Analysis of cell elongation in red algae by fluorescent labelling

The mechanism of cell elongation in five red algae, Griffithsia pacifica Kylin, G. tenuis C. Agardh, G. globulifera Harvey, Antithamnion kylinii Gardner, and Callithamnion sp. was studied using Calcofluor White ST as a vital, fluorescent cell-wall stain. In each alga elongation of intercalary shoot cells occurs primarily by the localized addition of new cell-wall material rather than by extension of pre-existing cell wall. Cell extension is localized in narrow bands in the lateral walls of a cell; there may be one or two bands per cell and these may be located at the top or bottom of the lateral wall. The number and location of bands of elongation are constant within a species but vary from species to species. Cell walls of elongating intercalary cells of each of these algae are essentially isotropic, indicating a net random orientation of cell-wall microfibrils.