Redefining the age of Clovis: implications for the peopling of the Americas

The Clovis complex is considered to be the oldest unequivocal evidence of humans in the Americas, dating between 11,500 and 10,900 radiocarbon years before the present (14C yr B.P.). Adjusted 14C dates and a reevaluation of the existing Clovis date record revise the Clovis time range to 11,050 to 10,800 14C yr B.P. In as few as 200 calendar years, Clovis technology originated and spread throughout North America. The revised age range for Clovis overlaps non-Clovis sites in North and South America. This and other evidence imply that humans already lived in the Americas before Clovis.     

Phytolith analysis of archeological soils: evidence for maize cultivation in formative ecuador

Soil samples from the archeological sites of Real Alto and OGCh-20, Santa Elena Peninsula, Ecuador, show the presence of cross-shaped silica bodies identifiable as maize (Zea mays L.) phytoliths by size comparison with known wild grass and maize phytoliths. These results support arguments for the cultivation of maize at 2450 B.C. in coastal Ecuador.     

Human occupations and climate change in the Puna de Atacama,Chile

Widespread evidence for human occupation of the Atacama Desert, 20 degrees to 25 degrees S in northern Chile, has been found from 13,000 calibrated 14C years before the present (cal yr B.P.) to 9500 cal yr B.P., and again after 4500 cal yr B.P. Initial human occupation coincided with a change from very dry environments to humid environments. More than 39 open early Archaic campsites at elevations above 3600 meters show that hunters lived around late glacial/early Holocene paleolakes on the Altiplano. Cessation of the use of the sites between 9500 and 4500 cal yr B.P. is associated with drying of the lakes. The mid-Holocene collapse of human occupation is also recorded in cave deposits. One cave contained Pleistocene fauna associated with human artifacts. Faunal diversity was highest during the humid early Holocene.     

Interhemispheric correlation of late pleistocene glacial events

A radiocarbon chronology shows that piedmont glacier lobes in the Chilean Andes achieved maxima during the last glaciation at 13,900 to 14,890, 21,000, 23,060, 26,940, 29,600, and >/=33,500 carbon-14 years before present ((14)C yr B.P.) in a cold and wet Subantarctic Parkland environment. The last glaciation ended with massive collapse of ice lobes close to 14,000(14)C yr B.P., accompanied by an influx of North Patagonian Rain Forest species. In the Southern Alps of New Zealand, additional glacial maxima are registered at 17,720(14)C yr B.P., and at the beginning of the Younger Dryas at 11,050 (14)C yr B. P. These glacial maxima in mid-latitude mountains rimming the South Pacific were coeval with ice-rafting pulses in the North Atlantic Ocean. Furthermore, the last termination began suddenly and simultaneously in both polar hemispheres before the resumption of the modern mode of deep-water production in the Nordic Seas. Such interhemispheric coupling implies a global atmospheric signal rather than regional climatic changes caused by North Atlantic thermohaline switches or Laurentide ice surges.     

Climate-driven ecosystem succession in the Sahara: the past 6000 years

Desiccation of the Sahara since the middle Holocene has eradicated all but a few natural archives recording its transition from a "green Sahara" to the present hyperarid desert. Our continuous 6000-year paleoenvironmental reconstruction from northern Chad shows progressive drying of the regional terrestrial ecosystem in response to weakening insolation forcing of the African monsoon and abrupt hydrological change in the local aquatic ecosystem controlled by site-specific thresholds. Strong reductions in tropical trees and then Sahelian grassland cover allowed large-scale dust mobilization from 4300 calendar years before the present (cal yr B.P.). Today's desert ecosystem and regional wind regime were established around 2700 cal yr B.P. This gradual rather than abrupt termination of the African Humid Period in the eastern Sahara suggests a relatively weak biogeophysical feedback on climate.     

Origins of agriculture at Kuk Swamp in the highlands of New Guinea

Multidisciplinary investigations at Kuk Swamp in the Highlands of Papua New Guinea show that agriculture arose independently in New Guinea by at least 6950 to 6440 calibrated years before the present (cal yr B.P.). Plant exploitation and some cultivation occurred on the wetland margin at 10,220 to 9910 cal yr B.P. (phase 1), mounding cultivation began by 6950 to 6440 cal yr B.P. (phase 2), and ditched cultivation began by 4350 to 3980 cal yr B.P. (phase 3). Clearance of lower montane rainforests began in the early Holocene, with modification to grassland at 6950 to 6440 cal yr B.P. Taro (Colocasia esculenta) was utilized in the early Holocene, and bananas (Musa spp.) were intensively cultivated by at least 6950 to 6440 cal yr B.P.     

玉米大豆间混作效益研究进展

本文综述了近年来国内外对玉米大豆间混作效益研究的进展,并论述了衡量间混作效益的某些指标和方法。     

玉米雌雄穗发生发展及生理特性研究进展

在研究和了解国内外研究成果的基础上,对玉米雌雄穗发生发展、生理特性以及环境因子对它们的影响等方面的研究进展进行简要概述,以期为今后深入开展玉米雌雄穗的研究和合理利用提供一定的科学依据。     

Carbon-14 dates at grande pile: correlation of land and sea chronologies

Sixteen radiocarbon dates extending back to 70,000 years provide a chronology for the continuous continental pollen record of Grande Pile. This record reflects climatic changes over the last 140,000 years in northeastern France. The cold period initiating the Middle Weichselian, dated previously at 55,000 years, is dated at 70,000 years before the present (B.P.) at Grande Pile. This event is marked by the disappearance of deciduous forests at this site. The Early Weichselian is placed before 70,000 years B.P. A correlation with the oxygen isotope stages from oceanic records is demonstrated until 70,000 years B.P. and attempted beyond.     

The last deglaciation event in the eastern central arctic ocean

Oxygen isotope records of cores from the central Arctic Ocean yield evidence for a major influx of meltwater at the beginning of the last deglaciation 15.7 thousand years ago (16,650 calendar years B.C.). The almost parallel trends of the isotope records from the Arctic Ocean, the Fram Strait, and the east Greenland continental margin suggest contemporaneous variations of the Eurasian Arctic and Greenland (Laurentide) ice sheets or increased export of low-saline waters from the Arctic within the East Greenland Current during the last deglaciation. On the basis of isotope and carbon data, the modern surface- and deep-water characteristics and seasonally open-ice conditions with increased surface-water productivity were established in the central Arctic at the end of Termination lb about 7.2 thousand years ago or 6,000 calendar years B.C.).     

Otolith delta 18O record of mid-Holocene sea surface temperatures in Peru

Peruvian sea catfish (Galeichthys peruvianus) sagittal otoliths preserve a record of modern and mid-Holocene sea surface temperatures (SSTs). Oxygen isotope profiles in otoliths excavated from Ostra [6010 +/- 90 years before the present (yr B.P.); 8 degrees 55'S] indicate that summer SSTs were approximately 3 degrees C warmer than those of the present. Siches otoliths (6450 +/- 110 yr B.P.; 4 degrees 40'S) recorded mean annual temperatures approximately 3 degrees to 4 degrees C warmer than were measured under modern conditions. Trophic level and population diversity and equitability data from these faunal assemblages and other Peruvian archaeological sites support the isotope interpretations and suggest that upwelling of the Peru-Chile current intensified after approximately 5000 yr B.P.     

The effects of artificial selection on the maize genome

Domestication promotes rapid phenotypic evolution through artificial selection. We investigated the genetic history by which the wild grass teosinte (Zea mays ssp. parviglumis) was domesticated into modern maize (Z. mays ssp. mays). Analysis of single-nucleotide polymorphisms in 774 genes indicates that 2 to 4% of these genes experienced artificial selection. The remaining genes retain evidence of a population bottleneck associated with domestication. Candidate selected genes with putative function in plant growth are clustered near quantitative trait loci that contribute to phenotypic differences between maize and teosinte. If we assume that our sample of genes is representative, approximately 1200 genes throughout the maize genome have been affected by artificial selection.     

玉米醇溶蛋白及其在农产品保鲜中的应用

玉米醇溶蛋白是玉米的主要储藏蛋白,约占总蛋白含量的50%～60%.近年来随着对玉米醇溶蛋白研究的不断深入,它的应用范围逐步扩大.本文介绍了玉米醇溶蛋白的组成、分子结构、分子形状及玉米醇溶蛋白的溶解性、成膜特性和提取方法;阐述了玉米醇溶蛋白在农产品保鲜中的应用,并对玉米醇溶蛋白的几种提取方法的优缺点进行了比较分析.旨在为玉米醇溶蛋白的提取、利用和玉米的综合开发提供依据.     

Phytolith evidence for early Holocene Cucurbita domestication in southwest Ecuador

Cucurbita (squash and gourd) phytoliths recovered from two early Holocene archaeological sites in southwestern Ecuador and directly dated to 10,130 to 9320 carbon-14 years before the present (about 12,000 to 10,000 calendar years ago) are identified as derived from domesticated plants because they are considerably larger than those from modern wild taxa. The beginnings of plant husbandry appear to have been preceded by the exploitation of a wild species of Cucurbita during the terminal Pleistocene. These data provide evidence for an independent emergence of plant food production in lowland South America that was contemporaneous with or slightly before that in highland Mesoamerica.     

The history of South American tropical precipitation for the past 25,000 years

Long sediment cores recovered from the deep portions of Lake Titicaca are used to reconstruct the precipitation history of tropical South America for the past 25,000 years. Lake Titicaca was a deep, fresh, and continuously overflowing lake during the last glacial stage, from before 25,000 to 15,000 calibrated years before the present (cal yr B.P.), signifying that during the last glacial maximum (LGM), the Altiplano of Bolivia and Peru and much of the Amazon basin were wetter than today. The LGM in this part of the Andes is dated at 21,000 cal yr B.P., approximately coincident with the global LGM. Maximum aridity and lowest lake level occurred in the early and middle Holocene (8000 to 5500 cal yr B.P.) during a time of low summer insolation. Today, rising levels of Lake Titicaca and wet conditions in Amazonia are correlated with anomalously cold sea-surface temperatures in the northern equatorial Atlantic. Likewise, during the deglacial and Holocene periods, there were several millennial-scale wet phases on the Altiplano and in Amazonia that coincided with anomalously cold periods in the equatorial and high-latitude North Atlantic, such as the Younger Dryas.     

三峡库区玉米地方资源的Giemsa C-带多态性研究

该文报道了三峡库区 37个地方资源GiemsaC—带的多态性 ,在资源间与资源内部存在一定的多态性。C—带的分布与总数目各不相同。各地方资源GiemsaC—带总数在 4～ 1 3之间 ,但主要集中于 9左右。不同材料有不同的变异系数 ,选育自交系应考虑其变异系数     

三峡库区玉米地方资源的Ciemsa C-带多态性研究

该文报道了三峡库区３７个地方资源Ｇｉｅｍｓａ Ｃ－带的多态性,在资源间与资源内部存在一定的多态性。Ｃ－带的分布与总数目各不相同。各地方资源Ｇｉｅｍｓａ Ｃ－带总数在４￣１３之间,但主要集中于９左右。不同材料有不同的变异系数,选育自交系应考虑其变异系数。     

Asynchronous climate changes in the North Atlantic and Japan during the last termination

Pollen records from the annually laminated sediment sequence in Lake Suigetsu, Japan, suggest a sequence of climate changes during the Last Termination that resembles that of the North Atlantic region but with noticeable differences in timing. An interstadial interval commenced a few centuries earlier [approximately 15,000 years before the present (yr B.P.)] than the North Atlantic GI-1 (B?lling) event. Conversely, the onset of a Younger Dryas (YD)-like cold reversal (12,300 to 11,250 yr B.P.) postdated the North Atlantic GS-1 (YD) event by a few centuries. Climate in the Far East during the Last Termination reflected solar insolation changes as much as Atlantic influences.     

外源DNA导入水稻的方法及性状变异研究

运用减压渗透法将玉米、小麦、小米、高粱、狼尾草的DNA导入水稻品种紫稻，可产生多种多样的变异类型．性状变异包括：生育期、株型、穗型、粒形、花粉育性等．有的是供体特有性状，有的是新性状。从变异后代中，获得了一批性状优良并能稳定遗传的材料．减压渗透法操作简单，转化率高，为谷类作物导入外源DNA提供了一条新途径．     

Modelling the Relationship Between Summer Maize NPK Uptake and Yield on the Basis of Soil Fertility Indices

Quantitative estimation of fertilizer requirements can help to increase maize （Zea mays L.） yields and improve the fertilizer use efficiency. The model for the Quantitative Evaluation of the Fertility of Tropical Soils （QUEFTS） was calibrated for maize by use of soil fertility data and fertilizer trials at different sites of the Huang Huai Hai river plain in China. The QUEFTS model accounts for interactions between nitrogen （N）, phosphorus （P） and potassium （K）. It describes the effects of soil characteristics on maize yields in four steps： （1） assessment of the potential supply of N, P and K based on soil chemical data; （2） calculation of the actual uptake of N, P and K, in function of the potential supply as determined in step 1 ; （3） draft the yield ranges as a function of the actual uptake of N, P and K as determined in step 2; （4） calculation of the maize yield based on the three yield ranges established in step 3. Data of field experiments with different fertilization treatments of various regions in China during the years of 1985 to 1995 were used to calibrate the QUEFTS model for summer maize. In step 1 the N, P and K recovered from their amount applied were described by new equations. The minimum and maximum accumulated N, P and K （kg grain kg^-1） in summer maize were determined as （21-64）, （126-384） and （20-90）, respectively. The simulated yields were in good agreement with the observed ones. It was concluded that the calibrated and adjusted QUEFTS model could be useful to improve fertilizer recommendations for maize in the Huang Huai Hai plain of China.