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以甜瓜品种‘羊角酥瓜’幼苗为试材,利用人工气候室进行亚低温处理(昼/夜18℃/12℃)6 d,研究外源褪黑素(MT)对亚低温条件下甜瓜幼苗叶片氮代谢酶[硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)和谷氨酸脱氢酶(GDH)]活性、叶片总氮、铵态氮、硝态氮和渗透调节物质含量的影响.结果表明:与对照相比,亚低温处理降低了甜瓜总氮、硝态氮及硝酸还原酶活性,增加了铵态氮含量,抑制了甜瓜幼苗的生长.外源MT可显著提高亚低温下甜瓜幼苗氮代谢酶的活性,尤其可显著提高叶片GS和GOGAT活性,从而有效降低铵态氮含量;外源MT还可以提高叶片脯氨酸、可溶性蛋白质和可溶性糖的含量,进而降低了亚低温对细胞膜的伤害,表现为甜瓜叶片相对电导率和丙二醛(MDA)含量较低.总之,在亚低温条件下,外源MT在一定程度上可通过降低甜瓜叶片铵态氮含量和促进渗透调节物质的积累,降低膜质过氧化水平,从而增加其对亚低温的适应性.
The effects of exogenous melatonin (MT) on the growth and development of melon seedlings under mild hypothermia were studied using the melon variety ’Croucher’ melon seedlings as test material under the conditions of mild hypothermia (day / night 18 ℃ / 12 ℃) The activities of nitrogen metabolism enzymes (NR, GS, GOGAT and GDH), leaf nitrogen, ammonium nitrogen, Nitrate nitrogen and osmotic adjustment substance.The results showed that compared with the control, the mild hypothermia treatment reduced the total nitrogen, nitrate nitrogen and nitrate reductase activity, increased the content of ammonium nitrogen and inhibited the growth of muskmelon seedlings Exogenous MT can significantly increase the activities of nitrogen metabolism enzymes in melon seedlings under mild hypothermia, especially significantly increase the activity of GS and GOGAT in leaves, thus effectively reducing the content of ammonium nitrogen. Exogenous MT can also increase the contents of proline, soluble protein and Soluble sugar content, and then reduced the damage to the cell membrane by mild hypothermia, which showed that the relative electric conductivity and the content of malondialdehyde (MDA) in melon leaves were lower.In conclusion, under the mild hypothermia, the exogenous MT could pass to some extent Reduce the content of ammonium nitrogen and promote osmotic adjustment in melon leaves Accumulation, reducing the level of lipid peroxidation, thus increasing its adaptability hypothermia.