Submitted to: Postharvest Physiology of Vegetables
Publication Type: Book / Chapter
Publication Acceptance Date: May 28, 2001
Publication Date: N/A
Interpretive Summary: Biomembranes are structures that are essential for the function and survival of all living cells. After fresh fruits and vegetables are harvested, biomembranes in their tissues undergo deteriorative changes which generally increase the rate of water loss and ultimately result in a decline in product quality. Storage regimes involving reduced temperatures and oxygen levels can often slow the rate of membrane changes that lead to tissue damage. In some cases, however, if these storage parameters are too extreme they can result in membrane dysfunction and severe tissue injury. This chapter reviews primarily the past decade of research on the chemical and physical changes that occur in cell membranes during postharvest storage of fresh vegetables, and how these changes are thought to influence shelf life and quality.
Maintenance of the requisite physical properties and functionality of cell membranes is essential for retention of quality during the storage life of fresh vegetables. Water loss and the consequent loss of turgor pressure, which cause shriveling, wilting and undesirable textural changes, are in part due to increased permeability of the plasmalemma and tonoplast. A number of postharvest physiological disorders, e.g. chilling injury, involve both increased water loss and leakage of electrolytes across cell membranes. In addition to their important barrier properties, membranes compartmentalize various life functions of the plant cell. The enzymatic activity of individual membranes, which is essential to their specific role in the cell, is greatly influenced by the composition of the lipid matrix. Membranes play a critical role in many vital activities, including energy transfer, hormone binding, signal transduction, plant-pathogen interactions, and transport of ions, solutes and macromolecules between compartments. Furthermore, even small changes in bilayer structure can significantly alter membrane function, and consequently the metabolic balance within a plant cell. Over the past decade there has been a surge in research focused on changes in membrane lipid metabolism during the course of postharvest life, much of it addressing the processes involved in membrane deterioration during normal and stress-induced senescence. Of primary importance are the senescence cascade of membrane phospholipid catabolism, and the generation of reactive oxygen species and plant defenses against oxidative stress. Other lipid changes due to aging or storage conditions may also alter membrane function.