Acclimation by suboptimal growth temperature diminishes photooxidative damage in maize leaves

Abstract

Leaves of Zea mays L. seedlings which developed at optimal (25°C) or suboptimal (15°C) temperature were exposed to high irradiance (1000 μmol m-2 s-1) and a severe chilling temperature (5 °C) for up to 24 h to investigate their ability to withstand photooxidative stress. During this stress, the degradation of the endogenous antioxidants ascorbate, glutathione and α-tocopherol was delayed and less pronounced in 15 °C leaves. Similarly, the decline in chlorophyll a, chlorophyll b, β-carotene and lutein was slower throughout the stress period. Faster development and a higher level of non-photochemical quenching (NPQ) of chlorophyll fluorescence, related to a stronger de-epoxidation of the larger xanthophyll cycle pool in 15 °C leaves, could act as a defence mechanism to reduce the formation of reactive oxygen species during severe chilling. Furthermore, plants grown at suboptimal temperature exhibited a higher amount of the antioxidants glutathione and α-tocopherol. The higher α-tocopherol content in leaves (double based on leaf area; 4-fold higher based on chlorophyll content) which developed at suboptimal temperature may play an especially important role in the stabilization of the thylakoid membrane and thus prevent lipid peroxidation.