Selective sweeps for recessive alleles and for other modes of dominance

A selective sweep describes the reduction of linked genetic variation due to strong positive selection. If s is the fitness advantage of a homozygote for the beneficial allele and h its dominance coefficient, it is usually assumed that h = 1/2, i.e. the beneficial allele is co-dominant. We complement existing theory for selective sweeps by assuming that h is any value in [0, 1]. We show that genetic diversity patterns under selective sweeps with strength s and dominance 0 < h < 1 are similar to co-dominant sweeps with selection strength 2hs. Moreover, we focus on the case h = 0 of a completely recessive beneficial allele. We find that the length of the sweep, i.e. the time from occurrence until fixation of the beneficial allele, is of the order of \({\sqrt{N/s}}\) generations, if N is the population size. Simulations as well as our results show that genetic diversity patterns in the recessive case h = 0 greatly differ from all other cases.     

Chemical and hydraulic signals regulate stomatal behavior and photosynthetic activity in maize during progressive drought

The objectives of this study were to investigate stomatal regulation in maize seedlings during progressive soil drying and to determine the impact of stomatal movement on photosynthetic activity. In well-watered and drought-stressed plants, leaf water potential (Ψ _leaf), relative water content (RWC), stomatal conductance (g _s), photosynthesis, chlorophyll fluorescence, leaf instantaneous water use efficiency (iWUE_leaf), and abscisic acid (ABA) and zeatin-riboside (ZR) accumulation were measured. Results showed that g _s decreased significantly with progressive drought and stomatal limitations were responsible for inhibiting photosynthesis in the initial stages of short-term drought. However, after 5 days of withholding water, non-stomatal limitations, such as damage to the PSII reaction center, became the main limiting factor. Stomatal behavior was correlated with changes in both hydraulic and chemical signals; however, changes in ABA and ZR occurred prior to any change in leaf water status. ABA in leaf and root tissue increased progressively during soil drying, and further analysis found that leaf ABA was negatively correlated with g _s (R ² = 0.907, p < 0.05). In contrast, leaf and root ZR decreased gradually. ZR in leaf tissue was positively correlated with g _s (R ² = 0.859, p < 0.05). These results indicate that ABA could induce stomatal closure, and ZR works antagonistically against ABA in stomatal behavior. In addition, the ABA/ZR ratio also had a strong correlation with g _s, suggesting that the combined chemical signal (the interaction between ABA and cytokinin) plays a role in coordinating stomatal behavior. In addition, Ψ _leaf and RWC decreased significantly after only 3 days of drought stress, also affecting stomatal behavior.     

Potential effects of warming on soil respiration and carbon sequestration in a subtropical forest

Aims

Subtropical ecosystems are receiving unprecedented changes in temperature as a consequence of anthropogenic activities, which potentially affects soil respiration (R _s) and carbon (C) sequestration. Due to the large amounts of C store and cycle in subtropical forests, investigations about how R _s and C sequestration respond to warming will be critical for our understanding of future global-scale climate and biogeochemical cycling.

Methods

In this study, we transferred soil samples and plant seedlings collected from a mixed forest to the growth chambers in two sites (300 m and 30 m a.s.l.), which induced an artificial warming of ca. 1 °C between the two corresponding forest mesocosms. We tested whether the modification of abiotic factors induced by the downward translocation could alter R _s and soil C sequestration. We also investigated the effects on the biotic factors by including root biomass and soil microbial biomass.

Results

Our results showed that R _s was greater in the warm site than in the control site, which were related to the higher aboveground biomass, litterfall and root biomass. R _s showed a significantly positive exponential relationship with soil temperature. The downward translocation tended to decrease soil C sequestration, which was attributed to the decreased C use efficiency of soil microorganisms and increased root growth under downward translocation.

Conclusion

R _s responded strongly to downward translocation, suggesting that climate warming exacerbated R _s and tended to reduce soil C sequestration. The ability of subtropical forests to act as CO₂ sink may be reduced under climate warming.

     

Gas exchange,carbon balance and stomatal traits in wild and cultivated rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) genotypes

Carbon balancing within the plant species is an important feature for climatic adaptability. Photosynthesis and respiration traits are directly linked with carbon balance. These features were studied in 20 wild rice accessions Oryza spp., and cultivars. Wide variation was observed within the wild rice accessions for photosynthetic oxygen evolution or photosynthetic rate (A), dark (R _d), and light induced respiration (LIR) rates, as well as stomatal density and number. The mean rate of A varied from 10.49 μmol O₂ m^?2 s^?1 in cultivated species and 13.09 μmol O₂ m^?2 s^?1 in wild spp., The mean R _d is 2.09 μmol O₂ m^?2 s^?1 and 2.31 μmol O₂ m^?2 s^?1 in cultivated and wild spp., respectively. Light induced Respiration (LIR) was found to be almost twice in wild rice spp., (16.75 μmol O₂ m^?2 s^?1) compared to cultivated Oryza spp., Among the various parameters, this study reveals LIR and A as the key factors for positive carbon balance. Stomatal contribution towards carbon balance appears to be more dependent on abaxial surface where several number of stomata are situated. Correlation analysis indicates that R _d and LIR increase with the increase in A. In this study, O. nivara (CR 100100, CR 100097), O. rufipogon (IR 103404) and O. glumaepatula (IR104387) were identified as potential donors which could be used in rice breeding program. Co-ordination between gas exchange and patchiness in stomatal behaviour appears to be important for carbon balance and environmental adaptation of wild rice accessions, therefore, survival under harsh environment.     

Nitrogen-induced variations in leaf gas exchange of spring triticale under field conditions

Nitrogen (N) is the key factor limiting photosynthetic processes and crop yield. Little is known about the response of leaf gas exchange of spring triticale (Triticosecale Wittm.) to N supply. The effect of N fertilizers on different gas exchange variables, i.e., photosynthetic rate (A), transpiration rate (E), stomatal conductance (g _s), instantaneous water use efficiency (WUE) and maximum quantum yield of photosystem II (PSII) (F _v/F _m), chlorophyll index (SPAD, soil–plant analysis development), and the relationship of these variables with yield were studied in spring triticale grown under field conditions. Six treatments of N—0, 90, 180, 90 + 30, 90 + 30 + 30 kg ha^?1 (applied as ammonium nitrate, AN) and one treatment of N 90 + 30 + 30 kg ha^?1 (applied as urea ammonium nitrate solution, UAN) were compared. The analysis of variance showed that throughout the triticale growing season, N fertilization had significant effects on A, WUE, g _s and SPAD. On average, N fertilizer application increased A values by 14–70%. E and F _v/F _m values were not influenced by N fertilization levels. The effect of growth stage and year on gas exchange variables and F _v/F _m and SPAD was found to be significant. At different growth stages, A values varied and maximum ones were reached at BBCH 31–33 (decimal code system of growth stages) and BBCH 59. With aging, values of A decreased independently of N fertilization level. The gas exchange variables were equally affected by both fertilizer forms. The interplay among grain yield, leaf gas exchange variables, F _v/F _m and SPAD of spring triticale was estimated. The statistical analysis showed that grain yield positively and significantly correlated with A and SPAD values throughout the growing season.     

Assessing biodegradation of furfuryl alcohol using <Emphasis Type="Italic">Pseudomonas putida</Emphasis> MTCC 1194 and <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> MTCC 1034 and its kinetics

The biodegradation of furfuryl alcohol (FA) in shake flask experiments using a pure culture of Pseudomonas putida (MTCC 1194) and Pseudomonas aeruginosa (MTCC 1034) was studied at 30 °C and pH 7.0. Experiments were performed at different FA concentrations ranging from 50 to 500 mg/l. Before carrying out the biodegradation studies, the bacterial strains were acclimatized to the concentration of 500 mg/l of FA by gradually raising 100 mg/l of FA in each step. The well acclimatized culture of P. putida and P. aeruginosa degraded about 80 and 66% of 50 mg/l FA, respectively. At higher concentration of FA, the percentage of FA degradation decreased. The purpose of this study was to determine the kinetics of biodegradation of FA by measuring biomass growth rates and concentration of FA as a function of time. Substrate inhibition was calculated from experimental growth parameters using the Haldane equation. Data for P. putida were determined as µ _max ?=?0.23 h^?1, K _s ?=?23.93 mg/l and K _i ?=?217.1 mg/l and for P. aeruginosa were determined as µ _max ?=?0.13 h^?1, K _s ?=?21.3 mg/l and K _i ?=?284.9 mg/l. The experimental data were fitted in Haldane, Aiba and Edwards inhibition models.     

Using hydrothermal time concept to describe sesame (<Emphasis Type="Italic">Sesamum indicum</Emphasis> L.) seed germination response to temperature and water potential

To quantify both temperature (T) and water potential (ψ) effects on sesame (Sesamum indicum L.) seed germination (SG) and also to determine the cardinal T _s for this plant, a laboratory experiment was carried out using hydrothermal time model (HTT). For this purpose, four sesame cultivars (‘Asbomahalleh’, ‘Darab’, ‘Dashtestan’ and ‘Yellowhite’) were germinated at seven constant T _s (20, 25, 30, 35, 37, 39 and 43 °C) at each of the following ψ _s (0, ? 0.12, ? 0.24 and ? 0.36 MPa; provided by PEG 8000). Germination rate (GR) and germination percentage (GP) significantly influenced by ψ, T and their interactions in all cultivars (P ≤ 0.01). There was no significant difference, based on the confidence intervals of the model coefficients, between cultivars, so an average of cardinal T _s was 14.7, 35.4 and 47.2 °C for the minimum (T _b), optimum (T _o) and maximum (T _c) T _s, respectively, in the control condition (0 MPa). Hydrotime values in all cultivars decreased when T was increased to T _o and then remained constant at T _s > T _o (15 MPa h^?1). An average value of ψ _b(50) was estimated to be ? 1.23 MPa at T _s ≤ T _o and then increased linearly (0.1041 MPa°Ch^?1, the slope of the relationship between ψ _b(50) and supra-optimal T _s) with T when T _s increased above T _o and finally reached to zero at T _c. The T _b and T _o values were not influenced by ψ, but T _c value decreased (from 47.2 for zero to 43.5 °C for ? 0.36 MPa) at supra-optimal T _s as a result of the effect of ψ on GR. Based on our findings, this model (as a predictive tool) and or the estimated parameter values in this study can easily be used in sesame SG simulation models to quantitatively characterize the physiological status of sesame seed populations at different T _s and ψ _s.     

Parasitism Rate of <Emphasis Type="Italic">Habrobracon hebetor</Emphasis> to <Emphasis Type="Italic">Ephestia kuehniella</Emphasis> Larvae: Residual Effect of Deltamethrin,Fenvalerate and Azadirachtin

Sublethal concentrations of chemical insecticides may cause changes in some behavioral characteristics of natural enemies such as functional responses. The residual effect of three synthetic insecticides including deltamethrin, fenvalerate and azadirachtin were studied on functional response of Habrobracon hebetor Say to Ephestia kuehniella Zeller larvae. Seven host densities (2, 4, 8, 16, 32, 64 and 96) were used during a 24 h period. The resulting data were appropriately fit to Type II functional response models in all treatments: (1) control (0.0916 h^?1; and T _h  = 0.2011 h); (2) deltamethrin (a = 0.0839 h^?1; and T _h  = 0.3560 h); (3) fenvalerate (a = 0.0808 h^?1 and T _h  = 0.3623 h); and (4) azadirachtin (a = 0.0900 h^?1 and T _h  = 0.2042 h). Maximum theoretical parasitism rate (T/T _h ) was 119.34 estimated for control wasps. There was no significant difference between the values of attack rates (a and a + D _a ) in all treatments while the handling time was statistically affected in female wasps treated with fenvalerate. Our findings will be useful in safe application of these insecticides in pest management programmes.     

Enantioconvergent hydrolysis of racemic styrene oxide at high concentration by a pair of novel epoxide hydrolases into (<Emphasis Type="Italic">R</Emphasis>)-phenyl-1,2-ethanediol

Objectives

To prepare (R)-phenyl-1,2-ethanediol ((R)-PED) with high enantiomeric excess (ee _p) and yield from racemic styrene oxide (rac-SO) at high concentration by bi-enzymatic catalysis.

Results

The bi-enzymatic catalysis was designed for enantioconvergent hydrolysis of rac-SO by a pair of novel epoxide hydrolases (EHs), a Vigna radiata EH3 (VrEH3) and a variant (AuEH2^A250I) of Aspergillus usamii EH2. The simultaneous addition mode of VrEH3 and AuEH2^A250I, exhibiting the highest average turnover frequency (aTOF) of 0.12 g h^?1 g^?1, was selected, by which rac-SO (10 mM) was converted into (R)-PED with 92.6% ee _p and 96.3% yield. Under the optimized reaction conditions: dry weight ratio 14:1 of VrEH3-expressing E. coli/vreh3 to AuEH2^A250I-expressing E. coli/Aueh2 ^A250I and reaction at 20 °C, rac-SO (10 mM) was completely hydrolyzed in 2.3 h, affording (R)-PED with 98% ee _p. At the weight ratio 0.8:1 of rac-SO to two mixed dry cells, (R)-PED with 97.4% ee _p and 98.7% yield was produced from 200 mM (24 mg/ml) rac-SO in 10.5 h.

Conclusions

Enantioconvergent hydrolysis of rac-SO at high concentration catalyzed by both VrEH3 and AuEH2^A250I is an effective method for preparing (R)-PED with high ee _p and yield.

     

Rearrangement of leaf traits with changing source-sink relationship in blueberry (Vaccinium corymbosum L.) leaves

The source-sink relationship is one of major determinants of plant performance. The influence of reproductive sink demand on light-saturated photosynthesis (P_max), dark respiration (R_D), stomatal conductance (g_s), intrinsic water-use efficiency (WUE_i), contents of soluble sugar (SSC), nitrogen, carbon, and photosynthetic pigments was examined in blueberry (Vaccinium corymbosum L. cv. ‘Brigitta’) during the final stage of rapid fruit growth. Measurements were performed three times per day on developed, sun-exposed leaves of girdled shoots with 0.1, 1, and 10 fruit per leaf (0.1F:L, 1F:L, and 10F:L, respectively) and nongirdled shoots bearing one fruit per leaf (NG). Girdling and lower fruit amount induced lower P_max, g_s, N, and total chlorophyll (Chl) and higher WUE_i, SSC, R_D, Chl a/b ratio and carotenoids-to-chlorophylls ratio (Car/Chl) for the 1F:L and 0.1F:L treatments. The impact of girdling was counterbalanced by 10F:L, with NG and 10F:L having similar values. Variables other than P_max, R_D, g_s, WUE_i, and SSC were unaffected throughout the course of the day. P_max and g_s decreased during the course of the day, but g_s decreased more than P_max in the afternoon, while WUE_i was increasing in almost all treatments. SSC increased from the morning until afternoon, whereas R_D peaked at noon regardless of the treatment. Generally, P_max was closely and negatively correlated to SSC, indicating that sugar-sensing mechanisms played an important role in regulation of blueberry leaf photosynthesis. With respect to treatments, P_max and N content were positively related, while R_D was not associated to substrate availability. The enhanced Car/Chl ratio showed a higher photoprotection under the lower sink demand. Changes in the source-sink relationship in ‘Brigitta’ blueberry led to a rearrangement of physiological and structural leaf traits which allowed adjusting the daily balance between carbon assimilation and absorbed light energy.     

Effects of phosphorus addition with and without nitrogen addition on biological nitrogen fixation in tropical legume and non-legume tree plantations

It is well documented that phosphorus (P) input stimulates biological nitrogen (N) fixation (BNF) in tropical forests with non-legume trees. However, in tropical legume forests with soil N enrichment and P deficiency, the effects of P availability and its combination with N on BNF remain poorly understood. In this study, we measured BNF rate in different compartments, i.e., bulk soil, forest floor, rhizosphere, and nodules, in two tropical plantations with legume trees Acacia auriculiformis (AA) versus non-legume trees Eucalyptus urophylla, (EU) in southern China after 4 years of P addition and combined N and P additions. The objective was to investigate how P addition and its combination with N addition regulate BNF in a tropical legume plantation, and to compare the effects with those in a non-legume plantation. Our results showed that total BNF rates were significantly higher in the P-addition plots than in the control plots by 27.4 ± 4.3 and 23.3 ± 1.7 % in the EU and AA plantations, respectively. Total BNF rates were significantly higher in the NP-addition plots than in the control plots by 27.7  ± 5.0 and 8.5 ± 1.4 % in the EU and AA plantations, respectively, which contrasted to our previous result that total BNF rates were significantly lower in N-addition plots than in the control plots in the AA plantation. These findings suggest that P input can stimulate BNF in tropical forest biome dominated by legume trees, even in consideration of elevated atmospheric N deposition. Thus, our study revealed the important role of P in regulating biological N input, which should be taken into account in the modeling of biogeochemical cycles in the future.     

Impact of elevated CO<Subscript>2</Subscript> in <Emphasis Type="Italic">Casuarina equisetifolia</Emphasis> rooted stem cuttings inoculated with <Emphasis Type="Italic">Frankia</Emphasis>

Impact of different levels of elevated CO ₂ on the activity of Frankia (Nitrogen-fixing actinomycete) in Casuarina equisetifolia rooted stem cuttings has been studied to understand the relationship between C. equisetifolia, Frankia and CO₂. The stem cuttings of C. equietifolia were collected and treated with 2000 ppm of Indole Butyric Acid (IBA) for rooting. Thus vegetative propagated rooted stem cuttings of C. equisetifolia were inoculated with Frankia and placed in the Open top chambers (OTC) with elevated CO₂ facilities. These planting stocks were maintained in the OTC for 12 months under different levels of elevated CO₂ (ambient control, 600 ppm, 900 ppm). After 12 months, the nodule numbers, bio mass, growth, and photosynthesis of C. equisetifolia rooted stem cuttings inoculated with Frankia were improved under 600 ppm of CO₂. The rooted stem cuttings of C. equisetifolia inoculated with Frankia showed a higher number of nodules under 900 ppm of CO₂ and cuttings without Frankia inoculation exhibited poor growth. Tissue Nitrogen (N) content was also higher under 900 ppm of CO₂ than ambient control and 600 ppm levels. The photosynthetic rate was higher (17.8 μ mol CO₂ m^?2 s^?1) in 900 ppm of CO₂ than in 600 ppm (13.2 μ mol CO₂ m^?2 s^?1) and ambient control (8.3 μ mol CO₂ m^?2 s^?1). This study showed that Frankia can improve growth, N fixation and photosynthesis of C. equietifolia rooted stem cuttings under extreme elevated CO₂ level conditions (900 ppm).     

Temperature sensitivity of soil respiration in a low-latitude forest ecosystem varies by season and habitat but is unaffected by experimental warming

Experimental warming of forest ecosystems typically stimulates soil respiration (CO₂ efflux), but most warming experiments have been conducted in northern latitudes (>?40°N) with relatively young soils. We quantified the influence of experimental warming on soil respiration (R_T) in two adjacent forest habitats—a mature, closed canopy forest and a gap where trees were manually removed— on highly-weathered Ultisols of the southeastern U.S. (33°N). Using temperature variation, both natural and induced by experimental warming, we also quantified the temperature sensitivity of R_T, defined as the activation energy, E_A in the Arrhenius equation. Experimental warming (either + 3 °C or + 5 °C above ambient) did not significantly increase soil respiration rate or cumulative CO₂ loss over the 3 years of the experiment, and did not influence the temperature sensitivity of soil respiration, once the influence of natural temperature variation was taken into consideration. Despite the absence of an experimental warming effect, we observed that E_A varied on monthly time scales, and varied differently in each habitat. Soil moisture and habitat also influenced R_T, but the effects were not consistent, and varied by month. Our results suggest that although R_T does depend on temperature, the sensitivity of R_T to temperature variation is influenced primarily by factors like microclimate and plant phenology that can change on relatively short (<?monthly) time scales. Thus, using the temperature sensitivity of R_T to predict future CO₂ losses due to warming is only reasonable if monthly variation in E_A is incorporated into models for lower-latitude subtropical ecosystems with highly weathered soils, such as those in this study. Finally, our results suggest that higher temperatures may not enhance R_T in highly-weathered, C-poor soils to the extent that has been reported in prior studies of high-latitude soils, which may constrain ecosystem-atmosphere carbon exchanges and feedbacks to the climate system.     

Photosynthetic responses of a wheat (Asakaze)–barley (Manas) 7H addition line to salt stress

The photosynthetic responses to salt stress were examined in a wheat (Triticum aestivum L. cv. Asakaze)–barley (Hordeum vulgare L. cv. Manas) 7H addition line having elevated salt tolerance and compared to the parental wheat genotype. For this purpose, increasing NaCl concentrations up to 300 mM were applied and followed by a 7-day recovery period. Up to moderate salt stress (200 mM NaCl), forcible stomatal closure, parallel with a reduction in the net assimilation rate (P _N), was only observed in wheat, but not in the 7H addition line or barley. Since the photosynthetic electron transport processes of wheat were not affected by NaCl, the impairment in P _N could largely be accounted for the salt-induced decline in stomatal conductance (g _s), accompanied by depressed intercellular CO₂ concentration and carboxylation efficiency. Both, P _N and nonstomatal limitation factors (L_ns) were practically unaffected by moderate salt stress in barley and in the 7H addition line due to the sustained g _s, which might be an efficient strategy to maintain the efficient photosynthetic activity and biomass production. At 300 mM NaCl, both P _N and g _s decreased significantly in all the genotypes, but the changes in P _N and L_ns in the 7H addition line were more favourable similar to those in wheat. The downregulation of photosynthetic electron transport processes around PSII, accompanied by increases in the quantum yield of regulated energy dissipation and of the donor side limitation of PSI without damage to PSII, was observed in the addition line and barley during severe stress. Incomplete recovery of P _N was observed in the 7H addition line as a result of declined PSII activity probably caused by enhanced cyclic electron flow around PSI. These results suggest that the better photosynthetic tolerance to moderate salt stress of barley can be manifested in the 7H addition line which may be a suitable candidate for improving salt tolerance of wheat.     

Wax Removal and Diamondback Moth Performance in Collards Cultivars

The diamondback moth Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae) is an herbivorous specialist on Brassicaceae species. Brassicas spp. plants developed a range of defenses (chemical, physical, and morphological) to prevent herbivores attack. In this study, we reported the antixenotic and antibiotic effects of outermost layer of two species of epicuticular wax of Brassicaceae, Brassica oleracea L. var. “Santo Antônio,” and Hybrid Kope F1 100MX, on larvae and adult of P. xylostella. In the choice experiment, P. xylostella adults showed an oviposition preference for collard cultivars Santo Antônio (control) and Hybrid Kope F1 100MX with wax removal. In the no-choice experiment, oviposition was 6.4 times higher in the Hybrid Kope F1 100MX with wax removal than without wax removal. There were significant differences among larvae feeding on leaf disks of Hybrid Kope F1 100MX in the treatments with (65.3 mg) and without wax removal (23.5 mg). The net reproduction rate (R ₀ ), and intrinsic (rm) and finite rates of increase (λ) of P. xylostella in the cv. Santo Antônio were bigger in the treatment without wax removal (R ₀  = 50.4, rm = 0.23 and λ = 1.26) than treatment with wax removal (R ₀  = 28.5, rm = 0.20 and λ = 1.22). However, only the R ₀ value was affected by mechanical wax removal in the Hybrid Kope F1 100MX (with wax removal R ₀  = 43.3 and without wax removal R ₀  = 30.8). In conclusion, the results indicate that collard’s wax is important to accessibility and development of P. xylostella, and its removal changes the resistance of collard’s varieties to P. xylostella.     

Oxygen transfer as a tool for fine-tuning recombinant protein production by <Emphasis Type="Italic">Pichia pastoris</Emphasis> under glyceraldehyde-3-phosphate dehydrogenase promoter

Effects of oxygen transfer on recombinant protein production by Pichia pastoris under glyceraldehyde-3-phosphate dehydrogenase promoter were investigated. Recombinant glucose isomerase was chosen as the model protein. Two groups of oxygen transfer strategies were applied, one of which was based on constant oxygen transfer rate where aeration rate was Q _O/V = 3 and 10 vvm, and agitation rate was N = 900 min^?1; while the other one was based on constant dissolved oxygen concentrations, C _DO = 5, 10, 15, 20 and 40 % in the fermentation broth, by using predetermined exponential glucose feeding with μ _o = 0.15 h^?1. The highest cell concentration was obtained as 44 g L^?1 at t = 9 h of the glucose fed-batch phase at C _DO = 20 % operation while the highest volumetric and specific enzyme activities were obtained as 4440 U L^?1 and 126 U g^?1 cell, respectively at C _DO = 15 % operation. Investigation of specific enzyme activities revealed that keeping C _DO at 15 % was more advantageous with an expense of relatively higher by-product formation and lower specific cell growth rate. For this strategy, the highest oxygen transfer coefficient and oxygen uptake rate were K _L a = 0.045 s^?1 and OUR = 8.91 mmol m^?3 s^?1, respectively.     

Molecular mapping of a rust resistance gene <Emphasis Type="Italic">R</Emphasis><Subscript><Emphasis Type="Italic">14</Emphasis></Subscript> in cultivated sunflower line PH 3

Sunflower, the fifth largest oilseed crop in the world, plays an important role in human diets. Recently, sunflower production in North America has suffered serious yield losses from newly evolved races of sunflower rust (Puccinia helianthi Schwein.). The rust resistance gene, designated R ₁₄ , in a germplasm line PH 3 originated from a wild Helianthus annuus L. population resistant to 11 rust races. PH 3 has seedling with an extraordinary purple hypocotyl color. The objectives of this study were to map both the R ₁₄ rust resistance gene and the purple hypocotyl gene-designated PHC in PH 3, and to identify molecular markers for marker-assisted breeding for sunflower rust resistance. A set of 517 mapped SSR/InDel and four SNP markers was used to detect polymorphisms between the parents. Fourteen markers covering a genetic distance of 17.0 cM on linkage group (LG) 11 were linked to R ₁₄ . R ₁₄ was mapped to the middle of the LG, with a dominant SNP marker NSA_000064 as the closest marker at a distance of 0.7 cM, and another codominant marker ORS542 linked at 3.5 cM proximally. One dominant marker ZVG53 was linked on the distal side at 6.9 cM. The PHC gene was also linked to R ₁₄ with a distance of 6.2 cM. Chi-squared analysis of the segregation ratios of R ₁₄ , PHC, and ten linked markers indicated a deviation from an expected 1:2:1 or 3:1 ratio. The closely linked molecular or morphological markers could facilitate sunflower rust-resistant breeding and accelerate the development of rust-resistant hybrids.     

The mathematical model of concentration polarization coefficient in membrane transport and volume flows

In this paper, the authors investigate the membrane transport of aqueous non-electrolyte solutions in a single-membrane system with the membrane mounted horizontally. The purpose of the research is to analyze the influence of volume flows on the process of forming concentration boundary layers (CBLs). A mathematical model is provided to calculate dependences of a concentration polarization coefficient (ζ _s ) on a volume flux (J _vm ), an osmotic force (Δπ) and a hydrostatic force (ΔP) of different values. Property ζ _s ?=?f(J _vm ) for J _vm ?>?0 and for J _vm ?≈?0 and property ζ _s ?=?f(ΔC ₁) are calculated. Moreover, results of a simultaneous influence of ΔP and Δπ on a value of coefficient ζ _s when J _vm ?=?0 and J _vm ?≠?0 are investigated and a graphical representation of the dependences obtained in the research is provided. Also, mathematical relationships between the coefficient ζ _s and a concentration Rayleigh number (R _C ) were studied providing a relevant graphical representation. In an experimental test, aqueous solutions of glucose and ethanol were used.     

Natural succession of grassland on the Loess Plateau of China affects multifractal characteristics of soil particle-size distribution and soil nutrients

Knowledge of the changes of soil properties and soil particle-size distribution (PSD) is important for quantifying soil quality and dynamics during natural succession. We applied multifractal theory to characterize the PSDs in five soil layers of nine croplands abandoned for less than 1 year, 2, 5, 7, 10, 15, 20, 30 and 35 years and evaluated the changes of soil organic carbon (SOC), total nitrogen (total N), total phosphorus (total P), soil texture and multifractal parameters [capacity dimension (D ₀), entropy dimension (D ₁), correlation dimension (D ₂) and Hölder exponent of order zero (α ₀)] during natural succession on the Loess Plateau of China. Rényi spectra (D _q ) and singularity spectra f(α) characterized the PSDs well and sensitively reflected the changes of heterogeneity of the surface soil (0–20 cm) during natural succession. SOC, total N and clay contents and the multifractal parameters increased significantly by the late stage of succession, mostly in the topsoil (0–10 cm). Natural succession thus effectively improved the soil physicochemical properties on the Loess Plateau of China, even though it was time-consuming. SOC and total N contents decreased with depth throughout the natural succession, but the multifractal parameters were higher in the topsoil only in the late stage. D ₁ and D ₂ were strongly and positively correlated with SOC and total N contents in the surface layers and with fine particles in all layers, suggesting that D ₁ and D ₂ may be sensitive and practical indices for quantifying changes in soil properties and erosion.     

Responses of Soil,Heterotrophic, and Autotrophic Respiration to Experimental Open-Field Soil Warming in a Cool-Temperate Deciduous Forest

How global warming will affect soil respiration (R _S) and its source components is poorly understood despite its importance for accurate prediction of global carbon (C) cycles. We examined the responses of R _S, heterotrophic respiration (R _H), autotrophic respiration (R _A), nitrogen (N) availability, and fine-root biomass to increased temperature in an open-field soil warming experiment. The experiment was conducted in a cool-temperate deciduous forest ecosystem in northern Japan. As this forest is subjected to strong temporal variation in temperature, on scales ranging from daily to seasonal, we also investigated the temporal variation in the effects of soil warming on R _S, R _H, and R _A. Soil temperature was continuously elevated by about 4.0°C from 2007 to 2014 using heating wires buried in the soil, and we measured soil respiratory processes in all four seasons from 2012 to 2014. Soil warming increased annual R _S by 32–45%, but the magnitude of the increase was different between the components: R _H and R _A were also stimulated, and increased by 39–41 and 17–18%, respectively. Soil N availability during the growing season and fine-root biomass were not remarkably affected by the warming treatment. We found that the warming effects varied seasonally. R _H increased significantly throughout the year, but the warming effect showed remarkable seasonal differences, with the maximum stimulation in the spring. This suggests that warmer spring temperature will produce a greater increase in CO₂ release than warmer summer temperatures. In addition, we found that soil warming reduced the temperature sensitivity (Q ₁₀) of R _S. Although the Q ₁₀ of both R _H and R _A tended to be reduced, the decrease in the Q ₁₀ of R _S was caused mainly by a decrease in the response of R _A to warming. These long-term results indicate that a balance between the rapid and large response of soil microbes and the acclimation of plant roots both play important roles in determining the response of R _S to soil warming, and must be carefully considered to predict the responses of soil C dynamics under future temperature conditions.