两种磷效率小麦在不同土壤上根际特征的差异

以磷高效型小麦小偃54和磷低效型小麦京411为研究对象设计三室根箱试验,通过测定生物量、吸磷量、pH和酸性磷酸酶,对比两种小麦在不同磷水平(P0 mg/kg土、100 mg/kg土)及两种不同土壤上(石灰性黑垆土、酸性红壤)根际特征的差异。试验结果表明,黑垆土上,增施磷肥使小偃54的总生物量增加了14.99%,京411增加了26.53%,总吸磷量二者分别增加了99.29%和83.70%;红壤的速效磷含量高,施肥仅提高了磷低效型小麦京411的生物量。黑垆土上磷胁迫并未造成小偃54与京411各部分生物量和吸磷量的显著性差异,但小偃54的根际pH降低值和酸性磷酸酶的活性却已显著高于京411;P0处理时,红壤上小偃54的地上部和总生物量显著高于京411,虽然红壤的速效磷含量高于黑垆土,但在P0处理时两种小麦在两种土壤上的生物量和吸磷量并无显著性差异。就根际分泌物而言,石灰性黑垆土上,小偃54的根系在低磷胁迫下通过降低pH和分泌酸性磷酸酶来活化土壤中难溶态的磷,而在红壤上小偃54的pH和酸性磷酸酶的活性保持稳定。酸性红壤中两种小麦酸性磷酸酶活性显著高于石灰性黑垆土。由此可见,两种磷效率小麦在两种不同性质土壤上活化机理存在差异。     

The Influence of Phosphorus Sources on the Growth and Rhizosphere Soil Characteristics of Two Genotypes of Wheat (Triticum aestivum L.)

A rhizobox experiment was conducted to investigate the effects of phosphorus (P) sources on the rhizosphere soil characteristics of two wheat genotypes Xiaoyan54 (P-efficient) and Jing411 (P-inefficient), which were colonized with an arbuscular mycorrhizal fungus and grown in Cumulic Haplustoll. The four P sources included a control (no added P), OP [organic P: sodium (Na)-phytate], IP [inorganic P: monopotassium phosphate (KH₂PO₄)], and OPIP (Na-phytate plus KH₂PO₄). The results showed that when no exogenous P was added the shoot biomass of Xiaoyan54 was 28% significantly higher than Jing 411. The acid phosphatase activity (APA) in the rhizosphere soil was significantly depressed when inorganic P was added; the APA for Xiaoyan54 was higher than that of Jing411 in most of the layers regardless of the P source. Inorganic and organic P fertilizer conditions did not significantly impact the soil pH relative to the control, and the pH did not significantly differ between the two genotypes. In conclusion, when no exogenous P was added, shoot biomass of Xiaoyan54 was greater than Jing411. This increase was promoted by greater soil APA but not soil acidification. The rhizosphere soil pH was not altered across different wheat genotypes or P sources, but APA was increased in the soil of control and OP-treated plants compared with IP- and OPIP-treated plants. The APA of Xiaoyan54 was higher than Jing411 for all of the P sources. The response mechanism of rhizosphere soil acidification is different from acid phosphatase exudation in plants receiving different P sources under arbuscular mycorrhizal fungus inoculation.     

Growth,P uptake and rhizosphere properties of wheat and canola genotypes in an alkaline soil with low P availability

The aim of the present study was to assess the role of soil type on growth, P uptake and rhizosphere properties of wheat and canola genotypes in an alkaline soil with low P availability. Two wheat (Goldmark and Janz) and two canola genotypes (Drum and Outback) were grown in a calcareous soil (pH 8.5) at two P levels [no P addition (0P) or addition of 200 mg kg⁻¹ P as Ca₃(PO₄)₂ (200P)] and harvested at flowering or maturity. Shoot and root dry weight, root length and shoot P content were greater in the two canola genotypes than in wheat. There were no consistent differences in available P, microbial P and phosphatase activity in the rhizosphere of the different genotypes. Shoot P content was significantly positively correlated with root length, pH and phosphatase activity in the rhizosphere. The microbial community composition, assessed by fatty acid methylester analysis, of the canola genotypes differed strongly from that of the wheat genotypes. The weight percentage bacterial fatty acids, the bacteria/fungi (b/f) ratio and the diversity of fatty acids were greater in the rhizosphere of the canolas than in the rhizosphere of the wheat genotypes. In contrast to the earlier studies in an acidic soil, only small differences in growth and P uptake between the genotypes of one crop were detected in the alkaline soil used here. The results confirmed the importance of root length for P uptake in soils with low P availability and suggest that the rhizosphere microbial community composition may play a role in the better growth of the canola compared to the wheat genotypes.     

不同形态无机磷对两种磷效率小麦根际特征的影响

以磷高效型小麦小偃54和磷低效型小麦京411为材料的砂培试验,通过测定植株生物量及吸磷量、根系形态特征、根际pH、磷酸酶活性,研究不同形态无机磷WP(KH2PO4),Al-P(AlPO4)和Fe-P(FePO4)对两种磷效率小麦根际特征的影响.结果表明,在WP处理下,两种磷效率小麦的地上部吸磷量、总吸磷量和磷吸收效率均显著高于其它处理,而其根冠比和磷利用效率却低于其他处理.除了根部吸磷量,小偃54的生物量和吸磷量有高于京411的趋势.除了WP处理,其他处理的小偃54的根冠比和地下吸磷量均高于京411.所有处理的小偃54的根长和根体积均显著高于京411,且不施磷条件(PO)下更为明显,小偃54根系长度是京411的1.6倍;此外,小偃54根系磷酸酶活性均比京411弱.除Al-P外,小偃54的根际酸化能力较京411强.由此可见,磷胁迫条件下,磷高效小麦根系形态特征改变是根际磷活化的主要机理之一,且受磷水平、磷形态及其溶解性的影响.     

Growth,phosphorus uptake,and rhizosphere microbial‐community composition of a phosphorus‐efficient wheat cultivar in soils differing in pH

In a pot experiment, the P‐efficient wheat (Triticum aestivum L.) cultivar Goldmark was grown in ten soils from South Australia covering a wide range of pH (four acidic, two neutral, and four alkaline soils) with low to moderate P availability. Phosphorus (100 mg P kg^–1) was supplied as FePO₄ to acidic soils, CaHPO₄ to alkaline, and 1:1 mixture of FePO₄ and CaHPO₄ to neutral soils. Phosphorus uptake was correlated with P availability measured by anion‐exchange resin and microbial biomass P in the rhizosphere. Growth and P uptake were best in the neutral soils, lower in the acidic, and poorest in the alkaline soils. The good growth in the neutral soils could be explained by a combination of extensive soil exploitation by the roots and high phosphatase activity in the rhizosphere, indicating microbial facilitation of organic‐P mineralization. The plant effect (soil exploitation by roots) appeared to dominate in the acidic soils. Alkaline phosphatase and diesterase activities in acidic soils were lower than in neutral soils, but strongly increased in the rhizosphere compared with the bulk soil, suggesting that microorganisms contribute to P uptake in these acidic soils. Shoot and root growth and P uptake per unit root length were lowest in the alkaline soils. Despite high alkaline phosphatase and diesterase activities in the alkaline soils, microbial biomass P was low, suggesting that the enzymes could not mineralize sufficient organic P to meet the demands of plants and microorganisms. Microbial‐community composition, assessed by fatty acid methylester (FAME) analysis, was strongly dependent on soil pH, whereas other soil properties (organic‐C or CaCO₃ content) were less important or not important at all (soil texture).     

Belowground interactions between intercropped wheat and Brassicas in acidic and alkaline soils

Our previous studies showed that, under P-limiting conditions, growth and P uptake were lower in the wheat genotype Janz than in three Brassica genotypes when grown in monoculture. The present study was conducted to answer the question if P mobilised by the Brassicas is available to wheat; leading to improved growth of wheat when intercropped with Brassicas compared to monocropped wheat. To assess if the interactions between the crops depend on soil type, the wheat genotype Janz and three Brassica genotypes (two canolas and one mustard) were grown for 6 weeks in monoculture or wheat intercropped with each Brassica genotype in an acidic and an alkaline soil with low P availability (with two plants per pot). Wheat grew equally well in the two soils, but the Brassicas grew better in the acidic than in the alkaline soil. In the acidic soil, monocropped Brassicas had a 3 to 4 fold greater plant dry weight (dw) and P uptake than wheat; plant dw and P uptake in wheat were decreased or not affected by intercropping and increased in the Brassicas. In the alkaline soil, dw and P uptake of the Brassicas was twice as high as in wheat, with intercropping having no effect on these parameters. The contribution of wheat to the total shoot dw and P uptake per pot was 4-21% and 32-40% in acidic and alkaline soil, respectively. Mycorrhizal colonisation was low in all genotypes in the acidic soil (1-6%). In the alkaline soil, mycorrhizal colonisation of monocropped wheat was 62%, but only 43-47% in intercropped wheat. Intercropping decreased P availability in the rhizosphere of wheat in the acidic soil but had no effect on rhizosphere P availability in the alkaline soil. Intercropping had a variable effect on rhizosphere microbial community composition (assessed by fatty acid methylester analysis (FAME) and ribosomal intergenic spacer amplification (RISA)), ranging from intercropping having no effect on the rhizosphere communities to intercropping resulting in a new and similar rhizosphere community composition in both genotypes. The results of this study show that intercropping with Brassicas does not improve growth and P uptake of wheat; thus there is no indication that P mobilised by the Brassicas is available to wheat.     

不同磷供应水平下小麦根系形态及根际过程的变化特征

以石麦15和衡观35两个品种小麦为试验材料,应用根袋栽培方式,研究了不同施磷量对小麦根系形态和根际特征的影响。结果表明,与施磷量P2O5 0.1 g/kg相比,高量供磷（P2O5 0.3 g/kg）条件下石麦15地上部生物量和磷累积量增加幅度大于衡观35;但不施磷处理衡观35地上部生物量降低幅度小于石麦15,磷含量和累积量高于石麦15,衡观35耐低磷能力较强。土壤供磷不足时,衡观35总根长中直径0.16 mm细根所占比例高于石麦15,根系平均直径较小;而高磷供应下,石麦15根系中直径0.16 mm细根长度较长,在总根长中所占比例较高。总根长和直径0.16 mm的细根长度与植株地上部磷累积量之间呈显著正相关关系。总根长越长尤其是细根越多,有利于促进植株对磷的吸收。与非根际土壤相比,高磷供应下根际土壤有机磷含量增加,微生物量磷含量降低;而供磷不足时根际土壤碱性磷酸酶活性较高,有机磷含量较低。与施磷量P2O5 0.1 g/kg相比,高量供磷下根际土壤pH值升高、碱性磷酸酶活性下降,不施磷处理根际土壤pH值降低。本研究表明,供磷不足时,小麦根系形态和根际过程均发生适应性变化,而高量供磷条件下,小麦植株根系形态的改变因品种而异。     

Soil phosphorus mobilization in the rhizosphere of cover crops has little effect on phosphorus cycling in California agricultural soils

Phosphorus (P) is a key limiting factor in many terrestrial ecosystems because most soil P is bound to soil minerals or organic matter. Increasing P cycling rates can increase P availability, including in agricultural soils that receive external P inputs. For example, cover crops may increase P cycling rates via plant uptake and P release during microbial decomposition. Cover crops and associated microbes may also change rhizosphere properties and stimulate soil P mobilization. We studied the potential of legume – fava bean (Vicia faba), vetches (Vicia dasycarpa, Vicia sativa, Vicia benghalensis) pea (Pisum sativum) – and cereal – rye (Secale cereale), wheat (Triticum aestivum), oat (Avena sativa) – cover crops to stimulate P cycling across management practices in two long-term systems trials in California. We measured cover crop biomass and nutrient content, P-mobilizing capacity (pH, organic acids, phosphatase activity) and soil P fraction changes in the rhizosphere. Cereals generally produced more biomass with similar P content compared to legumes, but higher C:P in cereal residues could favor microbial immobilization, delay residue mineralization and reduce P cycling rates. Legumes, especially fava bean, had the largest effect on rhizosphere properties by reducing pH and increasing organic acids concentrations and phosphatase activity. However, these changes in rhizosphere properties had a modest impact on soil P and did not increase soil P availability. Furthermore, we found no strong effect of management practices or soil P concentrations on soil P mobilization. Our results suggest that P mobilization in the rhizosphere of legumes is unlikely to increase P cycling rates in these soils, whereas P uptake and release in cereal biomass could have stronger effects.     

碳酸钙和根际作用对酸性红壤解磷微生物丰度的影响

选用玉米品种郑单958为试验材料,设置不添加碳酸钙(CK)、每千克土添加0.3g碳酸钙(Ca-0.3)和0.5g碳酸钙(Ca-0.5)3个碳酸钙处理,以相应处理未种植物土壤为非根际对照土壤,研究了碳酸钙和根际作用对酸性红壤磷酸酶活性及解磷微生物相关功能基因phoC和phoD丰度的影响。结果表明:碳酸钙添加能有效改善玉米生长,促进地上部氮、磷、钾和钙的吸收。土壤酸性磷酸酶(ACP)活性显著高于碱性磷酸酶(ALP)活性,表明酸性土壤中ACP在矿化有机磷方面占主导地位。根际土壤ACP、ALP活性和phoD基因拷贝数均显著高于非根际,而仅Ca-0.5处理ALP活性和phoD基因拷贝数显著高于CK,说明根际效应强于碳酸钙处理。phoC基因拷贝数与土壤铵态氮、硝态氮含量存在显著相关性,ALP活性和phoD基因拷贝数与土壤pH及铵态氮、硝态氮、有效磷、交换性钙含量均存在显著相关性。可见,碳酸钙和根际作用均影响酸性土壤解磷微生物功能和丰度,但根际效应更加明显,这些作用与土壤理化因子的改变密切相关。     

不同产地油菜秸秆制备的生物质炭对红壤酸度和土壤pH缓冲容量的影响

  目的  明确不同产地油菜秸秆制备的生物质炭对红壤酸度的改良和土壤pH缓冲容量的提升效果。  方法  将不同添加量的油菜秸秆炭分别与两种酸性红壤混合,然后进行室内培养试验,测定培养实验前后土壤pH、pH缓冲容量、土壤交换性盐基离子和土壤交换性酸。  结果  添加油菜秸秆炭显著提高了土壤的pH、pH缓冲容量、交换性盐基离子含量,显著降低了土壤交换性酸含量。说明添加油菜秸秆炭不仅可以改良红壤酸度,还能提高红壤的抗酸化能力,因而可以减缓土壤的复酸化。生长在碱性土壤上的油菜秸秆制备的生物质炭对红壤酸度的改良效果和对土壤pH缓冲容量的提升效果均优于生长在酸性土壤上的油菜秸秆制备的生物质炭,在5%添加水平下,前者使湖南红壤pH相比对照提高37.4%,后者使该土壤的pH提高22.4%;相应地,2种生物质炭分别使该土壤的pH缓冲容量分别提高41.4%和37.3%。2种油菜秸秆炭对红壤pH和pH缓冲容量的提升效果与其碱含量和表面官能团多少相一致。  结论  碱性土壤上生长的油菜秸秆制备的生物质炭对红壤具有更好的改良效果。     

不同磷源对作物根际效应影响的研究

本文通过网室盆栽和室内分析相结合的方法,研究了几种P源施入石灰性土壤后对作物根际生物活性性质的影响,结果表明:对于不同P源处理,小麦生长过程中根际、非根际微生物种群的数量及根际效应(R/B)有显著差异,其大小顺序为:K2HPO4>CaMg-P>SSP>FA>CK。微生物数量在生育后期达到高峰。作物根际磷酸酶活性随生育期的进展逐步增强。不同P源处理影响下的土壤磷酸酶活性有一定的差异,总体顺序为:FA>SSP >K2HPO4> CaMg-P>CK。土壤碱性磷酸酶活性显著地高于中性磷酸酶活性。     

两个水稻基因型根际磷素组分、pH以及磷酸酶活性的动态变化

A rhizobox experiment with two phosphorus （P） treatments, zero-P （0 mg P kg^-1） and plus-P （100 mg P kg^-1） as Ca（H2PO4）2.H2O, was conducted to study the chemical and biochemical properties in the rhizosphere of two rice genotypes （cv. Zhongbu 51 and Pembe） different in P uptake ability and their relationship with the depletion of soil P fractions. Plant P uptake, pH, phosphatase activity, and soil P fractions in the rhizosphere were measured. Both total dry weight and total P uptake of Pembe were significantly （P 〈 0.05） higher than those of Zhongbu 51 in the zero-P and plus-P treatments. Significant depletions of resin-Pi, NaHCO3-Pi, NaHCO3-Po, and NaOH-Pi, where Pi stands for inorganic P and Po for organic P, were observed in the rhizosphere of both Zhongbu 51 and Pembe under both P treatments. Pembe showed a greater ability than Zhongbu 51 in depleting resin-Pi, NaHCO3-Pi, NaHCO3-Po, NaOH-Pi, and NaOH- Po in the rhizosphere. HCl-Pi and residual-P were not depleted in the rhizosphere of both genotypes, regardless of P treatments despite significant acidification in the rhizosphere of Pembe under zero-P treatment. Higher acid phosphatase （AcPME） activity and alkaline phosphatase （AlPME） activity were observed in the rhizosphere of both Zhongbu 51 and Pembe compared to the corresponding controls without plant. AcPME activity was negatively （P 〈 0.01） correlated to NaHCO3-Po concentration in the rhizosphere of both Zhongbu 51 and Pembe, suggesting that AcPME was associated with the mineralization of soil organic P.     

红壤酸化及石灰改良影响冬小麦根际土壤钾的有效性

【目的】了解初始酸度对石灰改良红壤钾素有效性的效应,为酸化红壤改良提供依据和支撑。【方法】本试验以湖南祁阳典型的第四纪红土为基础,人为调节出土壤pH分别为4.0、4.5、4.8、5.2的土壤。每个酸度土壤的一半加石灰改良至pH 6.0 (石灰改良处理),另一半不变(酸化处理)。以该土壤进行了小麦盆栽试验。每个盆内放入一个尼龙网根袋,并添加供试红壤1.65 kg (根袋中加150 g)。小麦生长80天后收获,调查了小麦生物量和钾吸收量,测定比较了小麦根际和非根际土壤不同形态的钾含量变化。【结果】1)不同酸化土壤冬小麦生物量(地上部和根部)与初始pH显著正相关(P＜0.05),也与钾吸收量显著正相关(P＜0.05)。石灰改良处理冬小麦生物量均显著高于相应的酸化处理,也随初始pH升高而显著升高。2)不同酸化土壤冬小麦根际土壤速效钾随pH升高显著降低,非根际土壤的速效钾含量均显著高于相应的根际土壤(除pH 4.0外)。石灰改良处理根际土壤速效钾含量均显著低于相应的酸化处理,且非根际土壤显著高于对应根际土,非根际土壤速效钾含量随初始pH升高而显著下降。3)不同酸化土壤冬小麦根际土壤钾离子饱和度随pH升高而显著下降,非根际土壤钾离子饱和度则随pH升高呈增加趋势。石灰改良处理土壤各处理根际土钾离子饱和度均显著低于对应的非根际土,同时非根际土钾离子饱和度与酸化处理的变化趋势一致。4)不同酸化处理红壤冬小麦生物量与根际速效钾亏缺量呈极显著正相关(P＜0.01),冬小麦根际土壤速效钾亏缺率和冬小麦吸钾量及根际钾离子饱和度亏缺率均呈极显著正相关(P＜0.01);而石灰改良处理根际土壤速效钾亏缺率则与初始pH呈显著负相关(P＜0.05)。【结论】在本试验的pH范围内,酸化条件下,根际土壤速效钾含量随pH降低而升高,而冬小麦吸钾量及生物量均随pH升高而升高。表明酸化红壤影响冬小麦钾养分吸收的主导因素是土壤的酸度。施石灰降低了土壤的酸度,提高酸化红壤作物产量和吸钾量。红壤施用石灰校正酸化应在pH降到5.0之前进行。酸化红壤石灰改良后,还应注意适量补充钾肥。     

Dynamics and availability of phosphorus in the rhizosphere of a temperate silvopastoral system

A field rhizosphere study was carried out over a period of 12 months on a 6-year-old silvopastoral trial in New Zealand. The trial comprised radiata pine (Pinus radiata) with lucerne (Medicago sativa) and perennial ryegrass (Lolium perenne) understoreys. The study was initiated because of the unique interrelationships between roots in silvopastoral systems and a paucity of understanding about the processes involved in phosphorus (P) dynamics in temperate silvopastoral systems. Improving our understanding in this area has important implications for nutrient management in silvopastoral systems. Rhizosphere soils were analysed to determine inorganic (Pi) and organic (Po) P fractions, macroporous resin Pi and Po, phosphatase enzyme activity, microbial biomass carbon and pH. Concentrations of labile Pi were consistently greater and Po lower in tree rhizosphere soil compared to the companion understorey, indicating that radiata pine when grown with a productive understorey mineralised Po to a greater extent than either understorey species. Tree rhizosphere soil from under lucerne and lucerne rhizosphere soil contained the lowest concentrations of total Pi and Po compared with tree under ryegrass and ryegrass rhizosphere soils. This was partly attributed to higher levels of phosphatase enzyme activity in the lucerne rhizosphere soils. The results suggest the combination of lucerne with radiata pine may enhance greater utilisation of soil P, although this requires further investigation. Lower levels of labile Po, and higher levels of labile Pi and phosphatase enzyme activity, were determined in tree and understorey lucerne and ryegrass rhizosphere soils in spring compared with autumn. This data confirmed that overall rates of soil organic P mineralisation are greatest in spring.     

Ameliorating Effects of Fungus Chaff and Its Biochar on Soil Acidity

A biochar was generated from fungus chaff at 300 °C, and the ameliorating effects of fungus chaff and its biochar on an acidic Ultisol were compared using incubation experiments. Incorporation of fungus chaff and its biochar significantly increased soil pH and soil exchangeable base cations but decreased soil exchangeable acidity. The ameliorating effect was greater for the biochar than the fungus chaff, and thus the biochar was a better amendment for acidic soil than its feedstock of fungus chaff. The biochar ameliorated soil acidity mainly through the release of its contained alkaline substances, while fungus chaff increased pH of acidic soils through two mechanisms: release of alkaline substances and inhibition of soil nitrification. The incorporation of fungus chaff increased soil-available organic carbon and thus accelerated the microbial assimilation of inorganic nitrogen, while incorporation of fungus chaff biochar enhanced nitrification due to increased soil pH.     

氨基酸有机肥对棉花根际和非根际土壤酶活性和养分有效性的影响

在新疆石河子进行了2年不同氨基酸有机肥施用量的大田试验,测定棉花根际和非根际土壤酶活性和有效养分含量。结果表明,棉花根际土壤过氧化氢酶、蔗糖酶、磷酸酶、脲酶、纤维素酶活性高于非根际,且脲酶、纤维素酶活性达到显著差异。新陆早8号根际过氧化氢酶活性高于新陆早12号,但蔗糖酶、磷酸酶、脲酶、纤维素酶活性低于新陆早12号。根际碱解N呈显著降低,速效P呈增加趋势。膜下滴灌根际和非根际土壤过氧化氢酶、磷酸酶、脲酶、土壤pH及非根际的碱解N、速效P、根际的速效K较淹灌高,而土壤蔗糖酶、纤维素酶、根际碱解N、速效P、非根际的速效K较淹灌低。氨基酸有机肥对棉花根际和非根际土壤酶活性都有增加作用。土壤pH随着有机肥施用量的增加呈下降趋势,根际低于非根际。氨基酸有机肥增加了土壤碱解N、速效P、速效K含量。     

Effect of pH on enzyme stability in soils

The pH stability of urease, acid phosphatase, alkaline phosphatase and phosphodiesterase in soils was investigated by first incubating a soil sample at the indicated pH (1–13) for 24 h and then measuring the activity at its optimal pH under standardized conditions. Generally, the decline in enzyme activity in a pH-profile near the optimum pH range was due to a reversible reaction that involved ionization or deionization of acidic or basic groups in the active centre of the enzyme-protein. Irreversible inactivation of the enzyme was particularly evident at the lower and higher ranges of acidic and alkaline conditions. Results showed that the pH stability of soil enzymes was highly dependent on the soils being assayed. The variation among soils may be attributed to the diversity of vegetation, micro-organisms and soil fauna as sources contributing to the enzyme activity and to the protective sites which allowed entrapment of the enzyme within colloidal humus and organo-mineral complexes. Adherence of the enzyme-protein to the humic-clay fractions would allow some resistance to pH denaturation.     

Microbial biomass phosphorus and alkaline phosphomonoesterase activity in the rhizosphere of different wheat cultivars as influenced by inorganic phosphorus and farmyard manure

Wheat cultivars C 306, PBW 175, HD 1553, and HD 2329 were grown in an alkaline soil with and without inorganic P fertilizer and/or farmyard manure in a pot culture experiment. Microbial biomass P (MBP) and alkaline phosphomonoesterase (APM) activities were studied in rhizosphere soils of the above wheat cultivars at different physiological stages. Root weight and P uptake were also estimated simultaneously. Higher microbial biomass P was observed at crown root initiation (CRI) stage while APM activities were higher at panicle initiation (PI) stage. The HD cultivars showed higher MBP and APM activities at PI stage, while at CRI stage, the reverse was true. Though the application of inorganic P apparently showed higher APM activity, the ratio of APM activity and microbial biomass P (APM to MBP) decreased in the presence of inorganic fertilizer P. Inorganic P compared to FYM was the more dominant factor in reducing the APM to MBP ratio. Root weight did not correlate with grain yield. From step-wise regression analysis, it was revealed that microbial biomass P at both CRI and PI stages was a significant factor in influencing the P uptake in relation to grain yield of wheat.     

Phosphorus Speciation and Nutrient Stoichiometry in the Soil-Plant System During Primary Ecological Restoration of Copper Mine Tailings

The effects of plant vegetation on phosphorus(P) speciation, pH, total carbon concentration, total nitrogen concentration, and alkaline phosphatase activities were investigated to explore the P uptake strategy of plants in low-P soil and to determine the nutrient stoichiometric ratio changes in the rhizosphere of plants(Imperata cylindrica, Miscanthus floridulus, Zoysia sinica, Artemisia lavandulaefolia, Indigofera pseudotinctoria, and Conyza canadensis) which had grown for approximately 15 years in copper mine tailings, East China. The results showed that the average pH values in the rhizosphere decreased by 0.06–1.37 compared with those in the non-rhizosphere. The alkaline phosphatase activities of the rhizosphere were significantly higher than those in the non-rhizosphere.The mean concentrations of aluminum(Al)-and iron(Fe)-bound P and Ca_2-P(CaHPO_4) in the rhizosphere of all plants were 5.4% to 87.7%, 49.2% to 214.2%, and 86.6% to 147.6% higher than those in the non-rhizosphere, respectively. Except for Ca_8-P(Ca_8H_2(PO_4)_6)and Ca_(10)-P(Ca_(10)(PO_4)_6(OH)_2) in the rhizosphere, all kinds of inorganic P forms were negatively correlated with pH. Significant correlation was also observed among the concentrations of dominant forms of inorganic P, C, and N and alkaline phosphatase activities in the rhizosphere. Among the studied species, I. pseudotinctoria showed the most significant effect on enhancing soil available P concentration. The stoichiometric ratios of C:P and N:P were apparently higher in the rhizosphere than the non-rhizosphere, whereas these ratios were far below the ratios commonly observed in Chinese soils. These results indicated that the plant growth effectively affected P fractions possibly by changing pH, C and N concentrations, and alkaline phosphatase activity, in the rhizosphere in copper mine tailings.     

不同磷效率基因型小麦应对缺磷胁迫的表型及相关基因表达的研究

  【目的】  小麦是磷肥需求量最大的作物之一。为了探索小麦对磷的高效利用机制,本研究评价了不同磷效率基因型小麦在缺磷条件下的差异响应。  【方法】  本研究选取一个磷高效小麦基因型‘小偃54’和一个低效率型‘中国春’作为试验材料,设置正常供磷(+P)、缺磷(?P)和缺磷7天后恢复正常供磷(RP) 3个处理进行小麦水培试验,调查分析了小麦幼苗的表型、生理以及缺磷响应基因的表达随缺磷时间的变化趋势,及它们在不同磷效率小麦基因型间的异同。  【结果】  缺磷胁迫明显增加了两个小麦基因型的根冠比,但无论缺磷与否,磷高效基因型‘小偃54’的根冠比均大于磷低效基因型‘中国春’。随着缺磷时间的延长,小麦幼苗地上、地下部无机磷和总磷浓度逐渐降低,但不同基因型之间无明显差异。对缺磷的小麦幼苗恢复供磷后,磷耗竭的小麦幼苗体内无机磷含量迅速增加,‘小偃54’地上、地下部的无机磷含量均明显高于‘中国春’。缺磷响应信号基因TaIPS1和TaSPX3在缺磷6 h即被诱导表达,随着缺磷时间的延长表达量逐渐升高,且恢复供磷后表达量显著降低;缺磷早期‘中国春’中TaIPS1和TaSPX3的表达量比小偃54高,但在长期缺磷和缺磷后恢复供磷处理下又比‘小偃54’低,表明磷低效小麦基因型‘中国春’可能对体内磷稳态变化更为敏感。然而,两个根系特异表达的高亲和磷转运子TaPHT1.1/9 和TaPHT1.10均表现出缺磷早期表达受到抑制,而长期缺磷被诱导升高表达。未预料到的是,二者在复磷处理后的表达量明显高于缺磷处理。长期缺磷处理下,‘中国春’中TaPHT1.1/9的表达量明显低于‘小偃54’,但其TaPHT1.10的表达与‘小偃54’无显著差异,表明不同磷效率基因型小麦幼苗缺磷诱导表达的磷吸收转运子可能存在差异。除此以外,缺磷胁迫显著增加了‘中国春’根系DCB-Fe含量,但对‘小偃54’无明显影响。  【结论】  磷高效基因型小麦幼苗(‘小偃54’)比磷低效型(‘中国春’)具有更大的根冠比和更强的磷吸收能力。‘小偃54’根系中的磷转运子基因TaPHT1.1/9的表达也明显高于‘中国春’。然而,缺磷明显促进了磷低效基因型小麦根表铁的富集。今后将进一步研究小麦根表铁的富集对小麦幼苗磷高效吸收和利用的影响。