小麦节水高产的同化物运输机理及氮素调控效应研究

The yield formation in wheat is greatly influenced by the transport of photo-assimilates to grain sink via vascular bundles, but the transport mechanism was not known yet. Our previous studies have indicated that there were differences among different irrigation treatments in the vascular bundles of flag leaves and internode below spike in wheat. Based on the findings as aforementioned, in this study, we will systematically investigate the vascular bundle structures of leaf/stem/spike, the ultrastructures of abdominal vascular bundle phloem cell of grain and endosperm transfer cells；determine the transport rate of assimilates in vascular bundles, the transport and distribution of 13C assimilates, proliferation of endosperm cell, the enzymatic activities，starch accumulation and filling characteristics in grains under different soil relative water content conditions with different spike types wheat cultivars in field. In this process, we will adopt microscopic and ultrastructural observation, isotope tracer, enzymologic, physiological and biochemical approaches. Based on these studies, we can elucidate the transport mechanism of photoassimilate from photosynthetic organ to grain for water saving and high yielding of wheat, and to make clear the relationship between photoassimilate transport and the capacity, activity and assimilate accumulation in grain sink. Additionally, previous studies have elucidated soil relative water content for high-yield wheat, and our investigation in this study will further help to understand the regulatory effects that nitrogen fertilizer amount and the ratio of base and top topdressing work on the photoassimilate transport to grain，accumulation in grains, grain yield, water use efficiency and nitrogen use efficiency of different spike type wheat under water-saving and high-yield conditions, which will provide valuable guidance for establishing the cultivation pathway of wheat with water-saving, high-yield and highly efficient conditions in the North China Plain.

维管束通过介导光合同化物向籽粒库运输，对小麦产量形成有重要影响，但迄今其运输机理尚不明确。申请人前期研究发现小麦旗叶和穗下节间维管束结构在不同灌水处理间存在差异。在此基础上，本项目拟采用显微和超微观测、同位素示踪、酶学和生理生化等方法，系统观察大田不同土壤相对含水量下不同穗型小麦叶/茎/穗维管束结构、籽粒腹部维管束韧皮部细胞和胚乳传递细胞超微结构，测定维管束中同化物运输速率、13C同化物转运分配、籽粒胚乳细胞增殖动态、库活力相关酶活性和淀粉积累及灌浆特性等，从细胞水平揭示小麦获得节水高产的光合同化物向籽粒运输的机理，明确其与籽粒库容量和活力及同化物积累的互馈调节机制。在前期研究已明确小麦节水高产的土壤相对含水量基础上，探明节水高产条件下氮肥施用量和底追比例对不同穗型小麦光合同化物向籽粒运输、籽粒同化物积累、籽粒产量及水分和氮素利用效率的调控效应，为华北平原小麦节水高产高效生产提供依据。

本项目针对节水高产条件下小麦光合同化物向籽粒运输机理不明确的问题，以中穗型和大穗型小麦品种为试验材料，研究了不同土壤相对含水量下小麦旗叶光合特性、13C同化物积累分配、维管束结构、籽粒胚乳传递细胞超微结构、籽粒淀粉含量及其相关酶活性和灌浆特性，群体光截获和干物质生产、转运及分配特性等，结果明确了两种穗型小麦节水灌溉处理的旗叶净光合速率、蔗糖磷酸合成酶活性和蔗糖含量、13C同化物积累量及在籽粒的分配量和分配比例、穗下节间维管束数目和面积均高于不灌水处理，促进了光合同化物生产和向籽粒运输，籽粒淀粉含量和粒重较高；节水灌溉处理开花后的叶面积指数、光合有效辐射截获量和截获率、开花后生产的干物质对籽粒的贡献率均高于不灌水处理，是其籽粒产量增加10.69%-16.52%的重要原因；增加灌水至充分灌溉水平，上述指标和籽粒产量无显著提高，水分利用效率降低2.28%-7.27%。探明了节水高产条件下适宜的氮肥施用量和底追比例，中穗型品种济麦22施氮量为180 kg·hm-2的旗叶光合和叶绿素荧光参数、旗叶和穗下节间维管束面积、开花后生产的干物质及其对籽粒的贡献率均高于不施氮处理，籽粒产量提高23.31%；施氮量增至240和300 kg·hm-2，上述指标和籽粒产量无显著增加，氮肥偏生产力、氮肥吸收利用率和氮肥表观利用率降低。氮肥基追比例为5:5的旗叶光合和叶绿素荧光参数、籽粒潜在库容和库容指数、冠层光合有效辐射转化率和利用率显著高于其它基追比例处理，灌浆后期千粒重最高，籽粒产量和氮素利用效率比其它处理分别提高5.29%-16.17%和5.28%-12.58%。节水条件下小麦高产高效的适宜氮肥施用量为180kg/hm2，基追比例为5:5。研究结果可为华北平原小麦节水高产高效生产提供依据。