陆地植物对环境变化的响应

陆地植物起源以后，地球上的环境发生了巨大的变化。大气CO2浓度自泥盆纪早期的2000-4OOOμml•mol_1下降至石炭一二叠纪的300μml•mol_1左右，02浓度在泥盆纪至石炭一二叠纪时期，由20-30μml•mol_1上升到70-80μml•mol_1，随后又下降到目前的水平。陆地植物登陆后，形态结构也发生了显著的改变，气生部分表而分化出了通气结构--气孔器和保护结构--角质层。泥盆纪首选标志植物刺镰蕨（Drelpanophycus spinaefrmis）在整个泥盆纪，广布全世界。刺镰蕨的气孔器类型一直存在两种观点，一种认为刺镰蕨的气孔器是平列型，即气孔器山两个保卫细胞和两个副卫细胞组成：另一观点认为刺镰蕨的气孔器为不规则型，即气孔器仅有两个保卫细胞构成，不具副卫细胞。我们借助于扫描电镜、石蜡制片技术和叶表皮离析法，细致地研究了现代石松（Lycopodium japonicum）叶的横切而、表皮及气孔器的内外表面结构，并同刺镰蕨的表皮和气孔器进行了对比。认为刺镰蕨的气孔器和所有的化石石松类及现代石松类的气孔器一样，均属于不规则型。从而解决了关于刺镰蕨气孔器类型的长期争论的关键性科学问题。 胡桃科青钱柳属植物起源于晚白垩世的环北太平洋沿岸，化石植物最早发现于北美古新世和早始新世的Motana,，Wyoming，North Dakota，north Colorado地区，欧亚地区仅出现在渐新世至上新世的Kazakhstan、Germany、Romnania、Russia、Japan、中国云南远谋和四川米易地区。我们将采于吉林省珲春组始新世的叶化石鉴定为一青钱柳相似种，该化石成为东亚地区出现最早的青钱柳属植物，这一发现也支持晚白垩至早第三纪时期环北太平洋两岸曾经相连的观点，青钱柳属在晚白垩由北美起源，在始新世经东亚向欧亚大陆扩散，由于环境变迁，第四纪以后，青钱柳属仪剩一种植物分布于中国的亚热带地区。文中还利用共存分析方法估测出始新世吉林省珲春地区属于暖温带至亚热带气候。 统万城遗址位于我国黄土高原向毛乌素沙漠过渡地带的北缘，属于暖温带森林草原向温带干草原、温带荒漠草原过渡的地区，同时又是东部季风区向西北干旱区过渡的生态环境敏感带。今天统万城地区的自然景观属于沙漠，仅存稀疏的次生灌丛和草本群落。但是，通过对统万城城墙内的孢粉和木材进行的综合研究表明，在约1600年前，当地为温带草原，在塬面或山丘上分布有侧柏林，沟谷、河岸边生长喜温湿的乔木，河流、湖泊、沼泽中水生植物繁盛，在丘间低洼处或盐碱土上分布有灌木和草本植物。当时该地区的年均温为7.8 ℃-9.3℃，最热月平均温度23.0℃-24.9℃，最冷月平均温度-12℃-5.6℃，年较差28.5℃-3 8.2℃，年降雨量403.4-550．Omm，最大月降雨量83.8-123.9mm，最少月降雨量4.4-12.2mm，当时气候比现在温暖湿润，年均温比现在高出0.2-0.7℃，年降雨量也高出60--lOOmm。而如此的历史景观今天已经向南迁移，侧柏林或森林草原退缩至延安以南地区。在此近1600年的时间里，毛乌素沙漠分布范围不断扩大，其南部边缘推进了约200 km，推测沙漠扩展的速率达到平均125m/a。

芦笋抗氨基酸及氨基酸类似物突变体的筛选

由芦笋无菌苗诱导得到的愈伤组织，经甲基磺酸乙酯（EMS）诱变处理后，进行抗氧乙基半胱氨酸(AEC)和赖氨酸加苏氨酸(Lys十Thr)的突变体筛选工作，得到如下结果: ①AE C可抑制芦笋愈伤组织的生长，但此抑制作用可被赖氨酸或甲硫氨酸都分解除。利用AEC的抑制作用筛选得到抗0.5mMAEC的愈伤组织AR10并再生植株。AR10愈伤组织离开选择剂两代后仍保持对AE C的抗性。还发现抗性愈伤组织对2mM的半胱氨酸的抑制作用具有交叉抗性，对1mM的Lys+Thr的抑制作用有较弱的交叉抗性。AR10的再生植株一部分表出对A EC的抗性，另一部分则无抗性氨基酸分析表明，抗性愈伤组织内游离赖氨酸、苏氨酸、甲硫氨酸和异亮氨酸有所增加，而在开生植株中发现了半胱氨酸和赖氨酸的特异性增加（分别是对照的4•56和5 •39倍)。AR10的抗性机理目前尚不清楚。 ②2mM的Lys十Thr Lys+Thr对芦笋愈伤组织生长具有抑制作用。甲硫氨酸可部分解除.Ly s十Thr的抑制作用。用2mM的Lys+Thr筛选得到的抗性细胞系LTR2. LTR3，在离开选择压力一代，细胞增殖五倍的情况下仍保持对选择剂的稳定抗性。LTR2、L T R3愈价组织对A E C如仰制作用表现出部分的交叉抗性。另外还发现抗性系对苏氨酸(2mM )的生长抑制作用具有抗性，对赖氨酸(2mM)的生长抑制作用却无抗性，氨基酸分析表明。LTR2LTR3愈份组织内游离赖氨酸含量明显提高(分别是对照的2•18和2.67倍)，另发现一种峰值介于赖氨酸与游离氨之间的未知氨基酸增加更为显著(分别是对照的4•03和11•42倍)。这些结果表明抗性愈伤组织内氨基酸合成的某些关键酶可能发生了改变，对末端物的反馈抑制敏感性有所降低。

Mesoscale, cyclonic eddies as larval fish habitat along the southeast United States shelf: A Lagrangian description of the zooplankton community

The Charleston Gyre region is characterized by continuous series of cyclonic eddies that propagate northeastwards before decaying or coalescing with the Gulf Stream south of Cape Hatteras, NC, USA. Over 5 d, chlorophyll-a concentration, zooplankton displacement volume, and zooplankton composition and abundance changed as the eddy moved to the northeast. Surface chlorophyll-a concentration decreased, and zooplankton displacement remained unchanged as the eddy propagated. Zooplankton taxa known to be important dietary constituents of larval fish increased in concentration as the eddy propagated. The concurrent decrease in chlorophyll-a concentration and static zooplankton displacement volume can be explained by initial stimulation of chlorophyll-a concentration by upwelling and nutrient enrichment near the eddy core and to possible grazing as zooplankton with short generation times and large clutch sizes increased in concentration. The zooplankton community did not change significantly within the 5 d that the eddy was tracked, and there was no indication of succession. Mesoscale eddies of the region are dynamic habitats as eddies propagate northeastwards at varying speeds within monthly periods. The abundance of zooplankton important to the diets of larval fish indicates that the region can provide important pelagic nursery habitat for larval fish off the southeast coast of the United States. A month of feeding and growth is more than half the larval duration of most fish spawned over the continental shelf of the southeastern United States in winter.

水松生殖生物学的研究

本文运用组织化学技术、透射电镜技术，就水松雌雄配子体发育，精卵细胞形成和结构，受精作用以及细胞质遗传等问题进行了较为详细的研究。主要结果如下： 1 绒毡层发育与雄配子体发育，尤其与花粉外壁的形成关系密切。绒毡层组织在小孢子母细胞和减数分裂时期达到发育高峰。四分体阶段和游离小孢子发育前期，绒毡层细胞中内质网、脂体、线粒体非常活跃，参与孢粉素和乌氏体的形成和转移。乌氏体有球形、星芒状两种类型，它们主要参与花粉外壁内层和外壁外层的建成。小孢子发育后期绒毡层细胞开始明显解体。 2 减数分裂阶段，质体、线粒俺等细胞器和造粉体随细胞核和染色体的变化，出现有规律的迁移现象。减数分裂前期，细胞核移到细胞的一侧;各种细胞器和造粉体迁移到细胞的另一侧，并随染色体移向细胞中部而转移到细胞质周缘。减数分裂中期l和后期，各种细胞器和造粉体汇聚在赤道板丙侧分布。说明细胞质中微管系统在起调节作用。 3 花粉壁形成开始于四分体时期。片层状结构的外壁内层随纤维状原外壁的出现雨形成。外壁外层和花粉内壁在小孢子发育中期几乎同时形成。小孢子细胞和绒毡层组织共同参与了外壁内层和外壁外层孢粉素物质的合成、转运。水松成熟花粉由孢粉素组成的外壁外层、片层状结构的外壁内层及有分层状结构的内壁构成。 4 传粉到受精间隔要四个月左右的时间。六月上旬，花粉管和精原细胞抵达颈卵器上部。精原细胞富含淀粉粒、质体、线粒体和异形泡并分区分布。受精前，精原细胞分裂形成两个大小和形状相同豹精细胞。精细胞含有质体、线粒体和异型泡等细胞器。 5 雌配子体游离核持续时间长，从颈卵器原始细胞形成到卵细胞发育成熟所需时间较短。复合颈卵器结构，颈细胞和套层细胞形态结构特殊。中央细胞不经分裂，直接行使卵细胞的功能。 6 成熟卵细胞中除弋量各种形式的内含物外，细胞质被庞大的内质网包围、分割，形成网膜系统。质体、淀粉等细胞器被包含成大内含物。在卵核周围细胞质中没有发现质体和发育完好的线粒体存在。 7 受精作用发生在六月十日左右。雌雄核融合时，朝向精核一面的卵核形成凹陷，精核陷入其中与卵核进一步融合。精卵融合可发生在颈卵器的上部、中部、下部甚至底部。有旋转受精、两个精核同时与一个卵核受精及多卵细胞现象等。 8 新细胞质主要为雄性细胞质成分。合子转移到颈卵器基部分裂，形成原胚游离核。合子、新细胞质和游离核周围淀粉鞘显著。八游离核时期形成细胞壁，新细胞质和淀粉粒转移到原胚细胞中。 9 水松的质体和线粒体为父系遗传。

Multidirectional movements of sportfish species between an estuarine no-take zone and surrounding waters of the Indian River Lagoon, Florida

We examined movement patterns of sportfish that were tagged in the northern Indian River Lagoon, Florida, between 1990 and 1999 to assess the degree of fish exchange between an estuarine no-take zone (NTZ) and surrounding waters. The tagged f ish were from seven species: red drum (Sciaenops ocellatus); black drum (Pogonias cromis); sheepshead (Archosargus probatocephalus); common snook (Centropomus undecimalis); spotted seatrout (Cynoscion nebulosus); bull shark (Carcharhinus leucas); and crevalle jack (Caranx hippos). A total of 403 tagged fish were recaptured during the study period, including 65 individuals that emigrated from the NTZ and 16 individuals that immigrated into the NTZ from surrounding waters of the lagoon. Migration distances between the original tagging location and the sites where emigrating fish were recaptured were from 0 to 150 km, and these migration distances appeared to be influenced by the proximity of the NTZ to spawning areas or other habitats that are important to specific life-history stages of individual species. Fish that immigrated into the NTZ moved distances ranging from approximately 10 to 75 km. Recapture rates for sportfish species that migrated across the NTZ boundary suggested that more individuals may move into the protected habitats than move out. These data demonstrated that although this estuarine no-take reserve can protect species from fishing, it may also serve to extract exploitable individuals from surrounding fisheries; therefore, if the no-take reserve does function to replenish surrounding fisheries, then increased egg production and larval export may be more important mechanisms of replenishment than the spillover of excess adults from the reserve into fishable areas.

Temporal and spatial dynamics of spawning, settlement, and growth of gray snapper (Lutjanus griseus) from the West Florida shelf as determined from otolith microstructures

The goal of our study was to understand the spatial and temporal variation in spawning and settlement of gray snapper (Lutjanus griseus) along the West Florida shelf (WFS). Juvenile gray snapper were collected over two consecutive years from seagrass meadows with a benthic scrape and otter trawl. Spawning, settlement, and growth patterns were compared across three sampling regions (Panhandle, Big bend, and Southwest) by using otolith microstructure. Histology of adult gonads was also used for an independent estimate of spawning time. Daily growth increments were visible in the lapilli of snapper 11–150 mm standard length; ages ranged from 38 to 229 days and estimated average planktonic larval duration was 25 days. Estimated growth rates ranged from 0.60 to 1.02 mm/d and did not differ among the three sampling regions, but did differ across sampling years. Back-calculated fertilization dates from otoliths indicated that juveniles in the Panhandle and Big Bend were mainly summer spawned fish, whereas Southwest juveniles had winter and summer fertilization dates. Settlement occurred during summer both years and in the winter of 1997 for the southern portion of the WFS. Moon phase did not appear to be strongly correlated with fertilization or settlement. Histological samples of gonads from adults collected near the juvenile sampling areas indicated a summer spawning period.

全球变化的中国北方林生态系统生产力及其生态系统公益

基于我国北方林一兴安落叶松林的实际观测资料对国际著名的CENTURY模型进行了验证，进而模拟了我国北方林一兴安落叶松林的碳循环动态;结合全球变化的预测结果，模拟了全球气候变化下中国北方林生物量、生产力以及碳吸收能力的变化;并且预测了大兴安岭地区的自然干扰因子（林火）和人类活动（采伐、搂除枯枝落叶）对兴安落叶松林碳循环的影响。建立了综合反映兴安落叶松林生物学特性（年龄、蓄积量）及气候因素（年均温、年降水）共同作用下的兴安落叶松林净第一性生产力模型一材积驱动模型。评估了我国森林的生态系统公益价值，并建立了森林生态系统公益价值与其总生产力的回归关系。具体结果如下： (1) 我国北方林的植物总生物量为112. llt．hm-2，净第一性生产力为403. 07gC.m-2.a-l。 (2) 建立了兴安落叶松林的生物气候生产力模型： NPP= (0.3318ln (V/A) +0.4747)×30 (l_e-0'0009695E) 为基于森林资源清查资料与气候资料估算森林生产力提供了方法。 (3) 兴安落叶松林生态系统每年可净吸收碳2.65 t．hm-2，是一个重要的碳汇。 (4) 大气C02浓度倍增将使兴安落叶松林的净笫一性生产力增加9. 8%，并且提高了兴安落叶松林的碳汇功能。 (5) 温度上升将增加兴安落叶松林的生物量和净初级生产力，并且其碳汇功能也有所提高。对兴安落叶松林生长的主要限制因子是温度而不是水分。 (6) 林火使兴安落叶松林的生物量降低，但同时也促进了兴安落叶松的更新及幼树的生长，火烧后兴安落叶松林的生产力均有所增加。火烧的强度越大，烧死的森林生物量越多，火后的恢复期也越长。 (7) 一定强度的采伐有利于兴安落叶松林的更新和幼苗、幼树的生长，从而既得到了直接的经济效益，同时又可以保持一定的生态效益。 (8) 搂除枯枝落叶层在短时间内促进了兴安落叶松林的生长，但长期下去，则将导致土壤越来越贫瘠，不利于森林的生长。 (9) 兴安落叶松林所创造的生态系统公益的总价值约为2409.96×106US$．a-，其生态效益的价值是其所创造的经济价值的2.52倍，反映了生态效益的显著性。 (10) 在对我国各类型森林的生态系统公益价值评估的基础上建 立了森林生态系统公益价值与其生产力的回归关系：Va=108.25×1 06×(Tp)0'93，简化了生态系统公益价值的评估计算工作。

APPLICATION OF CENTRIFUGE MODELS IN THE STUDY OF AN INTERACTION PROBLEM.

Rigid retaining walls are considered. Both the backfill and the soil supporting the foundation of the model wall have been made of a single dry granular soil. Attention is limited to one grain.

Low power all-optical switch in a passive InGaAsP multiple quantum well waveguide

We demonstrate the use of resonant bandfilling nonlinearity in an InGaAsP/InGaAsP Multiple Quantum Well (MQW) waveguide due to photogenerated carriers to obtain switching at pulse powers, which can readily be obtained from an erbium amplified diode laser source. In order to produce gating a polarisation rotation gate was used, which relies on an asymmetry in the nonlinear refraction on the principle axes of the waveguide.

Optimisation of the chirp performance of electroabsorption modulators using a numerical system model

A model to simulate an electroabsorption modulator in a dispersive communications system is described and confirmed experimentally for a 5Gbit/s 100km system. Optimisation of the device shows that transmission of 10Gbit/s over 100km is possible.

眼镜王蛇泛素融合蛋白基因和核糖体蛋白L30 基因的克隆及分析

从广西产眼镜王蛇( Ophiophagus hannah) 毒腺中抽提总RNA , 经mRNA 纯化后构建眼镜王蛇毒腺 cDNA 文库。从所构建的cDNA 文库中, 随机筛选200 个克隆测序, 得到两个在进化上高度保守的基因: 泛素融 合蛋白基因(GenBank 登录号为AF297036) 和核糖体蛋白L30 基因(GenBank 登录号是AF297033) 。前者cDNA 的开放阅读框为387 bp , 后者为348 bp 。前者编码128 个氨基酸残基组成的泛素融合蛋白前体; 后者编码115 个氨基酸残基组成的核糖体蛋白L30 前体。由cDNA 序列推导出的氨基酸序列分析表明, 泛素融合蛋白前体包 括N - 末端的泛素结构域(76 个氨基酸残基) 和C - 末端的核糖体蛋白L40 结构域(52 个氨基酸残基) 。该蛋 白为一高碱性蛋白, C 末端含有一个“锌指”模式结构。与16 个物种比较的结果表明, 眼镜王蛇与脊椎动物的 泛素融合蛋白氨基酸序列相似度较高, 具有高度的保守性。

Temporal and Spatial Expression Patterns of Sox1 Gene in Xenopus laevis

克隆了非洲爪蟾的Sox1基因并研究了它在非洲爪蟾早期发育过程中的时空表达图式,比较了Sox1-3基因在发育的脑和眼中的表达图式.序列比对分析显示Sox1-3蛋白在其HMG框结构域具有高度的保守性.通过RT-PCR方法分析了Sox1基因在爪蟾早期不同发育时段的表达情况,结果显示Sox1基因从未受精卵到尾芽期均有表达,但表达强度有所差异.原位杂交结果显示,在早期卵裂阶段和囊胚期,Sox1基因主要在动物极表达;从神经板期开始,Sox1基因主要在中枢神经系统和眼原基中表达.在蝌蚪期,Sox1与Sox2、Sox3在脑部和眼睛的表达区域有所不同.对于爪蟾Sox1基因时空表达图式的研究将有助于阐明SoxB1基因家族在脊椎动物神经系统发生过程中的作用.