供磷水平影响禾谷类作物籽粒锌累积和有效性的作用机制及其调控

Zinc (Zn) is an essential micronutrient for both crop growth and human health, whereas the low concentration and bioavailability of Zn in cereal crop grains contribute a lot to Zn malnutrition worldwide. In resent decades, excess phosphorus (P) application resulted in P surplus in Chinese croplands, which negetively affected grain Zn accumulation and biaoavailability in cereal grains and accordingly to human health. Therefore, in this innovative project, the winter wheat and summer maize will be used as target crops to study the mechanisms of Zn accumulation in grains and its bioavailability as affected by P application levels under hydroponic and field conditions, and its management straties to satisfy the requirement of high yield and quality of cereal crops. The main contents of this study includes:(1) On the acidic soil and calcareous soil types, to study the effects of P application levels on Zn absorption, distribution in the plants and accumulation in the grain of the field crops; (2) to study the effects of P application levels on relative expression levels of genes related with Zn uptake (ZIP family) and root-to-shoot translocation (HMA family) in plant roots and Zn retranslocation in shoot part (YSL family) with hydroponic and field condition; (3) to study the effects of P application levels on Zn availability and retranslocation in vegetative organs with hydroponic culture and its contributions to grain Zn accumulation; (4) to study the effects of P application levels on Zn bioavailability, distribution and its speciation within wheat and maize grain with SEC-ICP-MS; (5) to study the physiological response of wheat and maize crops to varied P application levels with different methods of Zn application, and also its biofortification with Zn. This innovative study will give insights in the physiological and molecular mechanisms of Zn accumulation and bioavailability in crops and finally in cereal grains affected by P application levels, and will investigate integrated management including Zn application to satisfy both high grain yield and Zn enriched grain, which is very important for food security and human health.

锌是作物生长和人体发育所必需微量元素，农业生产中禾谷类作物籽粒锌含量及有效性低是引起居民缺锌的重要原因。近年来，大量施用磷肥导致农田中有效磷富集，进一步降低了禾谷类作物籽粒锌含量并影响到居民健康。因此，本研究拟以小麦、玉米为材料，结合营养液培养和大田试验，利用SEC-ICP-MS，HPLC,ICP，实时PCR等先进技术，通过研究磷供应水平（1）在酸性和石灰性土壤上对作物锌吸收、分配和累积的影响；（2）对作物锌吸收、转运相关基因如ZIP,HMA,YSL基因家族成员表达的影响；（3）对作物体内锌有效性及再转移的影响；（4）对作物籽粒锌有效性、分布和存在形态的影响，从不同层面阐明供磷水平影响禾谷类作物籽粒锌累积和有效性的生理和分子机制。并通过研究不同磷水平下，锌肥措施对小麦玉米营养生理和锌营养强化的影响，建立满足作物高产富锌的磷锌调控措施,为实现粮食安全和人体健康提供坚实的理论基础和技术支撑。

当前，由于禾谷类作物锌缺乏而导致的人体锌缺乏问题逐渐威胁到人体健康。而磷肥施入是造成籽粒锌浓度下降的重要因素之一。因此，研究磷肥对小麦玉米籽粒锌累积的作用机制对于揭示磷锌拮抗,并进一步提出缓解锌缺乏的方法具有重要的指导意义。本试验通过设置小麦、玉米盆栽和长期定位田间试验，研究供磷水平对小麦玉米根系锌吸收、分配和植株锌累积的影响及其生理和分子机制，以及磷肥对小麦、玉米籽粒锌分布、存在形态和有效性的影响，提出了合理的锌调控措施。主要的研究结果如下：.1..在石灰性土壤和紫色土壤中，磷肥施用对小麦锌营养的影响不同：在石灰性土壤中，磷肥显著降低了根系和植株的锌浓度；而在紫色土中，磷肥施用降低了植株锌浓度但没有影响根系锌浓度。同时，磷肥施用显著降低了石灰性土壤中的单位根干重的锌含量，而在紫色土壤中，单位根干重的锌含量随施磷量的增加而增加；.2..田间条件下，当施磷量从0增加至50 kg/ha，小麦根系和植株锌累积随施磷量的增加而增加，过量施磷（>50 kg/ha）降低了锌累积。而玉米上，磷肥施入降低了植株的锌累积量。供磷条件下，根系锌累积量与菌根侵染率具有较好的相关关系；根系吸收是影响籽粒锌累积的重要因素；.3..营养液培养条件下，随供磷水平增加小麦植株锌浓度下降。不供锌条件下，磷肥促进了老叶和地上部剩余部分中的锌向新叶和根系的再转移；.4..随供磷水平的增加，小麦根系单位根干重的吸锌量显著下降，小麦根中与锌吸收、转运相关基因的表达明显上调；.5..小麦籽粒以及面粉中中锌的生物有效性随施磷量的增加呈现显著下降的趋势，精粉中锌的有效性高于籽粒；.6..叶面喷施锌肥使小麦籽粒锌含量恢复到不施磷的水平，籽粒磷锌比降低了19%-53%，是一个有效改善籽粒锌营养的农学措施。. 这些结果揭示了在磷锌关系中，根系锌的吸收和籽粒锌的有效性是造成磷锌拮抗的关键环节。农业生产中，磷肥和锌肥的合理施用能够保证最大潜力的发挥锌的有效性。