根区土壤水分非均匀分布对玉米根系构型和生理特性的影响研究

Root architecture plays a crucial role in water acquisition and water use efficiency. However, researches on effect of soil moisture heterogeneity in the root zone caused by different irrigation methods and the underlying mechanisms are not sufficient, which is one of the scientific research topic to be resolved in the field of water saving irrigation. Therefore, this project will investigate systematically the effect of vertical and horizontal soil moisture heterogeneity in the root zone during surface and subsurface irrigation, and conventional and alternate partial root-zone irrigation on root architecture of maize plants by pot and field experiments. The correlations between root architecture, soil moisture heterogeneity, crop physiological characteristics, root-sourced abscisic acid and water use efficiency will be discussed. The optimal root architecture of maize with high yield and water use efficiency will be determined. The mechanism for high water use efficiency will be elucidated. The results from the project are of great importance to explain the responses of plants to soil moisture heterogeneity and improve water saving irrigation techniques as well as selection of drought stress new varieties, which can provide new theoretical and scientific basis to the research field of agricultural water saving.

作物的根系构型对水分吸收及利用效率起着关键作用，但目前对于由不同灌溉方式在根区空间造成的土壤水分不均匀分布对作物根系构型的影响及机理尚不明确，这也是节水灌溉领域亟需解决的科学问题之一。本项目以玉米为试验对象，拟采用盆栽试验和田间试验相结合的方法，系统研究地表和地下灌溉在根区产生的土壤水分分布垂直差异性及常规和分根交替灌溉所产生的土壤水分分布水平差异性对玉米根系构型的影响，探讨根系构型与土壤水分分布特征、作物生理特性、根源化学信号脱落酸及水分利用效率之间关系的机理。明确如何通过灌溉形成优质高产和水分高效利用的玉米根系构型，阐明提高作物水分利用效率的机理。本项目的研究成果对于明晰作物对根区土壤水分非均匀分布的响应，完善节水灌溉技术、选育抗旱节水新品种都具有重要的意义，可以为我国农业节水的研究领域提供新的理论和科学依据。

不同灌溉方式造成的土壤水分非均匀分布对作物根系构型、生理特性和水分利用效率的影响机理不明确。本项目利用稳定同位素技术等，研究发现不同灌溉方式显著影响了玉米的根系构型，主要体现在分根灌溉和亏缺灌溉在土壤剖面，特别是土壤深层和土壤表层的根系构型的显著差异，造成了水分利用效率的不同。与亏缺灌溉相比，分根灌溉增强了根源化学信号脱落酸传导，使气孔发生部分关闭，并提高了木质部汁液的pH值，进一步增强了对气孔的控制，优化了气孔对于气体交换的调控过程。与此同时，分根灌溉处理植株有更高的叶片光合速率，并提高了植株的氮素吸收和碳13组成，从而进一步增强叶片的光合能力，使叶片在降低气孔开度的基础上，显著提高了叶片水平的水分利用效率和整株水平的水分利用效率。分根灌溉产生了更强烈的土壤干湿交替过程，增强了土壤微生物活性，提高了土壤氮素的矿化率，并显著增强了植株的氮素吸收速率，因此提高了植株氮素吸收，促进玉米的水分利用效率的提高。