Botany · Ch 1 — Transport in Plants
Plasmolysis
Plasmolysis
Plasmolysis — What Happens When a Cell Loses Water
How a plant cell behaves in a given solution depends on comparing the solution's osmotic pressure to that of the cell's own cytoplasm:
- Isotonic — the external solution matches the cytoplasm exactly; no net water movement either way. A cell in this state is called flaccid.
- Hypotonic — the external solution is more dilute than the cytoplasm; water tends to enter the cell (it swells).
- Hypertonic — the external solution is more concentrated than the cytoplasm; water tends to leave the cell (it shrinks).
Plasmolysis is what happens when a cell placed in a hypertonic solution loses water — first from the cytoplasm, then from the central vacuole — so that the entire protoplast shrinks away from the rigid cell wall. Water here is simply moving from the cell's higher water potential to the surrounding solution's lower water potential. Figure 11.5 shows three states side by side: plasmolysed (protoplast pulled away from the wall), flaccid (protoplast just filling the wall, inflow and outflow balanced), and turgid (protoplast pressed firmly outward against the wall, net water entering). …
What this figure shows. Three square orange-background cells labelled A, B, C above, each containing one green cell with a visible cell wall outline and an internal white/pale vacuole shape and a small speckled nucleus, with a black 'H2O' label and arrow at the top of each cell. Cell A ('Plasmolysed', label below): the green protoplast is wavy/shrunken and pulled away from the square cell-wall outline on all sides, with the H2O arrow pointing OUT of the cell (away from it). Cell B ('Flaccid', label below): the green protoplast fills the cell wall snugly with only a small pale vacuole, H2O arrow pointing IN. Cell C ('Turgid', label below): the green protoplast is fully pressed/bulging against the cell wall with a larger pale vacuole, H2O arrow pointing IN more prominently — the three panels toget …