title: [Effects of exogenous melatonin on nitrogen metabolism and osmotic adjustment substances of melon seedlings under sub-low temperature].
abstract: The melon cultivar 'Yangjiaosu' was subjected to the treatment of 18 °C/12 °C (day/night) in an artificial climate chamber for 6 days, and the activities of nitrogen metabolism related enzymes [nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH) ] , the contents of total N, NO3(-)-N and NH4+-N as well as the osmotic adjustment substances of melon leaf were then determined. The results showed that, compared with the control, sub-low temperature treatment reduced the contents of total N, NO3(-)-N and the NR activity, but increased the content of NH4(+)-N, thereby leading to the growth inhibition of melon. Exogenous MT treatment significantly improved the activities of nitrogen metabolism related enzymes, especially the activities of GS and GOGAT, effectively reducing the content of NH4+-N. Moreover, MT treatment increased the contents of proline, soluble protein and soluble sugar, and alleviated the damage of sub-low temperature on the cell membrane by reducing the relative electrical conductivity and MDA content of melon leaves. In short, this work suggested that exogenous MT would enhance the sub-low temperature adaptability of melon by decreasing the leaf content of NH4-N, increasing the contents of osmotic adjustment substances and reducing the membrane lipid peroxidation levels.
authors.forename: Qing-hai
authors.initials: QH
authors.lastname: Gao
authors.forename: Shuang-shuang
authors.initials: SS
authors.lastname: Jia
authors.forename: Yong-mei
authors.initials: YM
authors.lastname: Miao
authors.forename: Xiao-min
authors.initials: XM
authors.lastname: Lu
authors.forename: Hui-min
authors.initials: HM
authors.lastname: Li
mesh_terms: D003080:Cold Temperature; D019662:Cucurbitaceae / Q000502:physiology*; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005970:Glutamate Synthase / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D008550:Melatonin / Q000494:pharmacology*; D050901:Nitrate Reductase / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D018515:Plant Leaves; D036226:Seedlings / Q000502:physiology
chemical_list: D005970:Glutamate Synthase; D005969:Glutamate Dehydrogenase; D050901:Nitrate Reductase; D005974:Glutamate-Ammonia Ligase; D008550:Melatonin; D009584:Nitrogen