Pan-Arctic soil moisture control on tundra carbon sequestration and plant productivity

Long-term atmospheric CO₂ concentration records have suggested a reduction in the positive effect of warming on high-latitude carbon uptake since the 1990s. A variety of mechanisms have been proposed to explain the reduced net carbon sink of northern ecosystems with increased air temperature, including water stress on vegetation and increased respiration over recent decades. However, the lack of consistent long-term carbon flux and in situ soil moisture data has severely limited our ability to identify the mechanisms responsible for the recent reduced carbon sink strength. In this study, we used a record of nearly 100 site-years of eddy covariance data from 11 continuous permafrost tundra sites distributed across the circumpolar Arctic to test the temperature (expressed as growing degree days, GDD) responses of gross primary production (GPP), net ecosystem exchange (NEE), and ecosystem respiration (ER) at different periods of the summer (early, peak, and late summer) including dominant tundra vegetation classes (graminoids and mosses, and shrubs). We further tested GPP, NEE, and ER relationships with soil moisture and vapor pressure deficit to identify potential moisture limitations on plant productivity and net carbon exchange. Our results show a decrease in GPP with rising GDD during the peak summer (July) for both vegetation classes, and a significant relationship between the peak summer GPP and soil moisture after statistically controlling for GDD in a partial correlation analysis. These results suggest that tundra ecosystems might not benefit from increased temperature as much as suggested by several terrestrial biosphere models, if decreased soil moisture limits the peak summer plant productivity, reducing the ability of these ecosystems to sequester carbon during the summer.     

Microencapsulation of Bacillus subtilis B99-2 and its biocontrol efficiency against Rhizoctonia solani in tomato

Biological control is a promising approach to protecting plants from disease. Bacillus subtilis has been widely used in agriculture for promoting plant growth and biocontrol. However, their short shelf life limits the application of biological pesticides. The objectives of this study were to develop a microencapsulation procedure of B. subtilis B99-2 using maltodextrin and gum arabic as wall materials to determine the optimum conditions of spray-drying in microencapsulation, evaluate storage stability of microcapsules, and assess their biocontrol efficiency against Rhizoctonia solani in tomato under field conditions. We microencapsulated the Bacillus thallus by spray-drying with various concentrations of the wall material. Maltodextrin was found to be an efficient wall material, especially at concentrations higher than 80%, while gum arabic did not affect the bacterial survival rate. The mean survival rate of B. subtilis was more than 90%, when spray drying was performed at 145 °C, with a feed flow rate of 550 mL h⁻¹, and a spray pressure of 0.15 MPa. B. subtilis microcapsule survival rate was 87.53% after 540 d of storage, which was a longer shelf life than that of wettable powders. Moreover, its biocontrol efficacy reached 79.91% when a dosage of 300 g hm⁻² was used, the microcapsule showed higher control efficacy than Thiram wettable powder against R. solani in tomato under field conditions. All these characteristics indicated that B. subtilis microcapsules have the potential to become a successful biocontrol product.     

乳酸菌微囊化工艺的初步研究

目的 对保加利亚乳杆菌、嗜热链球菌的微囊化工艺进行摸索。方法 采用喷雾干燥方法。结果 以Ｃ胶（１３．３ｍｌ）＋Ｂ胶（２０ｇ）微囊化对乳酸菌的保护效果较好,菌体存活率达３４．６％,而Ｃ胶（７５ｍｌ）＋Ａ胶（５０ｇ）微囊化对乳酸菌的保护效果最佳,菌体存活率７８％,冷冻干燥工艺结合微囊化技术,可获得较高存活率的乳酸菌活性。结论 微囊化技术可提高菌体的抗热性。     

Extreme drought pushes stream invertebrate communities over functional thresholds

Functional traits are increasingly being used to predict extinction risks and range shifts under long‐term climate change scenarios, but have rarely been used to study vulnerability to extreme climatic events, such as supraseasonal droughts. In streams, drought intensification can cross thresholds of habitat loss, where marginal changes in environmental conditions trigger disproportionate biotic responses. However, these thresholds have been studied only from a structural perspective, and the existence of functional nonlinearity remains unknown. We explored trends in invertebrate community functional traits along a gradient of drought intensity, simulated over 18 months, using mesocosms analogous to lowland headwater streams. We modelled the responses of 16 traits based on a priori predictions of trait filtering by drought, and also examined the responses of trait profile groups (TPGs) identified via hierarchical cluster analysis. As responses to drought intensification were both linear and nonlinear, generalized additive models (GAMs) were chosen to model response curves, with the slopes of fitted splines used to detect functional thresholds during drought. Drought triggered significant responses in 12 (75%) of the a priori‐selected traits. Behavioural traits describing movement (dispersal, locomotion) and diet were sensitive to moderate‐intensity drought, as channels fragmented into isolated pools. By comparison, morphological and physiological traits showed little response until surface water was lost, at which point we observed sudden shifts in body size, respiration mode and thermal tolerance. Responses varied widely among TPGs, ranging from population collapses of non‐aerial dispersers as channels fragmented to irruptions of small, eurythermic dietary generalists upon extreme dewatering. Our study demonstrates for the first time that relatively small changes in drought intensity can trigger disproportionately large functional shifts in stream communities, suggesting that traits‐based approaches could be particularly useful for diagnosing catastrophic ecological responses to global change.     

冷冻干燥对重组酵母乙型肝炎疫苗效力(抗原性)的影响

重组酵母乙型肝炎疫苗(酵母乙肝疫苗)加入保护剂后冷冻干燥,观察是否影响疫苗抗原性和稳定性。按5％和1％的比例,在酵母乙肝疫苗原液中分别加入蔗糖和明胶,低温冷冻干燥,制备3批冻干疫苗,分别进行体外相对效力和小鼠ED50测定。加保护剂冻干后酵母乙肝疫苗体外相对效力和小鼠ED50值较冻干前改变不大,而4℃放置和热加速后的稳定性均优于液体疫苗。因此现有酵母乙肝疫苗加入保护剂冻干后,显著提高了疫苗的稳定性,为进一步制备稳定的疫苗参考品打下了初步基础。     

Experimental study of the spray characteristics of biodiesel based on inedible oil

We studied the spray characteristics of inedible oil using experimental and simulation methods. Spray penetration, spray cone angle and spray tip speed were measured at different biodiesel ratios in a constant volume vessel with wide visualization and high back pressure, using a high-speed camera. The characteristics of biodiesel spray were simulated under the same conditions using Star-CD software. The experimental results showed that, as the ratio of biodiesel in the blends increased, spray penetration and spray speed increased, but the spray cone angle decreased. Throughout the spray injection period, the region at 0.05–0.475S (spray tip penetration) was a key area affecting spray cone angle. From 0.8 ms after injection, the spray penetration deviation ratios started to increase with increasing biodiesel blend ratios. Simulation results showed similar macroscopic spray characteristics to the experimental results for jatropha oil. The results also showed that the Sauter mean diameter of blend fuels was greater than that of diesel, and spray was more concentrated, due to the higher viscosity and surface tension of the biodiesel, compared with conventional diesel fuel. The macroscopic and microscopic spray properties of blended fuels containing 5%, 10% and 20% biodiesel were similar to diesel.     

Sprouted and Freeze‐Dried Wheat and Oat Seeds – Phytochemical Profile and in Vitro Biological Activities

This research was carried out to study phytochemical profile, in vitro antioxidant capacity, reducing power, anti‐hyperglycemic, anti‐inflammatory activities and simulated gastrointestinal digestion of 7‐day old cereal sprouts: spelt wheat ‘Nirvana’ (WSSpe), wheat ‘Simonida’ (WSSim), oat ‘Golozrni’ (OSG) and oat ‘Jadar’ (OSJ). OSG expressed significantly higher (P ≤ 0.05) total phenols (TPC) and flavonoids content (TFC), antioxidant capacities (DPPH and ABTS assays) and reducing power (EC₅₀^DPPH = 2.12 mg/ml; EC₅₀^ABTS = 0.87 mg/ml; EC_0.5^RP = 12.24 mg/ml) as well as anti‐hyperglycemic activity (EC₅₀^AHgA = 0.96 mg/ml). WSSpe had the highest content of chlorophyll (131.23 mg/100 g) and carotenoids (22.84 mg/100 g). WSSim possessed the most potent anti‐inflammatory activity (2.71 mg/ml), though not significantly different from OSG (2.77 mg/ml). The in vitro simulation of gastro‐intestinal digestion showed higher release of phenolic compounds in intestinal than in gastric fluid.     

Desiccation tolerance in Physcomitrella patens: Rate of dehydration and the involvement of endogenous abscisic acid (ABA)

The moss Physcomitrella patens , a model system for basal land plants, tolerates several abiotic stresses, including dehydration. We previously reported that Physcomitrella patens survives equilibrium dehydration to ?13 MPa in a closed system at 91% RH. Tolerance of desiccation to water potentials below ?100 MPa was only achieved by pretreatment with exogenous abscisic acid (ABA). We report here that gametophores, but not protonemata, can survive desiccation below ?100 MPa after a gradual drying regime in an open system, without exogenous ABA. In contrast, faster equilibrium drying at 90% RH for 3–5 days did not induce desiccation tolerance in either tissue. Endogenous ABA accumulated in protonemata and gametophores under both drying regimes, so did not correlate directly with desiccation tolerance. Gametophores of a Ppabi3a/b/c triple knock out transgenic line also survived the gradual dehydration regime, despite impaired ABA signaling. Our results suggest that the initial drying rate, and not the amount of endogenous ABA, may be critical in the acquisition of desiccation tolerance. Results from this work will provide insight into ongoing studies to uncover the role of ABA in the dehydration response and the underlying mechanisms of desiccation tolerance in this bryophyte.