2.7.2 Occurrence in Plants
In the plants resins usually occur in different secretory zones or structures. A few typical examples of such plant sources along with their specific secretary structures are given below:
(i) Resin Cells : Ginger–Zingiber officinale Roscoe (Family: Zingiberaceae);
(ii) Schizogenous Ducts : Pine Wood–Pinus polustris Miller.
or Schizolysogenous (Family: Pinaceae).
Ducts or Cavities
(iii) Glandular Hairs : Cannabis–Cannabis sativa Linne’. (Family: Moraceae)
The formation of resins in the plant is by virtue of its normal physiological functions. However, its yield may be enhanced in certain exceptional instances by inflicting injury to the living plant, for instance: Pinus. Furthermore, many resisnous products are not formed by the plant itself unless and until purposeful and methodical injuries in the shape of incisions are made on them and the secretions or plant exudates are tapped carefully, such as: Balsam of Talu and Benzoin. In other words, these resins are of pathological origin. One school of thought has categorically termed the secretion exclusively obtained from the naturally occurring secretory structure as the Primary Flow, whereas the one collected through man-made-incisions on the plant i.e., abnormally formed secretary structures, as the Secondary Flow.
In normal practice, it has been observed evidently that resins are invariably produced in ducts as well as cavities; sometimes they do not occur in the so called specialized-secretory structures, but tend to get impregnated in all the elements of a tissue, for example: Guaiacum Resin—is obtained from the heartwood of Guaiacum officinale Linn. and G. sanctum Linn., (Family: Zygophyllaceae) i.e., it is found in the vessels, fibres, medullary ray cells and wood parenchyma. In this particular instance, the resins occur as tyloses, achieved by chopping off the conduction in these areas so as to enhance the effective usage of root pressure and the capillaries in forcing both the nutritive contents and forcing water to reach the top end of these tall trees.
It is pertinent to mention here that in some exceptionally rare instances the resin occurs as a result of sucking the juice of the plant by scale insects and converting the sucked-juice into a resinous substance that ultimately covers the insect itself and twigs of the plant as well, for instance: Laccifer lacca (Family: Coccidae)-Shellac.
