膜下滴灌水稻根系生物学特征及对硝酸盐的响应机制

Plant roots are the main nutrient absorbing organs. Root morphogenesis is direct impact by nitrogen form, effectiveness and distribution. In recent years, drip irrigation under mulch technology was implemented in rice to propose a water-saving and efficient fertilizer cultivation technology. In our previous study, the difference of nitrogen (ammonia and nitrates) environment in rice soil between flooding and drip irrigation was found. Obviously, the rice root development has specificity feature to acclimate the drip irrigation. Furthermore, drip irrigation has the feature of fertilizer controllability, which gives us an opportunity to study the effect of nitrates on root growth in the filed in vivo. This project studies the rice root biology characteristics of drip irrigation under-mulch and its response mechanism to nitrates. Consequently, the regulation effects of nitrogen on the root configuration and physiology can be clarified. Further, the relationship between root configuration and ammonia and nitrates distribution in the soil can be revealed. In addition, the synergistic affect mechanism between root configuration and physiology can be clarified. This project also reveals the regulatory mechanism of root development to nitrates. Finally, the regulation technique of optimizing nitrogen fertilizer based on the root configuration can be proposed. Research results are conducive to guide rational application of fertilizer in drip irrigation rice. It is a great significance for improve the nitrogen use efficiency further in rice.

根系是作物吸收养分的主要器官。氮素形态、有效性和分布状况直接影响作物根系的形态建成。膜下滴灌水稻栽培技术是新疆近几年探索出的一种水稻节水节肥高效栽培技术。前期研究表明，膜下滴灌条件下稻田土壤的氨硝环境完全不同于漫灌，导致膜下滴灌水稻根系的建成具有特异性。同时膜下滴灌施肥技术具有可控性高的特点，为开展硝酸盐调控水稻根系生长的大田原位研究提供了契机。本项目从水稻根系生物学特征和硝酸盐调控两个方面着手，研究膜下滴灌水稻根系生物学特征及对硝酸盐的响应机制，明确膜下滴灌条件下氮素对水稻根系构型和生理功能的调控效应，阐明土壤氨和硝态氮分布与根系构型的关系，探明根系构型和生理功能两者的协同作用机制，揭示硝酸盐对水稻根系的调控机制，提出膜下滴灌水稻根系构型优化的氮素调控技术。研究结果有助于指导膜下滴灌水稻生产合理施肥，对进一步提高水稻氮素利用率具有重要指导意义。

根系是作物吸收养分的主要器官。氮素形态、有效性和分布状况直接影响作物根系的形态建成。但膜下滴灌条件下稻田土壤的氨硝环境完全不同于淹灌，导致膜下滴灌水稻根系的建成具有特异性。本文通过研究膜下滴灌与常规淹灌的水稻根系构型、生理特征及氮素效率的差异，土壤铵硝空间分布与滴灌水稻根系构型及生理协同效应的关系，不同氮素形态配比对滴灌水稻根系构型和生理的调控，明确了膜下滴灌水稻的根系生物学特征及对硝酸盐的响应机制。通过4年的研究得到如下主要结论：1）与常规淹灌水稻相比，相同施氮量滴灌水稻总根长、根系表面积、根系平均直径及根系体积较小，中量施氮20kg/亩各指标更高；水稻根系主要为0.1-0.3mm细根，滴灌细根显著减少，但占总根长的比例高于淹灌；水稻根系主要集中在0-10cm土层内，滴灌后各土层均有显著的减少；2）淹灌渐进方程β值更低，根系分布更接近土壤表面，滴灌反之。3）根系活力为滴灌、中量施氮较高；滴灌降低了根系总吸收面积、活跃吸收面积，但提高了活跃吸收面积比；滴灌氮代谢酶活性根系中同施氮量变化不显著，叶片中NR增加、GS减少、GOGAT也有增加趋势；4）滴灌地上部干物质积累显著下降，根冠比也有下降趋势；产量与淹灌相比也有降低，氮素利用效率差异不大；根系形态、生理特性及氮代谢酶活性与产量及氮肥偏生产力、农学利用率存在显著或极显著的相关性；5）施NH4+较NO3-水稻总根长、表面积、体积更高，根系平均直径有下降；细根量NH4+高于NO3-、占总根长比例差异不显著；6）施入NO3-后分布渐进方程β值更高，根系生长更趋向于土壤深部；7）总吸收面积、活跃吸收面积NO3-较NH4+低，但可提高活跃吸收面积比；氮素同化酶对NO3-和NH4+的响应明显；8）不同品种T-43 NH4+产量更高；垦-26 NO3-更高；根系形态、生理特性及氮代谢酶活性与产量及氮肥偏生产力、农学利用率也存在显著或极显著的相关性；9）不同形态配比，T-43以NH4+/ NO3- 90/10、垦-26以NH4+/ NO3- 75/25更优，为适合膜下滴灌水稻推荐的施用比例。.研究结果有助于指导膜下滴灌水稻生产合理施肥，对进一步提高水稻氮素利用率具有重要指导意义。