太白湖主要经济鱼类寄生蠕虫种类调查

2015年12月,采用形态学方法对长江中游的太白湖鱼类鳃和肠道寄生蠕虫进行了初步调查和种类鉴定。结果显示:在调查的15种131尾鱼中,共分离鉴定了36种寄生蠕虫,其中单殖吸虫30种,复殖吸虫1种,绦虫5种;对其中6种单殖吸虫的形态特征进行了重新描述。大部分鱼类的鳃部都感染单殖吸虫,只有4种鱼类的肠道感染寄生蠕虫,较低的体内寄生蠕虫多样性表明该湖泊的生态环境可能受到较严重的干扰。     

Current Knowledge of Equine Water Treadmill Exercise: What Can We Learn From Human and Canine Studies?

Equine water treadmills (WTs) are increasingly being found in research and therapy centers and private competition yards. However, the programs incorporating WT exercise for training and rehabilitation of horses are mainly based on anecdotal evidence due to the lack of scientific evidence available. This review aims to evaluate what is currently known about WT exercise for horses drawing on what is known from human and canine investigations. Studies of WT exercise have demonstrated that water depth, temperature, and speed have a significant effect on physiological responses in humans. The physiological studies in horses show many similarities to human responses with much evidence demonstrating that WT exercise is an aerobic form of exercise which does not appear to induce improvement in aerobic capacity when used within training programs. Equine and canine studies have shown that water depth can have a significant effect on the biomechanical responses to WT exercise, but little is known about the effect of different speeds at the various water depths. Key areas we would recommend for future research are as follows: how combinations of water depth and speed alter equine biomechanics compared to overland exercise, determination of long-term benefits of WT exercise, and how to use WT for rehabilitation for horses with specific injury.     

Soil physical changes and maize growth in a structurally fragile tropical soil due to mulching and duration between irrigation intervals

Under tropical meteorological conditions, the volume of soil explored by plant roots is crucial for crop growth as it allows increased water and nutrient use efficiency. We hypothesized that, under different irrigation intervals, leguminous mulch can extend the duration between irrigation events but maintain crop performance, because decreased evaporative fluxes also reduce constraints to root exploration imposed by mechanical stress. We evaluated the combined effects of leguminous mulch and irrigation intervals on soil physical properties to determine whether the growth and productivity of maize were modified in a structurally fragile tropical soil. The experiment involved the following treatments: 4‐day irrigation intervals with soil mulched (4C) or bare (4S), 6‐day irrigation intervals with soil mulched (6C) or bare (6S), 8‐day irrigation intervals with soil mulched (8C) or bare (8S) and 10‐day irrigation intervals with soil mulched (10C) or bare (10S). Mulch decreased soil penetration resistance and increased to 4 days the favourable time for root development in drying soil. Relative to bare soil, mulch with a 6‐day irrigation interval almost doubled nitrogen uptake post‐tasselling, which decreased nitrogen remobilization and increased the crop growth rate during this stage. These conditions had a positive effect on the transpiration rate and stomatal conductance as well as on the growth and yield of maize. A 6‐day irrigation interval with mulch compared to 4 days with bare soil resulted in similar conditions for root development, but greater uptake of nitrogen (102.73–78.70 kg/ha) and better yield (6.2–5.3 t/ha), which means greater efficiency in nitrogen and water use.     

Azospirillum brasilense mitigates water stress imposed by a vascular disease by increasing xylem vessel area and stem hydraulic conductivity in tomato

Water stress, with its negative consequences on plant growth and survival, can be mitigated by Azospirillum brasilense inoculation. In tomato, A. brasilense delays wilting caused by a vascular pathogen, Clavibacter michiganensis subsp. michiganensis, by yet unknown mechanisms. We studied morphological, anatomical and physiological changes induced by A. brasilense in tomato that relate to water stress tolerance, which could explain the deferral in symptom expression. For this purpose, tomato seeds were treated or not with A. brasilense BNM65, and 5 weeks later plants were challenged with C. michiganensis subsp. michiganensis or mock inoculated with water. There was a large growth promotion associated to Azospirillum: treated plants had higher total biomass and leaf area. In relation to water stress tolerance, Azospirillum treated plants had larger xylem vessel area, higher stem specific hydraulic conductivity, thicker stems, and lower shoot/root dry matter and specific leaf area. These changes were opposite to those induced by C. michiganensis subsp. michiganensis. We conclude that A. brasilense favoured a better adjustment of plant-water relations by several mechanisms, and thus, transitorily alleviated symptoms expression of a vascular disease.     

不同饲养密度对鳝苗的生长性能研究

本试验以水蚯蚓作为饵料,研究了60日龄鳝苗不同密度下的增重、存活率及饵料转化率。试验分3个密度组,其对应的密度分别为2000尾/m2、3000尾/m2、4000尾/m2,每个密度组设4个平行;试验时间为30d。结果表明:在本试验条件下,3个密度组鳝苗的增重率、存活率随着密度的增大呈下降趋势,而其饵料系数随着密度增大而增大;其中在4000尾/m2的密度下,鳝苗的增重率最低,仅为1.12±0.13;饵料系数最高,为5.71±1.37。     

汉阳地区五个湖泊沉水植物分布及富营养化现状

2011年7月—2012年4月对武汉市汉阳地区五个湖泊(后官湖,三角湖,南太子湖,墨水湖和龙阳湖)的水质及沉水植物进行了季节性调查,以了解湖泊富营养化现状及其对沉水植物的影响。结果显示:后官湖为中营养,而三角湖、南太子湖、墨水湖和龙阳湖为重度富营养,其中龙阳湖污染最重。共采集沉水植物7种,隶属于5科5属,主要种类为金鱼藻(Ceratophyllum demersum)、苦草(Vallisneria spiralis)和菹草(Potamogeton crispus)。沉水植物主要分布在后官湖沿岸带,其它四个湖泊中沉水植物已严重退化,仅在部分水域偶见。后官湖沉水植物盖度和生物量最大值出现在10月,分别为67.5%和5.58 kg/m~2,1月份较低,分别为29.3%和1.88 kg/m~2,优势种存在明显的季节更替。结果表明,汉阳地区湖泊沉水植物退化与富营养化引起的水下光照下降和高密度的水产养殖有关。     

青土湖干涸湖底2种典型固沙植物群落土壤粒径分布分形特征与养分关系研究

以石羊河流域下游青土湖干涸湖底人工梭梭林和白刺灌丛沙包土壤为研究对象，通过分析2种植物群落5种立地条件土壤粒径分布和分形特征及其与土壤养分的关系，揭示了湖底2种典型植物群落土壤粒度的分布特征。结果表明:1）研究区固沙植被0~10 cm土壤颗粒以细砂粒为主，没有粗砂粒，其中白刺灌丛沙包表层极细砂含量、土壤颗粒物分形维数较梭梭林和对照区高。2）土壤颗粒分形维数与各粒级颗粒百分含量的关系差异较大，分形维数与黏粒、极细砂含量呈显著正相关，与细砂、中砂含量呈显著负相关，但是与粉粒含量关系不显著。土壤颗粒分形维数越大，土壤所含的细粒物质越多。3）土壤分形维数D值、黏粒、粉粒含量与有机质（SOM）、全N（TN）呈正相关性，土壤颗粒物的分形维数越大、土壤黏粒、粉粒含量越高，则土壤有机质、全N含量越高。综合分析，固定白刺灌丛表层土壤沙化程度相对较低，其他类型风蚀严重，因此，应积极采取生物措施和工程措施开展生态修复防治风蚀和盐尘暴的发生。     

Accelerated ageingof wheat grains: Part I- Influence on rheological properties of wheat flour

Natural ageing is defined as handling and storage of freshly harvested grain for several years under storage condition to achieve suitable flour quality after milling. Accelerated ageing of wheat which is obtained using higher temperature during a specific storage time under controlled relative humidity may improve the quality of wheat flour. The present study addresses the effect of accelerated ageing on the rheological properties of wheat flour produced by freshly harvested wheat. The process of accelerated aging was performed by three different factors including rise in wheat moisture content (16, 18 and 20% w/w), control of storage temperature (30, 40 and 50°C) and control of the storage time (2, 5 and 8 days) using a central composite design. After the grain milling, rheological properties of wheat flour of different treatments were studied. Results indicated that promoting the storage time to 8 days and temperature up to 40°C could improve rheological properties such as dough stability, dough development time and farinograph quality number. This phenomenon may be due to oxidation and rearrangement of disulfide bonds resulting in increasing strength and improving flour quality. Increasing moisture content and storing in higher temperatures resulted in weakening rheological properties.