Effects of Melatonin on Morphological Characteristics, Mineral Nutrition, Nitrogen Metabolism, and Energy Status in Alfalfa Under High-Nitrate Stress

Abstract

Melatonin is an indoleamine small molecular substance that has been shown to play an important role in the growth, development, and stress response of plants. The effects of melatonin on the morphological characteristics, mineral nutrition, nitrogen metabolism, and energy status in alfalfa (Medicago sativa L.) under high-nitrate stress were studied. The alfalfa plants were treated with water (CK), 200 mmol L−1 nitrates (HN), or 200 mmol L−1 nitrates + 0.1 mmol L−1 melatonin (HN+MT), and then were sampled for measurements on days 0 and 10, respectively. The results showed that the HN treatment resulted in a decrease in the morphological characteristics (such as shoot height, leaf length, leaf width, leaf area, and biomass), phosphorus, soluble protein (SP), nitrogen-related enzymes activities and gene relative expression, adenosine triphosphate (ATP), and energy charge (EC). It also caused an increase in nitrogen, sodium, potassium, calcium, nitrate-nitrogen (NO3--N), ammonium-nitrogen (NH4+-N), adenosine diphosphate (ADP), and adenosine monophosphate (AMP). However, these parameters were conversely changed in the HN+MT treatment. Besides, these parameters were closely related to each other, and were divided into two principal components. It reveals that melatonin plays an important role in modulating the morphology, mineral nutrition, nitrogen metabolism and energy status, thereby alleviating the adverse effects of high-nitrate stress and improving the growth of alfalfa.

Melatonin and KNO3 Application Improves Growth, Physiological and Biochemical Characteristics of Maize Seedlings under Waterlogging Stress Conditions

“…Exogenous melatonin with KNO 3 promotes the antioxidant enzymes and enhances the nitrogen metabolism activities of maize under waterlogging stress conditions. The glutathione synthase (GS), nitrate reductase (NR), glutamate synthetase (GOGAT), and glutamate dehydrogenase (GDH) enzymes play important roles in nitrogen metabolism [ 58 ]. We found that under WL stress, the GS and NR were reduced compared with NWL and WLM.…”

Role of Melatonin and Nitrogen Metabolism in Plants: Implications under Nitrogen-Excess or Nitrogen-Low

“…In this case, melatonin increased nitrogen-excess tolerance through the up-regulation of NR, GS, GOGAT, and GDH enzymes. Furthermore, it reduced the total nitrogen levels (nitrate and ammonium content) and increased the biomass, length, width of leaves, and energy levels (P and ATP) and decreased the Na, K, and Ca mineral contents [ 48 ]. Similar results were obtained in soybean plants treated with melatonin in nitrogen-excess [ 49 ].…”

“…It also improved the contents of amino acid, protein, proline, and ureides, whilst up-regulating NR, NiR, NRT, GS, GOGAT, and GDH gene expression, consequently improving the growth and total biomass of soybean plants [ 56 ]. The authors suggested that melatonin regulated the assimilation, metabolism and transport of nitrogen, thereby maintaining the carbon/nitrogen balance [ 48 , 50 , 58 , 59 ].…”

Exogenous melatonin strongly affects dynamic photosynthesis and enhances water-water cycle in tobacco

“…Melatonin (MT) is an important hormone synthesized naturally in both plants and animals. Many recent studies have documented that MT is critical in several metabolic processes, including ROS scavenging systems ( Siddiqui et al, 2020a , b ), secondary metabolism ( Farouk and Al-Amri, 2019 ; Jahan et al, 2020 ), and modulation of nitrogen metabolism ( Qiao et al, 2019 ; Chen et al, 2021 ; Meng et al, 2021 ; Kaya et al, 2022 ). Therefore, MT plays a significant role in plants to cope with biotic and abiotic stresses ( Arnao and Hernández-Ruiz, 2015 , 2019 , 2020 ).…”