Plant Histochemistry: A Versatile and Indispensible Tool in Localization of Gene Expression, Enzymes, Cytokines, Secondary Metabolites and Detection of Plants Infection and Pollution

Plants are sources of active metabolites used in medicine and primary sources for isolation of natural products.The medicinal properties of plants are due to the presence of secondary metabolites, including flavonoids, alkaloids, tannins, and saponins, which are of great importance because they possess significant biological activities and the particular active constituents of many crude drugs are still unknown.Histochemical studies are used to confirm identification of cellular and tissue chemical components (secondary metabolites).Histochemical methods are employed in the identification, density of accumulation and distribution of chemical compounds within biological cells and tissues in different organs under microscopes using the color-stain reaction technique and photographic recording.These include the preparation of fixed variably stained specimens and then the examination under the microscopic devices.It is successfully applied in detection and localization of cellular components of active cell constituents such as proteins, carbohydrates, lipids, nucleic acids, and a range of ionic elements occurring in the cell solutions, in addition to identifying the characterization of secretory structures and the chemical nature of the secreted compounds.The methods played a role in describing and tracing the ultrastructure development during different plant growth stages so as the genetic bases of plant physiological and biochemical processes could be further elucidated.Histochemistry is the branch of histology dealing with the identification of chemical components of cells and tissues.Starch deposition occurs widely in the plant body, but the particularly common places of its accumulation are seeds, the parenchyma of the secondary vascular tissues in the stem and root, tubers, rhizomes and corn [1].Starch and proteins are the principal ergastic substances of the protoplast [2].Tannin is the heterogeneous group of phenol derivatives, usually related to glucosides.Tannins are particularly abundant in the leaves (xylem) of many plants [3].Saponins are the rare occurrence.Fats are widely distributed in the plant body and they probably occur in small amount in every plant cell [4].Fats are common reserve material inseeds, spores and embryos in meristematic cells.Glucosides are the degradation product of the carbohydrates.Alkaloids are the degradation product of protein.Many plants contain medicinally important secondary product [5].