Is resource allocation and grain yield of rice altered by inoculation with arbuscular mycorrhizal fungi?

Aims our study quantified the combined effects of fertilization and inoculation with arbuscular mycorrhizal fungi(AMF)on grain yield and allocation of biomass and nutrients in field-grown rice(Oryza sativa l.).Methods a two-factor experiment was conducted at a field site in northeast of China(in shuangcheng,Heilongjiang Province,songhua river basin):six nitrogen-phosphorus-potassium fertilizer levels were provided(0,20,40,60,80 and 100%of the local norm of ferti-lizer supply),with or without inoculation with Glomus mosseae.at maturity,we quantified the percentage of root length colonization by AMF,grain yield,shoot:root ratios,shoot N and P contents and nutrients allocated to panicles,leaves and stems.Important Findingsas expected,inoculation resulted in greatly increased AMF colo-nization,which in turn led to higher shoot:root ratios and greater shoot N contents.shoot:root ratios of inoculated rice increased with increasing fertilization while there was a significant interaction between fertilization and inoculation on shoot:root ratio.additionally,a F inoculation increased panicle:shoot ratios,panicle N:shoot N ratios and panicle P:shoot P ratios,especially in plants grown at low fertilizer levels.Importantly,inoculated rice exhibited higher grain yield,with the maximum improvement(near 62%)at the lower fertilizer end.our results showed that(i)AMFinoculated plants conform to the functional equilibrium theory,albeit to a reduced extent compared to non-inoculated plants and(ii)AMF inoculation resulted in greater allocation of shoot biomass to panicles and increased grain yield by stimulating N and P redis-tribution to panicles.

Characterization and biodegradation kinetics of a new cold-adapted carbamazepine-degrading bacterium, Pseudomonas sp. CBZ-4

Carbamazepine is frequently detected in waters and hardly eliminated during conventional wastewater treatment processes due to its complicated chemical structure and resistance to biodegradation. A carbamazepine-degrading bacterium named CBZ-4 was isolated at a low temperature （10℃） from activated sludge in a municipal wastewater treatment plant. Strain CBZ-4, which can use carbamazepine as its sole source of carbon and energy, was identified as Pseudomonas sp. by the 16S rRNA gene sequence. The composition and percentage of fatty acids, which can reveal the cold-adaptation mechanism of strain CBZ-4, were determined. Strain CBZ-4 can effectively degrade carbamazepine at optimal conditions： pH 7.0, 10℃, 150 r/min rotation speed, and 13% inoculation volume. The average removal rate of carbamazepine was 46.6% after 144 hr of incubation. The biodegradation kinetics of carbamazepine by CBZ-4 was fitted via the Monod model. Vmax and Ks were found to be 0.0094 hr^-1 and 32.5 mg/L, respectively.

Improvement of nitrification efficiency by bioaugmentation in sequencing batch reactors at low temperature

Bioaugmentation is an effective method of treating municipal wastewater with high ammonia concentration in sequencing batch reactors （SBRs） at low temperature （10℃）. The cold-adapted ammonia- and nitrite- oxidizing bacteria were enriched and inoculated, respectively, in the bioaugmentation systems. In synthetic wastewater treatment systems, the average NH4＋-N removal efficiency in the bioaugmented system （85%） was much higher than that in the unbioaugmented system. The effluent NH4＋ -N concentration of the bioaugmented system was stably below 8 mg. L1 after 20 d operation. In municipal wastewater systems with bioaugmentation, the effluent NH4＋- -N concentration was below 8 mg·L^-1 after 15 d operation. The average NH4＋ -N removal efficiency in unbioaugmentation system （about 82%） was lower compared with that in the bioaugmentation system. By inoculating the cold-adapted nitrite-oxidizing bacteria （NOB） into the SBRs after 10 d operation, the nitrite concentration decreased rapidly, reducing the NO2 -N accumulation effectively at low temperature. The func- tional microorganisms were identified by PCR-DGGE, including uncultured Dechloromonas sp., uncultured Nitrospira sp., Clostridium sp. and uncultured Thauera sp. The results suggested that the cold-adapted microbial agent of ammonia-oxidizing bacteria （AOB） and NOB could accelerate the start-up and promote achieving the stable operation of the low-temperature SBRs for nitrification.

Pseudomonas sp.ZXY-1,a newly isolated and highly efficient atrazine-degrading bacterium,and optimization of biodegradation using response surface methodology

Atrazine, a widely used herbicide, is increasing the agricultural production effectively, while also causing great environmental concern. Efficient atrazine-degrading bacterium is necessary to removal atrazine rapidly to keep a safe environment. In the present study, a new atrazine-degrading strain ZXY-1, identified as Pseudomonas, was isolated. This new isolated strain has a strong ability to biodegrade atrazine with a high efficiency of 9.09 mg/L/hr.Temperature, p H, inoculum size and initial atrazine concentration were examined to further optimize the degradation of atrazine, and the synthetic effect of these factors were investigated by the response surface methodology. With a high quadratic polynomial mathematical model（R^2= 0.9821） being obtained, the highest biodegradation efficiency of 19.03 mg/L/hr was reached compared to previous reports under the optimal conditions（30.71°C, pH 7.14, 4.23%（V/V） inoculum size and 157.1 mg/L initial atrazine concentration）.Overall, this study provided an efficient bacterium and approach that could be potentially useful for the bioremediation of wastewater containing atrazine.

Phenotypic plasticity in rice:responses to fertilization and inoculation with arbuscular mycorrhizal fungi

Aims Changes in the phenotype of crops(phenotypic plasticity)are known to play an important role in determining responses to nutrient availability,with the direction and magnitude of plasticity of individual traits being crucial for grain yields.Our study analysed the direction,magnitude and hierarchy of plastic responses of yieldrelated traits(i.e.biomass allocation and yield components)of rice(Oryza sativa L.)to nutrient availability.We estimated the effect of inoculation with arbuscular mycorrhizal fungi(AMF)on these characteristics of phenotypic plasticity.Methods A field experiment was carried out in northeast China,providing rice with six NPK fertilizer levels with or without inoculation with Glomus mosseae.At maturity,we quantified biomass allocation traits(shoot:root ratio and panicle:shoot ratio)and yield component traits(panicle number per hill,spikelet number per panicle,percentage of filled spikelets and seed weight).We also assessed the direction of change in each trait and the magnitude of trait plasticity.Important Findings In non-inoculated plants,we found that biomass allocation and seed-number traits(i.e.panicle number per hill,spikelet number per panicle and percentage of filled spikelets)responded to fertilization in the same direction,increasing with rising fertilization.Panicle formation was the most plastic trait,while seed mass was the least plastic trait.AMF inoculation nullified the relationship between most biomass allocation and seed-number traits(except for that between panicle:shoot ratio and the percentage of filled spikelets)but increased the magnitude of plasticity in biomass allocation traits without altering the hierarchy of traits’plasticity.These results underscore the importance of plasticity of yield-related traits per se,and the impact of AMF on plasticity,for maintaining rice yields under low fertilization regimes.