Relative Humidity Effects on the Postharvest Life of Fruits and Vegetables1

Abstract

We all pay lip service to the concept that fruits and vegetables are alive. Nevertheless, very little attention is paid to what must be a major trauma for most of them, being suddenly cut off at harvest from the water supply that has hitherto sustained them. While on the plant, the organs that we call fruits and vegetables participated in a dynamic traffic in water due to transpiration and to withdrawal of water by the plant in times of stress (40). At harvest, this suddenly ceases and for water, as well as other essential nutrients, they have to become what Biale has called “self sufficient harvested fruit” (8). This transition is minimal for those that are storage organs physiologically prepared for a long resting period (e.g. onions, cabbage, pumpkins, beets, carrots, potatoes) or are fruits2 that form a complete abscission layer preparatory to inevitable dehiscence (e.g. nuts, apples, pears, persimmons, plums, pomegranates, lychees). The water relations transition is maximal for those severed from the parent plant regardless of botanical independence or physiological maturity (e.g. okra, cauliflower, asparagus, corn-on-the-cob, leeks, celery, green beans, parsley, lettuce, green peas). Fruits that have a long harvest period from a single bloom (oranges, grapefruit, avocado) are intermediate. At the time of the fruit’s sudden severance from a hitherto assured water supply, humidity (as distinct from root-supplied water) becomes of critical importance. The trauma of this onset of harvested life should be a consideration in the handling of horticultural products.