Morphological and physiological characteristics of rice leaves in response to PASP-urea and optimized nitrogen management

Polyaspartic acid (PASP)-urea is known to increase crop yield. Field experiments were conducted to compare the morphological and physiological characteristics of the leaves between plots treated with urea (conventional urea or PASP-urea) and subject to different nitrogen (N) management methods [farmers’ standard fertilization practice (FFP, two splits) or optimized N management (ONM, four splits)] in Sichuan, China, in 2014 and 2015. A no-added-N plot served as the control. Grain yield was significantly associated with increased number of green leaves, total leaf area, chlorophyll concentration of rice leaves after the heading stage, photosynthetic rate per leaf lamina and accumulated temperature of senescence rate acceleration and deceleration. PASP-urea significantly enhanced the photosynthetic capacity of leaves to improve dry matter accumulation rate of the panicle after the heading stage over conventional urea, mainly by increasing the number of green lamina, leaf lamina area, chlorophyll concentration and photosynthetic rate per leaf lamina, as well as delaying senescence of the flag leaf. Compared with FFP, the ONM substantially improved the photosynthetic capacity of leaves to enhance dry matter accumulation rate of the panicle. Therefore, the ONM is a rational approach to applying PASP-urea that can improve grain yield by improving photosynthetic capacity.     

A trait-based characterization of cover plants to assess their potential to provide a set of ecological services in banana cropping systems

Cover plants are one of the means to increase the functional biodiversity of fields and to enhance the ecological functions of the communities. However, the design of cropping systems including cover plants relies largely on expert knowledge. There is a lack of methods to select the best suited cover plants according to their role in the agrosystem. We propose to use functional traits to select cover plants suited to sustain ecological services in the banana agrosystems of the French West Indies. Our objectives were (i) to characterize a collection of cover plants on a trait basis, according to their potential to provide the services expected in a banana agrosystem and (ii) to discuss the potential use of this characterization for the design of innovative multi-species banana cropping systems. In these systems, four main services are targeted, i.e. controlling weeds, controlling plant-parasitic nematodes, improving soil fertility and particularly N availability, and avoiding competition with banana for resource acquisition. Three experiments were conducted, under field and controlled conditions, to evaluate the potential of a collection of 28 tropical cover plants to achieve the functions related to these services. For each cover plant, a functional profile was constructed from a combination of plant traits that are easy to assess experimentally. It described plants’ potential to achieve the functions expected in a banana agrosystem. Functional profiles required for cover plant usages were also identified. The comparison of the plant functional profiles and the functional profiles required for their usages enabled us to select the best suited plants for each usage. However, these functional profiles rarely corresponded, meaning that a cover plant is rarely sufficient to achieve all the functions required for a usage. Functional complementarities obtained by the mixture of different species of cover plants are thus often required. Compared to classical approaches of innovative cropping system design based on the experimental testing of spatial and temporal plant combinations, such a trait-based approach saves time by focusing on a shortlist of cover plants best suited according to their functions in the agrosystem.     

黄土丘陵区不同土地类型下土壤养分特征—基于生态化学计量学

为探讨黄土丘陵区不同土地类型下土壤有机碳（SOC）、全氮（TN）、全磷（TP）含量特征，本研究以黄土丘陵区典型小麦地、云杉林地、苜蓿地为对象，基于实测数据，采用方差、相关统计分析，研究不同土地类型、不同土层深度（0~10 cm、10~20 cm、20~40 cm、40~60 cm、60~80 cm、80~100 cm）土壤SOC、TN、TP含量及其化学计量比。结果表明：3种不同土地类型土壤SOC、TN和TP含量均随土层深度增加而降低，其平均含量分别为12.19、0.33和0.48 g·kg^-1，小麦地和苜蓿地土壤SOC、TN和TP空间变异性较云杉林地偏大。SOC、TN含量为云杉林地>小麦地>苜蓿地，TP含量为云杉林地>苜蓿地>小麦地。土壤SOC、TN和TP间均存在显著正相关关系。小麦地C/P显著（P<0.05）高出苜蓿地41.96%，N/P显著高出云杉林地、苜蓿地28.57%、36.19%。3种不同土地类型土壤化学计量比（C/N、C/P、N/P）均值分别为：39.61、31.53、0.83，且其C/N大于中国平均值（12.3），C/P、N/P较全国平均值（61.0、5.2）明显偏小，黄土丘陵区C/N较稳定。土地类型对土壤C、N、P含量及其化学计量比存在不同程度的影响，合理调整土地利用结构有助于土壤养分的存留，有利于土壤生态的恢复。     

大学校园不同绿地类型的小气候特征

校园绿地小气候是城市生态环境效益评价的重要内容之一,是广大师生员工学习、工作和生活娱乐的重要场所。为了探明校园不同绿地类型的小气候特征及其对人体舒适度的影响,在广西大学校园内选择密林(A)、疏林(B)和草坪(C)3种植被类型分别建立固定样地,对主要气象要素进行同步观测研究。结果表明:(1)A、B和C日平均太阳辐射能依次为11.7w/m2、39.5 w/m2和177.3 w/m2,其中密林内仅占草坪的6.6%。(2)A、B和C日平均气温依次为24.9℃、25.2℃和25.6℃,其中密林内比草坪低0.7℃。(3)A、B和C日平均地面温度依次为23.8℃、25.2℃和27.9℃,其中密林内比草坪低4.1℃。(4)A、B和C日平均相对湿度依次为91%、89%和88%,其中密林内比草坪高3%(RH)。(5)A、B和C日平均温湿指数依次为24.4、24.5和24.8,其中密林内比草坪低0.4。研究结果初步说明,校园内密林型在白天对太阳辐射的削减、降温、增湿以及对人体舒适作用明显。     

New angiotensin-converting enzyme inhibitory peptide from Coix prolamin and its influence on the gene expression of renin-angiotensin system in vein endothelial cells

Coix seed, which is a traditional Chinese medicine, has been used to treat hypertension for thousands of years. It has been shown that Coix prolamin peptides display high levels of angiotensin I converting enzyme (ACE) inhibitory activity. Hence, we purified the ACE inhibitory peptides from Coix prolamin hydrolysates and evaluated the influence of the most potent peptide on the renin-angiotensin system (RAS) genes expression in human umbilical vein endothelial cells (HUVECs). In this study, Coix prolamin peptides were sequentially separated by ultrafiltration, ion exchange chromatography, gel filtration chromatography and RP-HPLC, while the peptide structure was analyzed by mass spectrometry. Next, in silico proteolysis, pharmacophore and molecular docking were further applied to screen and optimize the structure of peptides. Finally, a novel ACE inhibitory peptide VDMF was obtained, in which its influence on the gene expression of RAS signaling pathway in AngⅡ-injury HUVECs was evaluated by quantitative real-time PCR. VDMF significantly down-regulated ACE, AngII type 1 receptor (AT1R) and ACE2 mRNA expression in comparation with model group, while up-regulating Mas gene expression. Hence, we obtained a novel antihypertensive candidate that was derived from the Coix peptides, which could involve a multi-modulation mechanism that regulates blood pressure.     

An assessment of subsoil organic carbon stocks in England and Wales

It is estimated that half the soil carbon globally is in the subsoil, but data are scarce. We updated estimates of subsoil organic carbon (OC) in England and Wales made by Bradley et al. (2005) using soil and land‐use databases and compared the results with other published data. We estimated that the soils of England and Wales contained 1633, 1143 and 506 Tg of OC at 0–30, 30–100 and 100–150 cm depths, respectively. Thus, half of the soil OC was found below 30 cm depth. Peat soils accounted for the largest proportion, containing 44% of all the OC below 30 cm despite their small areal extent, followed by brown soils, surface‐water gley soils, ground‐water gley soils and podzolic soils. Peat soils had more than 25% of their profile OC per unit area in the 100–150 cm depth, whereas most other soils had <8% at this depth. The differences between soil types were consistent with differences in soil formation processes. Differences in depth distributions between land uses were small, but subsoil OC stocks in cultivated soils were generally smaller than in soils under grassland or other land uses. Data on subsoil OC stocks in the literature were scarce, but what there was broadly agreed with the findings of the above database exercise. There was little evidence by which to assess how subsoil OC stocks were changing over time.     

桨式路面清扫机的设计与研究

随着城市道路的迅速增加以及对市容环境要求的不断提升，道路清扫工作越来越凸显其重要性，各式各样的清扫工具也应运而生。简要介绍了现有的清扫设备，并针对其不足，在考虑节能环保的大前提下，设计了一种由现有电动车改装的路面清扫机。该机由电瓶提供动力，结构简单，类似人工扫把清扫路面，将机械操作与人的主动性很好地结合起来，在减轻工人劳动强度的同时，兼顾了制作成本，是一种适合中小型道路清扫的新型设备。     

Weed community responses to soil type during transition to no-till practice on smallholder farms in Zimbabwe

Understanding drivers of weed density and diversity is essential for the development of weed management strategies. Here, we compared temporal changes in weed density and diversity under no-till (NT) and conventional (CONV) tillage systems in cotton–maize rotations on loam, clay loam and sandy loam soils immediately after transition to NT in Kadoma, Zimbabwe. The effect of tillage system on weed density varied through the growth season and was dependent upon soil type and species composition of the weed community. Although weed responses to tillage system varied amongst species, we identified general trend effects on weed density on specific soils. At 3 weeks after crop emergence (WACE), weed density on loam soils was 76% and 96% higher in NT than in CONV during the 2009/2010 and 2010/2011 seasons, respectively, and on clay loam soils it was 37% and 33% higher in NT than CONV, respectively. Weed densities in NT and CONV were similar across all soil types at 6 WACE during the 2009/2010 and 2010/2011 seasons and at 9 WACE in 2009/2010. Tillage system did not affect weed density during the growth season on sandy loam soils. Weed diversity (Shannon index) was at least 75% higher in NT than CONV on loam and clay loam soils at 3 WACE during both seasons. It is likely these increases in weed densities following conversion to NT will exacerbate already prevalent weed management problems in the smallholder sector. Earlier weeding is recommended to suppress weed emergence and reduce likely associated crop yield losses.     

石羊河下游不同立地类型黑果枸杞种群分布格局

在样地调查的基础上,结合相邻格子取样方法,采用扩散系数(C)、丛生指标(I)、负二项参数(K)、聚块性系数(Ca)、平均拥挤指标(m*)、聚集度指标(G)、Moristia指数(Iδ)、Green指数(IG)等8个指标,对石羊河下游不同立地类型黑果枸杞种群分布格局、聚集强度进行了研究,结果表明:①沙地和盐碱地黑果枸杞个体数量较多,聚集程度相对较高,砾石和固定半固定沙地黑果枸杞的个体数量较少,聚集程度相对较低;②盐碱地和沙地黑果枸杞种群呈现聚集分布,固定半固定沙地和砾石样地相对于沙地和盐碱地的聚集程度有所减弱,有一定的随机趋势;③不同发育阶段的黑果枸杞种群格局类型总体呈现聚集分布的特点,随着龄级的增大,黑果枸杞种群分布格局表现出由聚集向均匀分布的变化趋势。     

清澜省级自然保护区红树林资源调查分析

通过样点实地调查,调查到海南清澜省级自然保护区具有真红树植物11科24种,半红树植物15科20种；根据组成种类,群落特征和立地条件,把红树林植物群落划分为12个红树林群系和4个半红树林群系。