Efficacy of root litter as a biofertiliser

The efficacy ofLeucaena leucocephala root litter as a natural biological fertiliser was assessed usingZea mays as a test plant. Up to 8% of the fine roots of the plants constituted root litter. This fine root litter was better than that ofTrigonella foenum-graecum at increasing the growth and productivity ofZea mays. The root litter increased the growth of maize shoots more than the growth of roots. This appears to be a general phenomenon when plant nutrients are insufficient, as in the present study.     

Variable effectivity of three vesicular-arbuscular mycorrhizal endophytes in Hedysarum coronarium and Medicago sativa

Summary Plants of Hedysarum coronarium L. and Medicago sativa L., inoculated with Glomus caledonium, were grown for 6 weeks in soils with increasing amounts of available phosphorus (P). H. coronarium showed no or very low levels of infection even at very low soil P content (4 ppm), while in M. sativa the highest soil P level (20 ppm) was associated with the lowest percentage of infection. Medicago sativa and H. coronarium grown for 16 weeks in a sandy soil showed clear effects of Glomus inoculation on shoot growth and P uptake. In M. sativa inoculation increased shoot growth and P uptake in all treatments considerably, while the P concentration in the shoot was depressed by G. caledonium. In H. coronarium inoculation with G. mosseae and G. occultum had only a modest impact on shoot growth; G. caledonium even depressed shoot growth significantly. Glomus inoculation had a positive impact on the P concentrations in the shoots of H. coronarium. The growth-depressing effect of G. caledonium on H. coronarium is discussed.     

Spore production by the vesicular-arbuscular mycorrhizal fungus Glomus monosporum as related to host species,root colonization and plant growth enhancement

Summary The vesicular-arbuscular mycorrhizal fungus Glomus monosporum was inoculated on grapevine (Vitis vinifera), red clover (Trifolium pratense), meadow grass (Poa pratensis) and onion (Allium cepa) as hosts in two experiments carried out in different environments. Grapevine and clover showed the largest growth response and spore production. Mycorrhizal infection was lowest in meadow grass. Very poor correlations were observed, on an overall basis, between spore production and per cent root infection or infected root length. Spore production per unit infected root length for each host species was a comparatively stable parameter; it was largest for grapevine and smallest for meadow grass in both experiments. Sporulation was positively correlated with growth enhancement by mycorrhizal plants, and growth increments per unit infected root followed the same trend as spore numbers per unit infected root, i.e. largest for grapevine and lowest for meadow-grass. It is concluded that the ability of G. monosporum to produce spores and to enhance plant growth per unit infected root length depends on the host plant species.     

Promotion of mycorrhiza formation and growth of willows by the bacterial strain <Emphasis Type="Italic">Sphingomonas</Emphasis> sp. 23L on fly ash

Re-vegetation of fly ash, the principal by-product of coal fired power stations, is hampered by its unfavourable chemical and physical properties for plant growth. In the present study, we evaluated the use of inoculation with a mycorrhiza-associated bacterial strain (Sphingomonas sp. 23L) to promote mycorrhiza formation and plant growth of three willow clones (Salix spp.) on fly ash from an over-burdened dump in a pot experiment. The high pH_H2O (8.7) and low nitrogen content (N_t = 0.1 g kg⁻¹) in combination with hydrophobicity of the particle surfaces caused low plant growth. Inoculation of the willows with Sphingomonas sp. 23L improved the nitrogen uptake by plants, increased plant growth and stimulated formation of ectomycorrhizae with an autochthonous Geopora sp. strain on all three willow clones. The ectomycorrhiza formed by the Geopora sp. was morphologically and anatomically described. The inoculation significantly increased the shoot growth of two Salix viminalis clones and the root growth of a S. viminalis x caprea hybrid clone. We conclude that inoculation with mycorrhiza promoting bacterial strains might be a suitable approach to support mycorrhiza formation with autochtonous site-adapted ectomycorrhizal fungi in fly ash and thereby to improve re-vegetation of fly ash landfills with willows.     

Inoculation response in kidney beans (Phaseolus vulgaris,L.) to vesicular-arbuscular mycorrhizal fungi and rhizobia in non-sterilized soil

The effect of dual inoculation on three local cultivars (Miss Kelly, Portland Red, Round Red) of red kidney beans (Phaseolus vulgaris, L.) with four strains of Rhizobium leguminosarum bv. phaseoli and three species of vesicular-arbuscular mycorrhizal (VAM) fungi was examined in a clay loam soil. Rhizobial strains B 17 and B 36, each paired with Glomus pallidum or G. aggregatum, were the most effective pairings for cv. Miss Kelly. Inoculation of Miss Kelly with any of these pairings significantly (P=0.05) increased growth, number of nodules, nodule dry weight, mycorrhizal colonization, and shoot N and P content than other pairings. The growth response by cv. Portland Red was significantly improved by pairings of B 36 or B 17 with any of the three VAM fungi. For both cultivars (Miss Kelly and Portland Red), CIAT 652 or T 2 paired with VAM fungi did not give a positive growth response. In contrast, for cv Round Red the T 2 rhizobial strain in combination with any of the three VAM fungi showed a significant (P=0.05) growth improvement in all parameters. Our results suggest that while dual inoculation of VAM fungi and rhizobia significantly improves the growth response by red kidney beans, the best pairings of VAM fungus and rhizobia for each cultivar need to be carefully selected.     

Co-selection of compatible rhizobia and vesicular-arbuscular mycorrhizal fungi for cowpea in sterilized and non-sterilized soils

Summary We selected two isolates of Rhizobium for cowpea (Vigna unguiculata) with sterilized soil tests and two different isolates by non-sterilized soil testing. The four rhizobia were then paired individually with either Glomus pallidum, Glomus aggregatum, or Sclerocystis microcarpa in separate, sterilized, or non-sterilized soil experiments. The purpose of the experiments was to determine the effect of soil sterilization on the selection of effective cowpea rhizobia, and to see whether these rhizobia differed in their effects on cowpea growth when paired with various vesicular-arbuscular mycorrhizal (VAM) fungi. Our experiments showed that the rhizobia selected in sterilized soil tests produced few growth responses in the cowpea compared to the other introduced rhizobia, irrespective of pairing with VAM fungi in sterilized or non-sterilized soil. In contrast, the two rhizobia initially selected by non-sterilized soil testing significantly improved cowpea growth in non-sterilized soil, especially when paired with G. pallidum. Our results suggest that it is important to select for effective rhizobia in non-sterilized soil, and that pairing these rhizobia with specific, coselected VAM fungi can significantly improve the legume growth response.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

荧光假单胞菌Pf.X16L2与丛枝状菌根真菌Glomus mosseae在小麦根圈内的相互关系

运用发光酶基因标记及其发光强度检测,SDH酶活染色等技术,在根盒－土壤微宇宙及塑料盒栽系统中,研究了发光酶基因（luxAB)标记的荧光假单胞菌菌株Pf.X16L2与丛枝状菌根真菌摩西球孢囊霉Glomus mosseae两者在小麦根圈的相互关系。Gl.mosseae对Pf.X16L2的种群密度和生理活性都有着抑制作用。因而能降低小麦根圈对Pf.X16L2的富集作用,而Pf.X16L2在一定程度上能提高Gl.mosseae的菌根感染率,但会降低菌丝中琥珀酸氢酶（SDH）活性,两者可共同促进小麦中后期的生长。     

Influence of soluble phosphorus fertilizer on the interaction between a vesicular-arbuscular mycorrhizal fungus and Azospirillum brasilense in barley (Herdeum vulgare L.)

Summary Pot-culture studies were carried out to examine the response of barley (Hordeum vulgare L.) to inoculation with Azospirillum brasilense and Glomus versiforme, singly and/or in combination, under varying levels of nitrogenous [(¹⁵NH₄)₂SO₄] and soluble phosphatic (single superphosphate) fertilizers. The interaction between both the endophytes led to increased growth and nutrition of the barley plants. Roots from plants inoculated with Azospirillum brasilense and Glomus versiforme exhibited very low acetylene reduction activity. N₂ fixation in the plants increased with the increase in plant growth but the mycorrhiza alone gave a low level of N₂ fixation in the plants compared to combined inoculation with both the endophytes.     

不同立地条件下黄花补血草种群生长、繁殖与土壤水分的差异

[目的]揭示不同立地条件下黄花补血草种群生长、繁殖与土壤水分的差异,为黄花补血草的管理提供科学依据。[方法]选取4个不同沙丘类型的黄花补血草地斑块作为试验样地,研究黄花补血草的生长、繁殖以及水分等。[结果](1)不同立地类型黄花补血草种群的生长与繁殖特征存在明显差异,它主要反映在单株地上生物量、高度、冠幅和密度方面;(2)不同类型的沙丘上黄花补血草单株生殖枝数、花量均存在显著差异的相关性;(3)不同立地类型的黄花补血草土壤含水量存在明显差异,但是在不同的土壤深度上土壤的含水率的差异不显著,丘间地不同土壤深度的土壤含水率差异比较大。[结论]干旱荒漠生境条件下最适宜生长的黄花补血草的沙丘类型为丘间地。     

压实对矿区废弃土壤含水量及植物生长的影响

[目的]探究不同压实处理对矿区废弃土壤含水量及植物生长的影响,为有效利用采石场废弃物和城市固体废弃物、改善矿区立地条件、进行植被修复提供依据。[方法]将砾石和城市固体废弃物按体积8∶2混合后进行不同程度压实处理,进行小区试验。[结果]压实显著提高基质含水量,减小各层含水量差异。随着压实程度增加,植物主要耗水层上移。不同植物受到压实的影响不同,刺槐和苜蓿在重度压实条件下生长明显受阻,侧柏生长量增加。植物在中等强度的压实条件下,能够通过调节自身,适应环境。[结论]一定程度的压实能获得理想的植物保存率和生长量,压实技术可以运用在废弃采石场植被修复工作中。     

Influence of arbuscular mycorrhizal fungi and salinity on growth,biomass, and mineral nutrition of<Emphasis Type="Italic"> Acacia auriculiformis</Emphasis>

The effect of salinity on the efficacy of two arbuscular mycorrhizal fungi, Glomus fasciculatum and G. macrocarpum, alone and in combination was investigated on growth, development and nutrition of Acacia auriculiformis. Plants were grown under different salinity levels imposed by 0.3, 0.5 and 1.0 S m^-1 solutions of 1 M NaCl. Both mycorrhizal fungi protected the host plant against the detrimental effect of salinity. The extent of AM response on growth as well as root colonization varied with fungal species, and with the level of salinity. Maximum root colonization and spore production was observed with combined inoculation, which resulted in greater plant growth at all salinity levels. AM fungal inoculated plants showed significantly higher root and shoot weights. Greater nutrient acquisition, changes in root morphology, and electrical conductivity of soil in response to AM colonization was observed, and may be possible mechanisms to protect plants from salt stress.     

Effect of phosphorus fertilization on blue-green algal inoculum production and nitrogen yield under field conditions

Summary Field experiments were conducted to assess the effects of the application of P on growth and N yield of inoculated and indigenous blue-green algae (BGA). Addition of 17.4 kg P ha^–1 in split applications led to the highest BGA biomass and N yield, 162 kg dry weight ha^–1 and 6 kg N ha^–1 per 15 days, respectively. When inoculum of Aulosira spp., Aphanothece spp., Gloeotrichia spp. were compared separately, Gloeotrichia spp. grew faster but Aulosira spp. fixed more N. The growth rate and N yield of Aulosira spp. decreased with high P applications, although growth continued until the application of 34.8 kg P ha^–1. The effects of P on inoculum production by local species compared with those collected from other states showed the superiority of the local culture. Applications of P also enhanced the growth and N yield of indigenous BGA, with Wollea spp. showing the best results.     

Effects of an arbuscular mycorrhizal fungus and two plant-parasitic nematodes on<Emphasis Type="Italic"> Musa</Emphasis> genotypes differing in root morphology

In this study, the effect of an arbuscular mycorrhizal fungus (AMF) and two migratory endoparasitic nematodes on Musa plant growth, including the root system, were examined. In addition, the AMF-nematode interaction was studied. Seven Musa genotypes with different root systems were selected. Based on their relative mycorrhizal dependency, two genotypes (Calcutta 4 and Obino l'Ewai) were selected for AMF-nematode interaction studies. The experiments were performed under greenhouse conditions. Mycorrhization with Glomus mosseae resulted in a significantly better plant growth even in the presence of nematodes. The effect of AMF on the root system was genotype-dependent and seemed to be related to the relative mycorrhizal dependency of the genotype. The nematodes also affected the root system, decreasing branching. Nematode population densities were significantly reduced in the presence of AMF, except for Pratylenchus coffeae in Obino l'Ewai. In the root system, it appeared that the decreased branching caused by the nematodes was counterbalanced by the increased branching caused by the AMF.     

宁夏半干旱区柠条锦鸡儿灌木林生长特征

[目的]揭示柠条锦鸡儿灌木林最大生长潜力,掌握其生长规律与更新过程,为柠条锦鸡儿林资源合理开发利用提供科学依据。[方法]针对宁夏半干旱区24a柠条锦鸡儿灌木林生长过程的定位监测资料,用定量分析方法揭示柠条锦鸡儿灌木林生长特征。[结果](1)柠条锦鸡儿灌木林的生长变化受水分影响,其变化趋势与土壤水分相吻合,表现为坡下部灌丛生长最好,坡中部次之,坡上部最弱。就坡中上部而言,0—8m土壤贮水量对柠条锦鸡儿灌木丛生长具有显著影响。生长中期的柠条锦鸡儿灌木林,其分枝数量、地径和地上生物量在不同生长坡位间表现出显著或极显著的差异性,而到生长的后期,随着生长年限的延长柠条生理生态特性发生了较大变化,植株衰老退化严重;(2)柠条锦鸡儿灌木林生长除受其自身生物学特性支配外,主要受环境因子和生长指标的双重影响,其生物量在坡下部受分枝数的影响,坡中部受分枝数、地径和株高的共同作用,坡上部则受地径、株高和冠幅的影响;(3)各生长因子均与积温和土壤蒸发量呈极显著的正相关关系,而积温在各生长坡位均为重要影响因子。[结论]水热条件是影响柠条锦鸡儿灌木林生长的主要限制因子。     

Effect of nitrogen on the yield response of Pennisetum americanum,Triticum aestivum and Zea mays to inoculation with Azospirillum brasilense under temperate conditions

Summary A nitrate-respiring strain, a denitrifying strain, and a non-nitrogen-fixing strain of Azospirillum brasilense were compared for their effect on the growth of pearl millet (Pennisetum americanum), wheat (Triticum aestivum) and maize (Zea mays) under temperate conditions in nitrogen-limited pot cultures. Increases in yield of Z. mays shoots occurred with all three strains when inoculation coincided with the addition of low levels of combined nitrogen. The inoculation of A. brasilense did not show any effect on the yield of P. americanum and T. aestivum. Increased numbers of A. brasilense became associated with Z. mays roots following the addition of low levels of combined nitrogen. Low and very variable rates of acetylene reduction activity were observed from excised roots of inoculated Z. mays plants without preincubation. Results indicate that inoculation of cereals with A. brasilense under temperate conditions has only a limited effect on plant growth.     

Control of pitch pine seed germination and initial growth exerted by leaf litters and polyphenolic compounds

We investigated the influence of three concentrations of water extracts of three leaf litter species (pitch pine, huckleberry and white oak) and a mixture of all litters on the germination of pitch pine seeds and initial seedling growth in a microcosm experiment. All three plant species are important components of the pine barrens ecosystems in New Jersey, where it has been seen that pine seedling recruitment occurs only after stand replacing fire or in disturbed sites, where surface organic soil horizons and leaf litter have been removed. Leaf litter extracts did not influence seed germination, but significantly reduced seedling growth at high concentrations. There was little difference between the leaf litter species in growth suppression. As charcoal is a natural residue on the forest floor following fire, its influence on growth suppression was examined; it has been shown to immobilize polyphenols. Charcoal removed the inhibitory effect of leaf litter extracts and allowed the fertilizer effect of nutrients leached from the leaves to enhance seedling growth, particularly at the higher concentration of litter extract used. Responses to litter extracts were compared to four pure phenolic compounds, catchecol, p-coumaric acid, p-hydroxybenzoic acid and tannic acid. None of these compounds suppressed pine seedling growth, suggesting that these phenolics are not allelopathic to pine seedlings. The results are discussed in the context of fire as a driving factor in these oligotrophic and seasonally dry ecosystems and the interactions between nutrient supply and allelopathic chemistry of different leaf litters.     

Phosphatase activity and cytokinin content in cowpeas (Vigna unguiculata) inoculated with a vesicular-arbuscular mycorrhizal fungus

We examined the effect of a vesicular-arbuscular mycorrhizal (VAM) fungus Glomus pallidum Hall on the phosphatase activity and cytokinin concentration in cowpea [Vigna unguiculata (L.) Walp] roots at successive stages of plant growth. Both acid and alkaline phosphatase activity were significantly (P=0.05) higher in mycorrhizal than in non-mycorrhizal roots 30 days after inoculation. Similarly, the cytokinin content was significantly increased in mycorrhizal roots compared to non-mycorrhizal roots. Our study suggests that these biochemical changes may improve the growth of mycorrhizal cowpea plants.     

土壤质地对柱花草生长发育、生物量及土壤肥力变化的影响

采用大田试验的方法,在云南省元谋县小雷宰流域内壤土、砂壤土和重壤土3种质地土壤上,以热研5号柱花草为材料,研究土壤质地对柱花草生长发育、生物量及土壤有机质、有机碳、全氮和全磷的影响。试验结果表明:3种土壤质地上种植柱花草,柱花草地上部和地下部生长量和生物量表现幼苗期增加缓慢,而分枝期后增加快的趋势。壤土耕性好,兼有砂土和重壤土的优点,有利柱花草地上部分的生长发育,柱花草地上部生长量、生物量及改善土壤肥力方面显著高于重壤土。砂壤土有利于柱花草根系向深层土壤生长,柱花草地下部生长量、生物量及根瘤显著高于种植在重壤土。在3种土壤质地种植柱花草后,土壤有机质、有机碳、全氮和全磷均有上升趋势。综合而言,通气性和保肥保水能力居中的壤土更适合柱花草的生长发育及干物质的积累。     

A new growth medium for the study of siderophore-mediated interactions

Summary A microbial growth medium, RSM, was developed to study the role of siderophores (microbial Fe-transport compounds) in the inhibition of the take-all pathogen, Gaeumannomyces graminis var. tritici, by Pseudomonas putida strain B10. The inorganic constituents of the medium were designed to mimic the rhizosphere while the organic composition was designed to promote rapid growth and siderophore production. The antibiosis experiments were highly reproducible and the antagonism appeared to be due to production of pseudobactin, the siderophore of B10. On plates amended with chrome azurol S, G. graminis did not produce siderophores while other fungi did. The growth of G. graminis on plates prepared with Fe chelate buffers was inhibited at a free ferric ion concentration of 10^–24.6 M, although three other fungi were not inhibited, even at 10^–25.5 M, presumably due to their greater production of siderophores. In liquid medium amended with Fe chelate buffers, both the doubling time and the lag phase of P. putida increased as the free ferric ion concentration was reduced. A wide variety of fungi and bacteria were found to grow on this medium. Because the inorganic composition of RSM is based on that of the rhizosphere, the development of this medium may be a first step towards the study of the chemistry and biology of the rhizosphere under well defined conditions.