硝态氮和细胞分裂素对玉米局部灌溉补偿生长的联合调控机制

Partial root-zone irrigation, which is an important measure of agricultural water-saving, has been widely adopted. The theoretical basis for benefits of partial root-zone irrigation is that plants can undergo compensatory growth. In other words, partial root-zone irrigation can maintain a higher level of plant growth rate compared to sufficient water supply, which may be attributed to the change of plant hormone induced by root nitrate absorption. In this study, the hydroponic experiment is conducted on maize seedlings grown in split-root containers, which consists of two treatment conditions: nitrate nitrogen addition to the roots and cytokinin (CKs) addition to the leaves. We first will explore effects of exogenous NO3- and CKs on maize growth, root hydraulic conductance, the contents of ABA, CKs and NO3- and related enzyme activity in roots, xylem sap and leaves. Based on the above research, the feedback regulation mechanism between CKs synthesis and NO3- absorption will be studied by statistical analysis of correlation analysis and path analysis. The mechanism of compensatory growth upon partial root-zone irrigation induced by root-absorbed NO3- and root-produced CKs will be investigated by studying growth-related factors, including the amount of ABA, CKs and NO3- and related enzyme activity in roots, xylem sap and leaves. The anticipated research results may be used to enrich and develop the theory of partial root-zone irrigation.

局部灌溉是有效的农业节水措施，植物补偿生长作用是其提出的重要理论依据，根系供应硝态氮后诱导的植物激素变化可能在作物补偿生长中扮演重要角色。本研究以玉米苗期为试验材料，采用控制条件下分根水培技术，在局部灌水条件下，运用根系供应硝态氮以及叶片喷施细胞分裂素（CKs）等手段，研究外源硝态氮和CKs供应对玉米生长状况、根系导水率以及根系、木质部汁液和叶片中脱落酸（ABA）、CKs和NO3-含量的影响，同时测定与CKs和NO3-合成转化有关酶活性。在上述研究的基础上，采用相关分析和通径分析等统计方法，探讨局部灌水条件下，内源CKs合成与根系吸收硝态氮之间的反馈调节作用；通过分析叶片和木质部汁液中ABA、CKs、NO3-含量和相关酶活性，揭示根系吸收的硝态氮和合成CKs对地上部补偿生长的调控机制，为丰富和发展局部灌溉理论提供重要依据。

局部灌溉是有效的农业节水措施，植物补偿生长作用是其提出的重要理论依据，根系供应硝态氮后诱导的植物激素变化可能在作物补偿生长中扮演重要角色。因此，本研究以玉米苗期为试验材料，采用控制条件下分根水培技术，运用根系供应硝态氮以及叶片喷施外源CKs等手段，研究了外源硝态氮和CKs对局部灌溉补偿生长的强化效应。并在此基础上，探索了根系吸收硝态氮对内源CKs的诱导作用以及内源CKs对硝态氮吸收能力的反馈调节机制，进一步揭示了硝态氮和CKs供应对局部灌溉补偿生长的联合调控机制，本研究对丰富和发展局部灌溉理论具有积极的意义。取得以下重要结果：（1）与局部恢复硝态氮供应相比，局部根区硝态氮亏缺1mM对玉米生长具有较高的补偿效应，并可显著提高氮素利用效率。（2）当根系局部供应硝态氮1mM13天时，更有利于强化局部-0.2MPa灌水处理的补偿生长效应，但根系补偿生长时间从3天时就开始发生。（3）前期亏水-0.2MPa后局部恢复供水条件下，均匀供应1mM硝态氮3天时玉米局部灌水的补偿生长效应开始发生，但在一定程度上会限制叶面积增大。（4）在局部-0.2MPa灌水基础上，叶片喷施CKs处理的地上部生物量和叶面积均较不喷施处理明显增大，地上部生长速率显著提高。（5）局部灌溉条件下，供应区根系吸收硝态氮后1天内诱导根系中CKs合成和转运，明显提高叶片中CKs含量，减少ABA和NO3-，9天时叶面积增大，13天时地上部生物量累积，表现出补偿效应。（6）当叶片中CKs累积到最佳水平，作为根系硝态氮饱和的信号来调节氮素吸收和转运，降低叶片中NO3-含量。