水稻品种根系改良特征及其与稻田甲烷排放的关系

The effects of rice cultivar evolution on the root morphology and physiology and their relationships with methane emission in paddy fields have not been clearly understood. With 24 typical rice cultivars (12 Indica cultivars and 12 Japonica cultivars) during the process of rice cultivar evolution as materials, the project is designed to investigate: (1) The characteristics of total methane emission and methane emission flux at main growth stages (mid-tillering stage, panicle initiation, heading stage, milky stage and maturity); (2) Changes of morphology (root number, length, density, diameter, weight, surface area and ultrastructure of root tip cells) and physiology (the root oxidation activity, total and active absorption area, hormones contents in root and the contents of hormones, organic acids, amino acids in root bleedings and the concentrations of ions and organic acids exuded from roots) at main growth stages and their relationships with methane formation and emission in paddy fields; (3) The regulating effects of water management and nutrient management (including wheat straw returning to the paddy field) on root morphology and physiology and methane emission. This study is expected to elucidate the effects of rice cultivar evolution on the morphological and physiological characteristics of rice root and their relationships with methane emission in paddy fields and put forward the cultivating approaches to regulating methane emission in paddy fields through the regulation of morphology and physiology of rice roots.

水稻品种改良对根系形态生理的影响及其与稻田甲烷排放的关系尚不清楚。本项目拟以我国水稻品种改良过程中24个代表性品种（籼稻和粳稻品种各12个）为材料，研究：（1）水稻品种改良过程中稻田甲烷总排放量和主要生育时期（分蘖中期、穗分化期、抽穗期、乳熟期和成熟期）甲烷排放通量的变化规律；（2）品种改良过程中水稻主要生育时期根系形态（根数、根长、根长密度、根直径、根重、根重密度、根表面积、根体积和根系超微结构）和生理（根系氧化力、根系总吸收表面积和活跃吸收表面积、根系激素浓度、根系伤流液中激素、有机酸和氨基酸组分和浓度以及根系分泌物浓度）的变化特点及其与稻田甲烷产生与排放的关系；（3）营养管理（含小麦秸秆还田）和水分管理对水稻根系形态生理和甲烷排放的调控作用。通过上述研究，阐明水稻根系形态生理的改良特征及其与稻田甲烷形成与排放的关系，提出通过调控根系形态生理来调控稻田甲烷排放的栽培途径和技术。

水稻品种改良对根系形态生理的影响及其与稻田甲烷排放的关系尚不清楚。本项目以我国水稻品种改良过程中24个代表性品种（籼稻和粳稻品种各12个）为材料，研究了其根系形态生理变化及其与稻田甲烷排放的关系，主要结果如下。.（1）品种改良显著提高了水稻产量。产量提高主要得益于总颖花量的大幅度提高，而每穗粒数增加是总颖花量提高的主要原因。现代超级稻品种的结实率较之前品种有所降低，这是限制其产量水平进一步发挥的主要原因。.（2）中粳水稻品种改良逐步提高了根干重、根冠比、根长、根数、根直径、根系伤流量、根系氧化力、根系总吸收表面积、根系活跃吸收表面积。孕穗期和抽穗期根系分泌物中苹果酸、琥珀酸和乙酸的浓度均随品种改良显著提高，酒石酸、柠檬酸的浓度则显著降低。品种改良改善了中粳水稻品种的根系形态和根系生理。.（3）不同年代水稻品种全生育期稻田甲烷排放通量的变化趋势基本一致。稻田甲烷排放总量随品种改良逐步降低。在水稻生长早期，稻田甲烷排放的品种间差异不明显。品种改良显著降低了水稻生育中后期稻田甲烷排放通量。.（4）孕穗至抽穗水稻根系主要形态和生理指标以及根系分泌有机酸浓度与稻田甲烷排放总量及对应时期的甲烷排放通量有密切关系。水稻根系形态生理演进与稻田甲烷排放密切相关。.（5）氮肥通过影响水稻根系形态（根重、根长和根数）、根系氧化力以及根系分泌有机酸浓度来影响水稻产量和稻田甲烷排放。轻度干湿交替灌溉有利于提高水稻产量并降低稻田甲烷排放。麦秸秆覆盖和麦秸秆掩埋还田可维持较高直播水稻产量并有利于稻田温室气体减排。采用实地氮肥管理和和玉米秸秆制成的沼渣，可获得较高水稻产量和较好的环境效益。.上述研究结果对阐明稻田甲烷排放的品种间差异及其机理有参考价值，对水稻高产栽培与稻田温室气体减排有一定的指导作用。