番石榴果实发育的初步研究

以东山月拔和二十一世纪这2个品种为试材，研究了番石榴（Psidium guajava L)果实的发育动态规律。结果表明：番石榴的果实发育呈现双“S”型；果实重量和果核重量的发育呈显著的正相关；推测果实发育后期为进行果实产期调控的关键时期；建议以果实发育的直径大小以及果实转蒂下垂作为确定进行产期调控的田间依据。     

我国北部农牧交错区城郊土地利用时空变化—以包头市为例

以包头市城郊区为例 ,在地理信息系统支持下 ,以乡镇 (苏木 )为研究单元 ,研究本地区土地利用时空动态变化过程 ,并分析其变化驱动因素。从微观角度分析了北方农牧交错区城郊区土地利用变化特征。农牧交错区是人类活动影响强烈之地带 ,土地利用变化与土地持续研究利用 ,对生态安全和地区持续发展具有十分重要的意义。     

Improving management for higher reproduction accelerates genetic improvement in closed herd of swine

The present study compared responses to selection at different conception rates and litter sizes at weaning in a simulated closed herd in a swine breeding program. The base population consisted of 10 males and 50 females, and 10 generations of selection was practiced by using individual phenotype or best linear unbiased prediction of breeding values for a trait with heritability (h²) of either 0.2 or 0.5. The probability of conception in a single mating was assumed to be 0.8, 0.9 or 1.0. Litter size at weaning was sampled randomly from a normal distribution with mean 8, 10 or 12 and variance 8.1225. Genetic response increased by approximately 6% for h² = 0.2 and approximately 5% for h² = 0.5 at generation 10 when conception rate was increased from 0.8 to 1.0. However, litter size at weaning did not affect response to selection. In conclusion, improving conception rate by environmental management increases genetic response indirectly in a breeding program of a closed swine herd.     

Effects of straw and silicon soil amendments on some foliar and stem-base diseases in pot-grown winter wheat

Four foliar and two stem-base pathogens were inoculated onto wheat plants grown in different substrates in pot experiments. Soils from four different UK locations were each treated in three ways: (i) straw incorporated in the field at 10 t ha⁻¹ several months previously; (ii) silicon fertilization at 100 mg L⁻¹ during the experiment; and (iii) no amendments. A sand and vermiculite mix was used with and without silicon amendment. The silicon treatment increased plant silica concentrations in all experiments, but incorporating straw was not associated with raised plant silica concentrations. Blumeria graminis and Puccinia recondita were inoculated by shaking infected plants over the test plants, followed by suitable humid periods. The silicon treatment reduced powdery mildew ( B. graminis ) substantially in sand and vermiculite and in two of the soils, but there were no effects on the slight infection by brown rust ( P. recondita ). Phaeosphaeria nodorum and Mycosphaerella graminicola were inoculated as conidial suspensions. Leaf spot caused by P. nodorum was reduced in silicon-amended sand and vermiculite; soil was not tested. Symptoms of septoria leaf blotch caused by M. graminicola were reduced by silicon amendment in a severely infected sand and vermiculite experiment but not in soil or a slightly infected sand and vermiculite experiment. Oculimacula yallundae (eyespot) and Fusarium culmorum (brown foot rot) were inoculated as agar plugs on the stem base. Severity of O. yallundae was reduced by silicon amendment of two of the soils but not sand and vermiculite; brown foot rot symptoms caused by F. culmorum were unaffected by silicon amendment. The straw treatment reduced severity of powdery mildew but did not detectably affect the other pathogens. Both straw and silicon treatments appeared to increase plant resistance to all diseases only under high disease pressure.     

草原灌丛化入侵:过程、机制和效应

草原灌丛化已成为全球性问题,也是生态学、畜牧学研究的热点问题。紧扣草原灌丛化过程、发生机理及其生态学后效等关键问题,介绍了国内外的最新研究进展。灌木入侵途径包括有意识引进入侵和自然入侵2类,入侵过程分为传播到达、定居建群和扩散入侵3个阶段。放牧、火烧、温室气体增加,干旱以及降水格局改变等均可导致草本向木本的转化,且机制复杂,主要有影响草本,木本植物盖度、水分利用效率、化感作用等。木本植物入侵打破了草原生态系统的稳定,表现出沃岛效应,影响动植物的分布以及生态系统的功能和服务。阐明草原“草本-木本”群落演替机制,可为我国研究草原灌丛化和管理提供理论借鉴。     

Contagious bovine pleuropneumonia within the 19th century miasmatic landscape

When contagious bovine pleuropneumonia (CBPP) was first detected on a farm north of Melbourne, at Bundoora, in 1858, the predominant theory of miasma was being challenged by contagionist theories of disease transmission. This well‐documented case was recorded during a period of change in the scientific assessment of disease and therefore affords an exploration of what aspects of the landscape were considered important for livestock health at the time. Although the introduction, vaccination programs and eventual eradication of CBPP on mainland Australia has been well explored, scholars have neglected this aspect of the disease's history. By comparing 19th century records of farmland with how the site appears today, it is also possible to highlight the limited information provided by contemporary texts, while at the same time developing an appreciation of the ways in which the perception of the rural landscape has changed. This differing perception has implications for the utilisation of these sources for veterinary and environmental historians seeking to understand the mid‐19th century agricultural landscape and how it relates to animal health.     

条斑紫菜烤制前后特征风味变化研究

为探讨烤制对条斑紫菜(Porpphyra yezoensis)主要风味物质的影响,研究烤制前后条斑紫菜挥发性成分的变化.采用电子鼻、FlavourSpec?风味分析仪和固相微萃取-气相色谱-质谱联用(SPME-GC-MS)对比分析条斑紫菜在烤制前后挥发性风味物质的组成变化.电子鼻分析结果显示,条斑紫菜烤制前后的挥发性成...     

转基因植物对环境生态平衡的影响

根据近年来国内外关于转基因植物的研究进展,结合维持生态平衡的3个主要因素,即物种组成、环境因素及信息系统,论述转基因植物对环境生态平衡的影响.     

源库调节对小麦籽粒灌浆及光合特性的影响

为探讨不同穗型超高产小麦品种的源库关系,通过剪叶和去穗处理研究了两个不同穗型小麦品种“兰考矮早八”和“豫麦49—198”的籽粒灌浆和光合特性。结果表明,两个品种的籽粒体积、千粒重、灌浆速率在花后15d之后均表现为去穗处理〉对照〉去叶处理。去叶处理使两个品种的千粒重、灌浆速率均有所下降．其中豫麦49—198较对照下降最大比例分别为24．4％和22％,兰考矮早八下降的最大比例分别为7．6％和9％;去穗处理使两个品种的千粒重和灌浆速率均有所增加,其中豫麦49—198较对照增加的最大比例分别为11．1％和17％,兰考矮早八增加的最大比例分别为12．2％和17．25％。源库改变对两个品种的光合特性均有影响,表现为对照旗叶〉去穗旗叶〉去叶倒二叶〉对照例二叶。随着灌浆进程,豫麦49—198去叶处理的倒二叶光舍速率较对照增加的比例从40％减为25％．兰考矮早八去穗处理的旗叶光合速率较对照下降的比例从27％减为20％。     

林火在空间上的波动性及其区域化行为

应用美国阿拉斯加州1950-2000年,加利福尼亚州1895-2001年及中国黑龙江省1980-1999年林火数据,分别计算出每年火灾发生的火场质心的经纬度坐标,用波谱分析研究其质心随年份的波动现象.结果表明:3个区域的林火的火场质心分别以一定的分布中心呈波动状态,其中火场质心在阿拉斯加州的分布中心为151.11°W、64.96°N,在加利福尼亚州的分布中心为120.02°W、37.11°N,在黑龙江省的分布中心为127.07°E、49.59°N.火场质心在美国阿拉斯加州和加利福尼亚州经度方向上均具有较强的周期性,阿拉斯加州的林火火场质心在经度方向的周期为4.2 a和6.25 a;加利福尼亚州的林火火场质心在经度方向上的波动周期为6.24 a和106 a.黑龙江省的林火火场质心在经纬度方向均具有较为明显的波动性,其周期为3.3 a和6.67 a.而阿拉斯加州和加利福尼亚州的林火火场质心在纬度方向上不具有周期性,林火发生以低频率的大面积火灾为主.