Loss of Pigments and Higher Methylglyoxal Contents in Leaves of Maize Seedlings Under Salinity Are Associated with Saline Susceptibility

Salinity is the most detrimental stress which impairs the growth and development of plants. Seven days old seedlings of two contrast genotypes of maize ( Zea mays L.), two tolerant genotypes (9120 and Super Gold) and two susceptible genotypes (Pacific 984 and PS999), were subjected to 12 dSm -1 salinity stress for five days and contents of chlorophyll ( Chl ), carotenoid (Car), methylglyoxal (MG) as well as activities of glyoxalase I (Gly I) and glyoxalase II (Gly II) were investigated in fully expanded leaves. Loss of Chl and Car contents were higher in the susceptible genotypes compared to those in tolerant genotypes. Production of MG was also higher in the susceptible genotypes, Pacific 984 and PS999, compared to that in tolerant ones under salinity stress. Under salinity, Pacific 984 showed 105 and 91% higher MG over 9120 and Super Gold, respectively, while PS999 showed 75 and 63% higher MG over 9120 and Super Gold, respectively. On the other hand, both of the tolerant genotypes showed higher Gly I and Gly II activities as compared to susceptible genotypes which played important role in reducing cytotoxic MG in tolerant genotypes.