The electron partitioning between the cytochrome and alternative respiratory pathways during chilling recovery in two cultivars of maize differing inchilling sensitivity

Chilling effects on respiration during the recovery period were studied in two maize (Zea mays L.) cultivars differing in their tolerance to chilling: Penjalinan, a chilling-sensitive cultivar, and Z7, a chilling-tolerant cul tivar. Both cultivars were exposed to 5 degrees C for 5 d, after which meas urements were taken at 25 degrees C. Chlorophyll fluorescence analysis in d ark-adapted leaves showed less damage in cv Z7 than in cv Penjalinan during recovery from the chilling treatment. Studies of the electron partitioning between the cytochrome and the alternative respiratory pathways during chi lling recovery using the oxygen isotope fractionation technique showed that , although total leaf respiration was not affected by the chilling treatmen t in either of the two cultivars, electron partitioning to the alternative pathway was significantly increased in the more stressed chilling-sensitive cv Penjalinan, suggesting that increased activity of the alternative pathw ay is not related to the plant tolerance to chilling. These results suggest a possible role of the alternative pathway in plants under stress rather t han specifically contributing to plant resistance to chiliing.