Plant metabolic responses and adaptation mechanisms to elevated night temperature associated with global warming

Nighttime temperature has been rising at a faster rate than daytime temperature, and this trend is predicted to continue in the upcoming decades. High night temperatures (HNT) during summer months are particularly detrimental to temperate plant species, including grass species. Elevated night temperature interrupts various physiological and metabolic processes, including carbohydrate, amino acid, and hormone metabolism. The HNT-inhibition of photosynthesis has been associated with accelerated leaf senescence, disruption of cellular membranes and photochemical reactions, as well as restriction of the carboxylation process. Respiration rate increases with HNT, which contributes to the loss of carbon and carbon deficits within plant tissues. The responses of amino acids to HNT vary among amino acids with variable functions, and some non-proteinogenic amino acids or nitrogen-rich compounds having roles in stress protection exhibit increases in content under HNT, suggesting the involvement of these compounds in plant adaptation to HNT. Hormones also vary in their responses to HNT with most growth-promoting hormones, such as cytokinins, auxins, and gibberellic acids, exhibiting a reduction in content, while the content of stress-related hormones, such as ABA and salicylic acid, increases under HNT conditions. The understanding of how HNT limits plant growth is just in its infancy, as many of the physiological and metabolic processes affected by HNT have not yet been investigated and are unavailable in the current literature. The mechanisms of how plants can adapt to this stress remain largely unknown, particularly the key metabolic pathways and molecular factors or networks. Further research addressing these unknown aspects is critically important for improving plant resilience against warmer nights, particularly through genetic modification and breeding efforts, as well as management practices.