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磷素是植物生长发育和产量提升所必需的大量营养元素之一,在植物生物合成、细胞分裂等生理生化过程中不可或缺[1]。土壤磷素主要是以有机磷和无机磷形式存在,磷素虽储量大,但绝大部分磷被土壤中铁铝离子等金属鳌合为难溶性磷酸盐不易被植物吸收利用[2-3]。为满足植物对磷的需求,往往需要施用大量磷肥,然而施用磷肥会带来环境污染且易被土壤固定,造成磷肥利用率低[4],当季利用率仅有10%~15%[5]。如何提高土壤磷库中磷素利用率,从而缓解土壤磷缺乏和大量施磷肥的矛盾是研究热点。解磷微生物在土壤磷循环过程中发挥着重要的作用,是破解土壤磷供应和植物磷需求矛盾的关注焦点。目前解磷微生物主要包括假单胞菌属(Pseudomonas)、芽孢杆菌属(Bacillus)、欧文氏菌属(Erwinia)、克雷伯氏菌属(Klebsiella)、沙雷氏菌属(Serratia)、曲霉菌属(Aspergillus)、青霉菌属(Penicillium)、小单胞菌属(Micromonospora)和链霉菌属(Streptomyces)等[6]。研究证实解磷微生物可通过释放有机酸、质子等酸解和酶解方式将土壤潜在磷库中的无效磷转化为有效磷供根系吸收而促进植物生长[7]。
毛竹(Phyllostachys edulis)主要分布于我国南方丘陵山区,是重要的经济竹种[6]。随着毛竹林面积扩大及间伐间隔期缩减,竹林资源质量下降,地力衰退,竹产业的可持续发展受到严重影响。研究显示,磷是毛竹林丰产和生态系统稳定性的首要限制因子之一[7]。因此,分离出高效解磷细菌是解决南方丘陵山区磷素供应不足的可行途径之一,研究团队从毛竹林土壤中筛选出1株具有解磷功能的产气肠杆菌(Enterobacter aerogenes),以往研究报道该菌株具有丰富的生物学特性,如具有ACC脱氨酶活性[6],但关于该菌株的解磷特性未深入研究,该菌株对毛竹生长及养分吸收的促进效果及机理尚不清楚,限制其进一步开发和利用。植物叶片的磷可分为无机磷、糖磷、核酸磷和残留磷4个组分,植株叶片的磷组分含量受环境的改变而发生改变,影响其叶片磷分配[8]。目前解磷微生物对植物叶片中不同形态磷组分的影响则未见报道。本研究拟在深入了解产气肠杆菌在不同碳、氮源及环境因子等条件下的解磷特性的基础上,通过盆栽试验评估该解磷细菌对毛竹实生苗的促生作用,明确该菌株对毛竹根系磷吸收和叶片磷组分积累的调控机制,以期为该菌株研制成生物肥料时发挥其最佳解磷功效,改善竹林土壤磷素营养提供依据,也有望揭示该解磷细菌对毛竹的促生机理,为毛竹专用生物肥料的应用提供参考。
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不同碳源对产气肠杆菌溶解Ca2(PO4)3能力的影响显著(图1A)。以葡萄糖和蔗糖为唯一碳源时,该菌株的溶解能力最强,分别为328.41 mg·L−1和337.76 mg· L−1;其次为果糖,解磷量为272.59 mg·L−1;以可溶性淀粉为碳源时,产气肠杆菌的解磷能力最低,为45.32 mg·L−1。不同氮源对产气肠杆菌的解磷能力也影响显著(图1B)。以硫酸铵为唯一氮源时,该菌株的解磷能力最强,为318.42 mg·L−1;其次为硝酸钾,解磷量为270.3 mg·L−1;以蛋白胨为氮源时,该菌株解磷能力最低,解磷量仅为25.25 mg·L−1。
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不同环境条件下产气肠杆菌对Ca2(PO4)3的溶解能力有显著差异(图2)。在装液量/体积比为1/5和2/5时该菌株具有较强的解磷能力,解磷量分别为314.92 mg· L−1和321.41 mg·L−1,装液量/体积比为3/5和4/5时,该菌株也具有较好的解磷能力,解磷量分别为297.16 mg·L−1和236.43 mg·L−1(图2A)。初始pH对产气肠杆菌的解磷能力有显著影响,初始pH值越大,解磷能力越强,当初始pH值5.5和6.5时,该菌株具有较强的解磷能力,解磷量分别为307.2 mg·L−1和318.82 mg·L−1,其次为初始pH值4.5、3.5和2.5时,在初始pH值1.5时解磷能力最低,解磷量为125.6 mg·L−1(图2B)。随着NaCl浓度升高,产气肠杆菌的解磷能力呈下降趋势,在NaCl浓度为0和1.0 g·L−1,该菌株解磷能力最大,解磷量分别为331.45 mg·L−1和328.72 mg·L−1,显著高于其它处理(图2C)。
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产气肠杆菌对5种难溶性矿质盐的溶解能力有显著差异(图3)。该菌株对CaHPO4和Ca2(PO4)3的溶解能力最强,解磷量分别为345.91 mg·L−1和331.83 mg·L−1,对FePO4和AlPO4也具有较好的溶解能力,其解磷量分别为253.61 mg·L−1和203.65 mg·L−1,对植酸钙的溶解能力最弱,其解磷量为179.63 mg·L−1(图3A)。在对5种磷源的溶解过程中,培养基pH均显著下降(图3B)。相关性分析表明,发酵液pH和产气肠杆菌对不同磷源的解磷量呈显著负相关(r=−0.54, n=25)。
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与对照相比,施用产气肠杆菌显著提高了土壤中有效磷含量,增幅为50.6%,而对根际土壤铵态氮和硝态氮含量无显著影响(表1)。施用菌剂显著增强了土壤酸性磷酸酶和脲酶活性,增幅分别为20.6%和21.0%;而对碱性磷酸酶和过氧化氢酶无显著影响(图4)。
表 1 接种产气肠杆菌对毛竹土壤有效养分含量的影响
Table 1. Effect of adding Enterobacter aerogenes on soil available nutrients of moso bamboo seedlings
观测指标
Observed variable对照
Control施用菌剂
Adding strain有效磷 Available P/(mg·kg−1) 4.62±0.38 b 6.96±0.45 a 铵态氮 Ammonium N/(mg·kg−1) 0.97±0.13 a 1.14±0.16 a 硝态氮 Nitrate N/(mg·kg−1) 2.11±0.25 a 2.42±0.28 a 注:同行不同字母表示差异显著(P<0.05),下同。
Notes: Different letters in the same row mean significant difference at 0.05 level. The same below. -
与对照相比,施用产气肠杆菌显著提高了根系磷和叶片核酸磷含量,增幅分别为21.7%和11.6%,显著降低了叶片残留磷含量,降幅为5.5%;而对叶片全磷、无机磷和糖磷含量无显著影响(图5)。与对照相比,施用产气肠杆菌菌剂显著提高毛竹实生苗的苗高、地径、生物量和叶片净光合速率,增幅分别为30.9%、23.4%、44.4%和42.1%(表2)。
图 5 施用产气肠杆菌对毛竹实生苗根叶磷和叶片磷组分含量的影响
Figure 5. Effect of Enterobacter aerogenes inoculation on root total phosphorus and leaf phosphorus functional fractions of moso bamboo seedlings
表 2 接种产气肠杆菌对毛竹实生苗生长指标的影响
Table 2. Effect of adding Enterobacter aerogenes on the growth variables of moso bamboo seedlings
观测指标
Observed variable对照
Control施用菌剂
Adding strain苗高 Seeding height/cm 22.42±0.65 b 29.36±1.27 a 地径 Ground diameter/cm 1.49±0.08 b 1.84±0.09 a 总生物量 Total biomass/g 3.62±0.21 b 5.23±0.13 a 净光合速率
Net photosynthetic rate/(μmol·m−2·s−1)2.57±0.36 b 3.65±1.86 a -
Pearson相关性分析结果显示,叶片磷组分与土壤理化性质和生长指标相关性不尽一致,其中叶无机磷和叶糖磷与土壤理化性质和生长指标并无相关性,叶核酸磷与土壤有效磷、土壤酸性磷酸酶、植株净光合速率、植株生物量、叶生物量和根系全磷呈显著正相关;叶残留磷与土壤有效磷、土壤脲酶、植株净光合速率、植株生物量、叶生物量和根系全磷呈显著负相关;叶全磷、pH与核酸磷呈显著负相关,与残留磷呈显著正相关(表3)。
表 3 叶片磷组分与各测定指标之间的相关性
Table 3. Correlation coefficients between leaf phosphorus fractions and each measured index
观测指标
Observed variable叶无机磷
Leaf inorganic P叶糖磷
Leaf sugar P叶核酸磷
Leaf nucleic P叶残留磷
Leaf residue P铵态氮 Ammonium N/ (mg·kg−1) 0.466 0.041 0.631 −0.607 硝态氮 Nitrate N/(mg·kg−1) 0.160 −0.461 0.628 −0.569 有效磷 Available P/(mg·kg−1) −0.130 −0.613 0.948** −0.961** pH值 pH value 0.253 0.217 −0.829* 0.895* 矿质氮 Mineral N/(g·kg−1) 0.282 −0.342 0.701 −0.647 叶全磷 Leaf total P/(g·kg−1) 0.234 0.432 −0.951** 0.979** 根系全磷 Root total P/(g·kg−1) 0.113 −0.321 0.927** −0.924** 叶生物量 Leaf biomass/g −0.291 −0.279 0.925** −0.941** 植株生物量 Plant biomass/g −0.252 −0.445 0.881* −0.937** 脲酶 Urease/(nmol·g−1) −0.666 −0.242 0.758 −0.848* 酸性磷酸酶 Acid phosphatase/(nmol·g−1) 0.314 −0.626 0.853* −0.788 碱性磷酸酶 Alkaline phosphatase/(nmol·g−1) −0.680 0.500 −0.055 −0.081 过氧化氢酶 Catalase/(nmol·g−1) −0.028 −0.841* 0.803 −0.777 净光合速率 Net photosynthetic rate/(μmol·m-2·s−1) 0.037 −0.359 0.949** −0.948** 注:*代表差异显著(P<0.05); **代表差异极显著(P<0.01)。
Notes: * means significant difference at P<0.05 level; ** means significant difference at P<0.01 level.
土壤产气肠杆菌的解磷特性及其对毛竹苗的促生作用
Phosphate Solubilizing Characteristics of Enterobacter aerogenes and Its Growth-promoting Effect on Phyllostachys edulis Seedlings
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摘要:
目的 探究土壤中具有解磷功能的产气肠杆菌的解磷特性及其对毛竹的促生效果。 方法 采用液体震荡培养法评价不同碳源、氮源和环境因子对产气肠杆菌解磷能力的影响,并采用温室盆栽法研究该菌株对毛竹根际土壤有效养分和酶活性、根系和叶全磷及叶磷组分含量的影响,并分析其对毛竹的促生作用。 结果 产气肠杆菌分别在碳源为蔗糖或葡萄糖、氮源为硫酸铵、初始pH值5.5~6.5、装液量1/5或2/5、盐离子浓度为0或1.0 g·L−1时溶解Ca2(PO4)3的能力最强;产气肠杆菌对Ca2(PO4)3和CaHPO4两种难溶性磷源的平均解磷量分别达331.83 mg·L−1和345.91 mg·L−1。与对照相比,施用产气肠杆菌处理毛竹根际土壤有效磷含量、磷酸酶活性、脲酶活性、叶片净光合速率分别增加50.9%、20.6%、21.0%和42.0%;毛竹实生苗地径、苗高和生物量分别提高31.0%、23.5%和44.5%。施用产气肠杆菌处理显著提高毛竹根系全磷和叶片核酸磷含量,显著降低叶片残留磷含量,但叶片全磷、无机磷和糖磷无显著变化。 结论 该产气肠杆菌具有对环境适应性较强的潜力,可助益提高根系磷吸收和叶片核酸磷积累而促进毛竹生长,是南方丘陵缺磷区竹林生物专用肥料研制的潜在菌株,具有较好的应用前景。 Abstract:Object This study aims to investigate the phosphate-solubilizing characteristics of Enterobacter aerogenes and its growth-promoting effect on Phyllostachys edulis. Methods The effects of different carbon sources, nitrogen sources, and environmental factors on phosphate solubilizing ability of E. aerogenes were evaluated by culture method of shaking liquid. The effects of the strain on available nutrients, enzyme activities, total phosphorus contents of roots and leaves, and phosphorus fractions of leaves in rhizosphere soil of P. edulis were studied using pot experiment in greenhouse. Results E. aerogenes displayed the strongest phosphate-dissolving capacity on tricalcium phosphate when the initial pH was 5.5~6.5, the volume of liquid was 1/5 or 2/5, and salt ion concentration was 0 or 1.0 g·L−1. Carbon source was sucrose or glucose, and nitrogen source was ammonium sulfate. The average phosphate solubilization of E. aerogenes to Ca2(PO4)3 and CaHPO4 was 331.83 mg·L−1 and 345.91 mg·L−1, respectively. Compared with the control treatment, the rhizosphere soil available phosphorus, phosphatase, urease activities and leaf net photosynthetic rate increased by 50.9%, 20.6%, 21.0% and 42.0% in P. edulis seedlings inoculated with E. aerogenes. The ground diameter, seedling height, and biomass accumulation were higher by 31.0%, 23.5% and 44.5%, respectively. Total phosphorus contents of roots and nucleic acid phosphorus contents of leaves in P. edulis significantly increased while residual phosphorus contents in leaves significantly decreased. Total phosphorus, metabolic phosphorus, and sugar phosphorus contents in leaves were steady due to inoculating E. aerogenes. Conclusion E. aerogenes has potential to highly adapt to the environment and improves the growth of P. edulis seedlings via increasing root phosphorus absorption and leaf nucleic acid phosphorus accumulation. It is also a potential strain for the development of special biological fertilizer for bamboo forest in phosphorus deficient area of Southern hills and has a good application prospect. -
表 1 接种产气肠杆菌对毛竹土壤有效养分含量的影响
Table 1. Effect of adding Enterobacter aerogenes on soil available nutrients of moso bamboo seedlings
观测指标
Observed variable对照
Control施用菌剂
Adding strain有效磷 Available P/(mg·kg−1) 4.62±0.38 b 6.96±0.45 a 铵态氮 Ammonium N/(mg·kg−1) 0.97±0.13 a 1.14±0.16 a 硝态氮 Nitrate N/(mg·kg−1) 2.11±0.25 a 2.42±0.28 a 注:同行不同字母表示差异显著(P<0.05),下同。
Notes: Different letters in the same row mean significant difference at 0.05 level. The same below.表 2 接种产气肠杆菌对毛竹实生苗生长指标的影响
Table 2. Effect of adding Enterobacter aerogenes on the growth variables of moso bamboo seedlings
观测指标
Observed variable对照
Control施用菌剂
Adding strain苗高 Seeding height/cm 22.42±0.65 b 29.36±1.27 a 地径 Ground diameter/cm 1.49±0.08 b 1.84±0.09 a 总生物量 Total biomass/g 3.62±0.21 b 5.23±0.13 a 净光合速率
Net photosynthetic rate/(μmol·m−2·s−1)2.57±0.36 b 3.65±1.86 a 表 3 叶片磷组分与各测定指标之间的相关性
Table 3. Correlation coefficients between leaf phosphorus fractions and each measured index
观测指标
Observed variable叶无机磷
Leaf inorganic P叶糖磷
Leaf sugar P叶核酸磷
Leaf nucleic P叶残留磷
Leaf residue P铵态氮 Ammonium N/ (mg·kg−1) 0.466 0.041 0.631 −0.607 硝态氮 Nitrate N/(mg·kg−1) 0.160 −0.461 0.628 −0.569 有效磷 Available P/(mg·kg−1) −0.130 −0.613 0.948** −0.961** pH值 pH value 0.253 0.217 −0.829* 0.895* 矿质氮 Mineral N/(g·kg−1) 0.282 −0.342 0.701 −0.647 叶全磷 Leaf total P/(g·kg−1) 0.234 0.432 −0.951** 0.979** 根系全磷 Root total P/(g·kg−1) 0.113 −0.321 0.927** −0.924** 叶生物量 Leaf biomass/g −0.291 −0.279 0.925** −0.941** 植株生物量 Plant biomass/g −0.252 −0.445 0.881* −0.937** 脲酶 Urease/(nmol·g−1) −0.666 −0.242 0.758 −0.848* 酸性磷酸酶 Acid phosphatase/(nmol·g−1) 0.314 −0.626 0.853* −0.788 碱性磷酸酶 Alkaline phosphatase/(nmol·g−1) −0.680 0.500 −0.055 −0.081 过氧化氢酶 Catalase/(nmol·g−1) −0.028 −0.841* 0.803 −0.777 净光合速率 Net photosynthetic rate/(μmol·m-2·s−1) 0.037 −0.359 0.949** −0.948** 注:*代表差异显著(P<0.05); **代表差异极显著(P<0.01)。
Notes: * means significant difference at P<0.05 level; ** means significant difference at P<0.01 level. -
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