Does nitrogen concentration affect relative uptake rates of nitrate,ammonium, and glycine?

Plant roots are exposed to a variety of nitrogen forms (e.g., nitrate, ammonium, amino acids) and take up these forms at different rates. Many studies have investigated whether plants prefer nitrate, ammonium, or amino acids; but studies may not be comparable because they used substrate concentrations between 100 and 2000 μmol L^–1. This study tests the hypothesis that substrate concentrations from 10 to 1750 μmol L^–1 affect plant preference for N forms. Nitrogen uptake by the herb Ocimum basilicum and the evergreen tree Eucalyptus regnans was examined by placing roots of intact seedlings in equimolar mixtures of nitrate, ammonium, and glycine in which one of the N forms was ¹⁵N‐labelled (and ¹³C‐labelled in the case of glycine). In both species, preference for N forms was affected by substrate concentration. At 10 μmol L^–1 (O. basilicum) or 10 and 50 μmol L^–1 (E. regnans), rates of N uptake did not differ among N forms. At substrate concentrations of 50 μmol L^–1 and greater O. basilicum took up ammonium the fastest, glycine the slowest, and nitrate at an intermediate rate. At substrate concentrations from 100 to 1750 μmol L^–1, E. regnans took up ammonium the fastest with glycine and nitrate taken up at slower rates. The absence of significant differences at lower concentrations was a true biological effect rather than a function of larger relative errors. This study demonstrates that substrate concentration has a large effect on plant preference for N forms, and sounds a warning for studies of N nutrition that do not consider the concentration‐dependence of plant preference for N forms.     

Do climate warming and plant species richness affect potential nitrification, basal respiration and ammonia-oxidizing bacteria in experimental grasslands?

Ammonia-oxidizing bacteria (AOB) are key organisms in the N cycle, as they control the first, rate-limiting step of the nitrification process. The question whether current environmental disturbances, such as climate warming and plant diversity losses, select for a particular community structure of AOB and/or influence their activity remains open. The purpose of this research was to study the impact of a 3 °C warming and of plant species richness (S) on microbial activity and diversity in synthesized grasslands, with emphasis on the nitrification process and on the diversity (community structure and richness) of ammonia-oxidizing bacteria (AOB). We measured soil chemical characteristics, basal respiration, potential nitrification and AOB diversity in soils under increasing plant species richness (S = 1, S = 3, S = 9) at ambient and (ambient +3 °C) temperature. Species were drawn from a 9-species pool, belonging to three functional groups: forbs, legumes and grasses. Mixtures comprised species from each of the three functional groups. Warming did not affect AOB diversity and increased potential nitrification at S = 3 only. Under warmed conditions, higher plant species richness resulted in increased potential nitrification rates. AOB richness increased with plant species richness. AOB community structure of monocultures under legumes differed from those under forbs and grasses. Clustering analysis revealed that AOB community structure under legume monocultures and mixtures of three and nine species grouped together. These results indicate that functional group identity rather than plant species richness influenced AOB community structure, especially through the presence of legumes. No clear relationship emerged between AOB richness and potential nitrification whatever plant species richness and temperature treatment. Our findings show a link between aboveground and belowground diversity, namely plant species richness, AOB richness and community structure. AOB richness was not related to soil processes, supporting the idea that increased diversity does not necessarily lead to increased rates of ecosystem processes.     

Is Dichogaster bolaui (Michaelsen, 1891) the first domicole earthworm species?

The term domicole, derived from the Latin domus (house) and colere (to inhabit), applies to species that are able (or adapted) to live in urban dwellings. Examples of domicole species include, for example, Psocoptera (dust lice) and Arachnida (spiders). However, so far, no earthworm species has been described as being capable of adapting to this type of niche. It seems, however, that the tropical species Dichogaster bolaui (Michaelsen, 1891) might be the first earthworm species to be defined as a domicole species.D. bolaui is native to eastern Africa. However, it has a wide distribution in tropical and subtropical regions. Additionally, it has been recorded in greenhouses in temperate countries and has also been observed in bathtubs and toilet bowls in Finland and Sweden. We collected data regarding the abundant presence of this species in bathtubs, showers, and sewer pipes in a student dormitory in Szombathely, Hungary, and in a private house in Haifa, Israel. Our data suggest that D. bolaui independently colonized the sewerage systems several times and established breeding populations and, therefore, has become a domicole.     

GM(0,N)灰色预测模型在云南小春作物产量预报中的应用

利用1972-2004年的云南小春作物单产和与其灰关联度最优的10个气象因子时间序列,采用原始序列和残差序列进行GM（0,N）预测建模,对云南小春作物产量趋势进行预测.结果表明：通过残差修正后所建立的云南省小春作物产量预测模型适用于产量趋势预报,通过了小概率统计检验,预报结果有一定的参考价值.     

Is there food competition between Hormogaster elisae (Oligochaeta,Hormogastridae) and soil microarthropods at El Molar (Madrid)?

In a previous paper [M. Gutiérrez, M. Ramajo, J.B. Jesús, D.J. Díaz, The effect of Hormogaster elisae (Hormogastridae) on the abundance of soil Collembola and Acari in laboratory cultures, Biol. Fertil. Soils 37 (2003) 231–236] we reported the negative effect of the earthworm Hormogaster elisae on microarthropods at El Molar (Madrid, Spain). This paper examines the possibility of food competition existing between them in laboratory cultures.Microcosms were constructed from plastic boxes and a cage made from 2 mm mesh, with two earthworms inside, was placed at the centre of each. The soil of the cage was enriched with defaunated soil sieved to 0.2 mm or with defaunated, homogenised topsoil (first 3 cm) to increase the quantity of organic matter. In the controls, earthworms were absent from both microcosm compartments. The microcosms were kept at 15 °C for 21 days before being dismantled and the microarthropods extracted using the Berlese–Tulgren method, identified and counted. The numbers inside and outside the cages were then compared, and the data obtained were subjected to analysis of variance (ANOVA).In the microcosms enriched with the ≤0.2 mm soil fraction, nearly all the microarthropods decreased in number inside the cages, when earthworms were present despite containing extra organic matter. In the controls, no significant differences were seen between the compartments, suggesting that these particles are not used as a food source by microarthropods. In the microcosms enriched with homogenised topsoil, the microarthropods were just as numerous in both compartments or indeed even more numerous inside the cage. This shows that this material nullifies the negative effect of earthworms on microarthropod numbers. The soil horizons closest to the surface might provide food resources used by both groups, for which they compete.     

Can the thermodynamic melting temperature of sucrose, glucose, and fructose be measured using rapid-scanning differential scanning calorimetry (DSC)?

The loss of crystalline structure in sucrose, glucose, and fructose has been shown to be due to the kinetic process of thermal decomposition (termed apparent melting), rather than thermodynamic melting. The purpose of this research was to investigate whether or not it is possible to scan quickly enough to suppress the kinetic process of thermal decomposition and reach the thermodynamic melting temperature of these sugars using a new rapid-scanning DSC. Indium, a thermodynamic melting material, and sucrose, glucose, and fructose were analyzed at three heating rates from 1 to 25 °C/min using standard DSC and at seven heating rates from 50 to 2000 °C/min using rapid-scanning DSC. Thermodynamic melting was achieved when the onset temperature (T(m onset)) of the endothermic peak leveled off to a constant value independent of heating rate. The T(m onset) for indium was constant (156.74 ± 0.42 °C) at all heating rates. In the case of fructose, the T(m onset) increased considerably until a heating rate of approximately 698 °C/min, after which the average T(m onset) for the remaining three heating rates was constant at 135.83 ± 1.14 °C. Thus, 135.83 °C is proposed to be the thermodynamic melting temperature of fructose. It is important to note that the heating rate at which this thermodynamic melting temperature is achieved is most likely influenced by the type and amount of trace components (e.g., water and salts) contained in the fructose, which are known to vary widely in sugars. In the case of sucrose and glucose, thermodynamic melting temperatures were not able to be obtained, because the upper limit heating rate used was not fast enough to suppress thermal decomposition and achieve thermodynamic melting, perhaps due to the higher apparent T(m onset) for sucrose and glucose compared to that for fructose.     

Does phosphite,a reduced form of phosphate contribute to phosphorus nutrition in corn (Zea mays L.)?

Although fungicidal properties of phosphite have been recognized, its use as a fertilizer-P is still being debated. The objective of this study was to evaluate the effect of foliar-applied phosphite (HPO₃^?2) on the growth and yield of corn (Zea mays L.). Traditional fertilizer-P was also applied to compare the efficacy of phosphite. Dry matter yield, grain yield, and tissue P concentrations (grain, leaf, and stem) were evaluated in two field and two greenhouse studies in Oklahoma for 2 years. A commercial phosphite solution which contains 200?g P kg^?1 was sprayed at the rate of 2.34?L ha^?1 at different growth stages. Foliar phosphite did not increase dry matter and grain yield. In general, P concentrations in the grain, leaf, and stem were unaffected regardless of number of applications. Farmers should take with caution while using phosphite as a fertilizer to correct P deficiency for corn production.     

‘Neodomesticates’ of the Himalayan allium spices (Allium species) in Uttarakhand,India and studies on eco-geography and morphology

Genetic Resources and Crop Evolution - The study on Himalayan allium spices was undertaken with specific reference to commercially important taxa belonging to the genus Allium viz. A. stracheyi...     

Does the influence of earthworms on water infiltration, nitrogen leaching and soil respiration depend on the initial soil bulk density? A mesocosm experiment with the endogeic species Metaphire posthuma

Soil compaction has a negative impact on both earthworm abundance and diversity. Recent studies, however, suggest that earthworm cast properties are not influenced by the initial soil bulk density. With time, earthworms could therefore transform soils with different bulk densities into a soil with the same physical state and thus with a similar ecological functioning. This study aimed to test this hypothesis in two laboratory incubation experiments. First, we measured the influence of soil bulk density (1.1 or 1.4?g?cm^?3) on the production of cast by the endogeic earthworm species Metaphire posthuma. In a second experiment, we investigated the effect of M. posthuma on water infiltration, NH ₄ ⁺ , and NO ₃ ^? leaching and soil respiration at the same two soil bulk densities. Although initially higher, earthworm casting activity in soil at 1.4?g?cm^?3 decreased until it reached the same level of activity as earthworms in soil at 1.1?g?cm^?3. This behavioral plasticity led to a transformation of compacted and loose soils, with their own functioning, to a third and similar state with similar hydraulic conductivity, nitrogen leaching, and soil respiration. The consequences for soil organization and soil functioning are discussed.     

Will future climate change threaten a range restricted endemic species, the quokka (Setonix brachyurus), in south west Australia?

Range-restricted species, such as regional endemics, possess traits that may make them particularly vulnerable to environmental change. The quokka, Setonix brachyurus, is a small macropod, endemic to south-western Australia and two adjacent islands. Climatic factors appear to play a role in defining the distribution of this species. Mainland populations are historically restricted to areas with an annual average rainfall in excess of 700 mm and their current distribution is almost completely confined within the 1000 mm rainfall isohyet. As such, the predicted increasing aridity of south-western Australia due to climate change is likely to threaten the continued persistence of the quokka on the mainland. To examine this possibility, we modelled the distribution of the quokka with Maxent using records of occurrence and a combination of historical climate (1961-1990) and habitat variables. Future projections of this distribution were then examined assuming two simple dispersal scenarios (zero and full migration) and three climate-change scenarios of increasing severity for 2030, 2050 and 2070. The predictive performance of the distribution model generated under historical climate conditions was high (AUC > 0.8), with annual precipitation contributing the most information to the model. Except for the low-severity climate-change scenario under the full dispersal assumption, the future projected distribution of quokka was shown to contract over time. The extent of range contraction tended to increase with the severity of the climate-change scenario, with the species predicted to lose almost all range by the year 2070 under the most extreme climate-change scenario. The results indicate the importance of identifying potential refuges for the quokka (i.e. areas where the species is predicted to persist) and defining management strategies to protect these areas from threatening processes.     

Effects of afforestation with four unmixed plant species on the soil–water interactions in a semiarid Mediterranean region (Sicily, Italy)

Purpose

An assessment of the effect of plant cover on the properties of four afforested soils in central Sicily was performed with the aim of discriminating among them after 60?years of afforestation.

Materials and methods

Chemical and biochemical soil analyses were coupled to fast field cycling (FFC) NMR relaxation investigations in order to monitor surface interactions of water in water-saturated soils.

Results and discussion

The traditional soil analyses revealed that the most stable soil properties such as soil texture and pH are not affected by 60?years of afforestation. Soils developed under eucalyptus trees showed larger amounts of hydrophilic organic matter as compared to the soils under pines and cypresses. FFC-NMR relaxometry data revealed that water, partitioned in clay-, loam-, and sand-type pores, showed longitudinal relaxation time values affected by the interactions with the soluble carbon content.

Conclusions

The results of the present study evidenced the potential of FFC-NMR relaxometry in differentiating the effect of diverse plant cover on chemical and hydrological properties of soils developed on the same parent material. In fact, in contrast with the traditional physicochemical and biochemical soil characterizations, which were unable to reveal differences among soils afforested with different plant species, FFC-NMR was capable of monitoring differences in water dynamics as affected by the presence of the most soluble soil organic material.     

Declining stocks of Lake Tana’s endemic Barbus species flock (Pisces, Cyprinidae): natural variation or human impact?

The only remaining species flock of endemic, large cyprinid fishes is found in Lake Tana, Ethiopia. A monthly experimental trawl program was conducted in 1991-1993 and 1999-2001, sampling 12 stations distributed over three habitats differing in depth and distance to shore. The aim was to compare the total abundance, spatial distribution and proportion of juveniles of the most common Barbus species in the Bahar Dar Gulf between both periods. We found a sharp reduction (75%) in total abundance, both in number and biomass of the Barbus species and even more (90%) in the number of juveniles between the two periods. However, the spatial distribution of the different Barbus species over the three habitats had not changed. High natural variability in fish stocks might be expected in environmentally unstable lakes. Although strongly pulsed (seasonal), Lake Tana is a relatively stable system. No major differences were found in abiotic parameters in 1990s that could have caused the dramatic changes in abundance. The most likely explanation is the negative impact of the motorised, commercial gillnet fishery targeting the spawning aggregations of these barbs. The drastic decline in juveniles points especially towards serious recruitment over-fishing. The results stress the need for the immediate development of a sound management plan focussing on fishing effort restrictions during the Barbus breeding season.     

Phylogenetic analysis of complete 5′ external transcribed spacers of the 18S ribosomal RNA genes of diploid Aegilops and related species (Triticeae, Poaceae)

PCR systems were designed to amplify the entire 5 external transcribed spacer (ETS) region of the 18S rRNA gene of all the diploid species of Aegilops and several other taxa closely related to domesticated wheat. Phylogenetic analysis was performed on the complete ETS sequences using the neighbor-joining, maximum parsimony, and maximum likelihood methods. Among the individual taxa studied, speciation in Secale is very recent. In the case of the A genome diploids, the results support the theory that the A genomes of wheat have experienced reticulate evolution owing to introgression. The B and G genomes of tetraploid domesticated wheats form a clade with Ae. speltoides in which the B genome diverged first and the G genome more recently. It was demonstrated that the complete ETS sequences of the Triticeae yield coherent phylogenetic information. The ETS is a useful tool for studying the phylogeny of closely related species.     

Molecular diversity of restriction enzyme sites, Indels and upstream open reading frames (uORFs) of 5′ untransalted regions (UTRs) of Waxy genes in Triticum L. and Aegilops L. species

5′ Untransalted regions (UTR) sequences of Waxy genes were amplified from all 81 Triticum L. and Aegilops L. species by PCR with specific primers. It was found that the sequence length at 7D loci was longer than that 7B and 7A. These sequences contained 170 singleton variable sites and 484 polymorphic sites and that the average length of Indels was 8.5?bp. There were abundant regions of restriction enzyme sites and two regions of simple sequence repeat, “GAA” and “CTGA”, in all sequences. A total of 65 uORFs were detected and classed into 37 types, with the variation in uORFs mainly due to single nucleotide polymorphisms (SNPs), and also to the presence of Indels. All sequences in tetraploids and hexaploids could be grouped into Types A, B, I, II, GI and GII based on sequence variation. Restriction enzyme sites, Indel polymorphisms and the classes of uORFs present together indicated that Type I was more similar to Ae. tauschii whereas Type II was more similar to Type B, and both more similar to Ae. longissima; Type A was more similar to Ae. speltoides. Population analysis was performed and Neighbour-joining trees derived from different species, types and accessions further confirmed that the ancestors of T. urartu, Ae. speltoides, Ae. longissima and Ae. tauschii were involved to the evolution of common wheat, and also implied that Ae. longissima might have participated later than Ae. speltoides. 5′ UTRs of Waxy genes in tetraploid and hexaploid species conserved characters from their respective progenitors when compared with diploid. For the first time, we are able to conclude there is abundant variation in SNPs, Indels and uORFs between 5′ UTRs of Waxy genes from different species related to common wheat, and suggest that further research could help to understand Waxy gene function more deeply and hence improve wheat breeding. Our results also show that three hexaploid species in China have unique diversity in the 5′ UTR of their Waxy gene.     

‘Kalhar’ [Blumea lacera (Burm.f.) DC. Asteraceae]: a wild species used in preparation of traditional cuisine “Umbadiyu” in Dungri (Valsad), South Gujarat,India

Genetic Resources and Crop Evolution - A plant species locally called ‘Kalhar’ [Blumea lacera (Burm.f.) DC.] was identified for plant genetic resources value during exploration and...     

Genetic identity and relationships of Iranian apple (Malus?×?domestica Borkh.) cultivars and landraces, wild Malus species and representative old apple cultivars based on simple sequence repeat (SSR) marker analysis

In order to shed light on the role of Iran in apple evolution and domestication, we chose to investigate the relationships of a collection of 159 accessions of wild and domesticated apples including Iranian indigenous apple cultivars and landraces, selected wild species, and old apple scion and rootstock cultivars from different parts of the world. The majority of the wild species belonged to M. sieversii, which is widely believed to be the main maternal wild ancestor of domestic apples, from Kazakhstan and M. orientalis, which is one of the probable minor ancestors of domestic apples, from Turkey and Russia located on the east and west of Iran, respectively. The accessions were assigned into six arbitrary populations for the purpose of generating information on genetic parameters. Nine simple sequence repeat (SSR) loci selected from previous studies in apple were screened over DNA extracted from all the accessions. Results showed that all SSR loci displayed a very high degree of polymorphism with 11–25 alleles per locus. In total, there were 153 alleles across all loci with an average of 17 alleles per locus. The SSR allelic data were then used for estimation of population genetic parameters, including genetic variation statistics, F-statistics, gene flow, genetic identity, genetic distance and then cluster analysis using POPGENE 1.32 software. The F-statistics and gene flow in particular, showed that there was more intra-population than between population variation. The genetic identity and genetic distance estimates, and the dendrogram generated from the un-weighted pair group arithmetic average (UPGMA) method of cluster analysis showed that the Iranian cultivars and landraces were more closely related to M. sieversii from Central Asia (east of Iran) and M. orientalis native to Turkey and Russia than to other accessions of Malus species. Also, the old apple cultivars from different parts of the world have a closer genetic relationship to M. sieversii, M. orientalis and the Iranian apples, than to other wild species. Based on these results, we suggest that the Iranian apples may occupy an intermediate position between the domesticated varieties and wild species. We propose that Iran could be one of the major players in apples’ domestication and transfer from Central Asia to the western countries.     

‘Ladakhi tea’ <Emphasis Type="Italic">Bidens pilosa</Emphasis> L. (Asteraceae): a cultivated species in the cold desert of Ladakh Himalaya,India

Bidens pilosa L., a less-known cultivated tea species was collected from cold desert of Ladakh Himalaya, Jammu and Kashmir, India during 2004. The freshly harvested leaves are used in preparation of ‘Ladakhi tea’ locally known as ‘Saja’ or ‘Soljaa’ in cold desert of Ladakh Himalaya, Western Himalaya, Jammu and Kashmir. The local inhabitants were growing this species in their kitchen garden for this use. In the present communication, the method of preparation of this beverage is also discussed.