An Uncommon Wall Thickening of Guard Cells

Four species of the family Zingiberaceae, Curcuma amada Roxb.,C. domestica Valet., Zingiber officinale Rose, Elettaria cardamomumMat.; one species of the family Cannaceae, Canna indica L.;one species of the family Rubiaceae, Coffea arabica L.; andone species of the family Theaceae, Camellia sinensis L. showedthe presence of wall thickening at the polar ends of the guardcells. This thickening may be restricted to the outer wall atthe polar regions or may also be extended to the common innercell wall (not the part of the inner wall abutting the stomatalpore). In C. sinensis the wall thickening may be restrictedonly to the common inner wall. The thick walls are PAS-positive.