Growth and antioxidant status of plant cells cultured with bovine haemoglobin solution.

Reactive oxygen species (ROS), such as superoxide (O2 •-), hydrogen peroxide (H2O2), and the hydroxyl radical (•OH), may be generated in plant cells during aerobic metabolism. ROS can impair cell activities, primarily through oxidative damage to lipids, proteins and nucleic acids (Halliwell and Gutteridge, 1999). Exposure of plants or their cells/tissues, maintained in vitro, to environmental stresses (e.g. temperature extremes, drought, high salinity, mineral deficiency) perturbs the balance between the ROS production and the quenching effects of antioxidant enzymes, leading to oxidative damage (Smirnoff, 1993; Foyer and Mullineaux, 1994; Schwanz et al., 1996). However, plants/cells possessing high activities of constitutive or induced antioxidant enzymes show increased resistance to such oxidative damage (Halliwell and Gutteridge, 1999; Niki, 2000).