Effect of modified carbon allocation on turgor, osmolality, sugar and potassium content, and membrane potential in the epidermis of transgenic potato (Solanum tuberosum L.) plants

The effects of modification in sugar concentrations on turgor pressure and membrane potential in epidermal leaf cells of transgenic potato (Solanum tuberosum cv. Desirée) plants were studied. Measurements of turgor pressure were performed by insertion of a micro pressure probe. Osmolality and sugar concentrations were determined by micro analysis of single cell extracts. Membrane potentials and cell diameters were calculated from repeated, computer-controlled scans with voltage-sensitive microelectrodes. Epidermal cells of sucrose transporter antisense plants showed a more than 100% elevation in osmolality and turgor pressure compared to the wild-type. As a consequence, cell diameters were enhanced in this transgenic line. However, membrane potentials were only slightly reduced in sucrose transporter antisense plants. In addition to sucrose transporter antisense lines, transgenic plants that were reduced in their capacity to accumulate starch due to antisense inhibition of the chloroplastic fructose-1,6-bisphosphatase (FBPase) were investigated. These antisense plants maintained membrane potential and turgor pressure comparable to the wild-type.