Relationships between some endogenous signal compounds and the antioxidant system in response to chilling stress in maize (Zea mays L.) seedlings

This study investigated the correlation between endogenous levels of some signal compounds [nitric oxide (NO), salicylic acid (SA), abscisic acid (ABA)] and the antioxidant system in response to chilling stress in maize (Zea mays L.). Seedlings grown for 12 or 19 days under normal conditions (24/20 degrees C) were exposed to chilling stress (10/7 degrees C) for 2 days. The levels of NO, SA, ABA, hydrogen peroxide (H2O2), superoxide anion (O-2(center dot-)), and malondialdehyde (MDA) were determined in leaves of seedlings harvested on day 14 and day 21. In the same seedlings, the activities of superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), and nitrate reductase (NR) were analyzed. Chilling treatment enhanced the levels of NO and ABA in the seedlings harvested on both day 14 and day 21 as compared with the control group. However, SA content was elevated by chilling treatment in 14-day-old seedlings, while it did not change significantly in 21-day-old seedlings. As compared with control plants, chilling treatment increased not only antioxidant enzymes activities but also contents of H2O2, O-2(center dot-), and MDA. NR regarding ABA and NO biosynthesis was increased by chilling in maize. The results showed that chilling stress caused oxidative damage, and changes in signal molecules (NO, SA, and ABA) and NR activity in maize.