藏鸡、茶花鸡染色体核型分析

运用改进的鸡外周血淋巴细胞培养-空气干燥法,分析了藏鸡、茶花鸡染色体核型.研究结果表明:藏鸡和茶花鸡的染色体形态十分相近,染色体2n众数均为78,但No.4、No.6染色体的形态存在一定的差别,即藏鸡分别为sm和m型,而茶花鸡分别为st和sm型.同时收集丝羽乌骨鸡、鹿苑鸡、狼山鸡、萧山鸡、北京油鸡的核型资料进行分析,发现鸟类核型进化可能是由不对称向对称发展的,着丝粒以及着丝粒周边区域的染色体重排可能是地方鸡种分化和形成的重要内在因素.     

新疆人工灌溉绿洲的形成和发展演变

新疆人工灌溉绿洲形成的自然条件取决于水文、地貌、土壤和植被,并与社会经济因素和生产活动方式、生产发展水平及人口增长密切相关.塔里木盆地的古绿洲多分布在河流中下游三角洲上;老绿洲多在冲积扇中下部和冲积平原;新绿洲则多在老绿洲的外围和边缘.吐鲁番盆地在依靠火焰山泉水灌溉时,绿洲在火焰山以南;18世纪以后,绿洲主要分布在依靠坎儿井灌溉的地方;20世纪50年代后,实行渠、库、井联合灌溉,绿洲原地不断扩大.天山北麓平原,绿洲最初在交通和军事据点,后发展成一条河一小块绿洲.1949年后由于农垦事业的发展,才将小块绿洲扩大连接成绿洲带.伊犁河谷,起初依靠山溪小河灌溉,绿洲只是小块分布在伊宁和霍城.此后,引伊犁河水,开发的土地多在河谷平原的阶地上,整个伊犁河谷成为新疆最大的绿洲之一.     

牛病毒性腹泻病毒及其进化研究进展

牛病毒性腹泻病毒（Bovine viral diarrhoea virus，BVDV）在我国发现有20多年，而在世界范珏来讲已有近100年的历史。由于牛病毒性腹泻病毒造成奶牛生产性能下降、繁殖障碍、持续感染等，是导劐集约化奶牛场严重亏损的重要原因。且牛病毒性腹泻导致的黏膜病致死率几乎1000A，已经严重阻碍养斗业的发展，但目前我国对牛病毒性腹泻还没有好的防控措施。文章对牛病毒性腹泻的发生历史总结，便于石牛病毒性腹泻病毒的诊断和预防中参考。     

Postcards from the past: charting the landscape-scale conversion of tropical Australian savanna to closed forest during the 20th century

Repeated sequences of digitised and geo-referenced historical aerial photography provide a powerful means of understanding landscape change. We use this method to demonstrate a landscape wide expansion of closed forest (42% increase in total coverage) in the Australian monsoon tropics over the past five decades. Retrospective habitat suitability models (HSI) of closed forest derived using four landscape measures (drainage distance, slope angle, aspect and elevation) for imagery taken in 1947 correctly forecast the subsequent spatial distribution of the expansion, with topographic fire protection primarily determining the closed-forest distribution. The dynamics of the closed forest-savanna boundary were predicted accurately by generalised linear models, with closed-forest expansion in fire-protected sites along forest edges and regression in the more fire-prone areas. Two factors may plausibly explain the expansion of closed forests. First, eco-ethnographic records stress the skilful use of fire by Aboriginal people in protecting isolated and locally resource-rich closed-forest patches. Second, the recent global increase in atmospheric CO₂ may be changing the competitive balance between savanna and forest by enabling C₃ trees to grow fast enough to escape the fire trap presented by flammable C₄ grasses.     

Virus impact at the interface of an ancient ecosystem and a recent agroecosystem: studies on three legume-infecting potyviruses in the southwest Australian floristic region

The southwest Australian floristic region (SWAFR) is an internationally recognized 'hot spot' of global biodiversity and has an endangered flora. It represents a unique interface between an ancient ecosystem and a recent agroecosystem, providing the opportunity to investigate encounters where the recipient of the virus is an introduced crop and the donor a native plant and vice versa. Phylogenetic analysis of the virus coat-protein genes was used to study isolates of three potyviruses representing different 'new encounter' scenarios at this interface. The incidence, symptomatology, host range, non-persistent aphid transmission and considerable genetic diversity of the first indigenous virus described from the SWAFR, where it infects the native legume Hardenbergia comptoniana , and its potential to damage lupin, a locally important, newly introduced cultivated grain legume, was studied. The name Hardenbergia mosaic virus is proposed for this virus. Two other examples of 'new encounter' scenarios involving other legume-infecting potyviruses studied were: Passion fruit woodiness virus , which has been found only in Australasia, where it damages recently introduced species of Passiflora and legumes; and Bean yellow mosaic virus, which is not indigenous to Australia and was introduced recently to the SWAFR, where it infects a number of introduced legumes, but also damages the local native legume Kennedia prostrata . Isolates of the former had considerable genetic diversity consistent with the virus being indigenous, while isolates of the latter virus from K. prostrata had a low genetic diversity consistent with recent arrival. This research illustrates how introduced viruses can damage indigenous plants and indigenous viruses can damage introduced cultivated plants within this unique ecosystem, and how human activities can facilitate damaging 'new encounters' between plants and viruses.     

变叶海棠变异类型的初步研究

应用形象化散点图研究变叶海棠的起源和进化。结果表明,其变异类型可能系变叶海棠和陇东海棠或花叶海棠之间的天然杂交种,该假设需要用现代新方法来证实。     

岱海游乐场孔孢粉分析及其2500年来古气候演化

本文通过对岱海游乐场钻孔剖面沉积物孢粉的定性、半定量分析,并结合岩性、岩相变化,初步恢复了该地区２５００年来古植被、古气候演化过程。研究结果表明,岱海湖盆自２５００年来植被类型有典型草原—灌丛草原—森林草原—灌丛草原的演化过程,古气候有较暖湿—较暖干—较冷干—较冷湿—较冷干的变化过程。     

90年代江苏淮南小麦产量性状演变及品质分析

分析了江苏省淮南片 1 989～ 1 999年连续 1 0年 (5轮 ) 4 5个小麦品种 (系 )的区试结果 ,其平均产量为 5 .0 661 t.hm- 2 ;年度 (轮次 )间的产量呈现低 -高 -低的演变趋势 ;在产量构成因素中 ,穗数较为稳定 ,且与产量关系不密切 ;而每穗粒数随着产量的起伏表现较大增减 ,与产量呈显著正相关 ;千粒重与产量呈极显著正相关 ,粒重大小基本决定产量高低。本地区目前应用推广小麦品种的出粉率均较低 ;蛋白质和面筋含量以苏麦 6号较高 ,但由于其面团稳定时间短 ,仍不适于制作面包 ;扬麦 1 5 8和宁麦 8号适合制作面条和馒头 ;宁麦 9号为较优质的饼干、糕点小麦。此外 ,还探讨了小麦产量育种的策略和品质改良的重点及要求。     

Soil CO2 evolution from Korean pine virgin forest at Changbai Mountain

The soil CO₂ evolution rate was measured in a virgin Korean pine forest. The results in June showed that the lowest value of evolution rate was 220 mg/(m²·h) and appeared at 6:00 a.m. The highest value was 460 mg/(m²·h) at 18:00. The rates of CO₂ evolution were related with soil temperature. On the basis of the constructed regression equation and the monthly average values of temperature, the magnitude of CO₂ evolution from Korean pine forest soil was 10.4 t/hm² during a growing season. This project was funded by the Opened Research Station of Changbai Mountain Forest Ecosystem, Chinese Academy of Sciences. Responsible editor: Zhu Hong