DOES THE ALTERNATIVE PATHWAY AMELIORATE CHILLING INJURY IN SENSITIVE PLANT-TISSUES

Free radical processes have been observed in senescence and several me mbrane-associated disorders of plants including chilling, freezing, an d desiccation injuries. The mitochondria of plant tissues exposed to l ow temperatures, and other abiotic and biotic stresses, produce supero xide and/or hydrogen peroxide when electron transport through the cyto chrome pathway is impaired due to the energy state of the cell or to s tress-induced physical changes in the membrane components. The superox ide and/or hydrogen peroxide produced can diffuse throughout the cell causing peroxidation of membrane lipids which results in membrane disr uption, increased permeability and metabolic disturbances, and eventua lly the visible symptoms of chilling injury. The alternative pathway o f electron transport in the mitochondria, which is induced by low temp eratures in some plant tissues, can mediate these degradative processe s by reducing the level of superoxide generated by the mitochondria.