Quantifying and Modeling the Influence of Temperature on Growth and Reproductive Development of Sesame

Ambient temperatures are major factors regulating the growth rates, yields, and geographical distribution of crop species. The cultivation of sesame (Sesamum indicum L.) is expanding with the rising demand in regions where it is not traditionally grown, and sub-optimal yields due to extremely low or high temperatures could occur. Currently literature lacks information on the temperature responses of sesame growth. An experiment was conducted to quantify the effects of different temperatures on vegetative growth and reproductive development of sesame, and to estimate its cardinal temperature limits (T_opt; T_min; T_max). Plants were subjected to six different day/night temperature treatments of 40/32, 36/28, 32/24, 28/20, and 20/12 °C using walk-in growth chambers. Vegetative growth of sesame was sensitive to low temperatures (<?15 °C), but tolerant of high temperatures. The cardinal temperature limits of 15.7 °C (T_min), 27.3 °C (T_opt), and 44.6 °C (T_max) were observed for rate of biomass accumulation. Sesame reached the flowering stage under moderate to high temperature conditions; however, reproductive yields progressively declined above 25 °C, and no seed yields were obtained beyond 33 °C. The estimated temperature limits could be employed to develop crop models for simulating management and adaptation strategies of sesame under current and future climate scenarios, and adaptation to regions where the crop is not currently grown. Future research should focus on understanding factors controlling the temperature tolerance of reproductive development in sesame, to provide a broader geographical adaptation.

     

Seedlings of the semi-shrub Artemisia ordosica are resistant to moderate wind denudation and sand burial in Mu Us sandland, China

Sand movement is a common stress for plants in dune ecosystems. Seedlings in such an environment often experience various degrees of denudation or burial. A field experiment was conducted with Artemisia ordosica, a dominant semi-shrub species in Mu Us sandland, China, to test seedling survival and growth under different degrees of denudation and burial. Seedlings from two cohorts with height of 5.0 ± 0.02 cm (S1) and 9.3 ± 0.09 cm (S2) were selected and randomly subjected to three denudation treatments (2.5, 5, and 10 cm), five burial treatments (2.5, 5, 7.5, 10, and 15 cm), or a control. S2 seedlings had a higher survivorship than S1 seedlings, especially under severe denudation (10 cm) and complete burial (5 cm in S1; 10 cm in S2). Seedling survivorship was unaffected by moderate burial (<5 cm in S1; <10 cm in S2) or denudation (<10 cm), but it was significantly reduced under complete burial or severe denudation. Seedling growth in leaf area, height, and biomass only declined in severe denudation or complete burial. Seedling burial led to higher biomass investment in shoots, while the reverse was the case in denudation. The results indicate A. ordosica is highly tolerant to moderate burial and denudation, showing adaptive responses that likely increase survival. Differences in responses between seedling cohorts suggest that large seedling size is beneficial for successful establishment in sandy environments and measures to prevent severe denudation and burial of recently germinated seedlings are necessary in attempts to restore steppe vegetations.     

Modelling the Effects of Water Stress and Temperature on Seed Germination of Radish and Cantaloupe

Cantaloupe (Cucumis melo L.) and radish (Raphanus sativus L.) are considered as important vegetables with potential for national and international markets due to their sugars, vitamins and minerals. This study arranged, therefore, to simultaneously investigate the effect of temperature (T) and water potential (ψ) on seed germination (SG) of these plants using two hydrothermal time (HTT) models and to determine cardinal Ts and base water potential (ψ_b(50)) for both species. The results indicated that SG of both species was more affected by ψ than T (p ≤ 0.001). At Ts below an optimum temperature (T_o) the ψ_b(50) was constant (− 0.582 and − 0.760 MPa for radish and cantaloupe, respectively) and then increased linearly by 0.0481 and 0.0446 MPa °C⁻¹ as T increased above T_o (as thermoinhibition) until 0 MPa at the ceiling temperature (T_c), respectively. As the first report, however, we observed that the T at which ψ_b(50) begins to change was the same here (that is, T_d = T_o), when determined by either model for both species. This result suggests that the assumption in Rowse and Finch-Savage’s model (T_d is often less and or very close to T_o) may be invalid in some cases. For both species, the base temperature (T_b) and T_o were not affected by ψ and were constant while there was an exception only for T_c for which the value declined with decreasing ψs (more negative). In general, the estimated T_b, T_o and T_c were 9.64, 21.3 and 33.0 °C for radish and 11.8, 28.3 and 45.7 °C for cantaloupe in the control condition (ψ = 0 MPa), respectively. The HTT models used here and their parameters, each with strengths and weaknesses, can be used as a predictive tool in both cantaloupe and radish SG simulation models. However, at first, we need to select an appropriate HTT model based on SG behavior of plant species and then use the best model for quantifying the response of SG across Ts and ψs.

     

Novel polycondensed biopolyamide generated from biomass-derived 4-aminohydrocinnamic acid

Biomass plastics are expected to contribute to the establishment of a carbon-neutral society by replacing conventional plastics derived from petroleum. The biomass-derived aromatic amine 4-aminocinnamic acid (4ACA) produced by recombinant bacteria is applied to the synthesis of high-performance biopolymers such as polyamides and polyimides. Here, we developed a microbial catalyst that hydrogenates the α,β-unsaturated carboxylic acid of 4ACA to generate 4-aminohydrocinnamic acid (4AHCA). The ability of 10 microbial genes for enoate and xenobiotic reductases expressed in Escherichia coli to convert 4ACA to 4AHCA was assessed. A strain producing 2-enoate reductase from Clostridium acetobutylicum (ca2ENR) reduced 4ACA to 4AHCA with a yield of > 95% mol mol⁻¹ and reaction rates of 3.4 ± 0.4 and 4.4 ± 0.6 mM h⁻¹ OD₆₀₀ ⁻¹ at the optimum pH of 7.0 under aerobic and anaerobic conditions, respectively. This recombinant strain reduced caffeic, cinnamic, coumaric, and 4-nitrocinnamic acids to their corresponding propanoic acid derivatives. We polycondensed 4AHCA generated from biomass-derived 4ACA by dehydration under a catalyst to form high-molecular-weight poly(4AHCA) with a molecular weight of M _n = 1.94 MDa. This polyamide had high thermal properties as indicated by a 10% reduction in weight at a temperature of T _d10 = 394 °C and a glass transition temperature of T _g = 240 °C. Poly(4AHCA) derived from biomass is stable at high temperatures and could be applicable to the production of high-performance engineering plastics.

     

Sedimentary Organic Carbon and Nitrogen Sequestration Across a Vertical Gradient on a Temperate Wetland Seascape Including Salt Marshes,Seagrass Meadows and Rhizophytic Macroalgae Beds

Coastal wetlands are key in regulating coastal carbon and nitrogen dynamics and contribute significantly to climate change mitigation and anthropogenic nutrient reduction. We investigated organic carbon (OC) and total nitrogen (TN) stocks and burial rates at four adjacent vegetated coastal habitats across the seascape elevation gradient of Cádiz Bay (South Spain), including one species of salt marsh, two of seagrasses, and a macroalgae. OC and TN stocks in the upper 1 m sediment layer were higher at the subtidal seagrass Cymodocea nodosa (72.3 Mg OC ha⁻¹, 8.6 Mg TN ha⁻¹) followed by the upper intertidal salt marsh Sporobolus maritimus (66.5 Mg OC ha⁻¹, 5.9 Mg TN ha⁻¹), the subtidal rhizophytic macroalgae Caulerpa prolifera (62.2 Mg OC ha⁻¹, 7.2 Mg TN ha⁻¹), and the lower intertidal seagrass Zostera noltei (52.8 Mg OC ha⁻¹, 5.2 Mg TN ha⁻¹). The sedimentation rates increased from lower to higher elevation, from the intertidal salt marsh (0.24 g cm⁻² y⁻¹) to the subtidal macroalgae (0.12 g cm⁻² y⁻¹). The organic carbon burial rate was highest at the intertidal salt marsh (91 ± 31 g OC m⁻² y⁻¹), followed by the intertidal seagrass, (44 ± 15 g OC m⁻² y⁻¹), the subtidal seagrass (39 ± 6 g OC m⁻² y⁻¹), and the subtidal macroalgae (28 ± 4 g OC m⁻² y⁻¹). Total nitrogen burial rates were similar among the three lower vegetation types, ranging from 5 ± 2 to 3 ± 1 g TN m⁻² y⁻¹, and peaked at S. maritimus salt marsh with 7 ± 1 g TN m⁻² y⁻¹. The contribution of allochthonous sources to the sedimentary organic matter decreased with elevation, from 72% in C. prolifera to 33% at S. maritimus. Our results highlight the need of using habitat-specific OC and TN stocks and burial rates to improve our ability to predict OC and TN sequestration capacity of vegetated coastal habitats at the seascape level. We also demonstrated that the stocks and burial rates in C. prolifera habitats were within the range of well-accepted blue carbon ecosystems such as seagrass meadows and salt marshes.

     

Latitudinal variation in growth and survival of juvenile corals in the West and South Pacific

Reef-building corals are found across > 30° of latitude from tropical to temperate regions, where they occupy habitats greatly differing in seawater temperature and light regimes. It remains largely unknown, however, how the demography of corals differs across this gradient of environmental conditions. Variation in coral growth is especially important to coral populations, because aspects of coral demography are dependent on colony size, with both fecundity and survivorship increasing with larger colonies. Here we tested for latitudinal variation in annual growth rate and survival of juvenile corals, using 11 study locations extending from 17° S to 33° N in the West and South Pacific. Regression analyses revealed a significant decline in annual growth rates with increasing latitude, whereas no significant latitudinal pattern was detected in annual survival. Seawater temperature showed a significant and positive association with annual growth rates. Growth rates varied among the four common genera, allowing them to be ranked Acropora > Pocillopora > Porites > Dipsastraea. Acropora and Pocillopora showed more variation in growth rates across latitudes than Porites and Dipsastraea. Although the present data have limitations with regard to difference in depths, survey periods, and replication among locations, they provide evidence that a higher capacity for growth of individual colonies may facilitate population growth, and hence population recovery following disturbances, at lower latitudes. These trends are likely to be best developed in Acropora and Pocillopora, which have high rates of colony growth.

     

E. coli Nissle microencapsulation in alginate-chitosan nanoparticles and its effect on Campylobacter jejuni in vitro

Microencapsulation enhances the oral delivery of probiotic bacteria. In this study, the probiotic Escherichia coli Nissle 1917 (EcN) was microencapsulated using alginate and chitosan nanoparticles. The result showed 90% encapsulation yield of EcN, and the encapsulated EcN displayed significantly (P < 0.05) increased survival in low pH (1.5), high bile salt concentration (4%), and high temperature (70 °C). The most effective cryopreservatives of EcN during freezing and thawing was skim milk and sucrose. Exposure to microencapsulated EcN significantly (P < 0.05) reduced the Campylobacter jejuni growth by 2 log CFU. The rate of EcN release from microcapsule was 9.2 × 10⁵ cell min⁻¹, and the appropriate model to describe its release kinetics was zero order. Importantly, the entrapment of EcN inside the microcapsule did not eliminate the exterior diffusion of EcN produced antioxidant compounds. In addition, the EcN microcapsule efficiently adhered to intestinal HT-29 cells and the pre-treatment of HT-29 cells with EcN-microcapsule for 4 h significantly (P < 0.05) reduced the invasion (1.9 log) of C. jejuni; whereas, completely abolished the intracellular survival. Furthermore, HT-29 cells pre-treated with encapsulated EcN in PCR array showed decreased expression (> 1.5-fold) of genes encoding chemokines, toll-like receptors, interleukins, and tumor necrosis factors. In conclusion, the alginate-chitosan microcapsule can provide effectual platform to deliver probiotic EcN and thereby can reduce the Campylobacter infection in chickens and humans.

     

Evaluation of the Impacts of Long-Term Enriched Artemia with Bacillus subtilis on Growth Performance,Reproduction, Intestinal Microflora,and Resistance to Aeromonas hydrophila of Ornamental Fish Poecilia latipinna

The present study investigated the effect of enriched Artemia with Bacillus subtilis on growth performance, reproductive factors, proximate composition, intestinal microflora, and resistance to Aeromonas hydrophila of ornamental fish, Poecilia latipinna. Using a completely randomized design, the experiment included three groups. The first group was fed with commercial food without any probiotic. The second group was fed with unenriched Artemia, and the last group consumed long-time enriched Artemia with Bacillus subtilis. The bacteria B. subtilis with a density of 1 × 10⁵ CFU mL⁻¹ was added daily to Artemia culture medium. The total microflora and Bacillus subtilis counts were significantly increased in enriched Artemia compared to the unenriched group (P < 0.05). In fish fed groups, growth factors did not show any significant difference (P > 0.05). The maximum relative fecundity (28.65 ± 2.52 egg number g⁻¹), fry production (62.93 ± 4.6 individual per female), and fry survival (70.97 ± 1.56%) obtained in the third group were found to be significantly more than those in the first and the second groups. Moreover, intestinal bacterial count for Bacillus revealed that the higher concentration of bacteria was significantly related to the third group (6.24 ± 0.11 log CFU g⁻¹) (P < 0.05). Maximum protein and fat contents were observed in fish fed with Bacillus-enriched Artemia; however, no significant difference was found between control and unenriched Artemia groups (P > 0.05). The highest amount of ash was observed in fish fed with commercial food without any probiotic (P < 0.05). At the end of the feeding period, each of the three groups along with positive group (oxytetracycline 100 mg kg⁻¹ of commercial food) was exposed to A. hydrophila (BCCM5/LMG3770) bacteria intraperitoneally. Based on the results, the lowest cumulative mortality was significantly found in group three (68.75 ± 3.6%) and positive group (62.5 ± 7.0%) compared to control and unenriched Artemia groups (P < 0.05). Hence, B. subtilis with a concentration of 1 × 10⁵ CFU mL⁻¹ during the period of Artemia culturing can improve the reproductive parameters, intestinal microflora, and resistance to pathogenic bacteria of Poecilia latipinna.

     

Habitat choice and seed–seedling conflict of Spartina alterniflora on the coast of China

To elucidate the seed–seedling conflict and the process of habitat choices during the expansion of S. alterniflora, densities of seeds and seedlings in three different habitats, foreland, Spartina meadow, and canopy gap patch, were measured. Statistical analyses of these measurements were performed to investigate the interaction between seeds or seedlings and environmental factors. Also, the process of habitat choice during the expansion of S. alterniflora was explored. The results show that, in the upper soil seed bank (0–5 cm), both the ratio of germinated seeds and the ratio of survival seedlings to total seeds do not differ significantly among the three habitats. However, in the lower soil seed bank (5–10 cm), these ratios differ significantly, suggesting the seed–seedling conflict of S. alterniflora generally occurs in the lower soil seed bank. The remarkable conflict occurs in the meadow habitat. Greenhouse experiments indicate that the germination rate decreases significantly and the mortality of pre-emerged seedlings increases significantly with increasing burial depth. The maximal burial depth of emerged seedlings varies with sediment types. Comparisons of burial depth effects on seedling height, mesocotyl length, coleoptile length, and root length show that the major responses of S. alterniflora pre-emerged seedlings to the burial treatments are the elongation of coleoptiles and mesocotyls, which favor seedling survival by enhancing aeration and accelerating emergence. These results suggest that burial treatment is a key selection factor, which leads to the seed–seedling conflict in recruitment of S. alterniflora population, and directly affects the expansion rate and the area infected by S. alterniflora. Handling editor: S. M. Thomaz Ziwang Deng: co-first author.     

Germination and emergence of Astrodaucus orientalis (L.) Drude populations influenced by environmental factors and seed burial depth

Astrodaucus orientalis is a weed species in cropping systems and rangelands in Iran. The effects of temperature, light, NaCl concentration, water potential, seed burial depth and crop residue cover were assessed on seed germination and seedling emergence of two populations of A. orientalis from Ardabil (Meshginshahr population) and East Azarbayjan (Tabriz population) provinces of Iran. The A. orientalis populations indicated different responses to environmental factors and burial depth. In the Tabriz population the greatest germination (88.5%) was observed in 20/12°C day/night temperature but in the Meshginshahr population (83.2%) it was obtained in 24/16°C day/night temperature. Over a broad range of light period (10–24 hr light) germination was 74–83%, but it decreased (less than 37%) under 24 hr dark in both A. orientalis populations. With respect to water potential, the C₅₀ parameters were −0.62 and − 0.49 MPa for Tabriz and Meshginshahr populations, respectively. The D₅₀ parameters (the burial depth that caused 50% decrease in emergence) for Tabriz and Meshginshahr populations were 2.42 and 3.13 cm, respectively. Generally, the results showed that emergence of both populations of A. orientalis was delayed as depth of burial increased up to 4 cm and in cropping systems a shallow tillage that locates the seeds to >4 cm of depth in soil could be used in order to suppress seedling emergence. Our findings also could be useful in integrated management of A. orientalis in winter annual crops and rangelands.     

Influence of Dietary Copper Methionine Concentrations on Growth Performance,Digestibility of Nutrients,Serum Lipid Profiles,and Immune Defenses in Broilers

A 42-day experiment was conducted to evaluate the influence of dietary copper (Cu) concentrations on growth performance, nutrient digestibility, and serum parameters in broilers aged from 1 to 42 days. Five hundred forty 1-day-old broilers were randomly assigned into 1 of the following 6 dietary treatments: (1) control (basal diet without supplemental Cu), (2) 15 mg/kg supplemental Cu (Cu15), (3) 30 mg/kg supplemental Cu (Cu30), (4) 60 mg/kg supplemental Cu (Cu60), (5) 120 mg/kg supplemental Cu (Cu120), and (6) 240 mg/kg supplemental Cu (Cu240), Cu as copper methionine. A 4-day metabolism trial was conducted during the last week of the experiment feeding. The results showed that dietary Cu supplementation increased the average daily gain and the average daily feed intake (P < 0.01). The feed gain ratio, however, was not affected by dietary Cu (P > 0.10). Additionally, dietary Cu supplementation increased the digestibility of fat and energy (P < 0.05). The concentration of serum cholesterol, triglycerides, and high-density lipoprotein cholesterol decreased with dietary Cu supplementation (P < 0.05). The activities of serum Cu-Zn superoxide dismutase (P < 0.05), glutathione peroxidase (P < 0.05), and ceruloplasmin (P = 0.09), on the contrary, were increased by Cu addition. For immune indexes, dietary Cu supplementation increased serum IgA and IgM (P < 0.05). In addition, the activities of serum ALT increased with increasing dietary Cu supplementation (P < 0.05). In conclusion, our data suggest that Cu supplementation can increase fat digestibility and promote growth. Additionally, dietary Cu supplementation can reduce serum cholesterol and enhance antioxidant capacity in broilers.

     

Seed burial depth,seedling emergence,and height as affected by animal trampling in marl soils

Depending on the plant species, animal trampling significantly affects vegetation by affecting seed burial in marl soil (MS). Soil seed bank dynamics (SSBDs) and seedling characteristics were investigated under light, moderate, and heavy grazing intensities in a MS and non-marl soil (NMS). Considering the seed characteristics and appendages, SSBDs and seedling characteristics significantly changed under grazing intensities (p?<?0.05) where the greatest change was observed in MS (more than NMS). Seed size and seed sphericity index showed a significant positive relationship with seed burial depth under heavy grazing, while the seed length and width and the presence of appendages had the strongest negative correlation with seed burial under exclosure/light grazing (p?<?0.05). Depth of 4–6 cm had the most seed numbers under heavy grazing. Moreover, heavy grazing reduced the diversity index in SSB by 34%, while the diversity index in vegetation has decreased by 41% compared to control.

     

Reproductive success of soybean (Glycine max L. Merril) cultivars and exotic lines under high daytime temperature

The objectives were to (a) quantify the effects of high daytime temperature (HDT) from gametogenesis to full bloom on photosynthesis and pod set in soybean (Glycine max L. Merril) genotypes and (b) assess the relationships among photosynthesis, cardinal temperatures for pollen germination, in vitro pollen germination percentage, canopy reflectance, and pod‐set percentage. Three field experiments were conducted, and Experiment I had HDT between gametogenesis and full bloom (36.5°C to 38.6°C) compared with Experiments II and III (29.5°C to 31.6°C; optimum temperature). HDT decreased photosynthesis (22%) and pod‐set percent (11%) compared with Experiment III. Cultivars had higher photosynthesis and pod‐set percent than plant introduction (PI) lines. The cultivars (i.e., IA3023 and KS4694) and PI lines (i.e., PI393540 and PI588026A) were HDT tolerant and susceptible, respectively. The decreased pod‐set percentage in susceptible genotypes (PI lines) was associated with pollen characteristics. Significant positive (r² ≥ 0.67) association between photosynthesis, cardinal temperatures for pollen germination (T_opt and T_max) with pod‐set percentage was observed. However, a negative (r² ≥ ?0.43) association between photosynthesis and pod set with canopy reflectance at visible spectrum was observed. In vitro pollen germination and canopy reflectance at visible spectrum can be used as a high‐throughput phenotypic tool for breeding HDT‐tolerant genotypes.     

Thermal acclimation of shoot respiration in an Arctic woody plant species subjected to 22 years of warming and altered nutrient supply

Despite concern about the status of carbon (C) in the Arctic tundra, there is currently little information on how plant respiration varies in response to environmental change in this region. We quantified the impact of long‐term nitrogen (N) and phosphorus (P) treatments and greenhouse warming on the short‐term temperature (T) response and sensitivity of leaf respiration (R), the high‐T threshold of R, and associated traits in shoots of the Arctic shrub Betula nana in experimental plots at Toolik Lake, Alaska. Respiration only acclimated to greenhouse warming in plots provided with both N and P (resulting in a ~30% reduction in carbon efflux in shoots measured at 10 and 20 °C), suggesting a nutrient dependence of metabolic adjustment. Neither greenhouse nor N+P treatments impacted on the respiratory sensitivity to T (Q₁₀); overall, Q₁₀ values decreased with increasing measuring T, from ~3.0 at 5 °C to ~1.5 at 35 °C. New high‐resolution measurements of R across a range of measuring Ts (25–70 °C) yielded insights into the T at which maximal rates of R occurred (T_max). Although growth temperature did not affect T_max, N+P fertilization increased T_max values ~5 °C, from 53 to 58 °C. N+P fertilized shoots exhibited greater rates of R than nonfertilized shoots, with this effect diminishing under greenhouse warming. Collectively, our results highlight the nutrient dependence of thermal acclimation of leaf R in B. nana, suggesting that the metabolic efficiency allowed via thermal acclimation may be impaired at current levels of soil nutrient availability. This finding has important implications for predicting carbon fluxes in Arctic ecosystems, particularly if soil N and P become more abundant in the future as the tundra warms.     

Effects of Chromium and Carnitine Co-supplementation on Body Weight and Metabolic Profiles in Overweight and Obese Women with Polycystic Ovary Syndrome: a Randomized,Double-Blind,Placebo-Controlled Trial

The primary aim of our study was to determine the influence of taking chromium plus carnitine on insulin resistance, with a secondary objective of evaluating the influences on lipid profiles and weight loss in overweight subjects with polycystic ovary syndrome (PCOS). In a 12-week randomized, double-blind, placebo-controlled clinical trial, 54 overweight women were randomly assigned to receive either supplements (200 μg/day chromium picolinate plus 1000 mg/day carnitine) or placebo (27/each group). Chromium and carnitine co-supplementation decreased weight (− 3.6 ± 1.8 vs. − 1.0 ± 0.7 kg, P < 0.001), BMI (− 1.3 ± 0.7 vs. − 0.3 ± 0.3 kg/m², P < 0.001), fasting plasma glucose (FPG) (− 5.1 ± 6.0 vs. − 1.1 ± 4.9 mg/dL, P = 0.01), insulin (− 2.0 ± 1.4 vs. − 0.2 ± 1.2 μIU/mL, P < 0.001), insulin resistance (− 0.5 ± 0.4 vs. − 0.04 ± 0.3, P < 0.001), triglycerides (− 18.0 ± 25.2 vs. + 5.5 ± 14.4 mg/dL, P < 0.001), total (− 17.0 ± 20.3 vs. + 3.6 ± 12.0 mg/dL, P < 0.001), and LDL cholesterol (− 13.3 ± 19.2 vs. + 1.4 ± 13.3 mg/dL, P = 0.002), and elevated insulin sensitivity (+ 0.007 ± 0.005 vs. + 0.002 ± 0.005, P < 0.001). In addition, co-supplementation upregulated peroxisome proliferator-activated receptor gamma (P = 0.02) and low-density lipoprotein receptor expression (P = 0.02). Overall, chromium and carnitine co-supplementation for 12 weeks to overweight women with PCOS had beneficial effects on body weight, glycemic control, lipid profiles except HDL cholesterol levels, and gene expression of PPAR-γ and LDLR. Clinical trial registration number: http://www.irct.ir: IRCT20170513033941N38.

     

Implications of climate warming on seedling emergence and mortality of African savanna woody plants

Seedling emergence from scarified seeds and mortality of different seedling cohorts of five African savanna woody species (Acacia polyacantha, A. sieberana, Bauhinia thonningii, Dichrostachys cinerea and Ziziphus abyssinica) were studied under field conditions at a site in central Zambia. The study was conducted over a 4-year period, from 2003 to 2007. The objectives of the study were to determine climate factors that significantly influence seedling emergence rate and mortality in order to assess likely responses of the studied species to a warmer climate. Mean seedling emergence rate was 12% in D. cinerea and Z. abyssinica, 17% in B. thonningii, 47% in A. poyacantha and 62% in A. sieberana. Climate factors did not significantly affect seedling emergence in A. sieberana while temperature significantly influenced seedling emergence rate in the other species. Under a 1° warmer climate, seedling emergence rate was predicted to decline in A. polyacantha, B. thonningii and Z. abysssinica but is likely to increase slightly in D. cinerea. Time of seedling emergence during the wet season did not appear to affect seedling survival. Temperature also significantly influenced seedling mortality in all the studied species such that under a warmer climate, mortality was predicted to increase in A. sieberana and D. cinerea but decrease in A. polyacantha, B. thonningii and Z. abyssinica. As the studied species exhibited differential optimum temperature conditions for seedling emergence and seedling survival, they are likely to respond to climate warming in different but predictable ways. The results of the study are useful to forest management and development of climate change adaptation strategies in southern Africa.     

Adaptation of soil microbial growth to temperature: Using a tropical elevation gradient to predict future changes

Terrestrial biogeochemical feedbacks to the climate are strongly modulated by the temperature response of soil microorganisms. Tropical forests, in particular, exert a major influence on global climate because they are the most productive terrestrial ecosystem. We used an elevation gradient across tropical forest in the Andes (a gradient of 20°C mean annual temperature, MAT), to test whether soil bacterial and fungal community growth responses are adapted to long‐term temperature differences. We evaluated the temperature dependency of soil bacterial and fungal growth using the leucine‐ and acetate‐incorporation methods, respectively, and determined indices for the temperature response of growth: Q₁₀ (temperature sensitivity over a given 10oC range) and T_min (the minimum temperature for growth). For both bacterial and fungal communities, increased MAT (decreased elevation) resulted in increases in Q₁₀ and T_min of growth. Across a MAT range from 6°C to 26°C, the Q₁₀ and T_min varied for bacterial growth (Q_10–20 = 2.4 to 3.5; T_min = ?8°C to ?1.5°C) and fungal growth (Q_10–20 = 2.6 to 3.6; T_min = ?6°C to ?1°C). Thus, bacteria and fungi did not differ significantly in their growth temperature responses with changes in MAT. Our findings indicate that across natural temperature gradients, each increase in MAT by 1°C results in increases in T_min of microbial growth by approximately 0.3°C and Q_10–20 by 0.05, consistent with long‐term temperature adaptation of soil microbial communities. A 2°C warming would increase microbial activity across a MAT gradient of 6°C to 26°C by 28% to 15%, respectively, and temperature adaptation of microbial communities would further increase activity by 1.2% to 0.3%. The impact of warming on microbial activity, and the related impact on soil carbon cycling, is thus greater in regions with lower MAT. These results can be used to predict future changes in the temperature response of microbial activity over different levels of warming and over large temperature ranges, extending to tropical regions.     

Effects of S-Abscisic Acid (S-ABA) on Seed Germination,Seedling Growth,and Asr1 Gene Expression Under Drought Stress in Maize

The objective of this study was to evaluate the ability of the phytohormone S-abscisic acid (S-ABA) to protect maize seedlings grown under drought stress and to measure their increased drought tolerance. The maize hybrids ‘Zhengdan 958’ (ZD958; drought tolerant) and ‘Xundan 20’ (XD20; drought sensitive) were treated with nutrient solutions of different concentrations (1, 2, 4, 8, and 10 mg/kg) of S-ABA under polyethylene glycol (PEG, 15% w/v, MW 6000) simulated drought stress. Optimal concentrations of S-ABA were designed to be sprayed onto the leaves of seedlings, and their effect on endogenous ABA, malondialdehyde (MDA), osmotic substances, antioxidant enzyme activities, and Asr1 gene expression in seedlings were studied. Results indicated that, under drought stress, S-ABA treatment significantly improved maize seed germination rate (GR), germination energy (GE), and seedling biomass (p < 0.05). After spraying 4 mg/kg S-ABA onto leaves, the endogenous hormone ABA, osmotic substances, antioxidant enzyme activities, and expressive quantity of the Asr1 gene were extended and MDA content dropped significantly (p < 0.05). Moreover, ZD 958 endogenous ABA content, osmotic substances content, antioxidant enzyme activity and Asr1 gene expressive quantity were higher than that of XD 20 (p < 0.05). In conclusion, S-ABA treatment increased the content of endogenous ABA, induced an increase in antioxidant enzyme activity and Asr1 gene expression level, reduced the oxidative damage caused by drought to maize leaves, and improved the adaptability of maize seedlings to withstand drought stress. The promoting effect of S-ABA on the drought-tolerant variety ZD 958 was more obvious (p < 0.05). These results serve as a reference for the use of S-ABA in mitigating drought stress in maize.

     

Effects of Lactobacillus rhamnosus ATCC 7469 on Different Parameters Related to Health Status of Rainbow Trout (Oncorhynchus mykiss) and the Protection Against Yersinia ruckeri

In the current study, we investigated the effect of a probiotic bacterium (Lactobacillus rhamnosus ATCC 7469) microencapsulated with alginate and hi-maize starch and coated with chitosan on improving growth factors, body composition, blood chemistry, and the immune response of rainbow trout (initial weight: 18.41 ± 0.32 g). Four experimental diets were formulated to feed fish for 60 days. They were control diet without any additive (C), diet added with beads without probiotic (E), a probiotic sprayed to the diet (L.r), and encapsulated probiotic supplemented diet (E-L.r). The results indicated that feeding with E-Lr significantly improved weight gain (84.98 g) and feed conversion ratio (0.95) compared to the other groups (P < 0.05). Also, fish fed E-Lr diet had a significantly higher value of whole-body protein (17.51%), total protein in the blood (4.98 g/dL), lysozyme (30.66 U/mL), alternative complement pathway hemolytic activity (134 U/mL), superoxide dismutase (203 U/mg protein), and catalase (528.33 U/mg protein) (P < 0.05) as compared to those fed the control diet. Similarly, a higher relative expression of immune-related genes such as interleukin-1 (Il-1) and tumor necrosis factor-alpha (TNF-1α) were reported in those fed E-L.r and L.r diets respectively. Interestingly, the fish fed dietary E-L.r had a significantly lower value of lipid in the whole body (4.82%) and cholesterol in the blood (160.67%) in comparison with those fed the control diet (P < 0.05). At the end of the experiment, all groups were challenged by Yersinia ruckeri where the survival rate of rainbow trout fed dietary E-L.r (70.36%) was statistically higher than that of the others (P < 0.05). Overall, the results suggested that encapsulated probiotic Lact. rhamnosus ATCC 7469 acted better than unencapsulated probiotic and has a potential to improve growth performance, flesh quality, and the immune response of rainbow trout.

     

Benefit of Dietary Supplementation with Bacillus subtilis BYS2 on Growth Performance,Immune Response,and Disease Resistance of Broilers

A strain of Bacillus subtilis (B. subtilis) BYS2 was previously isolated from Mount Tai, which is located in Tai’an City in the Shandong Province of China. The strain was then stored in the Environmental Microbiology Laboratory at Shandong Agricultural University. To evaluate the effect of the bacterium preparation in broiler production, we fed the bacterium (10⁶ CFU/g) to 1-day-old broilers and continued this feeding for 6 weeks to analyze its effect on growth and immune performance. We found that the average weight of the bacterium-fed group increased by 17.19% at weeks 5 compared to the control group (P < 0.05). The height of the villi in the duodenum and jejunum and the ratio of villi to crypt were significantly increased in the bacterium-fed group at weeks 5 (P < 0.05). Also, the IgG in the serum of broilers in the experimental group increased by 31.60% (P < 0.05) and IgM 30.52% (P < 0.05) compared with those in the control group. The expressions of the major pattern recognition receptors (PRRs), antiviral proteins, pro-inflammatory cytokines, and β-defensins were significantly higher than those in the control group (P < 0.05). Meanwhile, the bursa immune organ indices of broilers in the experimental group were significantly higher than those in the control group (P < 0.05). Also, after 5 weeks of continuous feeding, when infected with Escherichia coli (E. coli) O1K1 and Newcastle disease virus (NDV) F48E8, the content of bacteria and virus in tissues and organs of the experimental group decreased significantly, and the survival rate of infected chickens increased by 31.1% and 17.7%, respectively (P < 0.05). These results show that the anti-infective B. subtilis BYS2 could, to some extent, replace antibiotics to promote growth, improve innate immunity, and enhance disease resistance in broilers.