Water movement between epidermal cells of barley leaves - a symplastic connection?

Using the cell-pressure probe the possibility of symplastic wafer flow between cells of the upper epidermis of barley leaves was investigated. Cells analysed had either an intact or a more or less damaged cellular environment. Cell damage caused large pressure differentials (0.9 MPa) between damaged and adjacent intact cells. Turgor in cells adjacent to damaged cells decreased significantly. Turgor decreases were the larger the more the adjacent, damaged cell was leaking (decreases by 2.5-4.4%). In cells surrounded by a patch of leaking cells, turgor decreased the most, by 18.1-20.4%. In contrast, half-times of water exchange (T-1/2) Of cells were not affected by a damaged cellular environment. Assuming that in the barley leaf epidermis, plasmodesmata close at pressure-differentials at or exceeding 0.2 MPa as shown for, other plant cells (The Plant Journal 2, 741-750; Canadian Journal of Botany 65, 509-511), it is concluded that symplastic water dow contributes insignificantly to wafer exchange between cells. Mechanical damage to one individual cell is enough to induce significant turgor changes in neighbouring cells.