水稻甲烷排放与根系通气组织、泌氧能力和关键分泌物的关系

Many studies clearly suggest the possibility of reducing methane emission from the wetland rice ecosystem through appropriate selection of rice cultivars to achieve an economically feasible and technically sound mitigation option of methane emission from farmer ’s fields. Rice plants play a pivotal role in methane emission and more than 90% of CH4 released from a rice field during a growing season can be emitted by rice plant-mediated transport. Root eduates and rhizosphere oxygen concentration are the main factors to influence CH4 emission. To analysis the differences of root aerenchyma, root radial oxygen and main root eduates among rice cultivars and their relationship with CH4 emission, which is advantageous to reveal the mechanism on the significant differences of CH4 emission among cultivars. .It is practical significance to evaluate the ability of rice cultivar methane emission and to breed rice varieties with low methane emission and high yielding , if we can reveal the mechanism on the differences of methane emission amongst rice vultivars based on the root morphological characteristics. In this study, based on the preliminary researchs on rice cultivars with low methane emissions , we will study the following substances. Firstly,to compare the differences of root morphological characters,aerenchyma system and radial oxygen loss among rice cultivars.Secondly,to analysis the relationship between the root morphological characters, aerenchyma tissues and radial oxygen loss.Thirdly, research the influence of root morphological, the root morphological characters,aerenchyma tissues and radial oxygen loss on methane emission. Lastly,the main work is decided the key root morphological characteristics influencing methane emissions..The objective of this study is to explore the mechanism of methane emission differences among rice cultivars based on the root morphological characteristics, structure the root morphological index system to evaluate methane emission ability of rice varieties. At the same time, the result in this study can provide the reference of breeding rice cultivars with low methane emission by the genetic engineering technology, and it is of significance to select rice cultivars with low methane, which can effectively promote agriculture to deal with the climate change.

水稻根系分泌物、根际氧浓度是影响甲烷产生的重要因素。明确不同水稻品种间根系通气组织、泌氧能力和主要分泌物间的差异以及三者与甲烷排放的关系，有利于揭示不同水稻品种甲烷排放差异形成机理。因此，本研究以前期大田试验已筛选的甲烷排放量差异显著的高产水稻品种为研究对象，通过水培模拟试验，比较不同品种间主要生育时期根系通气组织、根系径向泌氧能力及关键分泌物的差异；研究水稻根系通气组织、泌氧能力、分泌物三者的相互关系以及三者与甲烷排放的相关性，揭示根系通气组织、泌氧能力、分泌物对甲烷排放的影响机理，确定影响水稻甲烷排放的根系关键特性，并构建基于水稻根系特征的品种甲烷排放能力评价的指标体系，提出低甲烷排放的水稻品种理想根型；同时通过室内模拟和大田试验实证评价指标的可靠性与实用性，以期为评价水稻品种甲烷排放能力提供一种新方法，同时为培育低甲烷排放高产水稻新品种提供科学依据。

稻田甲烷排放是温室气体的重要来源之一，相同的生长条件下不同水稻品种的甲烷排放速率差别很大，选用甲烷排放速率低的水稻品种进行推广对温室气体减排具有重要作用，然而缺乏可行的评价指标体系对不同品种的甲烷排放能力进行快速有效的评价。水稻根系既影响甲烷气体的产生、土壤微生物活性，又影响甲烷气体的传输，是评价不同品种甲烷排放能力的关键部分。本项目通过对约50个水稻品种的根系生长特性、根系泌氧、根系通气组织以及相关土壤特性指标的测定，明确了早晚稻甲烷排放呈先上升后下降的趋势，在分蘖期至孕穗期达到最大，随后下降至成熟期达最低。水培试验结果表明，早稻甲烷排放速率与根孔隙度（2017年r=0.571*；2018年r=0.402**）、根冠比（2017年r=0.567*；2018年r=0.857**）、根系活跃吸收面积（r=-0.351**）、单株根系泌氧（r=-0.798**）以及最长根长（r=-0.280*）呈极显著相关，此外，单株根系泌氧与根系空腔面积呈极显著正相关关系（r=0.738**）；上述结果与大田试验保持一致，因此通过本项目定性评价早稻甲烷排放速率的根系指标包括根孔隙度、根冠比、根系活跃吸收面积、单株根系泌氧、最长根长以及根系空腔面积。晚稻水培试验结果表明，甲烷排放速率与根孔隙度（r=0.722**）、根冠比（r=0.751**）、根系活跃吸收面积（r=0.314**）、单株根系泌氧（r=-0.634**）、铁载体含量（r=0.496**）呈显著相关，单株根系泌氧与根系空腔面积呈极显著正相关关系（r=0.711**）；上述结果与大田试验保持一致，因此通过本项目定性评价晚稻甲烷排放速率的根系指标包括根孔隙度、根冠比、根系活跃吸收面积、单株根系泌氧、根系分泌铁载体以及根系空腔面积。大田试验结果显示早晚稻产量与甲烷排放呈极显著负相关，表明双季稻高产低排是协同目标。在双季稻主推品种中，株两优819和陆两优996是较好的高产低排早稻品种，Y两优1号和泰优390是较好的晚稻品种。

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