水分胁迫下紫花苜蓿根源信号ABA应旱机制及其调控模型研究

Drought made forage plant to be senescence and death, the vegetation coverage declining and the yields decreasing with the adverse effects on the regional landscape ecology and grassland animal-husbandry production. Soil water stress directly acts on the forage root and affect the growth of above-ground parts and whole plants. Research on drought-tolerance mechanism of grassland plant roots, adaptive managements under the water stress and breeding in the new drought-resist varieties of forage grass has become a hot spot for the ecologists. The experiments on medicago sativa will be conducted to investigate the changes in the root-source signal ABA contents, stomata openings, root characteristics indices and the above-ground trait factors through modifying the water contents in the pot cultures in this study. The responding mechanism of root-sourced signal ABA to water stress and the physiological-ecological resistance mechanism of medicago sativa under water stress will be discussed and clarified to further enrich the physiological-ecological theories of grass forage on the adverse conditions of water stress based on a drought-resistant manipulating model. This study will provide the basic data and theoretical supports for water-saving and drought-tolerant varieties breeding and adaptable planting and division of medicago sativa in China under the global climate changes.

干旱引起草地植物衰老死亡，植被覆盖度降低且产草量下降，给区域景观生态和草地畜牧业生产带来不良影响。土壤水分胁迫直接作用于牧草根部进而影响地上部分及全株植物的生存生长。草地植物根系耐旱机制及其在水分胁迫下的适应性管理与抗旱牧草新品种选育已成为草地学家们的研究热点。本项目拟以紫花苜蓿为研究对象，采用盆栽控水模拟土壤干旱试验方法，通过观测紫花苜蓿根源信号ABA含量、叶片气孔导度、根系与地上部性状指标等的变化，探讨根源信号ABA对水分胁迫的响应机制，构建根源信号应旱特征调控模型，阐明水分胁迫下紫花苜蓿生理生态学机理，进一步丰富水分胁迫下草地植物逆境生理生态学理论，为全球气候变化下我国紫花苜蓿节水耐旱品种选育及其适宜性种植区划提供基础数据与理论支撑。

脱落酸（ABA）在植物响应水分胁迫的过程中扮演着重要角色，然而目前紫花苜蓿根源ABA应旱机制及其内在生物学机理尚不明确。项目首先通过对不同品种紫花苜蓿种子的萌发试验和苗期盆栽试验从形态学上确定了不同紫花苜蓿品种对水分胁迫的响应存在差异，这种差异在根冠比和比叶面积两个指标上表现尤为明显。然后，通过对不同品种紫花苜蓿进行不同生育期水分胁迫处理，初步探索了不同品种紫花苜蓿根源ABA在各个生育期对水分胁迫的响应机制。在分枝期、开花期和结荚期，中苜1号和敖汉紫花苜蓿根系ABA含量对水分胁迫的响应一致，即随着水分胁迫强度的增加，根系ABA含量也相应呈升高趋势；三得利紫花苜蓿根系ABA含量对水分胁迫的响应与前两者相比明显不同，随着水分胁迫强度的增加，其分枝期根系ABA含量呈升高趋势，开花期和结荚期则没有表现出明显的响应。研究还通过多元非线性回归分析，针对不同紫花苜蓿品种建立了以气孔导度（Y）为因变量，ABA含量（X1）、叶片相对含水量（X2）和土壤含水量（X3）为自变量的回归模型。最后，通过高通量测序技术在紫花苜蓿叶片和根系中发现了30个干旱胁迫应答的miRNA，其中多个miRNA与ABA信号通路相关，如miRNA159家族通过调控其靶基因MYB转录因子参与ABA信号通路。水分胁迫下miRNA组学特征的研究为进一步研究紫花苜蓿抗旱分子机理奠定了基础。