地膜覆盖对黄土高原地区两种种植密度下玉米叶片代谢组的影响

Effects of plastic film mulching on leaf metabolic profiles of maize in the Loess Plateau with two planting densities

在黄土高原地区,对覆膜条件下玉米叶片代谢组变化规律的研究是探索覆膜增产生理机制的重要方面。本研究采用气相色谱-四极杆-飞行时间质谱(GC-QTOF)技术,对2种覆膜方式(塑料膜覆盖和不覆盖)、2个密度(7.5×10^(4)株hm^(–2)和10.5×10^(4)株hm^(–2))和2个品种(郑单958和先玉335)的吐丝期玉米叶片进行了代谢组学分析。从差异代谢物个数来看,先玉335对覆膜的响应大于郑单958,较高的种植密度缩小了覆膜与无覆膜处理间叶片代谢的差异。主成分分析表明,覆膜处理和品种均对代谢物组成产生了重大影响。覆膜引起的代谢谱差异主要是由柠檬酸等有机酸和氨基酸造成的;品种引起的代谢组差异主要是由辛酸等烷酸和酚类造成的。相关分析表明,叶绿醇、白藜芦醇、葡萄糖-6-磷酸与玉米籽粒产量呈显著正相关关系,而甘油与之呈显著负相关关系。在覆膜条件下,与呼吸作用及清除光呼吸产物相关的缬氨酸、异亮氨酸及蛋氨酸,与三羧酸循环相关的异柠檬酸以及可减轻光抑制的蛋氨酸、N-乙酰基天冬氨酸等代谢物的水平整体呈升高趋势。以上结果表明,在覆膜条件下,消除光呼吸产物及减少光抑制的相关代谢物的积累是叶片净光合速率提高的代谢基础;抗氧化及能量代谢相关的代谢物在提高产量的过程中发挥了重要作用。

In the Loess Plateau,the study of leaf metabolomics under plastic mulching is an important step to explore the mechanism of plastic film mulching to increase grain yield in maize.Metabolomics analysis was performed on the leaves of two maize cultivars(Zhengdan 958 and Xianyu 335)under two planting densities(7.5×10^(4) and 10.5×10^(4) plant hm^(–2))and two mulching modes(plastic film mulching and no mulching)at silking stage using gas chromatography-quadrupole-time of flight mass spectrometry(GC-QTOF)technology.In term of the number of differential metabolites,the response of Xianyu 335 to plastic film mulching was greater than that of Zhengdan 958.The higher planting density reduced the difference in leaf metabolism between plastic film mulching and no mulching.The principal component analysis revealed that both the mulching treatment and the cultivar had significant impacts on the composition of the metabolites.The separation of metabolic spectrum along plastic film mulching was mainly driven by organic acids such as citric acid and amino acids;the separation along cultivar was mainly driven by alkanoic acids and phenols.Correlation analysis indicated that resveratrol,phytol and glucose-6-phosphate had significant positive correlations with maize grain yield,whereas glycerol had a significant negative correlation with it.Under plastic film mulching condition,the levels of valine,isoleucine and methionine related to respiration and elimination of photorespiration products;isocitrate related to tricarboxylic acid cycle,methionine,N-acetylaspartic acid and other metabolites that could reduce photoinhibition showed an overall increasing trend.These results indicated that,under plastic film mulching condition,the antioxidant and energy metabolism-related metabolites played important roles in increasing grain yield.The elimination of photorespiration products and the accumulation of metabolites to alleviate photoinhibition were the metabolic bases for the increase of net photosynthetic rate in maize leaves.