A novel histological approach for identification of alkaloid bearing plants

Abstract

Background and Objective: Alkaloids are only secondary metabolites which participate in plant metabolism and also translocated from one part to another. About 153 families have never been explored for alkaloids and no significant transport channel is reported so far for alkaloid movement from one cell to another after their production in the plant species. The major aim of this study is to sharpen the mind for the histological peculiarities of alkaloid bearing plants and to consider them adequately in forthcoming investigations on translocation of alkaloids. Materials and Methods: More than 100 plants/parts were studied histologically and histochemically, to differentiate the alkaloid and non-alkaloid bearing plants. The transverse/longitudinal sections were taken for all the samples using standard methods. These sections were screened for the presence/absence of alkaloids. Results: Anatomical studies of different plant parts viz., root, rhizome, stem, bark, leaf, petiole, fruit and seed were conducted. A constant histological feature i.e., pits on the cell wall and in the cell lumen of the tissues other than tracheary elements was noticed in all types of alkaloid viz., tropane, pyridine-piperdine, quinoline, isoquinoline, lupine, indole, steroidal alkaloids, alkaloidal amines and purine bases bearing plants/parts. Conclusion: The presence of alkaloids as secondary metabolite in any plant species can be detected by the microscopic structure i.e., cell wall pitting and pits in cell lumen due to plasmodesmata, other than tracheary elements, because this structure was observed in all alkaloid bearing plants only. Secondly, it may also help to locate the translocation of this diverse secondary metabolite. This novel histological finding may be applied to identify the new source of alkaloid from the unexplored plant families and may open new vistas for the chemical and biological point of view. The hypothesis of the finding is that the presence of plasmodesmata and pits in the cells even in sclereids/stone cells can provide a channel for the translocation of these secondary metabolites after their synthesis in the particular plant part. Further, physiological research is required to confirm all the activities related to the chemical and physical processes associated with this hypothesis.