Melatonin promotes plant growth by maintaining integration and coordination between carbon and nitrogen metabolisms
Melatonin-induced growth promotion of maize seedlings is associated with maintaining coordination between gene expressions and activities of key enzymes involved in carbon and nitrogen metabolisms.
Melatonin is a pleiotropic molecule that influences many diverse actions to enhance plant growth. The effect of melatonin on maintaining a necessary balance between carbon and nitrogen metabolisms that underpins the growth process in higher plants remains unclear. In this study, the influence of melatonin on nitrogen assimilation, mitochondrial respiration, and photosynthesis, which are major pathways related with carbon and nitrogen metabolism, was investigated on the basis of the seedling growth of maize. Melatonin applications (10, 100, and 1000 μmol L−1) significantly increased the growth parameters assessed by root elongation, plant height, leaf surface area, and the contents of protein, carbohydrate, and chlorophyll in comparison to the control seedlings. They also had a strong encouraging effect on the activities and gene expressions of enzymes (nitrate reductase, nitrite reductase, glutamine synthase, glutamate 2-oxoglutarate transferase, and NADH–glutamate dehydrogenase) involved in the nitrogen assimilation process. While melatonin applications elevated nitrate and nitrite concentrations, they markedly lowered ammonium content compared to control. Similarly, the activity of citrate synthase, the first enzyme of citric acid cycle providing carbon skeleton for nitrogen assimilation, was significantly augmented by melatonin applications. Moreover, melatonin considerably upregulated the gene expressions of citrate synthase and cytochrome oxidase, an enzyme responsible for ATP production. Remarkable increments were recorded at Rubisco activity and gene expressions of Rubisco and Rubisco activase in melatonin-treated seedlings. In conclusion, all these data put together reveal that melatonin-induced growth promotion of maize seedlings resulted from its coordinating effect on carbon and nitrogen metabolisms.
KeywordsMelatonin Nitrogen assimilation Mitochondrial respiration Photosynthesis Plant growth Maize
The experiments were conducted at the Laboratory of Plant Physiology (Ataturk University, Erzurum, Turkey) in 2016. The author would like to thank Ismail Hakki Tas for the helpful advice on various technical issues examined in this paper. The author, however, bears full responsibility for the paper.
Compliance with ethical standards
Conflict of interest
The author declares that he has no conflicts of interest in this work.
- Dische Z (1947) New characteristic color reactions of carbohydrates with SH compounds in H2SO4. Fed Proc 6:248Google Scholar
- Gao QH, Jia SS, Miao YM, Lu XM, Li HM (2016) Effects of exogenous melatonin on nitrogen metabolism and osmotic adjustment substances of melon seedlings under sub-low temperature. Ying Yong Sheng Tai Xue Bao 27:519–524Google Scholar
- Guo QF, Wang QC, Wang LM (2004) Chinese maize cultivation. Shanghai Science and Technology Press, Shanghai, pp 117–167Google Scholar
- Hattori A, Migitaka H, Iigo M, Itoh M, Yamamoto K, Ohtani-Kaneko R, Hara M, Suzuki T, Reiter RJ (1995) Identification of melatonin in plants and its effects on plasma melatonin levels and binding to melatonin receptors in vertebrates. Biochem Mol Biol Int 35:627–634Google Scholar
- Ida S, Morita Y (1973) Purification and general properties of spinach leaf nitrite reductase. Plant Cell Physiol 14:661–671Google Scholar
- Shi HT, Jiang C, Ye TT, Tan DX, Reiter RJ, Zhang H, Liu RY, Chan ZL (2015a) Comparative physiological, metabolomic, and transcriptomic analyses reveal mechanisms of improved abiotic stress resistance in bermudagrass [Cynodon dactylon (L). Pers.] by exogenous melatonin. J Exp Bot 66:681–694CrossRefGoogle Scholar
- Witham FH, Blaydes BF, Devlin RM (1971) Experiments in plant physiology. Van Nostrand Reinhold, New YorkGoogle Scholar
- Zhao N, Sun Y, Wang DY, Zheng J (2012) Effects of exogenous melatonin on nitrogen metabolism in cucumber seedlings under high temperature stress. Plant Physiol J 48:557–564Google Scholar