干湿交替灌溉条件下水稻与稗草的竞争过程及其机理

Alternate wetting and drying irrigation is the main irrigation pattern in the present rice production, and barnyardgrass (Echinochloa crus-galli) is the main malignant weed in the global paddy fields. At present, little is known about the competitive process and its mechanism between rice and barnyardgrass under wetting and drying irrigation. In this study, we use two rice cultivars, Nanjing 46 and Liangyoupeijiu, and four species of barnyardgrass, including Echinochloa crusgali (L.) Beauv. var. mitis (Pursh) Peterm., Echinochloa crusgalli (L.)Beauv., Echinochloa crusgalli var. breviseta and Echinochloa crus-pavonis (H.B.K) Schult as materials to reveal the competitive process between rice (at erarly stage) and barnyardgrass under alternate wetting and drying irrigation, researching on responses of root characteristics, characteristics of shoot growth and development (tillers, plant height, dry material accumulation, leaf area), physiological and biochemical process (photosynthetic performance, ATPase activity, indoleacetic acid, indoleacetic acid oxidas, ethylene evaluation rate, reactive oxygen species, oxidative stress index, total phenolic content, flavonids, phenylalnine ammonialyase, cinnamic acid-4-hydroxylase, P-coumaric acyl-CoA ligase activities and gene expression of key enzymes in phenylpropanoid metabolism), and furher abtain the cultivation technique that could moderate rice and barnyardgrass competition though regulating the nitrogen levels. It will be define the competitive mechanism between rice and barnyardgrass in term of the apparent morphological characteristics, physiology and biochemistry and gene expression researching and futher propose the technique of promoting rice growth and inhibiting barnyardgrass occurrence. Above results would provide theoretical basis and practical guidance for the high-yielding, water-saving and ecology-protecting of rice.

干湿交替灌溉是当前水稻生产上最主要的灌溉方式，稗草则是全球稻田最主要的恶性杂草。目前人们对于在干湿交替灌溉条件下，水稻与稗草竞争的过程及其机制知之甚少。本项目拟以4种稗草（无芒稗、稗、短芒稗和孔雀稗）和2个水稻品种（南粳44和两优培九）为材料，研究在干湿交替灌溉条件下水稻（生育前期）与4种稗草的竞争过程, 分析水稻根系特征、地上部生长发育特性（分蘖数、株高、干物质积累、叶面积变化）及生理生化过程（光合特性、ATP酶、吲哚乙酸氧化酶、吲哚乙酸、乙烯释放速率、活性氧、氧化应激指标、总酚含量、类黄酮、苯丙氨酸解氨酶、肉桂酸-4-羟化酶、对香豆酰-CoA连接酶活性及苯丙烷代谢关键酶基因表达量的变化），探讨缓解水稻与稗草竞争的氮肥施用技术。从表观特征、生理生化和基因表达方面明确水稻与稗草的竞争机理，提出促进水稻生长、抑制稗草发生的栽培技术，为水稻高产、节水、保护生态提供理论依据和实践指导。

干湿交替灌溉是当前水稻生产上最主要的灌溉方式，稗草则是全球稻田最主要的恶性杂草。目前人们对于在干湿交替灌溉条件下，水稻与稗草竞争的过程及其机制知之甚少。本项目拟以4种稗草（无芒稗、稗、西来稗和光头稗）和2种水稻（籼稻和粳稻）为材料，自水稻移栽至成熟分别与无芒稗、稗、西来稗和光头稗共生，以无稗草水稻处理为对照，研究在干湿交替灌溉条件下水稻与4种稗草的竞争过程。在此基础上进一步探讨了缓解水稻与稗草竞争的氮肥施用技术。结果表明，在干湿交替灌溉条件下，水稻与不同种稗草共生后水稻产量降低，减产幅度以西来稗最大，其次为无芒稗、稗，光头稗最小，籼稻减产幅度低于粳稻。与籼稻共生时，与对照（无稗草）相比，无芒稗、稗和西来稗均显著降低了水稻产量，光头稗处理差异不显著。对粳稻而言，四种稗草均降低了水稻产量。采用干湿交替灌溉后，四种稗草对水稻产量的影响较常规灌溉条件下减产幅度均增大。无芒稗、稗、西来稗和光头稗增加了水稻灌浆期叶片中丙二醛含量、降低了叶片中过氧化氢酶、过氧化物酶、超氧化物歧化酶活性和稻-稗共生群体冠层透光率。无芒稗、稗和西来稗处理还降低了籼稻水稻品种成熟期的干物质积累量和灌浆期的剑叶光合特性（光合速率、蒸腾速率和气孔导度）、根系氧化力、根系中吲哚-3-乙酸、玉米素+玉米素核苷，以及籽粒中ATP酶活性，光头稗则与对照（无稗草处理）差异不显著；对于粳稻而言，4种稗草均显著降低了上述生理指标，降低幅度为西来稗>无芒稗>稗>光头稗。稻-稗共生过程中水稻灌浆期冠层透光率、叶片抗氧化系统酶活性、光合特性、根系氧化力、根系中吲哚-3-乙酸、玉米素+玉米素核苷以及成熟期干物质积累量降低和灌浆期叶片丙二醛含量增加是水稻减产的重要原因。干湿交替灌溉条件下水稻与无芒稗、稗、西来稗和光头稗共生，不同施氮量对水稻产量的影响表现为：施氮量在0 kg N hm-2水平下，稗草对水稻产量无显著影响；在120 kg N hm-2水平下，西来稗显著降低了水稻产量，但无芒稗、稗和光头稗对水稻产量无显著影响；在240 kg N hm-2水平下，无芒稗、稗、西来稗和光头稗显著降低了水稻产量；在360 kg N hm-2水平下，无芒稗和西来稗处理水稻产量降低，但减产幅度明显减少，光头稗处理与无稗草处理差异不显著，表明通过增施氮肥能够减轻稗草对水稻产量的干扰。