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磷是植物生长发育所需的基本元素之一,土壤缺磷制约了大多数作物的生长。土壤中的无机磷容易被铁铝氧化物和氢氧化物以及钙离子等金属阳离子紧密吸附形成难溶化合物,导致土壤有效磷含量较低,抑制作物生长[1-2]。在传统农业生产中,农民经常通过大量施用磷肥来提高作物产量,然而70%~90%的磷肥不能被作物直接吸收利用[3]。世界上使用的磷肥主要是从不可再生的矿产资源中提取,过量施用磷肥不仅导致磷矿的储量逐渐枯竭,还会引起水体富营养化等生态环境问题[4]。为了缓解磷矿资源紧张,促进农业可持续发展,提高磷肥利用率至关重要[5-7]。
根际是土壤微生物与植物相互作用的重要区域,在此互作下能有效提高土壤养分利用率,促进植物养分吸收[8-9]。丛枝菌根真菌 (Arbuscular mycorrhizal fungi, AMF) 能在大多数陆地植物根系中定殖并形成共生体,有助于植物生长、营养吸收,增强植物抗逆性[10]。AMF产生广泛的菌丝网络能够探索更大的土壤范围,从而帮助寄主植物获得水分和养分,特别是磷[11-13]。在低磷环境下,接种AMF的植物根系通过增强特异性磷酸酶活性分泌更多的有机酸,进而活化土壤难溶性磷酸盐,有效促进植物生长和磷吸收[14-15]。
紫花苜蓿 (Medicago sativa) 是一种多年生优质蛋白草料,是黄土高原农业生态系统的重要组成部分。黄土高原地区大多数土壤的有效磷含量低于10 μg/g,土壤缺磷制约了该地主要栽培牧草紫花苜蓿优质高产[16]。紫花苜蓿对磷肥敏感,适度施磷能显著促进其生长,提高其产量和品质[17],但过量施磷不利于其正常生长发育[18]。AMF对豆科植物具有较好的侵染性,接种AMF可以促进紫花苜蓿生长发育,改善其品质。本研究采用盆栽试验,旨在研究施磷和接种AMF对紫花苜蓿生长和根际过程的影响,以期为黄土高原地区苜蓿增产和提高磷肥利用率提供参考。
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供试紫花苜蓿,品种‘金皇后’是美国新培育的优质品种,根系发达,抗旱、抗寒性极强,是同休眠级苜蓿品种中产量和消化率较高的优良品种。供试AMF菌种为Glomus mosseae BGC YN02,由北京农业科学院植物营养与资源研究所提供。
供验土壤黄绵土采自陕西省安塞县黄土高原中部 (36°30′N,108°5′E) 0—20 cm耕层,其土壤砂粒 45%、粉粒42%、粘粒13%,pH (H2O, 1∶5) 8.7,全钾、全氮、全磷和有效磷分别为 16.4、95.7、49.3和3.8 mg/kg,有机质 2.8 mg/kg。。土壤风干研磨过2 mm筛后高压蒸汽灭菌2 h (115 kPa,120ºC),备用。
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试验于2018年5月至9月在中国科学院水利部水土保持研究所的温室内进行。采用底部密封的非透明PVC管作为实验容器,每盆装4 kg灭菌土,添加N 150 mg/kg和K 100 mg/kg作为基肥。试验采用施磷和接种AMF双因素随机区组设计,共6个处理,每个处理4个重复。三个施磷水平为P 0、5、20 mg/kg(表示为P0、P5、P20);接菌处理 (+AMF) 土壤中混入20 g AMF菌剂,不接菌处理 (–AMF) 土壤中加入20 mL AMF菌剂过滤液,并混入20 g高温 (115 kPa, 120ºC) 灭菌后的AMF菌剂。
紫花苜蓿种子在30%(v∶v)H2O2溶液中浸泡消毒5 min,用去离子水反复冲洗干净,放入湿润的滤纸上置于25ºC恒温培养箱内发芽2 天,每盆播种20粒,两周后选长势良好大小一致的幼苗间苗10株。种植期间,定期称重浇水,使土壤含水量大约保持在60%田间持水量,所用水为纯净水。
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植物生长120天后分别收获每盆植物的地上部和地下部,轻轻摇动根系以清除多余的土壤,附着在根部的土壤为根际土[6],盆内剩余土壤充分混匀后为非根际土。将根际土和非根际土各自分为两部分保存,一部分风干用于测定土壤有效磷含量和土壤pH,另一部分保存在4℃环境下,用于测定碱性磷酸酶活性和微生物生物量磷。鲜根称取约1 g用于根际有机酸测定,剩余部分冲洗干净后取少许用于AMF侵染率测定,剩余部分和地上部分别装入牛皮纸袋,60℃烘干至恒重,称取干重后粉碎用于植物磷含量测定。
AMF侵染率的测定参考Phillips和Hayman[19]方法进行染色,Giovannetti和Mosse[20]方法计算,具体如下:约0.5 g鲜根放入10% (w∶v)KOH溶液中,90°C水浴加热40 min,用水冲洗干净后,加入2% (v∶v)HCl酸化,放入0.05%(w∶v) 台盼蓝中染色。将每个样品剪成1 cm左右的根段,随机抽取15根,分别装在3个载玻片上用光学显微镜观察。AMF侵染率在显微镜下使用网格线相交法计算。
植物地上部和地下部磷含量采用HNO3-HClO4(v: v = 4∶1) 消煮—钼锑抗比色法测定[21]。根际有机酸含量采用0.2 mmol/L CaCl2浸提—高效液相色谱法测定[22-23]。土壤pH采用去CO2水 (H2O,1∶5) 浸提—pH计测定[21]。土壤有效磷含量采用0.5 mol/L NaHCO3浸提—钼锑抗比色法测定[21]。土壤微生物量磷采用氯仿熏蒸萃取法测定[21]。土壤碱性磷酸酶活性采用磷酸苯二钠比色法测定[24]。
磷利用效率:植物干重除以植物磷累积量的商值[2]。
磷肥利用率:施磷处理与不施磷处理植物磷累积量的差值除以施磷肥量[2]。
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用Microsoft Excel 2016进行数据处理,用SPSS 20.0 (Tukey-test,P < 0.05) 进行方差分析和一般线性模型分析,所有图形均用Origin 2019绘制。
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由表1可知,紫花苜蓿地上部和地下部生物量随着磷施用量的增加而增加,同一磷水平下,+AMF处理均高于–AMF处理。+AMF处理植物根冠比随着磷施用水平的上升而下降,且低于相同磷水平下–AMF处理。+AMF处理紫花苜蓿根系均被AMF侵染,不同施磷水平对AMF侵染率没有显著影响。
表 1 黄绵土不同施磷水平和AMF处理紫花苜蓿植株生物量、根冠比和AMF菌根侵染率
Table 1. Dry biomass, root/shoot ratio and AMF root colonization of alfalfa under phosphorus-application rates with and without AMF inoculation in loessial soil
处理
Treatment地上部干重 (g/pot)
Shoot dry mass地下部干重 (g/pot)
Root dry mass根冠比
Root/shoot ratioAMF侵染率 (%)
AMF root colonization+AMF P0 2.63 ± 0.42 2.32 ± 0.34 0.79 ± 0.13 56 ± 12 P5 3.20 ± 0.52 2.56 ± 0.31 0.70 ± 0.19 45 ± 14 P20 3.59 ± 0.72 3.87 ± 1.48 0.66 ± 0.21 49 ± 18 –AMF P0 2.25 ± 0.54 1.97 ± 0.15 1.07 ± 0.14 P5 2.94 ± 0.59 2.29 ± 0.27 0.77 ± 0.05 P20 3.32 ± 0.83 3.15 ± 1.42 0.87 ± 0.26 显著性P值 Significance by two-way ANOVA analysis AMF 0.052 0.365 0.006 – P 0.003 0.012 0.036 0.654 AMF × P 0.865 0.947 0.376 – 注(Note):P0, P5 and P20 represent P application rate of 0, 5 and 20 mg/kg soil. -
由图1可知,地上部和地下部磷浓度均随着磷施加水平上升而显著增加,P5和P0处理间差异较小,P20处理显著升高。植株磷吸收总量随磷施加水平上升而显著增加,P20处理显著高于P0处理;在同一磷水平下,+AMF处理均高于–AMF处理。与接菌相比,施磷水平对植株磷吸收总量的影响更显著。
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如图2所示,接菌和施磷对根际羧酸盐 (包括草酸盐、柠檬酸盐、乙酸盐、丙二酸盐、苹果酸盐和酒石酸盐) 总含量均有显著影响,其中+AMF处理显著高于同一磷水平的–AMF处理 (1.2~2.7倍)。在+AMF处理中,羧酸盐总含量随施磷水平上升而显著下降,P0处理是P5处理的1.4倍、是P20处理的1.9倍。在–AMF处理中,施磷水平对羧酸盐总含量没有显著影响。土壤pH值随施磷水平上升而下降,根际土低于非根际土;在同一磷水平下,+AMF处理根际pH均低于–AMF处理。
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如图3所示,土壤碱性磷酸酶活性随着磷施加水平上升而显著下降。相同磷水平下,+AMF处理根际磷酸酶活性均低于–AMF处理;除P20处理外,其余处理根际磷酸酶活性均显著高于非根际磷酸酶活性。如图4所示,土壤微生物生物量磷随着磷施加水平上升而增加;同一磷水平下根际土微生物生物量磷显著高于非根际土,+AMF处理高于–AMF处理。土壤有效磷含量随磷施加水平上升而显著上升,相同磷水平下根际土的有效磷含量显著低于非根际土。接菌对土壤有效磷含量没有显著影响。
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如图5所示,P20处理的磷利用效率均显著低于P0处理。施磷和接种AMF对磷肥利用率均有显著影响,磷肥利用率随着磷施加水平上升而显著下降,且同一磷水平下+AMF处理显著高于–AMF处理。如图6所示,磷利用效率和根际土壤碱性磷酸酶活性、乙酸以及柠檬酸浓度均呈显著正相关。
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本试验研究了不同施磷水平下接种AMF对紫花苜蓿生长、磷吸收的影响及根际响应机制。结果表明,施磷和接种AMF提高了紫花苜蓿植株生物量和磷累积量,其中接种AMF可能是由于植物生长速度加快以及外部菌丝能更有效地捕获土壤磷[3]。Smith和Read[25]研究表明,土壤中磷的有效性是影响菌根共生的重要因素。一般而言,低磷土壤中AMF定殖率较高,高磷水平会抑制孢子的发育[26]。本试验结果显示,不同磷水平下AMF定殖率没有显著变化,且均达到一个较高的水平 (> 45%),说明在这3种磷水平下AMF和植物根系均能建立较好的共生关系。AMF与植物根系建立共生关系后,可以通过菌丝来吸收土壤中的磷以及其他营养元素并转运到寄主植物体内,从而促进植物生长[25]。以往的研究结果表明,有的时候接种AMF可以与施磷达到同样的效果[27-28]。AMF菌丝比植物根薄约10倍,可以抵达植物根系形成的枯竭区外并及时捕获磷酸盐[26],尤其是在低磷环境中更有利于菌根形成[29]。缺磷刺激了植物与AMF的共生关系,植物通过根外菌丝增加了对根系消耗区以外不稳定无机土壤磷库的利用[14,28,30]。
根际互作为植物调动和获取更多的养分至关重要[31]。接种AMF可通过影响植物根系分泌物如磷酸酶活性和有机酸的组成和数量来活化土壤难溶性磷酸盐,提高磷利用率。研究表明,增加土壤磷的有效性会减少根际土壤羧酸盐的含量[13,26]。随着施磷量的增加,根际碱性磷酸酶活性减弱,苜蓿根系释放的羧酸盐含量也显著降低。Ryan等[8]研究表明高磷土壤中由于根际羧酸盐的减少,接种AMF对植物磷含量的影响可能较小,甚至可能是负值;而低磷环境中接种AMF能刺激植物根系向周围土壤释放更多的分泌物。羧酸盐,特别是柠檬酸盐的释放,被认为是最有效的磷动员方式[32]。本试验结果显示,接种AMF能有效促进根系有机酸分泌,特别是乙酸和柠檬酸以活化难溶性磷酸盐。与此同时,接种AMF处理显著降低土壤pH值,通过诱导质子渗出来降低根际pH值,产生柠檬酸使之与铁铝离子螯和,释放铁铝结合态磷,同时分泌细胞外磷酸酶来水解有机磷,从而提高磷利用率[33-34]。
在P20处理中,接种和不接种AMF处理根际羧酸盐含量差值显著小于P0处理。研究表明,接种AMF仅在适宜磷浓度范围下促进植物生长,高于此范围接种与否效果相同,低于该范围植物通过羧酸盐调动土壤磷更为有效[35]。另一方面,AMF诱导根系分泌物成分和数量发生变化导致根际微生物群落发生改变,也决定了酶合成的潜力[36-37]。本试验结果也表明,接种AMF处理土壤微生物生物量磷增加,其中根际土显著高于非根际土。土壤微生物生物量磷是土壤中重要的活性磷库,根际土壤微生物生物量磷增加表明接种AMF可提高根际活性磷供应能力。除此之外,土壤碱性磷酸酶活性的差异也可以通过土壤微生物生物量的增加和微生物群落结构的变化来解释[38-39]。根际磷酸酶活性高可能是由根或者真菌释放导致[36,40]。结果表明,施磷和接种AMF对根际碱性磷酸酶活性有显著影响,接种AMF后根际碱性磷酸酶活性增强且显著高于非根际土,并和磷利用率呈显著正相关。较高的磷酸酶活性表明,在磷有效性较低的土壤中,植物倾向于从有机磷组分中获取磷[41]。
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在黄绵土中,AMF和紫花苜蓿根系能建立较好的共生关系。低施磷水平 (施磷量 ≤ 20 mg/kg) 对AMF侵染率没有显著影响。施磷和接种AMF均可以显著促进紫花苜蓿生长和磷吸收。低磷环境中,接种AMF可以扩大植物根系吸收范围,同时增强根际土壤碱性磷酸酶活性,促进根系分泌有机酸,特别是乙酸和柠檬酸,从而活化土壤难溶性磷酸盐,提高磷肥利用率。
低磷环境下黄绵土接种丛枝菌根真菌提高紫花苜蓿磷吸收的机理
Effect of arbuscular mycorrhizal fungal inoculation on alfalfa growth and phosphorus uptake in loessial soil under low phosphorus application levels
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摘要:
【目的】 磷极易被土壤吸附和固定,导致土壤中磷有效性较低。本文研究接种丛枝菌根真菌 (Arbuscular mycorrhizal fungi, AMF) 和低磷处理两者交互作用下对紫花苜蓿生长和磷吸收的影响,以期为提高碱性土壤中磷肥利用率提供理论依据。 【方法】 以黄绵土为和紫花苜蓿 (Medicago sativa) 为试验材料进行盆栽试验。在施磷0、5、20 mg/kg (P0、P5、P20) 3个水平下,分别设接种和不接种丛枝菌根 Glomus mosseae BGC YN02 (+AMF、–AMF) 处理。植物生长120天后测定了植株生物量、磷吸收量、AMF侵染率以及根际和非根际土壤的pH值、土壤碱性磷酸酶活性、土壤有效磷含量、土壤微生物生物量磷,分析根际有机酸的组成与含量。 【结果】 +AMF处理中植物根系均被AMF侵染,且施磷水平对侵染率没有显著影响;施磷和+AMF处理均显著提高了植株地上部、地下部生物量以及磷含量,其中P20+AMF处理生物量和磷含量最高;根际有机酸总量随施磷水平上升而显著降低,但+AMF处理有机酸总量高于–AMF处理,其中柠檬酸和乙酸的变化较为显著;施磷和+AMF显著降低土壤碱性磷酸酶活性,增加土壤有效磷含量和微生物生物量磷,且根际土壤碱性磷酸酶活性和微生物生物量磷均显著高于非根际土;施磷处理显著降低磷利用效率和磷肥利用率,+AMF处理显著提高磷肥利用率。 【结论】 碱性土壤 (黄绵土) 中,AMF和紫花苜蓿根系能建立较好的共生关系,低施磷水平 (施磷量 ≤ 20 mg/kg) 对AMF侵染率没有显著影响。施磷和接种AMF均可以显著促进紫花苜蓿生长和磷吸收。低磷环境中,接种AMF可以扩大植物根系吸收范围,同时增强根际土壤碱性磷酸酶活性,促进根系分泌有机酸,特别是乙酸和柠檬酸,从而提高磷肥利用率。 Abstract:【Objectives】 Phosphorus (P) is easily adsorbed and fixed by the soil, resulting in low P availability in the soil. This research investigated the interactive effects of AMF and low levels of P fertilizer on alfalfa growth and P-uptake to identify optimal methods for increasing P efficiency in alkaline soil. 【Methods】 A pot experiment was conducted using loessial soil and alfalfa (Medicago sativa) as test materials. The soil was treated with different P levels (0, 5 and 20 mg/kg, code as P0, P5, P20), and with AMF inoculation (20 g/L Glomus mosseae BGC YN02; +AMF) or without (–AMF). After 120 days of plant growth, the growth indices of Alfalfa, P concentrations in Alfalfa tissues, pH values, alkaline phosphatase activities, available P contents, and microbial biomass P in the rhizosphere and non-rhizosphere soil were analyzed. The composition and concentration of rhizosphere carboxylates were also measured. 【Results】 In +AMF treatments, alfalfa roots were all colonized by mycorrhiza, but P application rate had no significant effect on AMF root colonization. Both P application and AMF colonization significantly increased the dry mass and P concentrations of shoots and roots. The plant dry mass and P concentration in P20+AMF treatment were significantly higher than in the other treatments. The total amount of rhizosphere carboxylates, especially citrate and acetate, in +AMF treatments decreased with increase in P application rate, but they were still significantly higher than those in −AMF treatments. Phosphorus and AMF application significantly decreased soil alkaline phosphatase activity, but increased soil available-P and microbial biomass P. Alkaline phosphatase activity and microbial biomass P in rhizosphere was significantly higher than in non-rhizosphere. Phosphorus application significantly decreased P-uptake efficiency and P-utilization efficiency, and +AMF significantly increased P-uptake efficiency. 【Conclusions】 AMF and alfalfa roots has a good symbiotic relationship in alkaline loessial soil. Low level of P application (≤ 20 mg/kg) has no significant effect on AMF root colonization. Both P application and AMF colonization could significantly stimulate the growth and P uptake of alfalfa. In low P soil, inoculating AMF could broaden absorption area of root, increase alkaline phosphatase activity in rhizosphere and secretion of organic acids (especially citrate and acetate), and increase P utilization efficiency. -
Key words:
- alkaline phosphatase activity /
- legumes /
- loessial soil /
- P-utilization efficiency /
- root exudates
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表 1 黄绵土不同施磷水平和AMF处理紫花苜蓿植株生物量、根冠比和AMF菌根侵染率
Table 1. Dry biomass, root/shoot ratio and AMF root colonization of alfalfa under phosphorus-application rates with and without AMF inoculation in loessial soil
处理
Treatment地上部干重 (g/pot)
Shoot dry mass地下部干重 (g/pot)
Root dry mass根冠比
Root/shoot ratioAMF侵染率 (%)
AMF root colonization+AMF P0 2.63 ± 0.42 2.32 ± 0.34 0.79 ± 0.13 56 ± 12 P5 3.20 ± 0.52 2.56 ± 0.31 0.70 ± 0.19 45 ± 14 P20 3.59 ± 0.72 3.87 ± 1.48 0.66 ± 0.21 49 ± 18 –AMF P0 2.25 ± 0.54 1.97 ± 0.15 1.07 ± 0.14 P5 2.94 ± 0.59 2.29 ± 0.27 0.77 ± 0.05 P20 3.32 ± 0.83 3.15 ± 1.42 0.87 ± 0.26 显著性P值 Significance by two-way ANOVA analysis AMF 0.052 0.365 0.006 – P 0.003 0.012 0.036 0.654 AMF × P 0.865 0.947 0.376 – 注(Note):P0, P5 and P20 represent P application rate of 0, 5 and 20 mg/kg soil. -
[1] Turrión M B, Bueis T, Lafuente F, et al. Effects on soil phosphorus dynamics of municipal solid waste compost addition to a burnt and unburnt forest soil[J]. Science of Total Environment, 2018, 642: 374–382. doi: 10.1016/j.scitotenv.2018.06.051 [2] He H H, Peng Q, Wang X, et al. Growth, morphological and physiological responses of alfalfa (Medicago sativa) to phosphorus supply in two alkaline soils[J]. Plant and Soil, 2017, 416: 565–584. doi: 10.1007/s11104-017-3242-9 [3] Parihar M, Meena V S, Mishra P K, et al. Arbuscular mycorrhiza: a viable strategy for soil nutrient loss reduction[J]. Archives of Microbiology, 2019, 201: 723–735. doi: 10.1007/s00203-019-01653-9 [4] Nobile C M, Bravin M N, Becquer T, et al. Phosphorus sorption and availability in an andosol after a decade of organic or mineral fertilizer applications: Importance of pH and organic carbon modifications in soil as compared to phosphorus accumulation[J]. Chemosphere, 2020, 239: 124709. doi: 10.1016/j.chemosphere.2019.124709 [5] Cordell D, White S. Tracking phosphorus security: indicators of phosphorus vulnerability in the global food system[J]. Food Security, 2015, 7: 337–350. doi: 10.1007/s12571-015-0442-0 [6] Pang J, Ryan M H, Lambers H, et al. Phosphorus acquisition and utilisation in crop legumes underglobal change[J]. Current Opinion in Plant Biology, 2018, 45: 248–254. doi: 10.1016/j.pbi.2018.05.012 [7] Cordell D, Rosemarin A, Schroder J J, et al. Towards global phosphorus security: A systems framework for phosphorus recovery and reuse options[J]. Chemosphere, 2011, 84(6): 747–758. doi: 10.1016/j.chemosphere.2011.02.032 [8] Ryan M H, Tibbett M, Edmonds-Tibbett T, et al. Carbon trading for phosphorus gain: the balance between rhizosphere carboxylates and arbuscular mycorrhizal symbiosis in plant phosphorus acquisition[J]. Plant Cell & Environment, 2012, 35: 2170–2180. [9] Friesen M L, Porter S S, Stark S C, et al. Microbially mediated plant functional traits[J]. Annual Review of Ecology, 2011, 42: 23–46. doi: 10.1146/annurev-ecolsys-102710-145039 [10] He S, Long M, He X, et al. Arbuscular mycorrhizal fungi and water availability affect biomass and C∶N∶P ecological stoichiometry in alfalfa (Medicago sativa L.) during regrowth[J]. Acta Physiologiae Plantarum, 2017, 39(9): 199. doi: 10.1007/s11738-017-2493-7 [11] Smith S E, Read D J. Mycorrhizal symbiosis[M]. London: Academic Press, 1997. [12] Langer I, Syafruddin S, Steinkellner S, et al. Plant growth and root morphology of Phaseolus vulgaris L. grown in a split-root system is affected by heterogeneity of crude oil pollution and mycorrhizal colonization[J]. Plant and Soil, 2010, 332: 339–355. doi: 10.1007/s11104-010-0300-y [13] Peng Q, Wu M M, Zhang Z K, et al. The interaction of arbuscular mycorrhizal fungi and phosphorus inputs on selenium uptake by alfalfa (Medicago sativa L.) and selenium fraction transformation in soil[J]. Frontiers in Plant Science, 2020: 11. doi: 10.3389/fpls.2020.00966 [14] Wen Z H, Pang J Y, Tueux G, et al. Contrasting patterns in biomass allocation, root morphology and mycorrhizal symbiosis for phosphorus acquisition among 20 chickpea genotypes with different amounts of rhizosheath carboxylates[J]. Functional Ecology, 2020, 34: 1311–1324. doi: 10.1111/1365-2435.13562 [15] Shen J, Yuan L, Zhang J, et al. Phosphorus dynamics: From soil to plant[J]. Plant Physiology, 2011, 156: 997–1005. doi: 10.1104/pp.111.175232 [16] 孙洪仁, 曹影, 刘琳, 等. 中国北方紫花苜蓿土壤有效磷丰缺指标与适宜施磷量初步研究[J]. 中国土壤与肥料, 2016, (3): 30–36. Sun H R, Cao Y, Liu L, et al. Preliminary study on abundance-deficiency index of soil available P and appropriate phosphorus application rates for alfalfa in the North of China[J]. Soil and Fertilizer Sciences in China, 2016, (3): 30–36. doi: 10.11838/sfsc.20160305 [17] Fan J W, Du Y L, Turner N C, et al. Changes in root morphology and physiology to limited phosphorus and moisture in a locally-selected cultivar and an introduced cultivar of Medicago sativa L. growing in alkaline soil[J]. Plant and Soil, 2015, 392: 215–226. doi: 10.1007/s11104-015-2454-0 [18] Pang J Y, Ryan M H, Tibbett M, et al. Variation in morphological and physiological parameters in herbaceous perennial legumes in response to phosphorus supply[J]. Plant and Soil, 2010, 331: 241–255. doi: 10.1007/s11104-009-0249-x [19] Phillips J M, Hayman D S. Improved procedures for clearing roots and staining parasitic and vesicular-arbuscular mycorrhizal fungi for rapid assessment of infection[J]. Transactions of the British Mycological Society, 1970, 55: 158–160. doi: 10.1016/S0007-1536(70)80110-3 [20] Giovannetti M, Mosse B. An evaluation of techniques for measuringvesicular arbuscular mycorrhizal infection in roots[J]. New Phytologist, 1980, 84: 489–500. doi: 10.1111/j.1469-8137.1980.tb04556.x [21] 鲍士旦. 土壤农化分析[M]. 北京: 中国农业出版社, 2000. Bao S D. Analytical methods of soil agricultural chemistry[M]. Beijing: ChinaAgriculture Press, 2000. [22] 孙宝利, 黄金丽, 贺小蔚, 等. 高效液相色谱法测定土壤中有机酸[J]. 分析试验室, 2010, 29: 51–54. Sun B L, Huang J L, He X W, et al. Determination of organic acids in soil by high performance liquid chromatography[J]. Chinese Journal of Analysis Laboratory, 2010, 29: 51–54. doi: 10.3969/j.issn.1000-0720.2010.05.014 [23] Cawthray G R. An improved reversed-phase liquid chromatographic method for the analysis of low-molecular mass organic acids in plant root exudates[J]. Journal of Chromatography A, 2003, 1011(1–2): 233–240. doi: 10.1016/S0021-9673(03)01129-4 [24] 关松荫. 土壤酶及其研究法[M]. 北京: 中国农业出版社, 1986. Guan S Y. Soil enzyme and its research methods[M]. Beijing: China Agriculture Press, 1986. [25] Smith S E, Read D J. Mycorrhizal symbiosis[M]. London: Academic Press, 2008. [26] Urcoviche R C, Gazim Z C, Dragunski D C, et al. Plant growth and essential oil content of Mentha crispa inoculated with arbuscular mycorrhizal fungi under different levels of phosphorus[J]. Industrial Crops & Products, 2015, 67: 103–107. [27] Clark R B, Zeto S K. Mineral acquisition by arbuscular mycorrhizal plants[J]. Journal of Plant Nutrition, 2000, 23(7): 867–902. doi: 10.1080/01904160009382068 [28] 李芳, 徐丽娇, 谢伟, 等. 菌根化育苗对玉米生长和养分吸收的影响[J]. 植物营养与肥料学报, 2020, 26(1): 42–50. Li F, Xu L J, Xie W, et al. Effects of seedling mycorrhization on the growth and nutrient uptake of maize[J]. Journal of Plant Nutrition and Fertilizers, 2020, 26(1): 42–50. doi: 10.11674/zwyf.19084 [29] 吴强盛, 夏仁学, 邹英宁. 柑橘丛枝菌根真菌生长与根际有效磷和磷酸酶活性的相关性[J]. 应用生态学报, 2006, 17(4): 685–689. Wu Q S, Xia R X, Zou Y N. Arbuscular mycorrhizal fungal growth on citrus roots and its correlations with soil available phosphorus content and phosphatase activity[J]. Chinese Journal of Applied Ecology, 2006, 17(4): 685–689. doi: 10.3321/j.issn:1001-9332.2006.04.025 [30] Sawers R J H, Svane S F, Quan C, et al. Phosphorus acquisition efficiency in arbuscular mycorrhizal maize is correlated with the abundance of root-external hyphae and the accumulation of transcripts encoding PHT1 phosphate transporters[J]. New Phytologist, 2017, 214(2): 632. doi: 10.1111/nph.14403 [31] Bender S F, van der Heijden M G A. Soil biota enhance agricultural sustainability by improving crop yield, nutrient uptake and reducing nitrogen leaching losses[J]. Journal of Applied Ecology, 2015, 52: 228–239. doi: 10.1111/1365-2664.12351 [32] Gerke J. The acquisition of phosphate by higher plants: Effect of carboxylate release by the roots. A critical review[J]. Journal of Plant Nutrition and Soil Science, 2015, 178(3): 351–364. doi: 10.1002/jpln.201400590 [33] Corkidi L, Merhaut D J, Allen E B, et al. Effects of mycorrhizal colonization on nitrogen and phosphorus leaching from nursery containers[J]. Hortscience, 2011, 46(11): 1472–1479. doi: 10.21273/HORTSCI.46.11.1472 [34] Minemba D, Gleeson D B, Veneklaas E, et al. Variation in morphological and physiological root traits and organic acid exudation of three sweet potato (Ipomoea batatas) cultivars under seven phosphorus levels[J]. Scientia Horticulturae, 2019, 256: 108572. doi: 10.1016/j.scienta.2019.108572 [35] Lambers H, Martinoia E, Renton M. Plant adaptations to severely phosphorus-impoverished soils[J]. Current Opinion in Plant Biology, 2015, 25: 23–31. doi: 10.1016/j.pbi.2015.04.002 [36] Kandeler E, Marschner P, Tscherko D, et al. Microbial community composition and functional diversity in the rhizosphere of maize[J]. Plant and Soil, 2002, 238: 301–312. doi: 10.1023/A:1014479220689 [37] Miransari M. Interactions between arbuscular mycorrhizal fungi and soil bacteria[J]. Applied Microbiology & Biotechnology, 2011, 89: 917–930. [38] Ventura M, Zhang C, Baldi E, et al. Effect of biochar addition on soil respiration partitioning and root dynamics in an apple orchard[J]. European Journal of Soil Science, 2014, 65(1): 186–195. doi: 10.1111/ejss.12095 [39] Li S, Liang C, Shangguan Z. Effects of apple branch biochar on soil C mineralization and nutrient cycling under two levels of N[J]. Science of the Total Environment, 2017, 607: 109. [40] Wang Y L, Krogstad T, Clarke J L, et al. Rhizosphere organic anions play a minor role in improvingcrop species’ ability to take up residual phosphorus (P) in agricultural soils lowin P availability[J]. Frontiers in Plant Science, 2016, 7: 1664. [41] He H H, Wu M M, Guo L, et al. Release of tartrate as a major carboxylate by alfalfa (Medicago sativa L.) under phosphorus deficiency and the effect of soil nitrogen supply[J]. Plant and Soil, 2020, 449: 169–178. doi: 10.1007/s11104-020-04481-9 -