tissues. They include gums,
rubber, pectin, resins, tannins, essential oils,
fatty oils, drugs, dyes, sugars, starches, and
These are substances which are natural
derivatives of cellulose
carbohydrates and which are mucilaginous or
sticky when they are wet. They are sticky
substances obtained lrom the stems and
barks of trees.
They are soluble in water and some organic
reagents like alcohol, ether etc. A lot of gums
come from the Leguminosae, mainly from the
Tropics and Subtropics.
Examples of gums and their sources
Gum Arabic- Acacia senegal- fournd mostly in
NOrth Africa and Sudan. It is used 1n
Conlectionery, soft and alcoholic beverages. It is also used in pharmaceutical, cosme
thographic and offset preparations.It was extensively used as an adhesive, but this use
has almost entirely been replaced by synthetic
gum. Similarly its uses as a sizing and
finishing material in the textile industry have
also mostly given way to modern substitutes.
However, small quantities continue to be used
in paper making. Gum is also used to a
limited extent in polishes, contact insecticides
and pesticides, photographic emulsions and
pharmaceuticals. It belongs to the family
Sterculiaceae. Current production potential is
around 30,000 to 40.000 tonnes per annum,
of which bulk (80%) Originates in Sudan:
Nigeria being the second largest producer.
accounted for by the Sahelian count
Faso, Chad, Tanzania and Kenya).
timo for 70% to 800, the balance being
West Africa (Nigeria, Mali, Niger, Burkina
It is obtained from Sterculia urens, a large uee
1n central India. In other to obtain the gum,
incisions are made into the heartwood and thee
gum oozes into the incisions and accumulates
as large irregular knobs.
Collected, sorted and graded. It is used in the
textile, COsmetic, cigar, past and ice cream
industries. Of all the gum karaya produced
only 10% is used as a food additive; the
They are then
remainder goes into pharmaceutical products.
The pharmaceulical apphhcations ot gum
karaya include medical colostomy bag fixings,
dental fixatives and bulk laxatives. Colostomy
bag fixings is the most commorn use of gum
karaya, in which the gum’s qualities are
difficult to equal.
Guar gum- Cyanops tetragonolobs.
Guar gum can best be described as a natural
food thickener extracted from the guar bean.
The guar seeds are de-husked, milled and
Screened to obtain the guar gum. The guar
plant, also known as a cluster plant, grows
primarily in Pakistan and the northern
regions of India. Guar gum has significantly
thickening ability. This has made it a popular
additive in products such as puddings and ice
creams. It retards ice crystal growth in food
ke 1ce cream and sherbet. The seceds are
manually or mechanically separated and
processed into flour or sold as split seeds.
Guar gum is an important cash Crop for the
lndian and Pakistani economies. It is also
used in the paper industries as additives to
Rubber is obtained from the milky juice or
latex of various erect and climbing woocy
plants ol the tropics and sub-tropics. It 1S a
COagulate elastic latex. Rubbers are polymeric
materials ‘endowed with the properies of
application of force, the molecules straighten
out in the direction in which they are being
pulled: on release from being extended, they
arrangements. It is formed in the cytoplasm of
laticifers as a by-product of metabolism and
accumulates in the vacuole. Most rubber
spontaneously recover their normal, random
plants belong to the family Moraceae (Lagos
Apocynaceae are of poor grades because of
high percentage of resin and p0or percent of
from the family
There are about 50 spp available as sources
but only a few are of commercial importance.
Panama rubber Castilla elastica
Lagos silk rubber