An effective strategy to address the impacts of climate change on maize involves early planting, which mitigates drought stress during critical growth phases, preventing yield reductions. The research assessed two maize inbred lines (sensitive and tolerant to low temperature) under conditions of waterlogging stress. This is crucial since early sowing often faces both low temperatures and heavy rain. Morphological, biochemical, and molecular responses were recorded after 24 h, 72 h, and 7 days of stress during the growth stage of 5-day-old seedlings. The findings indicated a more pronounced decline in all morphological characteristics in the sensitive line. Both genotypes displayed an increased root-to-shoot ratio, suggesting that the shoots deteriorate more rapidly than the roots. Physiological evaluations demonstrated that the tolerant line was more effective in managing ROS levels compared to the sensitive line. The involvement of H₂O₂ in aerenchyma formation implies that the decreased POD activity and elevated MDA levels observed after seven days may be associated with aerenchyma development in the tolerant line. Genes essential for PSII function revealed that waterlogging adversely affected photosynthesis in the sensitive genotype. In summary, the low-temperature tolerant genotype exhibited significant resilience to waterlogging, indicating potential interaction between the pathways governing these two abiotic stressors.

Introduction: Earlier sowing is a promising strategy of ensuring sufficiently high maize yields in the face of negative environmental factors caused by climate change. However, it leads to the low temperature exposure of maize plants during emergence, warranting a better understanding of their response and acclimation to suboptimal temperatures.Materials and Methods: To achieve this goal, whole transcriptome sequencing was performed on two maize inbred lines – tolerant/susceptible to low temperatures, at the 5-day-old seedling stage. Sampling was performed after 6h and 24h of treatment (10/8°C). The data was filtered, mapped, and the identified mRNAs, lncRNAs, and circRNAs were quantified. Expression patterns of the RNAs, as well as the interactions between them, were analyzed to reveal the ones important for low-temperature response.Results and Discussion: Genes involved in different steps of photosynthesis were downregulated in both genotypes: psa, psb, lhc, and cab genes important for photosystem I and II functioning, as well as rca, prk, rbcx1 genes necessary for the Calvin cycle. The difference in low-temperature tolerance between genotypes appeared to arise from their ability to mitigate damage caused by photoinhibition: ctpa2, grx, elip, UF3GT genes showed higher expression in the tolerant genotype. Certain identified lncRNAs also targeted these genes, creating an interaction network induced by the treatment (XLOC_016169-rca; XLOC_002167-XLOC_006091-elip2). These findings shed light on the potential mechanisms of low-temperature acclimation during emergence and lay the groundwork for subsequent analyses across diverse maize genotypes and developmental stages. As such, it offers valuable guidance for future research directions in the molecular breeding of low-temperature tolerant maize.

Maize is one of the most important crop species worldwide, but also extremely susceptible to the effects of increasingly higher temperatures and drought during the summer and its flowering and grain filling stage. Different strategies are being utilized to ensure a satisfying yield potential and quality even in the extremely unfavourable environmental conditions, which are the result of climate change. Some of them are cropping pattern changes and sowing alterations, including earlier sowing. Since this implies the exposure to suboptimal temperatures during early developmental stages, it leads to a demand for developing maize lines tolerant to low temperatures during these stages. This research focuses on the first phase of germination, imbibition. Maize tolerance to low temperatures is a complex trait that includes different mechanisms and strategies that all work together to ensure adaptation and survival, such as cell membrane changes, antioxidative system activation, etc. Additionally, the low temperature response of different maize inbreds varies substantially, so recognizing the different ways in which they respond to low temperatures during imbibition and other earlier stages of development is crucial. To accomplish this, seeds of two maize inbred lines of contrasting susceptibility to low temperatures were selected and exposed to control (20? C) and low temperature (8?C) conditions during the first 24h of imbition and then further analyzed to assess their response. This included germination and tetrazolium assays; ascertaining membrane integrity by evaluating cell leakage and lipid peroxidation; determining the antioxidative capacity by assessing superoxide dismutase (SOD) and catalase (CAT) activity; and expression analysis of four genes included in the low temperature response (gibberellin insensitive dwarf 1 gibberellin receptor, gid1; fatty acid desaturases 2 and 6, fad2 and fad6; plastid-lipid-associated 2 protein, pap2). The results showed that, while there is not a significant difference in their germination rate, they differ in their survival rate, with more seeds of the tolerant genotype surviving the low temperature period. Significant differences between them were found in cell leakage (p<0,01), as well as gid1(p<0,05) and fad6 (p<0,05) gene expression assays. The present research brings light to our understanding of the effect of low temperatures on the first germination stage, - imbibition. It highlights the importance of choosing the right inbreds for earlier sowing and points to certain routes that could be taken for improving and accelerating the breeding process for low temperature tolerance.

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 (L_S and L_T) 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 L_S, while sorbitol and erythritol accumulated only in L_T. The findings show that both genotypes share core LT responses, while genotype-specific metabolic and photosynthetic adjustments distinguish LT tolerance during the emergence stage.