Effect Of Different Densities Research Articles

The Effect of Li2CO3 on Mechanical and Electrochemical Behavior of Li6.4La3Zr1.4Ta0.6O12 Solid-State Electrolyte

Li6.4La3Zr1.4Ta0.6O12 (LLZTO) is a very promising solid-state electrolyte for all solid-state battery. Due to its high ionic conductivity and chemical and electrochemical stability that can allow to use Li metal as anode with a high energy density as well as enhanced battery safety. However, there is little research to study the intrinsic mechanical properties of LLZTO which is a key factor that will influence the capacity fading and shortened lifetime of battery. In this study, we examine the effect of different densities on the elastic modules, hardness and toughness of Ta substituted LLZO solid-state electrolyte which will result the varieties of the mechanical and electrochemical performance. After annealing, the densities of the sample varied from 85% to 96% with the grain size from 3.5μm to 5.1μm. By introduction of the Li2CO3 additive, the grains become more connected and the number of pores at the grain boundaries becomes much smaller. The grain size rages from 3 to10μm. 5%-LLZTO has more strong grain boundary. It is suggested that the mechanical fracture happened during the Li plating process. Impedance of ion diffusion and electron transfer increase as density increase. Hardness decreases with increasing porosity and increasing grain size. The young’s modulus and the hardness increased from 121.9 to 138.8 Gpa and 4.54 to 11.26 Gpa for the 85% and 96% relative density samples, respectively. The results of this study reveal that the density of LLZTO was influenced by the amount of Li2CO3, so that the mechanical performance can be optimized through the selection of the microstructure, network, and properties of the active materials.

Optimizing Parasitoid and Host Densities for Efficient Rearing of Ontsira mellipes (Hymenoptera: Braconidae) on Asian Longhorned Beetle (Coleoptera: Cerambycidae)

Ontsira mellipes Ashmead is a gregarious larval ectoparasitoid of woodboring cerambycids. It is native to North America but can readily attack the exotic Asian longhorned beetle, Anoplophora glabripennis (Motschulsky). This study aimed to develop an efficient rearing system for this parasitoid, as a potential novel association biocontrol agent for the beetle, by investigating the effects of different densities of host (two, three, or four larvae) and parasitoid (one, two, three, four, five, six, seven, and eight female wasps) on Ontsira's parasitization efficiency and reproductive outcomes. Results showed that overall parasitism and total numbers of parasitized hosts or progeny produced increased with host and/or parasitoid densities, but the number of parasitized hosts or progeny produced per female parasitoid decreased with parasitoid density at each given host density. Nonlinear regression indicated a consistent pattern of mutual interference as parasitoid density increased. Additional experiments showed that superparasitism (indirect interference) did not occur probably because the parasitoid detects hosts through vibration cues from host feeding and attacked (thus paralyzed) hosts are no longer detectable. Thus, the interference probably results from direct or exploitative competition. Interestingly, female parasitoids responded to increased parasitoid density with a significant increase in clutch size. Overall, per capita parasitization efficiency or reproductive outcomes were optimized at a low parasitoid-host ratio but with large group size of hosts and parasitoids. Therefore, an optimal combination of exposing three or four parasitoids to four hosts is proposed for efficient mass-rearing of this parasitoid.

Shrimp rearing in biofloc integrated with different mullet stocking densities

This work compared the effects of different densities of Mugil curema integrated in the rearing of Litopenaeus vannamei in a biofloc system on the yield and ecological performance of the system. For that, an experiment lasting 55 days was conducted. Four groups were evaluated as follows: (a) T0: shrimp reared without mullet, (b) T10: shrimp reared with 22 fish per tank, (c) T20: shrimp reared with 43 fish per tank, and (d) T30: shrimp reared with 65 fish per tank, each treatment with four replicates. The sludge:biomass ratio was higher in the T0 treatment, while the T10–T20 treatments were more efficient, producing more biomass and less sludge. The use of water was 17% more efficient in all treatments with mullet. Mullet survival was higher in the T10 and T20 treatments (mean: 84 ± 8%) than in the T30 (61 ± 5%) treatment. The fish final biomass and yield limits of the system were 0.37 kg and 3.7 kg/m3 respectively. Finally, there was no increase in the total nitrogen output of the system up to the T10 density. In conclusion, it is possible to integrate mullet up to 3.7 kg/m3, increasing the yield in 20% and decreasing water use.

Interactive effects of different densities of Pedicularis kansuensis parasitism and Epichloё endophyte infection on the endogenous hormone levels and alkaloid contents of Stipa purpurea

Interactive effects of different densities of Pedicularis kansuensis parasitism and Epichloё endophyte infection on the endogenous hormone levels and alkaloid contents of Stipa purpurea

Plasticity on 'BRS 8381' Glycine max (L.) Merril Agronomic Attributes in Different Years of Cultivation in Roraima

Soy has high plasticity, which expands its capacity to adapt to different environmental and management conditions, through morphological changes in production components. Thus, the objective was to evaluate the effects of different densities of soybean cultivar BRS 8381 on agronomic characteristics. The experiment was implemented and conducted in a Cerrado area, in the Agua Boa of Embrapa Roraima experimental field. A randomized block design was used in a 2*4 factorial scheme, with four replications. The treatments consisted of two years of soybean cultivation (2015 and 2016), sown in four plant densities (10, 14, 18 and 22 plants per linear meter). Agronomic characteristics were evaluated: plant height; height of insertion of the first pod; stem diameter; number of nodes on the stem; number of pods per plant; number of branches per plant; dry mass of the plant; harvest index and grain yield. The highest average productivity of 'BRS 8381' soybeans in the Cerrado area of Roraima is obtained with a population of 387.448 plants per hectare. 'BRS 8381' plants at density 22 plants m-1 linear are not suitable for the Cerrado conditions of Roraima. The cv. BRS 8381 is influenced by rainfall and temperature factors in the Cerrado conditions of Roraima.

Effect of Different Density to Growth and Survival of Gurame Seedling

This study aims to determine the effect of different stocking density on the growth and survival of fish fry carp (Osphronemus gouramy). This study used an experimental method. The design used was completely randomized design (CRD) with three treatments and three replications. The results showed that the absolute growth in length and the highest weight shown on treatment A (3 heads / l) respectively of 1.09 and 0.9 g cm, followed by treatment B (5 animals / l) respectively of 0.9 cm and 0.84 g, and the lowest in treatment C (7 animals / l), respectively for 0.86 cm and 0.8 g. Gurame fish seed viability during the study showed treatment A by 82.86% whereas 72.67% of treatment B and C treatment amounting to 83.33%. The results of this study continue with the LSD (Least Significant Difference) with a confidence level of 99%. Keywords: Gurame seedling; Osphronemus gouramy; survival; density; growth

The effect of density as Skeletonema costatum bioremediation agent of copper (Cu) heavy metal concentration

Heavy metals copper (Cu) was microelements needed by organisms in small quantities. The type of plankton that could be used as a bioremediation agent because of its abundance and resistance in nature was Skeletonema costatum. This study aims to determine the effect of different density of Skeletonema costatum exposure Cu and Determine the effect of exposure to the growth of Skeletonema costatum. The design used in this research was an experimental method. This research using Completely Randomized Design (CRD) with three treatments and six replications. Treatment used was 5,000 cells/ml (A), 10,000 cells/ml (B), and 15,000 cells/ml (C) of cells density at 1 ppm Cu concentration. The results of this study prove that the density of Skeletonema costatum could affect Cu uptake levels with the absorption percentage of treatment A was78,62b ± 10.40; the absorption percentage of treatment B was 88,13ab ± 7.49; the absorption percentage of treatment C was 91,96b ± 4.87. Culture media that contained 1 ppm Cu concentration could affect the growth and growth phase of Skeletonema costatum. Skeletonema costatum that exposed cells with Cu has higher growth than with Cu reviews those not exposed.

Modeling the effects of sediment concentration on the propagation of flash floods in an Andean watershed

Abstract. Rain-induced flash floods are common events in regions near mountain ranges. In peri-urban areas near the Andes the combined effects of the changing climate and El Niño–Southern Oscillation (ENSO) have resulted in an alarming proximity of populated areas to flood-prone streams, increasing the risk for cities and infrastructure. Simulations of rapid floods in these watersheds are particularly challenging, due to the complex morphology, the insufficient hydrometeorological data, and the uncertainty posed by the variability of sediment concentration. High concentrations produced by hillslope erosion and rilling by the overland flow in areas with steep slopes and low vegetational covering can significantly change the dynamics of the flow as the flood propagates in the channel. In this investigation, we develop a two-dimensional finite-volume numerical model of the nonlinear shallow water equations coupled with the mass conservation of sediment to study the effects of different densities, which include a modified version of the quadratic stress model to quantify the changes in the flow rheology. We carry out simulations to evaluate the effects of the sediment concentration on the floods in the Quebrada de Ramón watershed, a peri-urban Andean basin in central Chile. We simulate a confluence and a total length of the channel of 10.4 km, with the same water hydrographs and different combinations of sediment concentrations in the tributaries. Our results show that the sediment concentration has strong impacts on flow velocities and water depths. Compared to clear-water flow, the wave-front velocity slows down more than 70 % for floods with a volumetric concentration of 60 % and the total flooded area is 36 % larger when the sediment concentration is equal to 20 %. The maximum flow momentum at cross sections in the urban area increases 14.5 % on average when the mean concentration along the main channel changes from 30 % to 44 %. Simulations also show that other variables such as the arrival time of the peak flow and the shape of the hydrograph at different locations along the channel are not significantly affected by the sediment concentration and depend mostly on the steep channel morphology. Through this work we provide a framework for future studies aimed at improving hazard assessment, urban planning, and early warning systems in urban areas near mountain streams with limited data and affected by rapid flood events.

Competitiveness of windmill grass (Chloris truncata) and feathertop Rhodes grass (Chloris virgata) in mungbean (Vigna radiata)

Windmill grass (Chloris truncata R.Br.) and feathertop Rhodes grass (Chloris virgata Sw.) are two weeds of the northern region of Australia that are rapidly expanding in range, being favoured by conservation agricultural systems and prevailing weed management using a narrow pool of herbicides. Information on competitiveness and seed-production dynamics of these weeds is lacking for mungbean (Vigna radiata (L.) Wilczek), a major summer crop in the region. Field studies were conducted to evaluate the effect of different densities of these weed species on crop yield of mungbean in the 2016–17 (2016) and 2017–18 (2017) seasons. Windmill grass reduced mungbean yields by 56% with 39 weed plants m–2 in 2016 and 55% with 47 weed plants m–2 in 2017. Windmill grass produced a maximum of 98708 seeds m–2 in 2016 and 118613 seeds m–2 in 2017, and there was 15–21% seed dispersal at crop harvest. Competition from feathertop Rhodes grass resulted in yield losses of 73% with 49 weed plants m–2 and 65% with 45 weed plants m–2. Feathertop Rhodes grass produced a maximum of 229514 seeds m–2 in 2016 and 367190 seeds m–2 in 2017, and seed dispersal at crop harvest was only 3–7%. Competition from both weed species resulted in a significant reduction in number of pods per m2, grains per pod and 1000-grain weight of mungbean. These results show that windmill grass and feathertop Rhodes are highly competitive against mungbean, and their timely management is crucial for minimising yield loss. Although both weeds produced a substantial number of seeds, seed dispersal at crop harvest was low, especially for feathertop Rhodes grass. The high weed-seed retention relative to maturity of mungbean may help in managing these problematic weeds through various means including weed-seed capturing and destruction

Kelp patch size and density influence secondary productivity and diversity of epifauna

Habitat‐forming ecosystem engineers are the foundation of many marine ecosystems where they support diverse and productive food‐webs. A reduction in their patch size or density may affect the productivity, biodiversity and stability of these ecosystems. We determined the effects of different densities and patch sizes of Ecklonia radiata (the dominant kelp in southern Australia) on the secondary productivity, species richness, diversity and community structure of understory epifaunal invertebrates and how associated environmental covariates modified by kelp affected those patterns. We assessed sub‐canopy epifauna across 28 artificial reefs with transplanted E. radiata consisting of seven different patch sizes (0.12–7.68 m2) crossed with four kelp densities (0–16 kelp m−2) over two years. Epifaunal secondary productivity associated with both natural algal and standardised rope fibre habitats decreased with patch size and was elevated when kelp was absent, however, it was also high in natural habitat when there was a high density of kelp. Epifaunal productivity was positively associated with sub‐canopy light and water flow but negatively associated with the biomass of the dominant understory alga, Ulva sp. Epifaunal diversity declined with a reduction in reef size as did richness which correlated with a loss of algal species richness. Community structure of epifauna also differed between small and large reefs, between reefs with and without kelp, between rope habitats at the centre and at the edge of reefs, and within natural habitat between reefs supporting high and low densities of kelp. Overall, these results indicate complex effects of E. radiata decline on epifaunal communities, with high secondary productivity associated with dense kelp stands, but also areas without kelp that are dominated by turf algae. While the loss of standing kelp from rocky reefs may result in declines in epifaunal biodiversity, where turf algae replaces kelp, the reefs may still support high secondary productivity.

Interference of turnipweed (Rapistrum rugosum) and Mexican pricklepoppy (Argemone mexicana) in wheat

AbstractTurnipweed [Rapistrum rugosum (L.) All.] and Mexican pricklepoppy (Argemone mexicana L.) are increasingly prevalent in the northern cropping regions of Australia. The effect of different densities of these two weeds was examined for their potential to cause yield loss in wheat (Triticum aestivum L.) through field studies in 2016 and 2017. There was 72% to 78% yield reduction in wheat due to competition from R. rugosum. Based on the exponential decay model, 18.2 and 24.3 plants m−2 caused a yield reduction of 50% in 2016 and 2017, respectively. Rapistrum rugosum produced a maximum of 32,042 and 29,761 seeds m−2 in 2016 and 2017, respectively. There was 100% weed seed retention at crop harvest. Competition from A. mexicana resulted in a yield loss of 17% and 22% in 2016 and 2017, respectively; however, plants failed to set seeds due to intense competition from wheat. Among the yield components, panicles per square meter and grains per panicle were affected by weed competition. The studies indicate a superior competitiveness of R. rugosum in wheat and a suppressive effect of wheat on A. mexicana. The results indicate that a wheat crop can be included in crop rotation programs where crop fields are infested with A. mexicana. High seed retention in R. rugosum indicates the possibility to manage this weed through seed catching and harvest weed seed destruction.

Diffraction of radio frequency waves by spatially modulated interfaces in the plasma edge in tokamaks

The use of radio frequency (RF) waves in fusion plasmas for heating, for non-inductive current generation, for profile control and for diagnostics has been well established. The RF waves, excited by antenna structures placed near the wall of a fusion device, have to propagate through density fluctuations at the plasma edge. These fluctuations can modify the properties of the RF waves that propagate towards the core of the plasma. A full-wave electromagnetic computational code ScaRF based on the finite difference frequency domain (FDFD) method has been developed to study the effect of density turbulence on RF waves. The anisotropic plasma permittivity used in the scattering studies is that for a magnetized, cold plasma. The code is used to study the propagation of an RF plane wave through a modulated, spatially periodic density interface. Such an interface could arise in the edge region due to magnetohydrodynamic instability or drift waves. The frequency of the plane wave is taken to be in the range of the electron cyclotron frequency. The scattering analysis is applicable to ITER-like plasmas, as well as to plasmas in medium sized tokamaks such as TCV, ASDEX-U and DIII-D. The effect of different density contrasts across the interface and of different spatial modulations are discussed. While ScaRF is used to study a periodic density fluctuation, the code is general enough to include different varieties of density fluctuations in the edge region – such as blobs and filaments, and spatially random fluctuations.

Approaching model of Manning’s coefficient due to an Effect of density and height of vegetation in open channel

The presence of vegetation growing in the channel can cause increasing the Manning’s coefficient. The magnitude of Manning’s coefficient is depended on the characteristic and type of vegetation. The purpose of the research is to study and model the effect of density and height of vegetation on Manning’s coefficient in open channel. The study was conducted in open channel with 15.5 m length, 0.5 m width and 1.0 m height. At the centre part of the channel is planted with Elephant grass (Pennisetum Purpureum). The effect of different density and height of vegetation were run with fixed discharge to measure the velocity and water profiles in order to obtain Manning’s coefficients. The effect of those variables on the developed model was evaluated using statistical analysis of variance and paired t-test with significance level of 0.05. The results showed that Manning’s coefficient is increasing as increasing density and height of vegetation. If compared to un-vegetated channel, Manning’s coefficient increase in between 4.92 - 54.07%. Based on statistical analysis, it is found that Fcalculation = 367.776 > Fcritic = 19.452, tcalculation = 12.298 and 22.464 > tcritic = 2.571 and R2 = 0,967, showing that the density and height of vegetation significantly influence on the Manning’s coefficient with strong correlation variables in the model.

樟树(Cinnamomum camphora)幼苗细根形态对氮磷添加和幼苗密度的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 樟树(Cinnamomum camphora)幼苗细根形态对氮磷添加和幼苗密度的响应 DOI: 10.5846/stxb201809041884 作者: 作者单位: 华南农业大学林学与风景园林学院 作者简介: 通讯作者: 中图分类号: 基金项目: 中央财政林业科技推广示范项目（2015-GDTK-07） Responses of fine root morphology of Cinnamomum camphora seedlings to nitrogen and phosphorus additions and planting density Author: Affiliation: College of Forestry and Landscape Architecture,South China Agricultural University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:全球氮沉降对森林生态系统结构和功能的影响已成为现代生态学研究热点之一，我国华南地区氮沉降的增长引起了土壤酸化和磷限制加剧等一系列生态问题。密度制约着植物个体对环境资源的吸收利用，是自然界中十分重要的选择压力之一。因此研究樟树（Cinnamomum camphora）幼苗的细根形态对氮磷添加和密度的响应，有利于了解亚热带树木根系对氮沉降和磷添加与林分密度的响应过程和机制，并为全球变化背景下樟树林生态系统的管理提供依据。本研究以1年生樟树幼苗为试验材料，选择氯化铵（NH4Cl）作为氮肥以模拟大气氮沉降，并且以二水合磷酸二氢钠（NaH2PO4·2H2O）模拟磷添加，氮磷处理设置4个水平，即对照、施N、施P和施N+P；种植密度设置10、20、40和80株/m2 4个水平。测定各处理樟树幼苗细根的根长、表面积、体积和根尖数，分析氮磷添加、密度和两者交互作用对樟树幼苗细根的影响。研究结果表明，与对照处理相比，N、P和N+P处理促进了幼苗细根长度、表面积、体积以及根尖数的增加。低密度条件下的N添加对幼苗根系形态的促进效果强于P添加。N+P处理对10、20、40株/m2幼苗根系形态的促进效果最佳，而各处理对80株/m2幼苗根系形态的促进效果均无显著性差异。随着种植密度的增大，幼苗细根长度、表面积、体积和根尖数均减少。樟树幼苗的细根长度、表面积、体积和根尖数在各密度间和不同氮磷添加处理间均有显著性差异，密度和氮磷处理间的交互作用对根系形态各指标均无显著影响。 Abstract:With the continuing deposition of atmospheric N and wide application of P fertilizer, N and P have become a major factor affecting the ecosystem C balance. Fine root morphological characteristics, such as the root length, surface area, volume, and tips, play a critical role in many functions, including nutrient absorption. Global N deposition and P addition induce changes in root morphology. Seedling density is an important factor affecting root morphology because of the enhanced resource competition among high density seedlings, which reflects the allocation ratio of photosynthetic C in the roots, and ultimately affects the overall plant C allocation balance. Understanding the effects of N and P additions and planting density on the fine root morphology is important to be able to improve fine root health. However, knowledge regarding the effects of N and P additions on the root morphology is limited, and it is still unclear how N and P additions and seedling density alter the fine root morphology of Cinnamomum camphora seedlings. In this study, the root morphology of C. camphora seedlings planted at different densities was evaluated, along with the root length, surface area, volume, and tips, in order to reveal the effects of N and P additions and plant density on the fine root morphological characteristics of this species. One-year-old C. camphora seedlings were used as test materials, and NH4Cl and NaH2PO4·2H2O were selected to simulate N deposition and P addition, respectively. N and P additions were performed with four different levels of treatment (control, N, P, and N+P), and seedlings were planted at four different densities (10, 20, 40, and 80 seedlings/m2). The results showed that the N, P, and N+P treatments increased the root length, surface area, volume, and tips of seedlings compared to those of the control treatment. The effect of N addition on root morphology was stronger than that of P addition under low planting densities. The N+P treatment had the greatest effect on the fine root morphology at densities of 10, 20, and 40 seedlings/m2, while there was no significant difference in the effect of each treatment at 80 seedlings/m2. With increased planting density, the length, surface area, volume, and tips of the seedling roots tended to decrease. The effects of different densities or treatments on the fine root length, surface area, volume, and tips of the seedlings were significantly different, but the interactive effect of density and N and P additions on the fine root morphology of the seedlings was not significant. 参考文献 相似文献 引证文献

Bellamya aeruginosa (Reeve) promote the growth of Elodea nuttallii (Planch.) H. St John in high nutrient environment

Elodea nuttallii (Planch.) H. St John is an invasive alien submerged macrophyte, which grows very fast and dominates in many Chinese waters. Bellamya aeruginosa (Reeve) is a widely distributed benthonic organism in China. This snail species rarely grazes submerged macrophytes and may promote their growth by feeding on epiphyte and phytoplankton. The above two species can commonly be found together in nature waters and their interaction may promote the growth of both species, which could disturb the ecological balance. In this paper, effects of different densities of B. aeruginosa at two different nutrient stages on water quality and the growth of E. nuttallii were studied. The results showed that the growth rates (GRs) of E. nuttallii were not significantly affected by different B. aeruginosa densities in the low nutrient (LN) stage. However, in the high nutrient (HN) stage, the GRs of the aboveground parts of E. nuttallii in the high density (HD) groups were considerably higher than the control (CK) and low density (LD) groups. The water chlorophyll (Chl) and nitrate-nitrogen (NO3-N) contents increased substantially with increasing B. aeruginosa density in the LN stage, while the Chl and NO3-N contents in the LD groups were significantly higher than in the HD and CK groups in the HN stage. The results of this paper indicated that B. aeruginosa could promote the growth of E. nuttallii by reducing the Chl contents in the water in high-nutrient environment rather than in low-nutrient environment, which highlighted that B. aeruginosa may strengthen the invisibility of E. nuttallii in eutrophic water caused by human activities.

Welfare indicators for laying Japanese quails caged at different densities.

In the way to reduce costs in the poultry production, high densities of birds are adopted in the production systems. Such high densities can lead to an inappropriate environment, compromising the welfare and decreasing the animal performance. In this work we aimed to evaluate the effects of different densities on the productive yield, egg quality and immunological aspects of Japanese quails. It was used 816 Japanese quails, during egg production phase, in a random design, with four treatments (121.43 cm2/bird; 106.25 cm2/bird; 94.44 cm2/bird and 85.00 cm2/bird) with six repetitions each. Results indicate density did not interfere on egg quality and all treatments can be considered excellent, once the Haugh Unit was 88.03. Therefore, higher densities decline the yield, decreasing the eggs weight (10.35 g), the laying percentage (88%), egg mass (9.16 g) and the week average feed consumption (157.35 g). IgY values were higher at smaller cage density, suggesting birds in this condition presented better immunological condition, related to welfare and stress factors, all linked to immunoglobulins IgY.

Effect of different densities of parthenium weed (Parthenium hysterophorus L.) on the performance of direct-seeded rice under aerobic conditions

ABSTRACTParthenium weed (Parthenium hysterophorus L.) is an emerging weed species in direct-seeded aerobic systems of rice production. This two-year field study was conducted to evaluate the effect of five different densities (0, 5, 10, 15 and 20 plants m−2) of parthenium weed on rice yield and yield-related attributes. Parthenium weed produced ca. 38 to 178% higher biomass at its densities of 10 to 20 plants m−2 as compared to the lowest density of 5 plants m−2. The paddy yield and yield-related attributes were negatively affected with an increase in the parthenium weed density. In both years, the highest reductions in number of rice panicles (14 to 17%), panicle length (10 to 11%), number of grains per panicle (11 to 18%), 1000-grain weight (8 to 21%) and paddy yield (30 to 35%) were recorded at the highest parthenium weed density (20 plants m−2) tested. However, the lower densities of 5 to 15 parthenium weed plants m−2 also caused 11 to 24% and 12 to 26% losses in paddy yield during the years 2016 and 2017, respectively. Therefore, this weed species should be controlled below the density of 5 plants m−2 to avoid the substantial yield losses (over 15%) in direct-seeded rice.

Effects of different densities of mixed-cropping on 13C-photosynthate distribution and grain yield of maize.

To explore the effects of different densities of mixed-cropping on 13C-photosynthate distribution and grain yield of maize, we measured photosynthetic characteristics, 13C-photosynthate distribution, dry matter accumulation, and grain yield under different planting densities (LD, 67500 plants·hm-2 and HD, 97500 plants·hm-2) under mixed-cropping (M, 1:1, 2:2) and monoculture of Zhengdan958 (ZD) and Denghai605 (DH). The results showed that with the increases of planting density, grain yield, 13C-photosynthate allocation to grain, dry matter accumulation, and leaf area index (LAI) increased, but the chlorophyll content and net photosynthetic rate decreased. No significant difference was observed between the monoculture and mixed-cropping at the density of 67500 plants·hm-2. However, at 97500 plants·hm-2, LAI, chlorophyll content, net photosynthetic rate and dry matter accumulation in mixed-cropping were higher than that in monoculture. Mixed-cropping promoted the transport of dry matter from the vegetative organs such as stem to the grain and the distribution of 13C-photosynthates to grain. Grain yield of summer maize significantly increased in mixed-cropping due to the increase of 1000-grain mass. Under high plant density, the mixed-cropping could enlarge photosynthetic area, maintain higher net photosynthetic rate, increase dry matter accumulation, improve the distribution of dry matter, promote the distribution of 13C-photosynthates to grains and thus increase the grain yield. Our results indicated that mixed-cropping could significantly increase the yield of close planting summer maize in Huang-Huai-Hai Plain.

The colonial ascidian Diplosoma listerianum enhances the occurrence of the hydrozoan Obelia sp. during early phases of succession

Recruitment patterns of sessile species often do not reflect the composition of the local propagule pool. This is, among other processes, attributed to the stimulation or inhibition of settlement by resident species. In an experimental study, we evaluated the effects of different densities of the ascidian Diplosoma listerianum on the settlement of the hydrozoan Obelia sp. For this, we monitored the cover of the dominant fouler Obelia sp. on vertically orientated PVC tiles, which were either bare or pre-seeded with two different densities (sparse or dense) of Diplosoma colonies, over the course of 8 weeks. The settlement tiles were deployed at two study sites in La Herradura Bay, Chile. The presence of D. listerianum enhanced the settlement or the growth or both of the colonial hydrozoan, but this effect disappeared within 4–8 weeks. Furthermore, we tested whether the initial enhancement of Obelia sp. by Diplosoma colonies goes back to the fact that larvae, which reject the ascidian tunic as a settlement substratum after a first contact, colonize nearby surfaces because of their limited mobility. However, we found no support for this assumption. We rather suggest that D. listerianum facilitated colonization indirectly by the accumulation of organic material in its vicinity and/or by its pumping activity. Initial resident-mediated enhancement of the hydrozoan was overridden by processes such as competition between later colonizers within the course of weeks and we could not detect any lasting effects of D. listerianum on the structure of the developing communities.

EFFECT OF DIFFERENT STOCKING DENSITY TO GROWTH RATE OF CATFISH (Clarias gariepinus, Burch) CULTURED IN BIOFLOC AND NITROBACTER MEDIA

Catfish is one of the freshwater commodities whose demand continues to increase in Indonesia. Intensive cultivation is done to meet market demand. Intensive cultivation is done by optimizing stocking density. The aim of this research was to know the effect of different density on feed productivity, growth, feed conversion ratio (FCR) and survival of catfish dumbo fry (Clarias gariepinus, Burch) in biofloc and nitrobacter media. This study used a completely randomized design (RAL) with 6 treatments and 3 replications. The test animalsused catfish dumbo (Clarias gariepinus, Burch) with an average weight of 0,6 ± 0,1g and an average length of 4 cm. Catfish dombo seeds are kept in tarpaulin ponds 2 m in diameter with water volume ± 1 m3 for 45 days and feeding 3% of biomass weight. The results showed that the different density of stockingin biofloc and nitrobacter media had increase on productivity, specific growth rate, feed efficiency and no significant effect on the survival of catfish dumbo fry.