A global experiment suggests climate warming will not accelerate litter decomposition in streams but might reduce carbon sequestration

The decomposition of plant litter is one of the most important ecosystem processes in the biosphere and is particularly sensitive to climate warming. Aquatic ecosystems are well suited to studying warming effects on decomposition because the otherwise confounding influence of moisture is constant. By using a latitudinal temperature gradient in an unprecedented global experiment in streams, we found that climate warming will likely hasten microbial litter decomposition and produce an equivalent decline in detritivore-mediated decomposition rates. As a result, overall decomposition rates should remain unchanged. Nevertheless, the process would be profoundly altered, because the shift in importance from detritivores to microbes in warm climates would likely increase CO(2) production and decrease the generation and sequestration of recalcitrant organic particles. In view of recent estimates showing that inland waters are a significant component of the global carbon cycle, this implies consequences for global biogeochemistry and a possible positive climate feedback.     

Interbasin water transfer, riverine connectivity, and spatial controls on fish biodiversity

Background

Large-scale inter-basin water transfer (IBWT) projects are commonly proposed as solutions to water distribution and supply problems. These problems are likely to intensify under future population growth and climate change scenarios. Scarce data on the distribution of freshwater fishes frequently limits the ability to assess the potential implications of an IBWT project on freshwater fish communities. Because connectivity in habitat networks is expected to be critical to species'' biogeography, consideration of changes in the relative isolation of riverine networks may provide a strategy for controlling impacts of IBWTs on freshwater fish communities.

Methods/Principal Findings

Using empirical data on the current patterns of freshwater fish biodiversity for rivers of peninsular India, we show here how the spatial changes alone under an archetypal IBWT project will (1) reduce freshwater fish biodiversity system-wide, (2) alter patterns of local species richness, (3) expand distributions of widespread species throughout peninsular rivers, and (4) decrease community richness by increasing inter-basin similarity (a mechanism for the observed decrease in biodiversity). Given the complexity of the IBWT, many paths to partial or full completion of the project are possible. We evaluate two strategies for step-wise implementation of the 11 canals, based on economic or ecological considerations. We find that for each step in the project, the impacts on freshwater fish communities are sensitive to which canal is added to the network.

Conclusions/Significance

Importantly, ecological impacts can be reduced by associating the sequence in which canals are added to characteristics of the links, except for the case when all 11 canals are implemented simultaneously (at which point the sequence of canal addition is inconsequential). By identifying the fundamental relationship between the geometry of riverine networks and freshwater fish biodiversity, our results will aid in assessing impacts of IBWT projects and balancing ecosystem and societal demands for freshwater, even in cases where biodiversity data are limited.     

Triadimefon enhances growth and net photosynthetic rate in NaCl stressed plants of Raphanus sativus L.

The effect of sodium chloride and triadimefon (TDM) on the chlorophyll (Chl) content, net photosynthetic rates (P_N), rate of transpiration (E), and intercellular CO₂ concentration (C_i) in Raphanus sativus was studied. The effect of NaCl salinity was partially ameliorated by TDM which caused increase in Chl content, P_N, and C_i. TDM also increased root dry matter production, decreased E, and increased the water use efficiency. This revised version was published online in June 2006 with corrections to the Cover Date.     

Feeding habit and food partitioning in a stream fish community of Western Ghats,India

The diet and feeding ecology of 12 cyprinid fishes were studied in the Thalayanai stream of southern India. The diet of Barbodes sarana, Danio aequipinnatus and Rasbora daniconius were specialized in terrestrial and aquatic insects. Hypselobarbus dobsoni and Garra mullya consumed vegetative matter and unicellular algae as their most important dietary component, respectively. Hypselobarbus curmuca and Hypselobarbus dubius specialized in crustaceans and molluscs. Puntius amphibious, Puntius bimaculatus, Puntius dorsalis, Puntius filamentosus and Puntius tambraparniei fed on variety of food resources (aquatic insects, algae and detritus) and their feeding intake varied between wet to dry seasons. Levin’s index of diet breadth showed the broadest diets for P. dorsalis in both seasons, whereas G. mullya had a narrow feeding spectrum in both seasons. Among co-existing species, diet overlaps were substantially low during both wet and dry season. These results suggest that feeding specialization and low diet overlap reduce inter-specific competition, allowing co-existence of these cyprinid fishes in this highly structured stream assemblage.     

SMS 2.0: an updated database to study the structural plasticity of short peptide fragments in non-redundant proteins

The function of a protein molecule is greatly influenced by its three-dimensional (3D) structure and therefore structure prediction will help identify its biological function. We have updated Sequence, Motif and Structure (SMS), the database of structurally rigid peptide fragments, by combining amino acid sequences and the corre-sponding 3D atomic coordinates of non-redundant (25%) and redundant (90%) protein chains available in the Protein Data Bank (PDB). SMS 2.0 provides information pertaining to the peptide fragments of length 5-14 resi-dues. The entire dataset is divided into three categories, namely, same sequence motifs having similar, intermedi-ate or dissimilar 3D structures. Further, options are provided to facilitate structural superposition using the pro-gram structural alignment of multiple proteins (STAMP) and the popular JAVA plug-in (Jmol) is deployed for visualization. In addition, functionalities are provided to search for the occurrences of the sequence motifs in other structural and sequence databases like PDB, Genome Database (GDB), Protein Information Resource (PIR) and Swiss-Prot. The updated database along with the search engine is available over the World Wide Web through the following URL http://cluster.physics.iisc.ernet.in/sms/.     

Enumeration, isolation and identification of diazotrophs from Korean wetland rice varieties grown with long-term application of N and compost and their short-term inoculation effect on rice plants

AIM: This study has been aimed (i) to isolate and identify diazotrophs from Korean rice varieties; (ii) to examine the long-term effect of N and compost on the population dynamics of diazotrophs and (iii) to realize the shot-term inoculation effect of these diazotrophs on rice seedlings. METHODS AND RESULTS: Diazotrophic and heterotrophic bacterial numbers were enumerated by most probable number method and the isolates were identified based on morphological, physiological, biochemical and 16s rDNA sequence analysis. Long-term application of fertilizer N with compost enhanced both these numbers in rice plants and its environment. Bacteria were high in numbers when malate and azelaic acids were used as carbon source, but less when sucrose was used as a carbon substrate. The combined application promoted the association of diazotrophic bacteria like Azospirillum spp., Herbaspirillum spp., Burkholderia spp., Gluconacetobacter diazotrophicus and Pseudomonas spp. in wetland rice plants. Detection of nifD genes from different diazotrophic isolates indicated their nitrogen fixing ability. Inoculation of a representative isolate from each group onto rice seedlings of the variety IR 36 grown in test tubes indicated the positive effect of these diazotrophs on the growth of rice seedlings though the percentage of N present in the plants did not differ much. CONCLUSIONS: Application of compost with fertilizer N promoted the diazotrophic and heterotrophic bacterial numbers and their association with wetland rice and its environment. Compost application in high N fertilized fields would avert the reduction of N(2)-fixing bacterial numbers and their association was beneficial to the growth of rice plants. SIGNIFICANCE AND IMPACT OF THE STUDY: The inhibitory effect of high N fertilization on diazotrophic bacterial numbers could be reduced by the application of compost and this observation would encourage more usage of organic manure. This study has also thrown light on the wider geographic distribution of G. diazotrophicus with wetland rice in temperate region where sugarcane (from which this bacterium was first reported to be associating and thereon from other plant species) is not cultivated.     

N-fertilizer saving by the inoculation of Gluconacetobacter diazotrophicus and Herbaspirillum sp. in micropropagated sugarcane plants

Colonization of micropropagated sugarcane plants by Gluconacetobacter diazotrophicus and Herbaspirillum sp. was confirmed by a dot-immunoblot assay. In all, a 45-day short-term and 180-day long-term experiments conducted on micropropagated sugarcane plants of Co 86032, a sugar rich popular variety in South India, indicated the usefulness of these diazotrophs as plant growth promoting bacteria. Co-inoculation of these two bacteria enhanced the biomass considerably under N-limited condition in the short duration experiment. In the long-term experiment, the establishment of inoculated Herbaspirillum sp. remained stable with the age of the crop up to 180 days, while there was a reduction in population of G. diazotrophicus for the same period. The total bio-mass and leaf N were higher in plants inoculated with G. diazotrophicus and Herbaspirillum sp. without N fertilization and also in plants with 50% of the recommended N (140 kg ha(-1)) than the plants fertilized with recommended dose of inorganic N (280 kg ha(-1)). This experiment showed that inoculation with these bacteria in sugarcane variety Co 86032 could mitigate fertilizer N application considerably in sugarcane cultivation.     

Amelioration of NaCl stress by triadimefon in peanut seedlings

Peanut (Arachis hypogaea L.cv. VRI-2) seeds were imbibed in distilled water(control), 30 mM NaCl (stressed) and 30 mM NaCl + 10 mg L^-1 triadimefon for 12 h and grown in a seed germinator with a day/night temperature of 30/22 °C and a photoperiod of 16 h with a PPFD of 250 µEm^-2 s_-1. Seedlings were irrigated with respective treatment solutions. Fifteen days old seedlings were harvested and used for the study. The NaCl stress decreased seedling growth, dry weight, photosynthetic pigments, protein content and the level of proline oxidase activity and it increased proline, glycine betaine content, protease and ATPase activities. Triadimefon treatment ameliorated the stress caused NaCl by increasing root growth, dry weight, chlorophyll, carotenoid, protein and glycine betaine contents and by decreasing proline accumulation, proline oxidase levels and ATPase. The stress amelioration conferred by triadimefon may be mediated by increased protein synthesis, osmoregulation and reduced energy requirement.     

Influence of Triadimefon on the Metabolism of NaCl Stressed Radish

The effect of triadimefon (TDM) on various biochemical parameters was studied in NaCl stressed radish (Raphanus sativus L.). Stress imposed by 80 mM NaCl decreased the protein content and proline oxidase activity, and increased the proline and glycine betaine contents, and protease, -glutamyl kinase and ATPase activities. The TDM treatment alleviated the stress by increasing protein, and glycine betaine contents, and by decreasing proline accumulation, and proline oxidase and ATPase activities.