Model estimates of methane emission from irrigated rice cultivation of China

A model developed by the authors ( Huang et al. 1998 ) was further validated against field measurements from various regions of the world and calibrated to estimate methane emission from irrigated rice cultivation of China. On the basis of available information on rice cultivated area, growth duration, grain yield, soil texture and temperature, methane emission from Chinese rice paddies was estimated for 28 rice cultivated provinces in mainland. The calculated daily methane emission rates, on a provincial scale, ranged from 0.15 to 0.86 g m^–2 with an average of 0.32 g m^–2. Five of the top six locations with higher daily methane emissions are located at a latitude between 28° and 31° N. A total amount of 9.66 Tg (1 Tg = 10¹² g) CH₄ per year, ranging from 7.19 to 13.62, was estimated to be released from Chinese rice paddy soils. Of the total, 45% is emitted from the single-rice growing season, and 19% and 36% are from the early-rice and the late-rice growing seasons, respectively. Approximately 70% of the total is emitted in the region located at latitude between 25° and 32° N. The emissions from rice fields in Sichuan and Hunan Province were calculated to be 2.85 Tg y^–1, accounting for ≈ 30% of the total. Comparisons of the estimated and the observed emission rates show that the estimates were, in general, close to the measurements at most locations.     

The Challenge of Pneumocystis carinii Culture1

ABSTRACT. Published and unpublished data on the cultivation of P. carinii were reviewed by a panel of investigators convened by the National Institutes of Health. Although several cell culture systems allow propagation of P. carinii for a limited time with modest rates of replication, these have not proved adequate for isolation of P. carinii in sufficient quantity to explore important basic biological investigation. Attempts at cell-free culture have yielded only transient proliferation. Because much of the unsuccessful work on cultivation of the organism has been unpublished, the panel agreed that these data may be useful to other investigators in designing experimental strategies for cultivation. Therefore, the purpose of this report is to make available this information to researchers, lest others unknowingly repeat unsuccessful methods. It is hoped that by documenting the history and the complexities of Pneumocystis culture, renewed interest and efforts will be directed toward this fundamental scientific challenge.     

Patterns of hydrological exchange and nutrient transformation in the hyporheic zone of a gravel-bottom stream: examining terrestrial—aquatic linkages

• 1 The terrestrial-aquatic interface beneath a riparian corridor was investigated as a region of hydrological and biological control of nutrient flux. Subsurface flow paths were defined from the channel toward the riparian zone and also from the riparian zone toward the channel using tracer-injection studies. Solute transport had a rapid channel component (m min^?1) and a slow hyporheic flow component (mh^?1, m day^?1). Subsurface flow beneath the riparian zone approximated a straight path entering at meanders but could also cross beneath the stream, possibly using relic channels.
• 2 Dissolved oxygen (DO) concentration in the hyporheic zone ranged from <1.0 to 9.5mgl^?1 due to permeability variations in bankside sediments. DO concentration was related to the proportion of stream water in the lateral hyporheic zone, indicating that the channel water was the DO source.
• 3 The magnitude and riming of lateral water exchange was linked to previously published studies of nitrification and denitrificarion. Both nitrification potential and channel exchange decreased with distance from the channel and were absent at sites lacking effective exchange, due to low DO. Field amendment of ammonium to an aerobic flow path indicated nitrification potential under natural hydrological conditions. Denitrification potential was inversely related to channel exchange and was insignificant in channel sediments. Field amendment of acetylene plus nitrate to a flow path with low DO and minimal channel exchange indicated denitrificarion of amended nitrate.
• 4 Comparison of hydraulic head to distribution of the biologically important solutes DO, ammonium, and nitrate was useful for interpreting previous findings and conceptualizing the riparian zone as a functioning ecotone between terrestrial and aquatic systems.

     

The Effect of Segment Length on Conductance Measurements in Lonicera fragrantissima

The effect of stem segment length on conductance measurementswas determined by repeatedly shortening the transport distancein isolated stem segments of Lonicera fragrantissima. If vesselends limit water flow, shorter segment lengths could resultin higher readings of K_h (hydraulic conductance per unit pressuregradient). The mean K_h in the successively shortened segmentsshowed no statistically significant change when shortened from20 to 2 cm, even though maximum vessel lengths ranged from 6to 14 cm. This suggests vessel ends may be less limiting towater flow than are vessel lumens. There was a statisticallysignificant drop in K_h (19%, s.e.=0·29%) when segmentswere shortened from 2 to 1 cm, regardless of the position ofthe segment within the branch. The K_h remained constant withapplied pressure in 2 cm segments while it was more variablewith applied pressure in 1 cm segments. Based on the paint-infusionmethod mean vessel lengths were from 0·6 to 1·2cm. The consistently lower K_h in 1 cm segments might be dueto an end effect in segments with a high percentage of cut openvessels. Within a branch, distal and proximal stem segmentshad lower K_h values than segments from intermediate positions,but nodes had no measurable impact on K_h. Longer segments allowfor more accurate and consistent measurements of K_h since theyintegrate localized variation in K_h while minimizing the segmentend effect. Key words: Vessel length, vessel end, hydraulic conductance, paint-infusion method, Lonicera fragrantissima     

Intraerythrocytic Development of Plasmodium knowlesi: Structure,Temperature- and Ca2+-Response of the Host and Parasite Membranes1

Thin-sectioning and freeze-etching electron microscopy were applied to explore the structure and the temperature- and Ca²⁺-response of the different host and parasite membranes during intraerythrocytic development of Plasmodium knowlesi in Macacca mulatta. The plasma membrane of uninfected erythrocytes is temperature- and Ca²⁺-responsive: chilling to 4°C and exposure to 5 mM Ca²⁺ induces a slight decrease in IMP-frequency and the emergence of small IMP-devoid patches on P-faces. On parasite infection, the erythrocyte membrane becomes modified as indicated by an enhanced temperature-response and the appearance of caveolae, ca. 70–90 nm in diameter. The frequency of these caveolae is increased in schizont-infected erythrocytes. Moreover, electron dense plaques, ca. 40 nm in width, appear just beneath the erythrocyte membrane in late trophozoites and schizonts, thus indicating a further modification of the host cell membrane during parasite development. The membrane of the parasitophorous vacuole, derived from the host plasma membrane, dramatically reduces the IMP-frequency especially on the P-face upon parasite infection. This leads to an apparent reversal of the IMP-distribution persisting throughout the whole infection cycle. The parasite plasma membrane forms local compaction domains with the nuclear envelope in ca. 30% of the ring-stages and trophozoites, which disappear in late trophozoites and schizonts. Moreover, the IMP-frequency on plasma membrane fracture faces almost doubles during parasite development. Chilling induces a decrease in the IMP-frequency on P-faces of the plasma membrane. Surprisingly, however, the parasite plasma membrane and the vacuolar membrane respond to externally applied Ca²⁺ with almost a doubling of the IMP-frequency. The different parasite endomembranes also undergo characteristic changes during parasite development.     

Evidence for Carboniferous origin of the order Mantodea (Insecta: Dictyoptera) gained from forewing morphology

Homologies of the forewing venation pattern of the order Mantodea (Insecta: Dictyoptera) consistent with the accepted insect wing venation groundplan are proposed. A comparative morphological analysis was carried out based on a broad taxonomic sample of extant taxa. Besides macromorphological aspects, focus is given to the pattern of the tracheal system as a basis for establishing primary homologies. All extant praying mantids exhibit a composite stem composed of the posterior radius (RP) and the media (M) and most praying mantids exhibit a fusion of the anterior branch of RP + M with the anterior radius (RA). The wing venation of the species ?Mesoptilus dolloi, previously assigned to the polyphyletic fossil assemblage ‘Protorthoptera’, is re‐interpreted in the light of the new homology statement. Our interpretation suggests that it is a putative stem‐Mantodea, as are some other ‘protorthopterous’ taxa. This hypothesis implies that the total‐group Mantodea arose as soon as the Late Carboniferous, i.e. about 175 million years earlier than previously estimated. This analysis contributes to the view that most of the Late Carboniferous ‘Protorthoptera’ are stem‐representatives of the major polyneopteran clades (e.g. cockroaches, grasshoppers and crickets, rock‐crawlers), suggesting a survivorship of several main Pterygota lineages at the end‐Permian extinction event higher than previously expected. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 156 , 79–113.     

Revision of the Boophis majori group (Amphibia: Mantellidae) from Madagascar, with descriptions of five new species

A systematic revision of the Malagasy frogs hitherto attributed to the Boophis difficilis group is presented. The difficilis holotype is not conspecific with other specimens hitherto named Boophis difficilis but belongs to the B. tephraeomystax group based on lack of webbing between fingers and the presence of heterogeneously granular ventral skin. Rhacophorus difficilis Boettger, 1892 is considered as junior synonym of Boophis tephraeomystax. The Boophis difficilis group is dissolved and its species are transferred to a new species group named after Boophis majori , the oldest of the included taxa. All species of the B. majori group, their type specimens, and their geographical distributions are revised based on new morphological, bioacoustic and ecological data. Five new species of the group from the eastern rainforests of Madagascar are described. Morphological differentiation within the B. majori group is low, although some species can be distinguished by characters such as snout-vent length, relative tympanum size, or coloration. The most reliable character for species identification are advertisement calls which are strikingly different between most species of the group. Species diversity in Boophis is highest in central eastern Madagascar and gets lower at the northern and southern borders of the island. Available data do not allow a comprehensive phylogenetic analysis of the B. majori group, but a northern subgroup of small species without red coloration and a southern subgroup of larger species with distinct red pigments can be distinguished. Osteological data for B. miniatus are provided. Within Boophis , representatives of all species groups except the B. tephraeomystax group are characterized by a synapomorphic reduction of the anterolateral hyoidal process.