Light and temperature influence phosphorus absorption by slash pine

Abstract

One‐year‐old slash pine seedlings (Pinus elliottii Engelm.) accumulated more radioactive phosphorus in needles at a 15–10°C day‐night temperature and 2500 foot candles than at higher temperatures and reduced light. Rate of phosphorus uptake was related to concentrations of ethanol‐soluble carbohydrates but not to those of starch or all carbohydrates. Results suggest that temperature and light can be important for optimum phosphorus nutrition of slash pine.     

Variable effects of emergence-promoting rhizobacteria on conifer seedling growth under nursery conditions

Summary Inoculation of white spruce (Picea glauca Voss.) seed with Bacillus polymyxa strain L5 under nursery conditions significantly increased the number of seedlings that emerged after sowing. No significant effects on seedling emergence were detected when white spruce seed was inoculated with Bacillus polymyxa strain L6, or when Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seed was inoculated with either strain L5 or L6. However, white spruce seedlings originating from L5-inoculated seed had significantly lower root dry weights when measured 13 weeks after sowing, and reduced shoot dry weights 26 weeks after sowing compared with uninoculated controls. Inoculation of white spruce seed with strain L6 also resulted in seedlings with decreased root dry weights compared with uninoculated controls 13 weeks after sowing, but the significant inhibition of root growth was not apparent 26 weeks after sowing. Douglasfir seedlings originating from L5-inoculated seed had significantly lower root and shoot dry weights compared with uninoculated controls 13 but not 26 weeks after sowing. Inoculation of Douglas-fir seed with strain L6 resulted in seedlings with decreased root collar diameters and shoot dry weights 13 weeks after sowing, and lower root dry weights 26 weeks after sowing compared with uninoculated controls. These results demonstrate that the effects of bacterial inoculation on seedling emergence and on plant growth are independent, and that emergence-stimulating bacteria may inhibit subsequent seedling growth.     

Solar-heating soil for control of damping-off diseases

Solar-heating (45–52°C) moist soil under 50μm thick clear plastic sheeting during summer (Jan.–Feb.) significantly reduced pre-emergence damping-off disease of Pinus radiata D. Don (radiata pine) and Eucalyptus obliqua L'Herit (messmate and stringybark) seed, and also post-emergence mortality among P. radiata seedlings.Phytophthora cinnamomi Rands, Fusarium oxysporum Snyder and Hansen, and Pythium sp. could not be re-isolated from artificially inoculated pine roots after exposure to the solar-heating treatment. Natural infectious propagules of P. cinnamomi were also undetectable in solar-heated soil for up to 16 months following treatment, though infectious propagules of Pythium were detected at low level. The treatment also controlled 11 weed species. Solar-heating a potting mixture temporarily suppressed disease incidence in nursery stock, possibly due to an increase in antagonistic microorganisms.Solar-heating moist soil appears to be particularly attractive in forest nursery practice, as it provides a simple, effective, non-toxic and non-polluting technique for control of soil-borne diseases and weed species.     

Responses of soil dissolved organic matter to long-term plantations of three coniferous tree species

Tree species have significant effects on the availability and dynamics of soil organic matter. In the present study, the pool sizes of soil dissolved organic matter (DOM), potential mineralizable N (PMN) and bio-available carbon (C) (measured as cumulative CO₂ evolution over 63 days) were compared in soils under three coniferous species — 73 year old slash (Pinus elliottii), hoop (Araucaria cunninghamii) and kauri (Agathis robusta) pines. Results have shown that dissolved organic N (DON) in hot water extracts was 1.5–1.7 times lower in soils under slash pine than under hoop and kauri pines, while soil dissolved organic C (DOC) in hot water extracts tended to be higher under slash pine than hoop and kauri pines but this was not statistically significant. This has led to the higher DOC:DON ratio in soils under slash pine (32) than under hoop and kauri pines (17). Soil DOC and DON in 2 M KCl extracts were not significantly different among the three tree species. The DOC:DON ratio (hot water extracts) was positively and significantly correlated with soil C:N (R² = 0.886, P < 0.01) and surface litter C:N ratios (R² = 0.768, P < 0.01), indicating that DOM was mainly derived from litter materials and soil organic matter through dissolution and decomposition. Soil pH was lower under slash pine (4.5) than under hoop (6.0) and kauri (6.2) pines, and negatively correlated with soil total C, C:N ratio, DOC and DOC:DON ratio (hot water extracts), indicating the soil acidity under slash pine favored the accumulation of soil C. Moreover, the amounts of dissolved inorganic N, PMN and bio-available C were also significantly lower in soils under slash pine than under hoop and kauri pines. It is concluded that changes in the quantity and quality of surface litters and soil pH induced by different tree species largely determined the size and quality of soil DOM, and plantations of hoop and kauri pine trees may be better in maintaining long-term soil N fertility than slash pine plantations.     

AM真菌对田间山银花生长、矿质营养及绿原酸含量的影响

Lonicera confusa, a traditional Chinese medicine herb for treating cold, flu, acute fever, and so forth, is often grown artificially in acidic soils and suffers from phosphorus (P) deficiency. A five-year field experiment was carried out to study the colonization rate, growth, nutrition, and chlorogenic acid content of Lonicera confusa seedlings inoculated with arbuscular mycorrhizal (AM) fungi, Glomus etunicatum and Glomus intraradices. Before transplanting into a field, both AM-inoculated and uninoculated control plants were cultured in nursery beds. In the plants inoculated with the AM fungi, the colonization rate decreased linearly with time and a greater decrease was observed in the plants inoculated with G. intraradices than with G. etunicatum, while the AM colonization increased from 0% to 12.1% in the uninoculated control plants 5 years after transplanting. Plant height, crown diameter, number of new branches, and flower yield increased significantly by AM inoculation as compared to the uninoculated control. Phosphorus concentrations in leaves and flowers increased, and plant uptake of nutrients, e.g., nitrogen (N), P, and potassium (K), was also enhanced significantly by AM inoculation. The Lonicera confusa seedlings had a better response to inoculation of G. intraradices than G. etunicatum in both growth and chlorogenic acid content in flowers. In contrast, both plant P uptake and P concentrations in leaves and flowers were similar between two fungal inoculations. The positive responses of Lonicera confusa to AM inoculation in growth, nutrient uptake, flowering, and chlorogenic acid content in flowers suggested that AM inoculation in nursery beds could promote the plant growth and increase chlorogenic acid content in flowers of Lonicera confusa when grown on acidic and P-deficient soils.     

The role of arbuscular mycorrhizal fungi and cattle manure in the establishment of Tocoyena selloana Schum. in mined dune areas

In mined dune areas, revegetation with manured seedlings of native species is a common practice. Establishment of mycorrhized Tocoyena selloana seedlings in the mined coastal sand dunes of Northeast Brazil was tested. In greenhouse, seedlings were grown in substrates with 0, 5, 10, 15 or 20% cattle manure proportions and inoculated with Acaulospora longula, a mixture of native arbuscular mycorrhizal fungi (AMF) or uninoculated. The seedlings responded positively to the inoculation, but growth was limited in the absence of manure, independently of inoculation, and was higher with fertilizing doses ≥10%. The seedlings transplanted to the field were grown in a substrate with 16.5% manure and inoculated with A. longula or Gigaspora albida. After 13 months, 19 AMF species were identified in the rhizosphere and the inoculated plants were more colonized than those uninoculated. Plants associated to G. albida were taller and those associated to A. longula had a tendency of higher biomass than the uninoculated ones. Even though this tendency was not statistically significant, considering the effect on height and the low cost of inoculation it may be a feasible practice to maximize environment restoration.     

Ectomycorrhizal Fungi and Associated Bacteria Provide Protection Against Heavy Metals in Inoculated Pine (Pinus Sylvestris L.) Seedlings

The roles of ectomycorrhizal fungi and bacteria associated with corresponding fungal species in distribution of heavy metals within roots and shoots of inoculated pine (Pinus sylvestris L.) seedlings were determined in this study. The mycorrhizal fungi forming different morphotypes were identified by PCR-RFLP using respective primers for an internal spacer transcribed region (ITS) of fungal rDNA. Amongst five fungal species detected, three were identified as Scleroderma citrinum, Amanita muscaria and Lactarius rufus. These fungi used for inoculation of pine seedlings significantly reduced translocation of Zn(II), Cd(II) or Pb(II) from roots to shoots, and the pattern of metal-accumulation was dependent on the fungal species. Ectomycorrhizae-associated bacteria identified as Pseudomonas were used as an additional component of the pine inoculation. These dual root inoculations resulted in higher accumulation of the metals, especially Zn(II), in the roots compared to the inoculation with fungal species alone. Consequently, dual inoculation of pine seedlings could be a suitable approach for plant protection against heavy metals and successful planting of metal-polluted soils.     

<Emphasis Type="Italic">Pseudomonas</Emphasis> sp. strain AKM-P6 enhances tolerance of sorghum seedlings to elevated temperatures

A thermotolerant strain AKM-P6 of Pseudomonas sp. possessing plant growth-promoting properties was isolated from rhizosphere of pigeon pea grown under semiarid conditions in India. The effect of inoculation with AKM-P6 on survival and growth of sorghum seedlings at elevated temperatures (ET) was investigated under sterile and nonsterile soil conditions. Inoculation with strain AKM-P6 helped sorghum (var CSV-15) seedlings to survive and to grow at elevated temperatures (47–50°C day/30–33°C night) up to 15 days while uninoculated plants died by the fifth day of exposure to elevated temperature. Under sterile and nonsterile conditions, significantly higher root and shoot biomass were recorded in inoculated seedlings as compared to uninoculated control at ET, but this difference was nonsignificant at ambient temperature. Inoculation induced the biosynthesis of high-molecular weight proteins in leaves under elevated temperature, reduced membrane injury, and improved the levels of cellular metabolites like proline, chlorophyll, sugars, amino acids, and proteins. Scanning electron microscopy studies confirmed the colonization and establishment of the organism on the root surface. The 16SrDNA sequence of the strain AMK-P6 showed 97% homology with that of Pseudomonas aeruginosa in the existing database. The results indicate that Pseudomonas sp. strain AKM-P6 can enhance tolerance of sorghum seedlings to elevated temperatures by inducing physiological and biochemical changes in the plant.     

Effects of Arbuscular Mycorrhizal Fungi on Growth and Yield of Cucumber Plants

Abstract

In two pot experiments, cucumber (Cucumis sativus L. cv. Jinlu No. 3) seedlings were each inoculated with one of three arbuscular mycorrhizal fungi (AMF), Glomus mosseae, Glomus intraradices, or Glomus versiforme, or uninoculated. Seedling growth and weight of single fruit were investigated. The results indicated that growth of seedlings was significantly enhanced by G. mosseae, inhibited by G. versiforme, and not significantly influenced by G. intraradices. The dry weight of seedlings inoculated with G. mosseae was 1.2 times its counterparts. The concentrations of nitrogen (N) and phosphorus (P) in roots and magnesium (Mg), copper (Cu), and zinc (Zn) concentration in shoots were increased by inoculating the three AMF, and potassium (K) and iron (Fe) concentrations in shoots decreased significantly. The weights of single fruit of plants preinoculated with G. mosseae and G. versiforme were about 1.4 and 1.3 times higher than those from the uninoculated treatment, respectively.     

Effects of Shrub Islands Created by Rhodomyrtus tomentosa (Aiton) Hassk. on the Growth,Chlorophyll Fluorescence,and Chloroplast ultrastructure of Pine Seedlings in Degraded Land of South China

In degraded land of South China, the shrub Rhodomyrtus tomentosa (Aiton) Hassk. grows in aggregations and creates “shrub islands” with increased soil porosity and soil moisture but reduced soil nutrient content and light penetration. Previous researches indicated that these shrub islands can facilitate establishment of broad‐leaved tree seedlings. Because conifers are commonly used in reforestation projects, we determined whether shrub islands created by R. tomentosa also facilitate coniferous seedlings. Two common conifers, the native Pinus massoniana and the exotic Pinus elliottii, were transplanted on shrub islands and in open spaces (controls) between islands, and their growth, chlorophyll fluorescence, and chloroplast ultrastructure were investigated. Neither of the pine species was facilitated by the shrub islands. P. elliottii grew obviously higher in the open than under the R. tomentosa canopy, while P. massoniana was not facilitated by shrub islands, but it was not hindered either. The reduced growth of P. elliottii on shrub islands was associated with dilation of thylakoids in chloroplasts of mesophyll cells, lowered chlorophyll content, and reduced electron transport rate values. The results of this study indicate that P. elliottii should be transplanted in open spaces, and P. massoniana can be transplanted in open spaces or on shrub islands as part of restoration efforts, and the restoration technology of shrub island should be carefully used in degraded land of South China according to the species identity. Copyright © 2015 John Wiley & Sons, Ltd.     

Use of mycorrhizal seedlings on recovery of mined dunes in northeastern Brazil

The exploitation of minerals from coastal dunes in northeastern Brazil requires subsequent revegetation for ecosystem recovery. In mined dunes areas, we have compared the growth of Guazuma ulmifolia and Tabebuia roseo-alba seedlings using substrates containing 10 or 15% of cattle manure, uninoculated or inoculated with a mixture of native arbuscular mycorrhizal fungi (AMF) or exotic AMF (Acaulospora longula). The inoculated plants had a higher percentage of colonization than those that were uninoculated. Plants of G. ulmifolia had the highest growth when inoculated with native AMF and fertilized with 10% manure or inoculated with A. longula and fertilized with 15% manure. In general, fertilization with 15% manure did not produce greater seedling development and had a negative effect on the effectiveness of the symbiosis. Twenty one AMF species were recorded in the planting areas at the end of the experiments, with a predominance of species that form acaulosporoid spores in areas with T. roseo-alba and gigasporoid spores in areas with G. ulmifolia plants. The incorporation of 10% cattle manure and native AMF in the substrate of T. roseo-alba and G. ulmifolia seedlings contributes to the initial establishment of plants in the field and to the incorporation of AMF propagules in the soil of the revegetated mined dunes.     

Do oribatid mites (Acari: Oribatida) show a higher preference for ubiquitous vs. specialized saprotrophic fungi from pine litter?

Previous studies of oribatid mite feeding preferences for different saprotrophic fungi were limited to ubiquitous fungal species, whereas saprophytes specialized to decompose particular substrates have been neglected. We examined the preference of seven oribatid mite species (Adoristes ovatus, Eniochthonius minutissimus, Eueremaeus silvestris, Nothrus silvestris, Oppiella subpectinata, Porobelba spinosa and Spatiodamaeus verticillipes) for nine autochthonous saprotrophic fungi from Scots pine litter (Pinus sylvestris). Among the fungal species offered were specific coniferous litter colonizers (Allantophomopsis lycopodina, Ceuthospora pinastri, Hormonema dematioides, Scleroconidioma sphagnicola, Verticicladium trifidum, Marasmius androsaceus and Sympodiella acicola) and two ubiquitous species (Cladosporium herbarum and Oidiodendron griseum). The fungi were inoculated on fragments of pine needles and offered simultaneously and separately to the mites. Our main hypothesis, that oribatid mites (usually occurring in more than one type of ecosystems) would prefer the ubiquitous fungal species rather than those specific to pine litter, was supported only partly. The ubiquitous C. herbarum was highly preferred by all studied mites, but most of them preferred one or more of the specialized fungi with similar intensity. The basidiomycete M. androsaceus along with sterile needles were consistently avoided by all mites in all experiments. Our results do not support the hypothesis, that the “true” fungivorous oribatid mites in traditional sense are more selective fungal feeders than are the “unspecialized” panphytophagous ones. We observed no gradation in preference of fungi for oribatid mites as a group, but rather a discontinuous and dynamic mosaic with particular mites preferring particular fungal species. This heterogeneous mosaic shapes the feeding niches occupied by particular oribatid mite species and probably reduces competition for food source among numerous species coexisting in a given habitat and time.     

Survival of sclerotia of Macrophomina phaseolina and Sclerotium cepivorum after drying and wetting treatments

Exposure of sclerotia of Macrophomina phaseolina to 0 and 33% relative humidity (r.h.) for 12 weeks and of Sclerotium cepivorum to 0, 33 and 55% r.h. for 20 weeks did not reduce their germinability on agar. Exposure to 78% r.h. caused high loss of germinability in M. phaseolina and complete loss in S. cepivorum. After 7-day exposures respective moisture contents of sclerotia of M. phaseolina and S. cepivorum were 1 and 2% at 0% r.h.; and 10 and 14% at 78% r.h. M. phaseolina sclerotia held at 0% and 33% r.h. in desiccators for several times up to 12 days did not decrease in subsequent survivability in moist soil, unlike sclerotia held at 78% r.h. for 4 days.More sclerotia of M. phaseolina were colonized by fungi and Streptomyces spp. on alkaline soil than on acid soil. On alkaline soil twice as many sclerotia were colonized after exposure to 0% r.h. as after exposure to 33, 55 and 78% r.h. Colonization of S. cepivorum sclerotia was as high on acid as on alkaline soil and 3 times as high on sclerotia treated at 0% r.h. as on those treated at higher r.h. Attempts to ascertain the effects of colonization on sclerotial viability were unsuccessful. Incubation of sclerotia of M. phaseolina in moist Rumsford sandy loam (50% m.h.c.) for 20 weeks reduced survivability by 43%. At room temperature, alternate drying and wetting of soil containing sclerotia did not appreciably affect survivability of either pathogen. Survivability of S. cepivorum sclerotia was highest when the sclerotia were incubated in air-dried soil (2–3% m.h.c.) for 20 weeks.Incidence of white rot on onion seedlings transplanted to S. cepivorum-infested soil was higher in soil that had been air-dried for 20 weeks than in soil that had been alternately wetted and dried. Sclerotia that were exposed to 0% r.h. for 7 days before soil incubation produced little white rot.     

Survival of bacteria introduced into soil by means of transport by Lumbricus rubellus

Four strains of bacteria, Rhizobium leguminosarum biovar trifolii, Pseudomonas fluorescens, Pseudomonas cepacia, and Flavobacterium sp., were introduced into loamy sand and then transported by earthworms of the species Lumbricus rubellus to uninoculated soil. Cell densities recovered from the earthworm gut and casts (both expressed per gram dry material) were significantly lower (up to 3 log units) than cell densities recovered from the inoculated soil. Total bacterial counts in casts were similar to those in the inoculated soil. In casts excreted into a sterile environment numbers of colony-forming units (CFU) increased, suggesting a favourable environment for growth. In casts excreted in a non-sterile environment, cell densities of introduced strains decreased. Casts therefore did not offer the introduced bacteria a protective micro-environment for survival in the bulk soil. Transport by worms of R. leguminosarum biovar trifolii and of P. fluorescens appeared to occur mostly by means of cast production; with the Flavobacterium sp. and P. cepacia a large proportion of the cells was possibly transported on the skin of earthworms.     

Tomato seedling development is improved by a substrate inoculated with a combination of rhizobacteria and fungi

Chile's seedling production industry has been growing for the last 10 years, and demand has actually reached 1250 million seedlings per year. This system has special relevance due to the high cost of seeds. In addition, there is an increasing demand for substituting synthetic agrochemicals. Therefore, the potential use of plant growth-promoting rhizobacteria (PGPR) in tomato production has been investigated. Before sowing, the micro-organisms provided by Biogram S.A. were inoculated into the substrate diluted in 250 mL/L unchlorinated water. The experiment was laid out in a ‘split-plot’ design with the two plant substrates as main plots and the inoculants as subplots, including six replicates per treatment. Tomato seedlings were grown using two different plant substrates: a mixture of 70% peat and 30% perlite by volume, and a substrate with 20% peat, 20% perlite and 60% compost by volume, both inoculated with Bacillus subtilis or Pseudomonas fluorescens or Bioroot®, which is a commercial product containing B. subtilis, P. fluorescens, Trichoderma harzianum, yeast, algae and Nocardia. For control, uninoculated tomato seedlings were grown on the respective plant substrates. Variance analysis did not identify significant interactions between substrate type (main plots) and inoculation treatment (subplots), P ≤ 0.05. There were significant differences between inoculants (P ≤ 0.05). Means were compared by using the Tukey's multiple range test. Tomato growth in terms of leaf area (cm²/plant) and shoot and root dry weight (g/10 plants) was improved for the seedlings grown on the substrate with 70% peat and 30% perlite, compared to the compost containing an alternative that is valid for both uninoculated perlite peat and all inoculated treatments where perlite peat was outstanding. Inoculation with Bioroot® improved the leaf area, shoot dry weight, root dry weight, radical contact area, volume of roots and root forks compared with the control without inoculation, when both plant substrates were analysed together. Thus, inoculation with Bioroot® can be recommended as an alternative to tomato seedling growers' dependence on synthetic agrochemicals.     

Characterization of Heavy Metal-Resistant Endophytic Yeast Cryptococcus sp. CBSB78 from Rapes (Brassica chinensis) and Its Potential in Promoting the Growth of Brassica spp. in Metal-Contaminated Soils

A Cd-, Pb-, Zn-, Cu-resistant endophytic yeast CBSB78 was isolated from surface-sterilized rape roots. The isolate was identified as Cryptococcus sp. based on the ITS1?C5.8S?CITS2 sequence analysis. The strain was resistant to 20 mM Cd²⁺, 20 mM Pb²⁺, 10 mM Zn²⁺, and 7 mM Cu²⁺. The yeast CBSB78 was a low indole-3-acetic acid (IAA) producer and possessed low 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. Overall, 29.4?C244 % of survival rates increased and the dry weight of Brassica alboglabra showed a 41.1 % increase when it was inoculated into the seedlings. The inoculation of CBSB78 could also increase the extraction amounts of Cd, Pb, and Zn by B. alboglabra simultaneously in the multi-metal contaminated soils, which showed the potential to improve extraction efficacy of Cd, Pb, Zn by B. alboglabra seedlings in the field.     

Detection of GFP-labeled Paenibacillus polymyxa in autofluorescing pine seedling tissues

Paenibacillus polymyxa P2b-2R is a bacterium that originated from internal lodgepole pine (Pinus contorta var. latifolia (Dougl.) Engelm.) seedling stem tissue and fixes nitrogen (N) in association with pine and western red cedar (Thuja plicata Donn.). To evaluate endophytic colonization by this microorganism, we generated P. polymyxa P2b-2Rgfp, a green fluorescent protein (GFP)-labeled derivative of P2b-2R, and grew pine seedlings that were inoculated with the marked strain in a N-limited soil. Tissue disintegration during sample preparation precluded examination of needles for the GFP-labeled endophyte but GFP was detected on roots and in stems of 2- to 14-week-old pine seedlings using confocal laser scanning microscopy. Due to excessive autofluorescence of seedling tissues, labeled bacteria were clearly discernible only in stem tissues of 4- and 6-week-old seedlings. P2b-2Rgfp colonized the root surface extensively and was detected inside the stem cortex, primarily intracellularly. Some labeled bacteria appeared to contain endospores and none were detected in vascular tissues. We conclude that P. polymyxa P2b-2R is capable of endophytic colonization of pine seedlings with specific colonization sites that include the stem cortex but that GFP labeling is of limited value for localization of endophytic bacteria in pine seedling tissues.     

Variation of N,P, K,Ca, Mg,Mn, Zn,and al in slash pine foliage

Abstract

The seasonal patterns of foliage nutrient concentrations and contents were monitored for two growing seasons in an 11‐year—old Pinus el1iottii stand. In the first growing season after needle initiation, N, P, K, Mg, and Zn concentrations decreased, but this was followed by an increase in the fall and winter months. Another drop in concentration of all elements, except P, occurred in the second growing season. Decreases in total contents indicated that this drop was a result of translocation to other tissues. In contrast to the mobile elements, the concentration and fascicle contents of Ca, Mn, and Al increased with aging of the needles.

Between‐tree variability was least for N, P, and Zn and the N, K, Mg, Mn, and Zn in the current foliage had consistently lower variation than that in the 1‐year‐old foliage. Between‐tree variation for K was lower in the winter than the spring.

For pine foliage, recommended sampling period for N, P, Mg, and Zn is mid to late summer and for the other elements it is late fall to late winter.

There are several sources of variation that influence the level of nutrients in tree foliage. The most important of these, apart from the tree nutrient status, are seasonal fluctuations, variation between trees, and age of needles . Smaller sources of variation are associated with position of the needles within the crown, diurnal changes, year to year variation, and analytical errors^1,2. These variables must be studied in order to develop suitable sampling techniques and in Pinus this has been undertaken for P. banksiana ¹, P. taeda ³, P. strobus ⁴, P. resinosa ⁴, P. sylvestris ⁵, and P. radiata ^6,7. However, foliage sampling has not been studied in detail for slash pine (Pinus elliottii Englem var. elliottii) and earlier studies with other pines have been largely confined to temperate or cool climates.

This study reports the variation in elemental concentrations with season, age of foliage, and between slash pine trees growing in a subtropical climate in Florida.     

Fungal growth and effects of different wood decomposing fungi on the indigenous bacterial community of polluted and unpolluted soils

Thirty-two different basidiomycete isolates were inoculated separately into contaminated soil and the soil colonization ability was assessed visually. Large differences in the colonization ability and growth patterns were found between the different fungi. Phospholipid fatty acids (PLFAs) were extracted from the soils of the seven isolates with the best colonizing ability. All PLFAs that were not found in pure cultures of the seven fungi were considered as bacterial PLFAs. The bacterial PLFA data were subjected to principal component analysis (PCA) to indicate changes in the indigenous bacterial community. The experiment was repeated in a sandy agricultural soil. The bacterial PLFA patterns were altered when fungi were inoculated into soil, irrespective of whether it was polluted or not. In particular the PLFA cy19:0, indicative of Gram-negative bacteria, was higher in fungal-inoculated soil than in uninoculated controls. The PLFA patterns for each fungal treatment were distributed more or less similarly in the PCA plots of both contaminated and sandy agricultural soil. Soil inoculated with Antrodia vaillantii, Hypholoma fasciculare or Recinicium bicolor was considerably different from the control along PC 1. Soil inoculated with Phanerochaete chrysosporium was characterized by different values along PC 2 compared with the other fungal soils.     

N2-fixation and growth promotion in cedar colonized by an endophytic strain of Paenibacillus polymyxa

Inoculation of western red cedar with Paenibacillus polymyxa P2b-2R, an endophytic diazotroph of a pine, was previously shown to result in biological nitrogen fixation (BNF) in seedlings grown under N-limited conditions, but biomass accumulation was reduced after a 9-month growth period. To determine if the seedling growth reduction was temporary, we inoculated cedar seed with strain P2b-2R and grew seedlings for up to 13 months in a N-limited soil mix containing 0.7 mM of available N labeled as Ca(¹⁵NO₃)₂. P2b-2R developed a persistent endophytic population comprising 10²–10⁶?cfu g^?1 plant tissue inside pine roots, stems, and needles. At the end of the growth period, P2b-2R had reduced ¹⁵N foliar N abundance by 36 % and increased shoot biomass by 46 % compared to controls. Our results indicate that inoculated seedlings derived 36 % of foliar N from the atmosphere and suggest that BNF by P. polymyxa can significantly enhance growth of cedar in a N-limited soil if seedlings are grown for a sufficient amount of time. These findings support the hypothesis that endophytic diazotrophs may facilitate regeneration and growth of western red cedar at N-poor sites.