LIFE SCIENCE FOR GENERAL UNDERSTANDING: PLANTS --IV

LIFE SCIENCE FOR GENERAL UNDERSTANDING:      PLANTS --IV

[ON REQUEST FROM Cdr. V. KRISHNAN]

PLANTS – 4

DEFENSIVE PROTECTION IN PLANTS

Quite an array of defensive features is found among plants. These are Structural, surface coat, Chemical substances, Secondary metabolites and so on.

Structural items

Structurally, thorns, prickles, hooks are strong protectives which defend plants from being plucked or grazed by animals. They injure the invader and frighten any further attempt.

Stinging hairs

These are emergences from stem / leaf surface and have slender sharp pointed tips. They pierce the tissue of the invader and break within to release irritant fluid. It causes profuse itch and causes agony to the invader.

Crystals and spicules

Several plant structures contain different salt crystals and oxalates.   Any  chewing animal can feel prickly pungence and it is a strong disincentive to devour the plant.

Gums and exudates

Several trees have different exudates which ooze from tree barks and clog as crystalline deposit on the stem. [Neem]. They carry several products which are collectively involved in plant protection.

Other secondary metabolites

Latex

Latex is a milky thick fluid which drops from cut ends of plants. Some plants have thin yellow semitransparent latex. These are common in dry land plants like cacti, hedge plants like Tirucalli etc. Latex is a powerful deterrent against grazing animals. Some natives use latex as wound healer for human injuries.

Oils, Resins Tannins and phenols of varied chemical composition arise in old plants. They carry a number of organic products which are not easy to digest. So, by sheer perception of odour, animals avoid using such leaves for feeding. All such tannins, phenols, Terpenes and similar derivatives have complex chemistry. Many of them are found to possess potent medicinal value. The medicinal property of such plant parts deters the animal from indiscriminate grazing. Several of them are inherently anti bacterial/ anti-microbial in action. In view of such properties herbal medicines are widely used by hill tribes as antidotes to several disorders, insect bite / snakebites.

Adathoda

Adathoda is a popular herbal drug against cough and throat disorders. The drug is an alkaloid ‘ VASICIN’ which is employed in allopathic syrups as antidote for cough. The bitter alkaloid safeguards the plant from grazing animals.

Knowledge on Secondary metabolites in plants is an expanding area of research involving bio-chemistry, microbiology, Immunology in deciphering the applicability of such drugs or their analogues. Undoubtedly Botanical science is a fascinating area if we are inclined to critically bridge disparate signals which relate to human physiology / Drug science.

Prof. K. Raman