Spraying produces with freshwater containing 0% salt to make them more firm and plump means that the water is hypotonic for the plants.
Being a hypotonic solution means that the concentration of salt in the cells of the plants is higher than that of the water. It is as opposed to hypertonic solutions which have higher solute/salt concentration than that of the cell or isotonic solutions which have the same solute concentration as that of the cell.
By spraying farm produce with hypotonic solution, water will enter the cells of the plant by osmosis, making them become more firm and plump.
Ordinarily, if a cell continues to take in water from a hypotonic solution, it will become turgid and may eventually burst due to over-turgidity. However, the presence of a cell wall in plant cells prevents the content of the cell from bursting by acting as a guard.
More on hypotonic solutions can be found here: https://brainly.com/question/4237735
