Oxidized and reduced nicotinamide adenine dinucleotide phosphate levels of plants hardened and unhardened against chilling injury.

Pea plants (Pisum sativum L. var. Alaska) subjected to low temperature (5 degrees ) in the light acquired resistance against chilling injury.Unhardened plants maintained high NADP and low NADPH levels during illumination at 25 degrees but hardened plants had low NADP and high NADPH levels in the light. When the unhardened plants were transferred to the dark room at 25 degrees , their NADPH levels decreased immediately. On the other hand, hardened plants maintained a high NADPH level for a few hours even in the dark.