兰州烟洞沟黄土剖面古环境演变研究

兰州烟洞沟黄土剖面共划分出 １９ 个孢粉组合的带,根据孢粉组合的纵向变化,将 １．７ Ｍ ａ． Ｂ． Ｐ．以来的古植被和古气候变迁分为 １２ 个阶段,归纳为 ６ 种孢粉植物群类型。兰州地区受青藏高原不断隆升的影响,第四纪以来冰期干冷程度逐渐加强。这里既没有阔叶林与针叶林之间的更替,更没有常绿 阔叶林与落叶阔叶林之间的更替,只能出现暗针叶林、疏林草原、灌丛草原、荒漠之间的变化;在暖期中,阔叶树种花粉含量从未达到或超过孢粉总量的 ４０％ ,其植被应以疏林草原或灌丛草原为主。冷期中以藜科为主的孢粉植物群所反映的环境最为干旱。处于东亚季风逐渐取代西风环流控制的兰州地区,第四纪期间气候和植被所经历的多种形式的演化过程,并非重复的循环。     

猪野泽不同位置沉积物碳酸盐含量与花粉保存

孢粉是恢复古气候、古植被重要的代用指标。根据已有的研究成果,猪野泽孢粉组合所指示的全新世气候环境变化存在较大分歧。湖泊碳酸盐沉积可以指示碱性沉积环境,而碱性环境对孢粉的腐蚀较大,影响花粉的保存。所以,研究湖泊沉积物中碳酸盐含量与孢粉保存的关系,可以探讨该区域花粉保存是否受到过盐湖沉积的影响,并可进一步探讨该区域花粉组合的差异是否与花粉保存有关。结果表明：在猪野泽全新世两个成湖期,高碳酸盐含量与高孢粉浓度相对应。虽然,高碳酸盐含量对应的强碱性环境对孢粉的腐蚀性大,但当时猪野泽成湖期内气候温暖湿润,孢粉输入量非常大,以至于碱性沉积环境不足以改变孢粉的浓度。因此,猪野泽不同位置沉积物碳酸盐含量与花粉保存情况无明显相关关系,以上分歧的出现不是由孢粉保存引起的。     

塔里本盆地北部全新世地层中的孢粉组合与古环境

通过对塔里木盆地北部全新世地层中２７块样品的孢粉分析，根据其组合特征并结合表土花粉分析，本区全新世以来除了塔里木河中游隐域性植被成分随着河流改道变化频繁外，两侧显域性的早生、超旱生荒漠植被成分无明显变化，它们的生境反映了气候环境总的形势是持续干旱的。但全新世地层中孢粉种属和丰度的变化，蒿属、藜科和麻黄花粉相对数量的增减也说明了在干旱背景中本区气候有微弱的干湿波动，表现为全新世早期和晚期气候偏凉湿，中期气候干暖，但干暖期鼎盛阶段略湿。     

塔里木盆地北部全新世地层中的孢粉组合与古环境

通过对塔里木盆地北部侠析世地层中２７块样品的孢粉分析，根据其组合特征并结合表土花粉分析，本区全新世以来除了塔里木河中游隐域性植被成分随着河流改道变化频繁外，两侧显域性的旱生，超旱生荒漠植被成分无明显变化，它们的生境反映了气候环境总的形势是持续干旱的。     

一万年以来西安东郊的植被和气候

通过对西安东郊半坡大围沟剖面的地质调查、密集采样和孢粉分析,讨论该区植被的演替。论证了全新世古气候环境的特征,总结了早、中、晚全新世在该区发育的植被及其所代表的气候环境。从该剖面17个样品中分析出了大量孢粉,做出了黄土地层的孢粉图式。据该剖面上孢粉组合变化的分析,得出了全新世的植被与相应的气候在时间上的演变与空间上的分布范围。结果表明中全新世气候温暖湿润;晚全新世温凉干旱。     

西北干旱地区表土孢粉与植被关系研究进展

较全面地综述了西北干旱地区表土孢粉与植被和气候关系的研究进展, 讨论了部分有指示意义的花粉,如云杉、杨、桦、禾本科、豆科等代表性花粉以及花粉浓度、A/C(蒿属Artemisia/藜科Chenopodiaceae)比值等问题.并提出了自己的一些见解和未来进一步开展工作的方向:如,在新疆某些地区很少发现桦属花粉可能属个别现象;可以根据藜科的生理习性解释草原区植被的A/C值较低即表明草原植被退化严重;进一步开展杨属(Populus)和桦属(Betula)花粉在林中的代表性、西北地区Ch(藜科Chenopodiaceae)/Po(禾本科Poaceae)值的研究,以及草原带与森林带之间的过渡地带的孢粉组合研究;今后需要将整个中国西北干旱区作为一个整体来研究,以深入了解孢粉-植被-气候的关系.     

策勒绿洲塔格勒剖面孢粉分析的初步结果

根据位于策勒绿洲与荒漠交错带的塔格勒剖面孢粉记录的初步研究表明,近７００ａＢ,Ｐ,来此地区气候的干旱状况持续未变,但期间仍有几次相对湿润期,即在剖面距顶２．７－２．０ｍ段,１．８－１．９ｍ段和０．８－０．６ｍ段孢粉组合特征显示出当时植被生长条件较好,生长环境相对湿润的特征,地层沉积物特征也有相应体现。     

一万多年来乌伦古湖地区花粉组合及其古环境

本文通过对新疆乌伦古湖钻孔剖面进行孢粉分析研究，划分出５个花粉组合带及３个组合亚带。结合岩性特征，介形虫资料及＾１４Ｃ测年数据，详细讨论了一万多年来该区古气倏变迁及湖泊环境演变历史，其古气候经历了由冷湿（１２－１０ｋｇＢ．Ｐ．）→温湿→温干→温湿（３－１ｋａＢ．Ｐ．）的变化过程。于晚冰期后期（１２－１０ｋｇＢ．Ｐ．），乌伦古湖开始成湖，此后，随着气候的变化，湖泊曾出现两次较大规模的退缩，约７－５ｋ     

古洪水事件判别以及微形态学在古洪水事件判别中的应用

古洪水研究是全球变化研究的热点问题,而研究古洪水的关键是如何有效地寻找及准确判定古洪水平流沉积.在综述古生物学、考古学、沉积学、地球化学对研究古洪水事件作用的基础上,结合微形态研究方法,对古洪水和其他层位薄片的微形态进行了对比分析,表明二者在颗粒特征、矿物组合、孔隙及微垒结等方面存在明显的区别,说明微形态能够用来研究和判别古洪水事件,为古洪水研究提出了一个新的研究思路.     

关中富平地区近一万年植被和气候的讨论

为了了解黄土高原中部近一万年以来古气候演化特征,通过对关中富平剖面的地质调查、密集采样和31个样品的孢粉分析,将孢粉图式划分为Ⅰ、Ⅱ、Ⅲ三个带分别代表早、中、晚三个时期的孢粉带:Ⅰ带为松-菊-香蒲组合带,以草本植物花粉占优势,针叶树植物花粉含量较高为特征;Ⅱ带为松-栎-蒿-环纹藻组合带,以乔木花粉增加,草本植物花粉减少为特征;Ⅲ带为栎-松-蒿组合带,以草本植物花粉增加,乔木花粉减少为特征。结果表明:早全新世植被为森林草原-干草原,气候干凉-干冷;中全新世植被为森林草原与针阔叶混交林草原,气候温暖半湿润;晚全新世植被为森林草原或疏林草原,气候干旱偏暖-温凉干旱。     

奈曼旗过牧沙漠化草地在封育条件下植被的演变及其恢复

对内蒙古奈曼旗沙漠化草地封育2年、3年和8年保护地围栏内、外植被调查,通过聚类分析分出9个植物群落类型。研究表明:沙漠化草地封育后植被盖度增加,植物群落类型增多。同时促进了沙漠化草地中沙丘的固定,并使地表起伏趋于平缓。在强烈发展中的沙漠化土地中进行草地封育,生物量至少在8年内呈提高趋势。计算表明,封育效果和封育时间成正比,但以封育2、3年内的植被恢复较快。     

小麦白粉菌的联合致病性分析

 根据传统应用的生理小种研究方法存在着因鉴别品数的不同及其数目的改变而引起小种命名的混乱;同小种不同菌株致病性不同及有限的鉴别寄主不能及时区分出危险性小种等问题,本文改用病菌群体对品种的毒力频率和联合致病性方法,用河南各地的90个小麦白粉菌株分别接种9个已知抗性基因的品系和8个推广或区试品种所得到的侵染型资料,分别计算菌株群体对各对品种的联合致病性系数和联合毒性系数.结果表明本省小麦白粉菌群体中的V₁和V₃c、V₁和V₅及V₃b和V₃C等毒性基因是联合的;花培28和周80—48及周80—48和郑州831等品种组合搭配种植可有效地控制小麦白粉病.因此这套方法对生产和抗病育种的作用是直接的.文中提出应根据研究对象和研究目的不同,选择适当的研究方法,以提高病原物致病性研究结果的有用性.     

Relationship between ineffective R-genes and expansion rate of lesions on potato leaves, caused by Phytophthora infestans

Progenies from eight tetraploid potato crosses were assessed for the association between ineffective R- genes and lesion expansion rate (LER) in mm per day on detached leaves that had been inoculated with Phytophthora infestans . In two of the progenies, a significant association between ineffective R- genes and LER was measured, which could be an indication of residual effects. No association was found in the other progenies. These results and other corroborative evidence do not support an approach to plant breeding based on the stacking of R- genes to accumulate residual resistance effects. Using the same detached-leaf test, differences in aggressiveness between two isolates of P. infestans could be measured in all eight progenies. LER values were consistent with previously published ranges and were distributed continuously and unimodally in all progenies, suggesting that differences in relative aggressiveness of isolates were probably not affected by R- genes.     

Measure of multilocus correlation as a new parameter for study of plant pathogen populations

ABSTRACT The measure of multilocus correlation for diallelic loci was developed to augment use of other diversity indices in the study of multilocus structure of populations. This measure provides information not revealed by other parameters for measuring multilocus association and linkage disequilibrium among pairs of loci. Relationships between the measures of multilocus correlation and association and all commonly used indices for diversity within populations are also described. A number of hypothetical examples demonstrate that the measure of multilocus correlation describes unique aspects of multilocus structure of populations compared with the measure of multilocus association and phi coefficient of association. The measure of multilocus correlation can be used for analysis of independence of differentiating characters for a given population-the necessary condition of valid applications of the bootstrap method across differentials. Comparisons of the measures of multilocus correlation and association with the measures of diversity within population show that they reveal different aspects of population structure. As an adjunct to standard diversity indices, the measure of multilocus correlation may reveal subtle differences in diversity within populations even if the standard index fails to distinguish between the populations. A new measure of population uniformity also was developed to characterize another aspect of diversity within populations not detected by standard indices.     

Variation in severity of cashew powdery mildew (Oidium anacardii Noack) disease in Tanzania: Implications for research and extension

Abstract

Cashew trees in farmers’ fields in two contrasting areas in southern Tanzania were surveyed for growth, powdery mildew development, amounts and applications of sulphur, pest damage and nut yield by village‐based extension workers in 1993. There was a wide range of powdery mildew levels on cashew flowers, apples and nuts at both the Tunduru (inland) and Newala (western Makonde plateau). In both Newala and Tunduru application of sulphur dust was associated with reduced severity of blossom powdery mildew. Sulphur usage commenced later in Newala than Tunduru though this was associated with earlier onset of blossoming in the latter district. Farmers in both areas applied similar numbers of rounds of sulphur, however in Newala more sulphur was applied per tree reflecting the bigger trees found in this district. There was a highly significant (P < 0.001) negative association between use of sulphur and severity of blossom powdery mildew irrespective of nut yield. There was a strong positive association (P < 0.01) between use of sulphur and more than one nut per panicle from harvests in October, no significant association in November and a significant negative association (P < 0.05) between use of sulphur and more than one nut per panicle in December. The survey highlighted areas in Newala where there were higher powdery mildew levels, through either lack of sulphur application or poor control by late application of sulphur, with relatively high numbers of nuts per panicle. Conversely, areas were identified where despite control of cashew powdery mildew severity by application of sulphur nut yield remained relatively low. The results suggest that final yield results from an interaction of factors of which cashew powdery mildew is only one. There was a highly significant (P < 0.01) association between the number of sulphur rounds and severity of cashew powdery mildew (Newala data only) but no significant association between number of rounds of sulphur and yield taken during October. Pest damage estimates from cashew nuts showed no consistent pattern in either region. Survey results suggest that there is considerable potential in the optimization of sulphur usage as a strategy for control of powdery mildew.     

江苏省移栽油菜田杂草防治阈期研究

综合多点试验,建立移栽油菜栽后有草或无草天数与油菜产量损失率之间的函数关系,研究了江苏省油菜田杂草的防治阈期。结果表明：油菜栽后有草天数（x)与油菜产量损失率（y)之间符合方程y=26.09/(1 43.35e^-0.0417x),栽后无草天数（x)与油菜产量损失率（y)之间符合方程y=0.00001 26.52e^-0.0227x。江苏省油菜田杂草的防治阈期约为栽后41－96d,相当于油菜全生育期的19．5％－45．7％,油菜处于7－9叶期,此前田间杂草的发生量占总量的90％左右。在此阈期内保持田间无草,既能保证杂草造成的减产率低于3％,又能充分发挥杂草在田间生态系统中所起的积极作用。     

Phenotypic influences on the incidence of infection by Ascochyta fabae in spring varieties of faba beans (Vicia faba)

Spring beans with a range of different growth habits were assessed for resistance to Ascochyta fabae. Variation in the incidence of both foliar and pod infection was recorded but there was no association between the two. The larger-podded broad bean types had a higher incidence of pod infection relative to foliar infection than the smaller-podded field beans. The effect of straw length on the incidence of A. fabae was investigated using exogenously applied gibberellin to sensitive and insensitive cultivars. This confirmed the association between long straw and low incidence of pod disease.     

Mycelial compatibility reactions of Australian Fusarium graminearum and F. pseudograminearum isolates compared with AFLP groupings

Using the mycelial reactions of 435 combinations of 14 Fusarium pseudograminearum and 15 F. graminearum isolates, it was demonstrated for the first time that mycelial reactions/barrage formation cannot be clearly used to distinguish F. graminearum and F. pseudograminearum. Mutually compatible isolates produced very different patterns of compatibility with other isolates. However, about 60% of pairings between F. graminearum and F. pseudograminearum isolates were compatible, indicating common ancestry. The Mantel tests used to determine any possible associations between mycelial compatibility reactions and AFLP genotypic diversity data revealed no association between the two systems in either species. In addition, no association was found between mycelial compatibility reactions and sexual reproduction in the two species. Implications of the higher frequency of mycelial compatibility reactions observed in F. pseudograminearum than in F. graminearum are discussed.     

山西省主要玉米对矮花叶病抗病性的鉴定及利用

1997～1998年选取山西省当前推广和拟推广玉米杂交种及亲本自交系,采用自然感染与人工接种相结合方法,对MDMV抗性和F1抗性遗传进行了研究,旨为选育推广抗病品种提供依据.试验结果表明,双亲抗×抗、感×抗,其杂种F1抗性表现显性效应,F1病情指数0～8.2,均可达到抗病保产的目的,但感×抗必须在无病区制种才能获得成功.试验认为抗×抗是选育抗MDMV杂交种最佳组配方式,感×抗应视为过渡组配方式加以利用,而感×感,F1病情指数31.9～37.5,产量损失严重,应禁止在病区制种与推广.