Low-Temperature Stress Signatures in Maize During Emergence: Linking Osmoprotectants, Antioxidative Enzymes, and Photosynthetic Performance.

Early sowing is one of the most promising strategies for mitigating the adverse effects of climate change on maize production in temperate regions. A rapid and strong initial response is critical for seedling survival and can indicate early-sowing tolerance. Consequently, a better understanding of the early mechanisms underlying the establishment of low-temperature (LT) tolerance during early development in maize, including the emergence stage, becomes essential. However, research data on the LT response during emergence are limited. In this study, 5-day-old seedlings of two maize lines with contrasting tolerance to LT (LS and LT) were subjected to low-temperature treatment (10/8 °C) for 24 h, after which metabolites important for LT response were profiled (phenolic compounds, sugars, and sugar alcohols). Activities of several antioxidative enzymes, as well as photosynthetic efficiency, were also examined. Trehalose and inositol accumulation as well as increased peroxidase and superoxide dismutase activities were common to both genotypes. A significant decrease in photosynthetic efficiency, as well as flavonoid and glucose accumulation, was detected only in LS, while sorbitol and erythritol accumulated only in LT. The findings show that both genotypes share core LT responses, while genotype-specific metabolic and photosynthetic adjustments distinguish LT tolerance during the emergence stage.