PLANT SECRETIONS

 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

toxins.

 

4.1 GUMS

 

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.

 

other

 

and

 

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has almost entirely been replaced by synthetic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.

exports,

 

the

 

world

 

dominates

 

Sudan

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

 

Karaya Gum-

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

pulp

 

4.2 RUBBER

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

extensibility: Withthe

 

flexibility

application of force, the molecules straighten

out in the direction in which they are being

 

and

 

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

silk),

Apocynaceae.

Apocynaceae are of poor grades because of

high percentage of resin and p0or percent of

rubber

 

rubber) and

from the family

 

Euphorbiaceae (Para

 

Rubbers

 

There are about 50 spp available as sources

but only a few are of commercial importance.

These include

 

Para-rubber

 

Hevea

(Euphorbiaceae)

 

brasiliensis

boee0901

 

Panama rubber Castilla elastica

 

Indian rubber

Lagos silk rubber

(Moraceae)

-Landolphia rubber

-Cerea rubber

 

Fiscus elastica

 

Funtumia

 

elastica

 

Landolphia kirkii

 

Manihot

 

glaziori

 

 

 

 

 

 

 

 

 

 

 

Updated: February 9, 2020 — 6:53 pm

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