CONCENTRATIONS OF VACUOLAR INORGANIC-IONS IN INDIVIDUAL CELLS OF INTACT WHEAT LEAF EPIDERMIS

A method is described for quantitative determination of the major inorganic constituents of individual cells of higher plants. The approach utilizes a modified pressure probe to extract samples of undiluted vacuolar sap from single cells. Subsamples of constant volume are taken from these sap samples and are freeze-dried on to thin films along with similarly-sized droplets of standards. The films are placed in a scanning electron microscope and elemental content of the freeze-dried material is determined by X-ray microanalysis. The method has been used to compare levels of a range of ions in two distinct types of epidermal cell from a young wheat leaf and, in association with nanolitre osmometry, was used to assess the relative importance of the inorganic ions in the generation of turgor pressure in these cells. It was found that the concentrations of the major inorganic ions within the vacuole was constant both within and between two anatomically distinct groups of epidermal cells on a leaf.