不同AM菌根菌分泌的磷酸酶对根际土壤有机磷的影响

以三叶草为材料,利用3室隔网培养方法,研究了4种AM菌根菌侵染三叶草后对根际土壤酸性和碱性磷酸酶活性以及菌丝酶活性对土壤有机P的影响。结果表明,接种AM菌根菌 (9周) 对根际土壤酸性和碱性磷酸酶活性均有增强作用,但作用强度主要取决于菌丝在土壤中的生长状况,Glomus属菌根菌在整个菌丝室 (0~6cm) 都影响土壤磷酸酶的活性,其活性在整个菌丝室中都比Gigaspora的高。同一属不同种的根际土壤磷酸酶活性差异不大。AM菌根根际土壤磷酸酶对土壤有机P的降解有很强的促进作用。     

丛枝菌根根外菌丝对不同形态氮素的吸收能力

本试验以玉米为宿主植物,以Glomus mosseae和Glomus intraradices为接种剂,采用空气隔板分室-半液培系统,在植株收获前48 h向菌丝室供应15N标记的不同形态氮素,探讨丛枝菌根根外菌丝吸收传递不同形态氮素的能力。结果表明,丛枝菌根根外菌丝吸收传递15N能力因菌种和氮素形态而异。丛枝菌根真菌G.intraradices吸收传递15N的能力高于G.mosseae,根外菌丝吸收传递不同形态15N的能力为15NH4+>15N-Gln>15N-Gly>15NO3-。根外菌丝吸收传递的15N对植株氮营养的贡献仅为0.004%~0.032%。     

丛枝菌根对三叶草根际磷酸酶活性的影响

以三叶草为材料,利用三室隔网培养方法,探讨了取自肥料长期定位试验中多年施用与不施用有机肥的田间小区土壤上,接种菌根菌（G.mosseae）对根际土壤酸性和碱性磷酸酶活性的影响。植物生长9周后,收获测定菌丝生长室土壤酸性磷酸酶和碱性磷酸酶活性,并对磷酸酶产生位点进行细胞化学定位。结果表明,接种丛技菌根菌对根际土壤酸性和碱性磷酸酶活性均有增强作用,但作用程度在有机服小区土壤上要大于无机肥小区土壤。根际土壤酸性磷酸酶原位化学定位结果表明,菌丝周围有明显的酸性磷酸酶的反应产物,说明报外丛枝菌根菌丝能直接向外分泌磷酸酶。     

VA菌根真菌外生菌丝对难溶性无机磷酸盐的活化及利用Ⅰ. 32P间接标记法

采用三室栽培装置培养三叶草,接种VA菌根真菌Glomus mosseae.将根系与VA菌根真菌外生菌丝隔开,在菌丝室施用5种磷酸盐和32P间接标记磷肥,研究外生菌丝对难溶性磷酸盐的活化利用能力.结果表明,外生菌丝可以活化吸收磷酸二钙、磷酸八钙、磷酸铝和磷酸铁,无法活化利用磷酸十钙;各种磷酸盐被活化吸收的量及其对三叶草磷营养的贡献率的大小顺序是磷酸二钙>磷酸八钙、磷酸铝>磷酸铁.     

A菌根真菌外生菌丝对难溶性无机磷酸盐的活化及利用Ⅰ.~(32)P间接标记法

采用三室栽培装置培养三叶草 ,接种VA菌根真菌Glomusmosseae。将根系与VA菌根真菌外生菌丝隔开 ,在菌丝室施用 5种磷酸盐和32 P间接标记磷肥 ,研究外生菌丝对难溶性磷酸盐的活化利用能力。结果表明 ,外生菌丝可以活化吸收磷酸二钙、磷酸八钙、磷酸铝和磷酸铁 ,无法活化利用磷酸十钙 ;各种磷酸盐被活化吸收的量及其对三叶草磷营养的贡献率的大小顺序是磷酸二钙 >磷酸八钙、磷酸铝 >磷酸铁     

VA菌根菌丝对紧实土壤中磷的吸收

本文采用三室隔网盆栽试验方法,选择三种土壤容重(1.3;1.6;1.8g/cm3)来模拟自然条件下不同紧实度对植物根系生长的抑制情况,探讨了接种VA菌根真菌Gmosseae对三叶草植株生长和对土壤磷吸收的影响。结果表明随着土壤容重的增加,三叶草根系生长受到抑制的程度随之加重。当土壤容重为1.8g/cm3时,根系基本不能生长,而菌丝却能在其中伸展并吸收养分。表现为1.8土壤容重的处理菌根植物的含磷量明显高于无菌根植物。而在低容重的处理中两者却没有显著差异。说明VA菌根真菌能缓解甚至消除土壤机械阻力对植物生长的胁迫。     

不同施磷水平下 AM 真菌发育及其对玉米氮磷吸收的影响

【目的】不同丛枝菌根 (abuscular mycorrhizal,AM) 真菌菌种 (株) 因其分离地点及宿主的不同,其生理发育与生态功能差异显著,尤其是土壤养分状况对其影响更明显。研究不同土壤磷水平对 AM 真菌侵染宿主及生长发育繁殖的影响,以及不同 AM 真菌对玉米生长及氮磷吸收的影响,可以深化了解 AM 真菌与土壤磷的关系。 【方法】采用盆栽试验,以玉米为宿主植物,土壤灭菌后分别添加 0、50、200、500 mg/kg 4 个水平的磷营养 (P0、P50、P200、P500),并分别接种 6 种 AM 真菌,以不接种为对照。测定了 AM 真菌侵染率、丛枝丰度、孢子数、菌丝密度、玉米植株氮磷比 (N/P) 生态化学计量特征,讨论了不同土壤磷水平与 AM 真菌生长发育间的关系,以及 AM 真菌对玉米吸收利用氮、磷的影响。 【结果】在 P50 条件下,AM 真菌的侵染率、根内丛枝结构、根外生物量 (孢子数、菌丝密度) 显著高于不加磷 P0 和 P200 和 P500 处理,而且 AM 真菌侵染及生长发育指标在高磷水平时,显著下降。不同磷水平处理下,不同 AM 真菌对玉米的侵染能力及生物量存在明显差异。在 P0 和 P50 条件下,接种 G.m 处理侵染率达到 75%,菌丝密度达 240 m/g,显著高于其他五个 AM 真菌。AM 真菌 C.c、R.a、C.et 的菌根侵染状况及生物量次之,D.s、D.eb 最差。在高磷 P200 和 P500 条件下,仅有 F.m 真菌处理的侵染状况及生物量最高。在 P0、P50 水平下,接种 F.m、R.a、D.eb 显著降低了植株氮含量;在不加磷 (P0) 水平下,接种处理均显著促进了玉米植株中磷含量的提高,在 P50 水平下,F.m 植株磷含量显著高于不接种对照;在 P0、P50、P200 水平下,接种 AM 真菌处理降低了玉米植株中 N/P 比,且不同菌种间存在差异,接种真菌 F.m 处理的 N/P 比明显最低。 【结论】土壤添加低量磷 (50 mg/kg) 更适合 AM 真菌的侵染及生长发育,也利于菌根效应的发挥。侵染能力及效应以耐高磷菌种 F.m 最好,然后依次为 C.c、R.a、C.et。在适量磷条件下,接种 AM 真菌能够调节植株体 N/P 比达到平衡,改善植物营养状况,促进玉米生长。     

丛枝菌根根外菌丝对铵态氮和硝态氮吸收能力的比较

采用空气隔板分室法并结合15N标记技术,以玉米为宿主植物并接种Glomus mosseae和Glomus intraradices,比较了这两种真菌根外菌丝对铵态氮和硝态氮吸收传递能力的差异。结果表明,丛枝菌根根外菌丝吸收传递氮的能力因菌种和氮素形态而异。两种真菌根外菌丝吸收传递NH4+-N能力均高于NO3--N;G. intraradices根外菌丝吸收传递氮的能力高于G. mosseae,这可能与两种真菌根外菌丝生长量有关。     

AM菌对三叶草吸收、累积重金属的影响

采用4室根箱培养系统,探讨了Cu、Zn、Pb、Cd 4种重金属复合污染土壤中,丛枝菌根菌对三叶草生长及吸收、累积重金属的作用,结果表明:重金属Cu 100mg/kg、Zn 600mg/kg、Pb 300mg/kg、Cd 10mg/kg的复合污染对三叶草生物量影响较小,但土壤重金属处理使丛枝菌根菌Glomus intraradices和Glomus caledonium对三叶草的侵染率分别降低53%和56%,菌种G.intraradice的菌丝密度降低73%;接种菌根真菌能明显减少重金属复合污染土壤中三叶草对Cu、Cd和Pb的吸收,并强化根系在限制重金属Pb和Cd向地上部运输中的作用,地上部Pb和Cd含量分别下降24.2%~55.3%和65%~97.9%,使三叶草地上部Cd和Pb含量均低于我国牧草重金属安全含量,提高了三叶草可食部分的质量;不同菌根真菌对三叶草吸收、累积及分配重金属的影响有明显差异,Glomus intraradices对减少三叶草对重金属的吸收及其在地上部可食部分的累积的作用大于Glomus caledonium。丛枝菌根菌对于强化三叶草根系对重金属的固持作用,调节生态系统中重金属的生物循环,减轻重金属对食物链的污染风险方面起着重要作用。     

丛枝菌根真菌根内菌丝碱性磷酸酶活性与菌根共生效应的研究

试验研究 3种丛枝菌根真菌根内菌丝碱性磷酸酶活性与菌根共生效应的结果表明 ,3种丛枝菌根真菌对宿主植物的效应不同 ,与接种G .spp处理和未接种对照相比 ,接种G .m和G .i处理显著增加玉米地上部和根系干物质量、P浓度和吸P量 ,但后两者间无显著差异 ;而接种G .spp处理与对照无显著差异。播种后 35d时接种G .m和G .i处理根内菌丝碱性磷酸酶活性显著高于接种G .spp处理 ,而前二者间无显著差异 ,且随生长时间的变化趋势相似 ,35d时酶活性最高 ,35～ 5 0d呈迅速下降趋势 ,至 70d时酶活性仍下降且趋于平缓。G .spp酶活性则一直处于较低水平 ,随生长时间的延长略有起伏。即接种不同丛枝菌根真菌时 ,根内菌丝碱性磷酸酶活性高的菌根真菌对玉米生长促进作用较大 ,可提高玉米P营养状况 ;反之则对玉米生长和P营养状况无明显促进作用 ,且与对照无显著差异。出苗后 35d时根内菌丝碱性磷酸酶活性是预测丛枝菌根真菌对玉米生长效应的有效生理指标之一。     

Effect of a vesicular-arbuscular mycorrhizal fungus (Glomus epigaeus) on herbicide uptake by roots

 Vesicular-arbuscular mycorrhizal (VAM) fungi increase root uptake of P and other minerals, but their role in the uptake of herbicides has received far less attention. These experiments were conducted to determine the effect of the VAM fungus, Glomus epigaeus (Daniels and Trappe), on the absorption of atrazine and trifluralin by roots of corn and soybean. Atrazine uptake by excised corn-root segments was consistently increased by the VAM fungus, but VAM enhancement of atrazine uptake by soybeans was less than that observed for corn. Roots from corn grown for 8 weeks in the greenhouse prior to the experiment took up 25 pmol mm^–3 root, whereas non-mycorrhizal roots took up only 11 pmol mm^–3 root. Soybean and corn root uptake of trifluralin was also enhanced by VAM infection. Addition of P did not increase herbicide uptake by non-VAM plants. The direct role of VAM hyphae on atrazine uptake was demonstrated using a two-chamber system, where only the fungal hyphae had access to ¹⁴C-atrazine-treated soil. Hyphal systems of the fungus were able to remove and transfer ¹⁴C-atrazine residues from soil to corn plants, demonstrating direct uptake of the herbicide by the fungal hyphae. Received: 1 July 1998     

Uptake and partitioning of 32P and 65Zn by white clover as affected by eleven isolates of mycorrhizal fungi

We compared the effect of eleven mycorrhizal fungi populations (Glomus spp.) from two different climatic regions (Iran vs. Switzerland) on the uptake and partitioning of ³²P and ⁶⁵Zn by white clover (Trifolium repens L. var. Milkanova). Fungi significantly differed in the colonization of roots with hyphae, vesicles or arbuscules and in their effect on the uptake of ³²P or ⁶⁵Zn by white clover. Fungi also differed in their effects on the percentages of ³²P or ⁶⁵Zn transported to the plant tops. There was no relationship between the uptake of ³²P and that of ⁶⁵Zn in plants colonized by different fungi. Isolates Z7 and Q12 (from Iran) were superior to Swiss isolates for their effect on the uptake of zinc (Zn) by white clover. Among the Swiss isolates, that from Langwiese and Hausweid resulted in the highest and lowest partitioning of both ³²P and ⁶⁵Zn to the plant tops, respectively. We conclude that the effectiveness of vesicular arbuscular mycorrhizae in uptake of phosphorus (P) and Zn may be nutrient specific and that some fungal isolates may also affect the relative partitioning of P and Zn between plant roots and tops.     

Phosphate,Fe and Mn uptake of N2 fixing red clover and ryegrass from an Oxisol as affected by P and model humic substances application. 1. Plant parameters and soil solution composition

The effect of humic substances on P-availability in soil is still debated. Therefore, the effect of model humic substances synthesized from hydroquinone on P, Fe, and Al solubility in a strong P fixing Oxisol and on P acquisition by red clover and ryegrass was investigated. After 4 months of incubation, P concentration of soil solution had increased by a factor of > 10 at the highest humic level (50 g humics kg^?1 soil), accompanied by a similar increase in Fe and Al concentrations. Soil samples with 0, 10, 30, 50 g humics kg^?1 soil were planted with red clover and ryegrass. Red clover showed a small increase of shoot yield and a moderate increase of P uptake after humics addition. High humics levels increased slightly Fe concentration in the shoots but strongly that of Mn leading to Mn toxicity. Ryegrass showed a strong increase in shoot yield after humics addition of about 150 % at the highest humics level compared to the control without humics. At each humic level, P application (100 mg kg^?1 soil) had no effect on P uptake of red clover and a small effect on P uptake by ryegrass. The relatively small effect of humics and P application on shoot yield of clover compared to grass can be explained by chemical P mobilization of red clover via exudation of citrate (about 12 μmol citrate g^?1 soil). This agrees with the finding that P solubility increased in the soil under red clover but not under ryegrass from the first to the second harvest, indicating that red clover mobilized P.     

Mycorrhizal dependency of two hawaiian endemic tree species: Koa and mamane 1

Vesicular‐arbuscular mycorrhizal (VAM) fungi have been proposed as a low‐input solution to the problem of inadequate phosphorus (P) levels in many tropical and subtropical soils. To determine the mycorrhizal dependency of two Hawaiian endemic tree species, mamane (Sophora chrysophylla Seem.) and koa (Acacia koa Gray), seedlings were grown in the greenhouse with and without the VAM fungus, Glomus aggregatum Schenck and Smith emend Koske, at three levels of soil solution P (0,0.02, and 0.20 mg P/L) in a volcanic ash soil. Inoculation significantly increased colonization of roots by the VAM fungus in both mamane and koa seedlings. At 0.02 mg P/L, mamane inoculated with the VAM fungus had significantly greater subleaflet P concentrations at 48 days after planting (DAP), and significantly greater leaf areas, shoot dry weights, and root lengths at harvest compared to uninoculated plants. At 0 mg P/L, koa grown in association with the VAM fungus had significantly greater subleaflet P concentrations at 41 DAP, and significantly greater leaf areas, and dry weights of leaves, stems, and roots at harvest. Mamane was highly dependent on the VAM association for maximum growth, while koa was moderately dependent on the VAM association. These results demonstrate that P uptake and early growth of mamane and koa can be increased significantly at low soil P levels by inoculating seedlings with an effective VAM fungus. Future research needs to demonstrate continuing positive growth benefits of VAM fungal inoculation after transplanting from the nursery to field conditions.     

In situ labeling of legume residues with a foliar application of a 15N‐enriched urea solution

Abstract

Conventional methods for labeling of legume residues with ¹⁵N for the measurement of the transfer of nitrogen (N) to a succeeding crop are inadequate for zero‐tillage management where the residue is chemically desiccated. The study tests the feasibility of in situ labeling of legumes with ¹⁵N for the study of N transfer to a succeeding crop. A single foliar application of ¹⁵N‐labeled urea was misted onto the stems and leaves of second cut red clover and alfalfa in the field in 0.75 x 0.75 m microplots. Nitrogen content and ¹⁵N enrichment were determined for above‐ and below‐ground plant parts. Overall, recovery of the foliar applied ¹⁵N in the forage was 30% and 57% for the alfalfa and red clover, respectively. Of the nitrogen recovered, approximately 70% and 30% were recovered in the above‐ and below‐ground plant parts, respectively, for both forage species. Atom % ¹⁵N was similar for the red clover and alfalfa for each of the above‐ground plant parts and was slightly lower in the crown and roots for the red clover than for the alfalfa. Values of atom % ¹⁵N ranged from 0.5 for fine roots to 1.5 for leaves above 0.20 m from the ground. Labeling of the plant material was not uniform between plant parts but was adequate for many studies of N transfer to a succeeding crop.     

Response of pineapple to mycorrhizal inoculation and fosetyl‐Al treatment

Abstract

A pot experiment was conducted in the greenhouse to determine the influence of vesicular‐arbuscular mycorrhizal (VAM) inoculation on growth of pineapple (Ananas comosus, cv.’Smooth Cayenne') and its interaction with fosetyl‐Al in a Wahiawa soil (Tropeptic Eutrustox) at soil solution P levels of 0.003, 0.02 and 0.2 mg/L. Pineapple crowns were dipped in a solution of fosetyl‐Al before planting. Inoculation of soil with the fungus Glomus aggregatum (Schenck & Smith emend. Koske) significantly increased VAM colonization of pineapple roots at soil solution P levels of 0.003 and 0.02 mg/L. VAM inoculation also increased mycorrhizal effectiveness measured six weeks after planting. At harvest, pineapple grown in the inoculated soil at the lowest P level had significantly higher D‐leaf P concentration and plant fresh weight than that grown in the uninoculated soil. Fosetyl‐Al appears to have no significant effect on VAM‐pineapple interaction.     

Use of nutrient: phosphorus ratios to evaluate the effects of vesicular arbuscular mycorrhiza on nutrient uptake in unsterilized soils

Summary Red clover was grown in soil previously treated with P at various rates, and growth, nutrient uptake, nutrient uptake in relation to phosphorus values, and levels of vesicular-arbuscular mycorrhizal (VAM) infection were determined. The soil was a silty clay loam and Glomus lacteum was the only fungus colonizing the plant roots. An examination of the effects of various rates of P application and of VAM colonization on nutrient (P, K, Ca, Mg, Mn, Fe, and Zn) uptake showed that the Mg : P ratio significantly increased and the Mn : P ratio significantly decreased with increasing VAM infection. It is concluded that in the Trifolium pratense-Glomus lacteum symbiosis, mycorrhizae improve Mg uptake and depress Mn uptake.     

Growth response of field-grown Siratro (Macroptilium atropurpureum Urb.) and Aeschynomene american L. to inoculation with selected vesicular-arbuscular mycorrhizal fungi

Summary The effect of inoculation with a selected isolate of Glomus etunicatum Becker and Gerdemann and one of G. intraradices Schenck and Smith on the growth and nutrient content of Macroptilium atropurpureum Urb. cv. Siratro and Aeschynomene americana L., at applied P levels of 10, 30, 60, and 120 kg ha^-1, was studied under field conditions. At all P levels and for all harvests, the shoot dry mass of Siratro and A. americana were greater for the plants inoculated with the vesicular-arbuscular mycorrhizal (VAM) fungi than the control plants. Differences between the VAM fungus-inoculated and the control plants were most marked between 30 and 90 kg ha^-1 of applied P and diminished at 120 kg ha^-1. At the first harvest of Siratro, the plants inoculated with G. etunicatum had a greater shoot dry mass than those inoculated with G. intraradices, for all levels of applied P. However, for subsequent harvest of Siratro and for the one harvest of A. americana the response of shoot dry mass to the two VAM fungi was equivocal. Fungal inoculation gave at least a 30% saving in the amount of P fertilizer required (40 kg ha^-1) for the maximum yield. The plants inoculated with VAM fungi had a greater tissue concentration and total content of P and N than the control plants at low and intermediate levels of applied P. The percentage of root colonized by VAM fungi for the inoculated plants of the two legumes increased linearly with P additions up to 60 kg ha^-1. The conclusion is that under amended (limed and fertilized) soil conditions, inoculation with selected VAM fungi can improve the establishement and growth of forage legumes in fields that contain ineffective populations of native VAM fungi.     

Contribution of arbuscular mycorrhizal fungi to utilization of organic sources of phosphorus by red clover in a calcareous soil

A glasshouse pot experiment investigated the uptake by arbuscular mycorrhizal (AM) fungi associated with red clover of three organic sources of P added to a sterilized calcareous soil of low P availability. Each pot was separated into a central compartment for plant growth and two outer compartments for external mycelium using 30-μm nylon mesh to restrict the roots but allow hyphal penetration. Plants in the central compartments were inoculated with the AM fungus Glomus versiforme and uninoculated controls were included. Plants were harvested on three occasions: 5, 7 and 10 weeks after sowing. Application of each of the three organic P sources (lecithin, RNA and sodium phytate) or inorganic P (KH₂PO₄) at 50 mg P kg⁻¹ to the outer compartments of mycorrhizal and uninoculated pots increased the yield, P concentration and total P uptake of red clover compared with pots to which no P was applied, with no differences among P sources in non-mycorrhizal plants but differences observed in mycorrhizal plants both 7 and 10 weeks after sowing suggesting differences in availability of the four P sources to AM mycelium. The contribution of external mycelium to plant uptake of applied P increased with time. The three organic P sources made smaller contributions to plant P nutrition than KH₂PO₄ at the first and second harvests. At the third harvest, the contribution from KH₂PO₄ was 23%, while those from lecithin, RNA and sodium phytate were 23, 17 and 31%, respectively. This suggests that with the mediation of AM fungi, soil organic P sources can make a contribution to host plant P nutrition comparable to that of soluble orthophosphate.