TRACING STOMATAL ONTOGENY THOUGH FOLIAR HISTOCHEMICAL STUDY IN ACANTHACEAE

The stomatal complex of Acanthaceae, is analysed correlating the evidences from ontogeny and histochemistry. In mature stomatal complex, the mesogenous subsidiary cells bracket the guard cells in a ?C? shaped manner. Due to the unusual curvature of the subsidiary cells, the epidermal cells adjacent to the stomatal complex also acquire a ?C? shape irrespective of their ontogeny which, are perigenous in origin how ever resemble mesogenous subsidiary cells morphologically. From ontogenetic point of view these cells may be referred to as perigenous encircling cells. The functional association of mesogenous subsidiary cells to guard cells is indicated by epidermal histochemisty. When tested with Mercuric Bromophenol Blue (MBB) for total proteins, the guard cells of Strobilanthes ciliatus showed deep blue colour while the subsidiary cells were clearly differentiated by the dark shade of the peripheral region due to metachromatic reddish hue with MBB. Staining reaction with Toluidine Blue `O? indicated the presence of phenolic compounds with blue-green coloration in the diallelomesogenous complex of Justicia gendarussa. In Strobilanthes barbatus when tested for total lipids with Sudan III or IV, both guard cells and subsidiary cells were characterised by single large reddish orange lipid globules. These were absent in other epidermal cells and perigenous encircling cells. When subjected to PAS reaction, the mesogenous subsidiary cells of Peuderanthemum malabaricum gave less PAS positive results than both guard cells and epidermal cells. Epidermal histochemistry clearly distinguishes mesogenous stomatal complex from the morphologically similar perigenous cells and ordinary epidermal cells. The mesogenous subsidiary cells differ functionally from the morphologically similar perigenous encircling cells. These cells should be considered different from the diallelomesogenous? group of subsidiary cells characteristic of Acanthaceae. It is inferred that allelocytic stoma is mesogenous in origin and the terms mesoperigenous and diallelomesogenous are not applicable to acanthaceous stomata.