不同土壤类型下桃树水分运转动态的数学模拟

为定量的刻画不同土壤类型和水分条件对桃树蒸腾作用的影响,根据不同土壤的水分特征曲线、气孔导度模型、冠层蒸腾模型和水分传输模型模拟出不同土壤类型下桃树的水分运转动态。数值模拟表明,在逐步干旱过程中,各类土壤维持桃树蒸腾的时间依次为壤土砂土改良粘土砂壤土粘土;桃树散失的水分总量依次为砂土壤土改良粘土砂壤土粘土。在整个干旱周期过程中,气孔导度和叶片水势均呈波动式减小,其总体趋势与土壤水势相一致。计算表明,砂土的保水能力最差,粘土的可利用水最少,壤土维持蒸腾的时间最长,粘土用有机物改良后可利用水和维持蒸腾的时间显著增加。     

高大气CO2浓度下氮素对小麦叶片光合能量分配的调节

探讨了施氮量对高大气CO₂浓度下小麦功能叶光合能量传递与分配的影响,进而明确氮素对小麦叶片光合作用适应性下调的能量分配调节作用。采用开顶式气室盆栽法,通过测定小麦拔节期和抽穗期不同大气CO₂浓度和施氮水平下的叶氮浓度、光合速率–胞间CO₂浓度(P_n–C_i)响应曲线和荧光动力学参数,测算光合电子传递速率和分配去向。与在正常CO₂浓度(400 μmol mol^-1)条件下相比,在高大气CO₂浓度(760 μmol mol^-1)下,小麦叶氮浓度显著下降,N200处理(200 mg kg^-1)叶片抽穗期叶氮浓度的下降幅度较拔节期高335.7%。N200处理较N0处理(0 mg kg^-1)提高小麦叶片光适应下PSII反应中心最大量子产额(F_v′/F_m′)、光化学效率(Φ_PSII)和开放比例(q_P),降低非光化学猝灭系数(NPQ)。高大气CO₂浓度下,小麦叶片光化学反应的非环式光合电子传递速率(J_c)和Rubisco羧化速率(V_c)显著升高,而光呼吸的非环式光合电子传递速率(J_o)和Rubisco氧化速率(V_o)明显降低;施氮使J_c、J_o、V_c和V_o值均呈上升趋势,而且J_c和V_c达到显著差异。高大气CO₂浓度下J_o/J_c和V_o/V_c显著降低,施氮后小麦拔节期叶片J_o/J_c和V_o/V_c降低,但抽穗期J_o/J_c升高而V_o/V_c无明显变化。叶氮浓度与小麦叶片J_c、J_o和V_o均呈显著线性正相关,而且高大气CO₂浓度下小麦叶片J_c、J_o和V_o对氮浓度的敏感性降低。高大气CO₂浓度下,小麦叶片PSII反应中心开放比例增加,非光化学耗能降低,更多的光合电子进入光化学过程;施氮后使小麦叶氮浓度增加,提高光合能力,改变了能量分配,这是高氮条件下光合作用适应性下调被缓解的一个关键因素。     

Modelling the dispersal of Calanus finmarchicus on the Newfoundland Shelf: implications for the analysis of population dynamics from a high frequency monitoring site

We investigated the drift of passive particles on the Newfoundland Shelf and western Labrador Sea using numerical simulations to assess the possible sources of plankton collected at a high frequency sampling site (S27; 47.55°N, 52.59°W) located near the coast of Newfoundland, Canada. We also summarized data detailing the seasonal stage succession of Calanus finmarchicus at that site, as well as along three oceanographic sections sampled in the spring, summer and autumn across the adjacent continental shelf. Simulations indicated that the Labrador and Newfoundland Shelves represent the major sources of particles transiting through the S27 site, with relatively minor contributions from the western Labrador Sea which are significant during a few months each year. The latter point may be affected by uncertainty in the representation of cross‐shelf transport associated with seasonal or short‐term variations in atmospheric and oceanic forcing, which may also affect the strength and location of bifurcation of the inner branch of the Labrador Current around the Grand Banks. Nevertheless, our results indicated that drift along the inner shelf is likely to be the primary source of copepods collected at S27 throughout most of the year. This in turn suggested that there may be a higher degree of connectivity between conditions in coastal areas of Newfoundland and those in Baffin Bay and west Greenland than with the southern half of the Labrador Sea.     

蓄水坑灌条件下土壤水氮运移的研究进展

为了提高蓄水坑灌条件下土壤水氮的利用率,减少由于灌施不当造成的资源浪费和环境污染,综述了蓄水坑灌土壤水分入渗过程中的变水头入渗、土壤水分分布特性、土壤水分蒸发特性、影响因素以及肥液入渗过程中氮素的分布特性和数值模拟等方面的研究进展和存在问题,提出了蓄水坑灌法今后应亟需加强的研究方向,为蓄水坑灌理论与技术的进一步研究奠定基础。     

基于道路网络影响的物流运输成本研究

物流一直被认为是企业利润的重要来源.随着我国城市化进程的加快,道路网络相应地发生了变化,物流运输成本也随之而变.文章重点分析了道路等级和路网结构对物流运输成本的影响,以优化物流企业的运输路径,增加其经济利润.     

设施条件下灌水量对膜孔灌土壤水氮运移分布影响研究

通过模拟设施条件下不同灌水量灌施硝酸钾肥液试验,分析测定了灌后不同时间的土壤含水率和硝态氮分布。研究表明,不同灌水量的土壤含水率和硝态氮质量分数随着时间延长逐渐减小,以膜孔中心最大,远离膜孔中心逐渐变小;随着灌水量增大,相同位置的土壤含水率变大,而相同位置的土壤硝态氮质量分数变小;增大灌水量对土壤含水率和硝态氮分布的影响有利于植物对水分和硝态氮的吸收。     

稀饲料管道输送技术研究

生猪规模化养殖中人工加料劳动强度大,耗费劳动力多,此外还造成6%的饲料洒落浪费。随着我国生猪规模化养殖比重增大,饲料机械化输送成为必然发展趋势。稀饲料管道输送的研究开发可有效利用了农副产品废弃物及食品工业废液,实现资源的合理利用,降低饲料成本。可提高饲料转化率和日增重率,增大养猪场的经济效率。为解决随着稀饲料浓度增大出现的沉降和阻塞现象,延长管道输送距离,研究了制浆设备中饲料的搅拌混配及打浆,管道输送中的临界流速、摩阻损失以及加气减阻等问题。     

蔗糖载体调控作物“源、库”分配的研究进展

蔗糖是植物光合作用及物质转运的主要形式,植物体内重要的信号物质,并且为植物生长代谢提供碳源与能量。而在蔗糖转运过程中,蔗糖载体（SUT）发挥着不可替代的作用。首先介绍了植物中“源、库、流”理论和蔗糖载体基因分离,阐述了蔗糖载体在蔗糖由“源”到“库”转运过程中发挥的作用,及与农艺性状的关系,并阐明蔗糖在植物体生长发育过程中的作用。归纳总结了蔗糖载体介导的蔗糖跨膜转运过程,进而探讨了蔗糖跨膜转运存在的问题。     

A novel iron transporter in Streptococcus iniae

Streptococcus iniae is a major pathogen that results in considerable economic loss to fish farms. Restricted availability of iron is a huge obstacle to survival for pathogenic bacteria during infection, and iron acquisition is important in bacterial virulence. In this study, S. iniae HD‐1 was shown not to produce siderophores (low‐molecular‐weight compounds) but rather to require iron‐containing proteins for growth under iron‐restricted conditions. The adenosine triphosphate (ATP)‐binding‐cassette (ABC) transporter system (ftsABCD), which is cotranscribed by four downstream genes, namely, ftsA, ftsB, ftsC and ftsD, was identified as responsible for haem utilization of S. iniae. Analysis of the corresponding recombinant protein, FtsB, indicated that it is a putative lipoprotein which plays a role in haem utilization and is produced in vivo during infection with S. iniae HD‐1, and therefore may be a potential candidate antigen for a streptococcal vaccine.     

Physiological changes during simulated live transport of Cancer pagurus and recovery in holding tanks

The trade of live Cancer pagurus in Portugal is totally dependent on imports, mainly from UK. Animals are transported for 48–58 h in conditions that promote high mortalities (40–60%) due to cumulative stressors. The present work aimed to optimize transport, by comparing the physiological responses of edible crab during different simulated live shipment systems for 48 h and recovery conditions: (a) immersed crabs at 12°C; and (b) air‐exposed crabs at 4°C and subsequent recovery at 16°C with and without pre‐acclimation. Both simulated transport systems induced physiological stress, culminating in 25% mortality in immersed conditions and only 4% in air‐exposed conditions. Both systems elicited anaerobic responses marked by hyperglycaemia and increased l ‐lactate concentration in haemolymph. At the end of the recovery period only air‐exposed animals resumed to l ‐lactate and pH control values, the lowest mortality was achieved with crabs acclimated at the lowest temperature (from 6 to 16°C at 1.5°C/h). Overall, results showed that crabs can be transported in air‐exposed conditions at 4°C and acclimated from 6 to 16°C and reach similar physiological conditions than the traditional transport in immersed conditions at 12°C.