Why do grocery stores spray their fresh produce with water?

In nature plants maintain a water balance by constantly replacing water lost to the atmosphere by water absorbed by the roots. If water loss exceeds water replacement, the plant wilts. Harvested produce, whole to partial plants, have no means of replacing water lost and they quickly wilt. Leafy vegetables like lettuce & spinach would wilt fastest. Waxy skinned vegetables like cabbage and fruits like cucumber and apples will wilt most slowly. To keep produce firm and fresh, they are sprayed with water. Vegetables like potatoes and onions have skins that retard water loss so well they don't need spraying.  more