外源镁对厚皮甜瓜结果期氮代谢的影响

Effect of exogenous magnesium on nitrogen Metabolism in muskmelon fruiting period

镁是植株生长发育过程中必不可少的元素之一,研究外源施镁对厚皮甜瓜果实生长发育期叶片氮代谢的影响,可以为厚皮甜瓜生产中补充镁肥提供理论依据。以厚皮甜瓜品种‘农大103’为试验材料,试验设5个处理:0(CK)、20、40、60和80 mg/L。待雌花开放时开始处理,在处理7 d后开始采样,取生长点倒数第4片功能叶,共取5次,测定硝态氮、铵态氮含量以及硝酸还原酶(NR)、谷氨酰胺合成酶(GS)和谷氨酸合酶(GOGAT)活性,待授粉后42 d在每个小区随机采摘5个果实,测定果实品质等相关指标。试验结果表明:与CK对比,20、40和60 mg/L处理的硝态氮含量显著降低、铵态氮含量显著增加,80 mg/L处理则与CK差异不显著。20、40和60 mg/L处理的NR活性、GS活性、GOGAT活性都显著高于CK,80 mg/L处理的NR活性前期显著高于对照,后期呈下降趋势,80 mg/L处理的GS活性显著低于CK,而GOGAT活性则高于CK且显著低于40、60 mg/L。在本试验条件下,外源镁处理可以显著促进厚皮甜瓜幼苗叶片中硝态氮的分解与铵态氮的积累,提高氮代谢相关酶活性,优化植株氮素生理利用效率。各处理浓度中,40 mg/L的处理与其它处理相比效果最佳。

Magnesium can improve the photosynthesis of plants and has an important effect on the physiological metabolism and fruit quality of plants. We studied the effect of exogenous magnesium application on nitrogen metabolism in the leaves of muskmelon fructescence to provide theoretical basis for exogenous supplement of magnesium in the production of muskmelon. The thick skinned melon “Nongda103” was used as the test material,and five treatments were set as 0mg/L(CK), 20, 40, 60 and 80 mg/L. Treatments started when the female flowers opened. The fourth functional leaf from the bottom of the growth point were collected 5 times as a sample pool after 7 days treatment, followed by examination of the content of nitrate nitrogen, ammonium nitrogen and activity of nitrate reductase(NR), glutamine synthetase(GS) and glutamate synthase(GOGAT). Five fruits were randomly picked from each plot 42 days after pollination to evaluate the fruit quality related indicators. The results showed that the nitrate nitrogen contents of leaves at 20, 40, and 60 mg/L treatments were significantly reduced, while the ammonium nitrogen contents were significantly increased. The nitrate nitrogen content of leaves at 80 mg/L treatment was not significantly different from CK. The activities of NR, GS and GOGAT at 20, 40, and 60 mg/L treatments were significantly higher than that of CK. The NR activity at 80 mg/L treatment was significantly higher than that of the control in the early stage, but reduced in the late stage. The GS activity at 80 mg/L treatment was significantly lower compared with CK, GOGAT activity was higher than CK and significantly lower than that at treatments 40 and 60 mg/L. The results suggested that exogenous magnesium application can significantly increase the activities of enzymes related to nitrogen metabolism to optimize the physiological utilization efficiency of plant nitrogen and thus promote the decomposition of nitrate nitrogen and the accumulation of ammonium nitrogen in the leaves of muskmelon. The findings supported 40mg/L magnesium as the best application concentration for muskmelon production.