SIMILARITIES BETWEEN POSTISCHEMIC INJURY TO ANIMAL-TISSUES AND POSTANOXIC INJURY IN PLANTS

The return to air after periods of oxygen deprivation has long been known to be associated with injury from active radicals in a variety of animal tissues (post-ischaemic injury or reperfusion injury). In plants, a similar sequence of events has been suspected, but only on the basis of indirect evidence of peroxidative damage to membrane lipids. The role of free radicals in causing such injury was investigated in the rhizomes of two Iris species, one tolerant of anoxia (Iris pseudacorus) and one intolerant (Iris germanica). Rhizomes of both species were subjected to total anoxia for 7 days. In the following post-anoxic period, when normal air supply was restored, the generation of active radicals was detected by Electron Paramagnetic Resonance (EPR) only in the anoxia-intolerant I. germanica. Radical generation was exclusively in the rhizodermis and never observed in the rhizome cortex. The radicals were successfully scavenged with the antioxidants ascorbic acid and reduced glutathione. A direct parallel can therefore be drawn between post-ischaemic injury in animal tissues and post-anoxic injury in plants on the basis of direct observation of active radical generation in sensitive tissue. The avoidance of this type of injury is discussed in relation to variation in flooding tolerance, anoxia and other stresses in higher plants.