【作者】 张伟；

【导师】 邹春琴； 陈新平；

【作者基本信息】 中国农业大学 ， 植物营养学， 2017， 博士

【摘要】 全球锌营养缺乏严重影响人体健康。日常饮食中较低的锌摄取量是造成人体缺锌的重要因素之一,尤其是以谷类作为主要食物来源的人群。研究表明,农业生产中大量磷肥的施用显著降低了小麦、玉米籽粒锌浓度。但是田间条件下,磷肥施用如何影响根层土壤有效锌与根系在空间上的匹配、如何影响锌的吸收以及在植株体内的转移和再转移过程,最终影响其在籽粒中的累积等还不清楚。因此,本研究利用田间试验和盆栽试验,研究了磷肥施用水平对高产小麦玉米锌营养的影响,并对其作用机制进行了初步探讨。主要研究结果如下:1.磷肥施用显著影响小麦和玉米产量。在田间条件下,小麦和玉米籽粒产量对磷肥的响应均符合线性-平台的模型:当施磷量分别超过50和12.5 kg P ha-1时,继续施磷不再增加小麦和玉米的产量。同时,达到小麦和玉米叶面积指数和光合速率平台的土壤有效磷(Olsen-P)临界浓度分别为17.7 mg kg-1和12.4 mg kg-1。在小麦上,随着施磷量的增加(0-50 kg ha-1),根系干重、根表面积、根系体积和根长密度显著增加,继续增加施磷量(>50 kg ha-1)小麦根系特征参数没有继续增加;在玉米上,相同的拐点出现在25 kg ha-1的供磷水平。2.田间条件下,磷肥施用显著降低了小麦和玉米根系锌浓度以及单位根干重的吸锌量。在小麦上,随着磷肥施用量从0增加至50 kg ha-1,根系锌累积量增加;但当施磷量高于50 kg ha-1,根系锌累积量开始下降。同样,在玉米上,根系锌累积量的最高值出现在25 kg ha-1供磷水平,过低或者过高的磷肥投入均会降低根系锌的累积。3.根系形态特征和根系菌根侵染率是影响根系锌累积的重要因素。在小麦开花期,根系干重随施磷量的增加有利于根系锌的累积;但根系和植株锌累积量以及成熟期籽粒锌累积量随着菌根侵染率的增加(4%-39%)先增加后下降(>39%)。玉米盆栽试验的结果进一步表明随着施磷量的增加,菌根侵染率的降低部分解释了根系及总的锌累积量的降低(19%),尤其是在低锌土壤中。从根系与植株锌浓度比值的角度,磷肥用量并没有影响锌由根系向地上部的转移。4.在植株锌累积层面上,磷肥施用降低了小麦植株锌浓度和玉米各器官锌浓度。尽管磷肥施用增加了拔节期小麦植株锌累积量,但开花以后植株锌累积量先随磷肥增加(0-50 kg ha-1)而显著增加,然后显著下降(>50kgha-1)。玉米植株锌累积量随施磷量的增加而下降。5.磷肥施用影响小麦玉米花后锌吸收和锌再转移对籽粒锌累积的贡献。在小麦上,籽粒锌的累积主要依靠花后锌从植株向籽粒的再转移(约占47-70%),且随施磷量增加,锌向籽粒的再转移效率呈现下降的趋势;而在玉米上,籽粒锌的累积主要依靠花后的锌吸收(约占67-85%),且花后锌的吸收比例随施磷量增加呈现下降的趋势。6.随着磷肥用量的增加,小麦玉米籽粒锌浓度和锌的生物有效性显著下降。与全麦粉和粗粉的锌生物有效性相比,标准粉、面包粉和精粉的锌生物有效性更高。同时,磷肥施用增加了玉米籽粒的磷/锌、磷/铁、磷/锰和磷/铜的摩尔比值,降低了铁锰铜锌的生物有效性。综上所述,在磷锌拮抗关系中,磷对锌的抑制过程可能主要发生在根系对锌的吸收:较高土壤有效磷导致菌根侵染率显著降低,根系锌吸收显著下降,籽粒锌浓度下降。同时磷肥施用使得籽粒植酸浓度增加,这两方面的综合作用使得籽粒锌的有效性显著下降。更多还原

【Abstract】 Zinc(Zn)deficiency is a serious and worldwide threat to human health.A main cause of Zn deficiency is the low intake of Zn in the daily diet,especially for people who rely on cereals as staple foods.Although research has shown that phosphorus(P)fertilizer application significantly decreases the concentration of Zn in wheat and maize grain,detailed information on how P application affects Zn transport in wheat and maize is lacking.A long-term field experiment and a pot experiment are therefore conducted to determine how P application affects the movement of Zn from soil to grain under high-yield conditions.The main results were as follows:1.The responses of grain yield in wheat and maize to P application were consistent with a linear-plateau model,i.e.,yield increased as the P application rate increased to 50 and 12.5 kg P ha-1 for wheat and maize,respectively,but then plateaued at higher application rates.The soil Olsen-P concentration at which leaf area index(LAI)and photosynthetic rate(Pn)plateaued was about 17.7 mg kg-1 for wheat and 12.4 mg kg-1 for maize.The soil P application at which root dry weight,root surface area,and root length density plateaued was 50 kg ha-1 for wheat and 25 kg ha-1 for maize.2.P application significantly decreased the Zn concentration in roots and the specific root Zn uptake(total Zn accumulation g-1 root).Zn accumulation in wheat roots increased with increasing P application from 0 to 50 kg ha-1 but decreased as the P application rate exceeded 50 kg ha-1.Similarly,Zn accumulation in maize roots was higher when P was applied at 25 kg ha-1 than at lower or higher rates.3.The negative effects of P application on Zn accumulation in roots were associated with changes in root morphology(root dry weight,root surface area,root length density,and root volume)and in colonization of roots by arbuscular mycorrhizal(AM)fungi.For wheat,the accumulation of Zn in roots and shoots(flowering stage)and in grain(maturity stage)increased as AM colonization increased from 4%to 39%but then decreased at higher levels of AM colonization.In a pot experiment with maize,the decrease in AM colonization caused by P application partly(19%)explained the antagonism between P application and Zn accumulation in roots,especially in a Zn-deficient soil.P application did not affect the ratio of Zn concentration or Zn accumulation roots vs.shoots.4.P application decreased the concentration of Zn in wheat shoots and the concentrations of Zn in all maize tissues.In wheat,P application increased the accumulation of Zn in shoots at the jointing stage;after the flowering stage,Zn accumulation in shoots increased as the P application rate increased from 0 to 50 kg ha-1 but then decreased at higher rates of P application.In maize shoots,P application decreased the accumulation of Zn.5.P application significantly affected the contribution of post-anthesis Zn uptake and post-anthesis Zn remobilization to grain Zn accumulation in wheat and maize.For wheat,grain Zn remobilization from shoot to grain of post-anthesis contributed 47-70%of grain Zn accumulation.Share of grain Zn accumulation provided by remobilization decreased with increasing P application.For maize,Zn uptake of post-anthesis contributed 67-85%of grain Zn accumulation and P application decreased the share of grain Zn accumulation provided by Zn uptake.6.As the P application rate increased,the concentration and bioavailability of Zn in wheat and maize grain and flour decreased.Zn bioavailability was higher in standard flour,bread flour,and refined flour than in grain or coarse flour.P application also increased the ratio of P:Zn,P:Fe,P:Mn,and P:Cu and decreased the bioavailability of micronutrients in maize grain.In conclusion,’P induced Zn deficiency’ mainly results from the negative effects of P on uptake of Zn by roots and on Zn bioavailability in grain.P application decreases Zn bioavailability in grain by decreasing the AM colonization of roots and by increasing the phytic acid concentration in grain.更多还原