The cell surface membranes of cells of flower, though semi-permeable, allows water to pass through cell via aqua proteins embedded in the membrane.
This is true since water goes from inside of cell to the extracellular environment when water potential inside the cell is higher than water potential outside the cell via process of osmosis (water goes from an area of high water potential down a concentration gradient to an area of low water potential). Cells in the flower became plasmolysed (cell surface membranes tear away from the cell walls) as the volume of water in cell decreases.
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