Cruise report: regional assessment of ecosystem condition and stressor impacts along the northwestern Gulf of Mexico Shelf. NOAA Ship 'Nancy Foster' NF-11-07-RACOW (August 8-16, 2011)

This cruise report is a summary of a field survey conducted along a portion of the U.S. continental shelf in northwestern Gulf of Mexico (GOM), at navigable depths along the coastline seaward to the shelf break (~100m) from about 89°30' W to 95°28' W longitude, August 8 – 16, 2011 on NOAA Ship Nancy Foster Cruise NF-11-07-RACOW. Synoptic sampling of multiple ecological indicators was conducted at each of 34 stations throughout these waters using a random probabilistic sampling design. The original study design consisted of 50 stations extending from the Mississippi delta all the way to the U.S./Mexican border, but vessel failures precluded sampling at 16 stations within the western-most portion of the study area. At each station samples were collected for the analysis of benthic community structure and composition; concentrations of chemical contaminants in sediments and target demersal biota; sediment toxicity; nutrient and chlorophyll levels in the water column; and other basic habitat characteristics such as salinity, temperature, dissolved oxygen, turbidity, pH, sediment grain size, and organic carbon content. Other indicators, from a human-dimension perspective, were also recorded, including presence of vessels, oil rigs, surface trash, visual oil sheens in sediments or water, marine mammals, or noxious/oily sediment odors. The overall purpose of the survey was to collect data to assess the status of ecosystem condition and potential stressor impacts throughout the region, based on these various indicators and corresponding management thresholds, and to provide this information as a baseline for determining how such conditions may be changing with time. While sample analysis is still ongoing, some preliminary results and observations are reported here. A final report will be completed once all data have been processed.

Bartonella species detection in captive, stranded and free-ranging cetaceans

We present prevalence of Bartonella spp. for multiple cohorts of wild and captive cetaceans. One hundred and six cetaceans including 86 bottlenose dolphins (71 free-ranging, 14 captive in a facility with a dolphin experiencing debility of unknown origin, 1 stranded), 11 striped dolphins, 4 harbor porpoises, 3 Risso's dolphins, 1 dwarf sperm whale and 1 pygmy sperm whale (all stranded) were sampled. Whole blood (n = 95 live animals) and tissues (n = 15 freshly dead animals) were screened by PCR (n = 106 animals), PCR of enrichment cultures (n = 50 animals), and subcultures (n = 50 animals). Bartonella spp. were detected from 17 cetaceans, including 12 by direct extraction PCR of blood or tissues, 6 by PCR of enrichment cultures, and 4 by subculture isolation. Bartonella spp. were more commonly detected from the captive (6/14, 43%) than from free-ranging (2/71, 2.8%) bottlenose dolphins, and were commonly detected from the stranded animals (9/21, 43%; 3/11 striped dolphins, 3/4 harbor porpoises, 2/3 Risso's dolphins, 1/1 pygmy sperm whale, 0/1 dwarf sperm whale, 0/1 bottlenose dolphin). Sequencing identified a Bartonella spp. most similar to B. henselae San Antonio 2 in eight cases (4 bottlenose dolphins, 2 striped dolphins, 2 harbor porpoises), B. henselae Houston 1 in three cases (2 Risso's dolphins, 1 harbor porpoise), and untyped in six cases (4 bottlenose dolphins, 1 striped dolphin, 1 pygmy sperm whale). Although disease causation has not been established, Bartonella species were detected more commonly from cetaceans that were overtly debilitated or were cohabiting in captivity with a debilitated animal than from free-ranging animals. The detection of Bartonella spp. from cetaceans may be of pathophysiological concern.

在异倍性水平多胚苗水稻的特征特性研究

通过无融合生殖方式固定水稻杂种优势是水稻育种中极具诱惑力的研究内容之一。自从1979年以来，我国水稻无融合生殖充种研究主要集中在筛选和鉴定水稻多胚苗材料。根据前人的研究结果，具有无融合生殖特性的植物大多数为多倍体。本试验以多胚苗水稻APIV及其衍生系为研究材料，在二倍体[APIV_((2))]、同源三倍体[APIV_((3))]和同源四倍体[APIV_((4))]水平，对其多个世代中的特征特性，其中包括形态学特征，遗传学和胚胎学特性进行了研究，旨在探讨在多倍性水平筛选水稻无融合生殖种质的可能性，获得如下主要研究结果： 1.在二倍体APIV_((2))的多个世代中，只发现单胚苗、双胚苗和三胚苗植株，多胚苗频率比较低(4.67～5.14%)，多胚苗性状的表达在一定程度上受到环境因素的影响，并且，多胚苗植株的成活率比较低(11.70～17.39%)，大部分多胚苗植株在三叶期之前死亡，这很可能与其胚乳的营养供应有关。根据APIV_((2))的多胚苗性状在多个自交世代和杂交世代中的表达特点，多胚苗性状不是显性性状，也不是隐性性状，而是一种比较特殊的数量性状。 2.胚胎学的研究结果表明，在APIV_((2))的2857个子房的胚囊中没有观察到与不定胚生殖有关的特异生殖现象;APIV_((2))在发生受精之前的胚囊构型包括正常蓼型胚囊（76.5%）、退化型胚囊（16.0%）和变异型胚囊（7.5%），在变异型胚囊中包括双卵卵器胚囊（86.7%）和三卵卵器胚囊（13.3%）;APIV_((2))的双受精与前人在正常二倍体水稻中所观察到的结果大致相符;在不同季节的颖花和同一季节同一稻穗的不同颖花内多卵和多胚苗频率存在着明显差异。 3.在同源四倍体水稻的诱导中对种芽进行预处理，促使其胚芽鞘明显伸长后再进行诱导处理是诱导成功的关键技术。在同源四倍体APIV_((4))的同一稻穗中强势颖花的多卵频率要明显地高于弱势颖花的多卵频率。在APIV_((4))去雄后的颖花中意外地观察到了单胚和双胚现象。同源四倍体水稻APIV_((4))的有性生殖能力明显变弱，在花药内正常花粉粒少而败育花粉粒多;在受精前正常胚囊数少而退化胚囊数比较多（36.0%）;花粉管进入胚囊的时间比较晚;双受精频率低而单受精频率高。 4.异倍性水稻间具有一定的可交配性，但其结实率比较低（0.20～-1.64%），通过常规杂交方法所获得的同源三倍体成活植株的频率更低（0.07%）。在湖南湘潭的秋季条件下同源三倍体水稻植株雄性完全败育，但有部分稻穗能结实（0.59%～7.71%)，由此可获得饱满种子和不饱满种子。 5.通过子房培养可以获得异倍性水稻间杂种植株。在APIV_((4))/APIV_((2))杂交组合的子房培养中出现了一株双胚苗;同源三倍体成活植株的获得率仍然比较低（0.78%），但比通过常规杂交法首先获得种子，进而获得同源三倍体成活植株的效率要倍出11.14倍。根据试验结果，提出了6个问题进行讨论。认为在杂交后代中有可能筛选到多胚苗发生频率更高的单株;多胚苗性状是比较复杂的数量性状;同源四倍体水稻的有性生殖能力明显变弱;通过合理配组和复重授粉可以提高异倍性水稻间的杂并结实率;通过子房培养可以明显提高获得同源三倍体成活植株的效率;在多倍体水稻中筛选无融合生殖种质在比二倍体水稻中筛选可能更容易成功。

Age determination and growth of the night shark (Carcharhinus signatus) off the northeastern Brazilian coast

Age and growth of the night shark (Carcharhinus signatus) from areas off northeastern Brazil were determined from 317 unstained vertebral sections of 182 males (113–215 cm total length [TL]), 132 females (111.5–234.9 cm) and three individuals of unknown sex (169–242 cm). Although marginal increment (MI) analysis suggests that band formation occurs in the third and fourth trimesters in juveniles, it was inconclusive for adults. Thus, it was assumed that one band is formed annually. Births that occur over a protracted period may be the most important source of bias in MI analysis. An estimated average percent error of 2.4% was found in readings for individuals between two and seventeen years. The von Bertalanffy growth function (VBGF) showed no significant differences between sexes, and the model derived from back-calculated mean length at age best represented growth for the species (L∞=270 cm, K=0.11/yr, t0=–2.71 yr) when compared to the observed mean lengths at age and the Fabens’ method. Length-frequency analysis on 1055 specimens (93–260 cm) was used to verify age determination. Back-calculated size at birth was 66.8 cm and maturity was reached at 180–190 cm (age 8) for males and 200–205 cm (age ten) for females. Age composition, estimated from an age-length key, indicated that juveniles predominate in commercial catches, representing 74.3% of the catch. A growth rate of 25.4 cm/yr was estimated from birth to the first band (i.e. juveniles grow 38% of their birth length during the first year), and a growth rate of 8.55 cm/yr was estimated for eight- to ten-year-old adults.

Impact of hatchery releases on the recreational fishery for Pacific threadfin (Polydactylus sexfilis) in Hawaii

The Pacific threadfin (Polydactylus sexfilis) is considered one of the premier Hawaiian food fishes but even with catch limits, seasonal closures, and size limits, catches have declined dramatically since the 1960s. It was identified as the top candidate species for stock enhancement in Hawaii, based on the decline in stocks, high market value, and importance of the fishery. In the stock enhancement program for Pacific threadfin, over 430,000 fingerlings of various sizes were implanted with coded wire tags and released in nursery habitats along the windward coast of Oahu between 1993 and 1998. Because few Pacific threadfin were present in creel surveys conducted between 1994 and 1998, Oahu fishermen were offered a $10 reward for each threadfin that was caught (for both hatchery-reared and wild fish). A total of 1882 Pacific threadfin were recovered from the reward program between March 1998 and May 1999, including 163 hatchery-reared fish, an overall contribution of 8.7% to the fishery. Hatchery-reared fish accounted for as high as 71% of returns in the release areas. Hatchery-reared fish were recovered on average 11.5 km (SD=9.8 km) from the release site, although some had moved as far away as 42 km. Average age for recovered hatchery-reared fish was 495 days; the oldest was 1021 days. Cultured Pacific threadfin juveniles survived and recruited successfully to the recreational fishery, accounting for 10% of fishermen’s catches on the windward side of Oahu. Recruitment to the fishery was highest for the 1997 release year; few juveniles from earlier releases were observed. Presence of a few large, fully developed females in the recreational fishery suggested that hatchery-reared fish can survive, grow, and reproductively contribute to the population. Implementation of an enhancement program that is focused on juveniles and perhaps large females, as part of an integrated fishery management strategy, could speed the recovery of this fish population.

青蒿开花与青蒿素生物合成相关性的研究-金丝桃和百金花二苯甲酮合酶基因的克隆，异源表达及功能分析

第一部分：青蒿开花与青蒿素生物合成相关性的研究 青蒿素是从中药青蒿中分离出的倍半萜内酯化合物，目前是世界上唯一有效的治疗脑型疟疾和抗氯喹恶性疟疾的药物。青蒿植株中青蒿素含量在开花期最高，但是目前尚不清楚开花与青蒿素生物合成的关系。为此，我们用光周期（短日照）诱导青蒿提前开花，不仅同时获得了开花与不开花的青蒿植株，而且还成功地在同一植株上诱导部分分枝开花，另一部分分枝保持营养生长状态。这一实验体系为研究青蒿开花与青蒿素生物合成的相关性奠定了基础。实验结果表明，开花与不开花青蒿植株青蒿素含量有明显差异。开花植株的青蒿素含量在前2周内逐渐提高，第三周（开花期）达到最高，并保持一周左右，在随后的2周内下降。青蒿植株开花后，叶片便开始老化变黄，逐渐死亡。未开花青蒿植株的青蒿素含量动态在前三周内与开花植株类似，但是这种高青蒿素含量状态能保持较长时间，至少在随后的2周内没有下降。未开花植株的叶片依然保持绿色。这一结果表明，开花不是导致青蒿素含量提高的直接原因。 扫描电镜观察结果表明，幼嫩叶片上的毛状腺体( trichrome)结构是完整的，而在老化的叶片上，则观察到了相当比例(40-50%)破损的腺体。这可能是导致青蒿素含量下降的直接原因。 不同生态型青蒿对光周期的反应是不同的。在北京地区，本地青蒿在8月初便开始开花，而来自四川武陵的青蒿则要到9月份才能开花。根据这一特性，采用“南蒿北栽”的方法，能够使青蒿保持较长时间的营养生长状态，延长适于采收的时间。 第二部分：金丝桃和百金花二苯甲酮合酶基因的克隆，异源表达及功能分析 植物次生代谢物山屯酮( Xanthones)仅存在于龙胆科和藤黄科植物中。它们具有抑制单胺氧化酶，细胞毒素及抗肿瘤活性。 含有1 3个碳原子的二苯甲酮是山屯酮生物合成的中间产物，是由二苯甲酮合酶催化合成的，这一反应是山屯酮生物合成的关键步骤。二苯甲酮合酶已经在金丝桃和百金花细胞悬浮培养系统中检测到，并进行了细致的生化水平上的研究。本研究是在上述研究的基础上，进一步克隆该酶的基因，并进行异源表达及功能分析工作，以便更好地了解和调控山屯酮的生物合成。 用PCR和RT-PCR技术，从金丝桃cDNA文库和逆转录产物中分别克隆到一个基因HBPS1和HBPS2，从百金花cDNA文库中克隆到一个基因CBPS1。HBPS1含有1402个碱基，其开放阅读框架编码390个氨基酸，分子量为42.7 kDa，等电点为6.55。HBPS2含有1398个碱基，其开放阅读框架编码395个氨基酸，分子量为42.8 kDa，等电点为5.78。CBPS1含有1383个碱基，其开放阅读框架编码389个氨基酸，分子量为42.7 kDa，等电点为7.88。与GenBank中序列同源性比较结果表明：在氨基酸水平上，HBPS1与茶（Camellia sinensis）查尔酮合酶的同源性高达92%，HBPS2与萝卜（Raphanus sativus）查尔酮合酶的同源性为64%，CBPS1与茶（Camellia sinensis）查尔酮合酶的同源性为71%。HBPS1与HBPS2的同源性仅为62%。 将三个新克隆的基因的ORF整合到载体pGEX-G上的谷胱甘肽还原酶S基因下游，构建成转化质粒，并在大肠杆菌中诱导表达。结果表明，这三个基因的ORF片段均能被表达成约68 kDa的产物，这与期望的结果一致。 活性检测结果表明，HBPS1是查尔酮合成酶，其底物为香豆酰辅酶A和丙二酸单酰辅酶A，对这两种底物的亲和性KM分别为：香豆酰辅酶A 2.8μM，丙二酸单酰辅酶A，11.2μM。最适反应条件是350C，pH7.0，DTT浓度10 μM。 HBPS2是二苯甲酮合酶，其底物是苯甲丙氨酰辅酶A，和丙二酸单酰辅酶A，对这两种底物的亲和性KM分别为：苯甲丙氨酰辅酶A 2.4 μM，丙二酸单酰辅酶A 9.6μM。最适反应条件是350C，pH 6.5，DTT浓度50 μM。而CBPS1则没有检测到任何活性。从同一种植物中同时获得了查尔酮合酶和二苯甲酮合酶，对研究这两种十分相近的酶的差异表达，酶促反应机制等问题将非常有利。

Age and growth of the estuarine dolphin (Sotalia guianensis) (Cetacea, Delphinidae) on the Paraná Coast, southern Brazil

Teeth of 71 estuarine dolphins (Sotalia guianensis) incidentally caught on the coast of Paraná State, southern Brazil, were used to estimate age. The oldest male and female dolphins were 29 and 30 years, respectively. The mean distance from the neonatal line to the end of the first growth layer group (GLG) was 622.4 ±19.1 μm (n=48). One or two accessory layers were observed between the neonatal line and the end of the first GLG. One of the accessory layers, which was not always present, was located at a mean of 248.9 ±32.6 μm (n=25) from the neonatal line, and its interpretation remains uncertain.The other layer, located at a mean of 419.6 ±44.6 μm (n=54) from the neonatal line, was always present and was first observed between 6.7 and 10.3 months of age. This accessory layer could be a record of weaning in this dolphin. Although no differences in age estimates were observed between teeth sectioned in the anterior-posterior and buccal-lingual planes, we recommend sectioning the teeth in the buccal-lingual plane in order to obtain on-center sections more easily. We also recommend not using teeth from the most anterior part of the mandibles for age estimation. The number of GLGs counted in those teeth was 50% less than the number of GLGs counted in the teeth from the median part of the mandible of the same animal. Although no significant difference (P>0.05) was found between the total lengths of adult male and female estuarine dolphins, we observed that males exhibited a second growth spurt around five years of age. This growth spurt would require that separate growth curves be calculated for the sexes. The asymptotic length (TL∞), k, and t0 obtained by the von Bertalanffy growth model were 177.3 cm, 0.66, and –1.23, respectively, for females and 159.6 cm, 2.02, and –0.38, respectively, for males up to five years, and 186.4 cm, 0.53 and –1.40, respectively, for males older than five years. The total weight (TW)/total length (TL) equations obtained for male and female estuarine dolphins were TW = 3.156 × 10−6 × TL 3.2836 (r=0.96), and TW = 8.974 × 10−5 × TL 2.6182 (r=0.95), respectively.

水母雪莲类黄酮次生代谢分子调控研究—cDNA 文库构建、关键酶及Myb 转录因子基因的克隆及其功能的初步鉴定

水母雪莲（Saussurea medusa Maxim）为名贵珍稀中药材，其主要药用成分为类黄酮，尤其是3-脱氧类黄酮。目前关于雪莲的研究主要集中在采用细胞培养生产类黄酮等方面，但对于雪莲类黄酮生物合成的分子机制了解甚少，极大限制了这一珍贵资源的利用。本研究采用水母雪莲红色系愈伤组织及悬浮细胞为材料，构建cDNA文库，从中克隆水母雪莲类黄酮次生代谢中的相关基因并对这些基因进行了深入的生物信息学分析、转基因研究初步确定其功能，以期了解雪莲类黄酮次生代谢的分子机制，为提高类黄酮的合成奠定基础。主要结果如下： 1. 成功地构建了水母雪莲红色系愈伤组织与悬浮细胞cDNA文库，原始文库滴度达到4×106pfu/ml，扩增文库滴度接近1011 pfu/ml，重组率达98%。PCR检测插入片段，均在0.5kb到3kb之间，1kb以上占62%。从文库中检测到了chs、dfr及Myb转录因子SmP，文库覆盖度达到要求且为PCR筛选文库提供了可能。 2. 采用部分简并引物，通过RT-PCR克隆了水母雪莲查尔酮异构酶基因Smchi特异探针，并根据这一探针序列设计特异引物，采用TD-PCR法筛选cDNA文库，获得Smchi cDNA序列，全长831bp，编码一个232氨基酸残基的蛋白。根据cDNA序列克隆了Smchi DNA序列，结果表明Smchi基因无内含子。Smchi cDNA序列与翠菊chi基因高度同源，ORF区域同源性高达84%，但推测氨基酸序列则只有79.3%。Smchi mRNA具有复杂的二级结构。SmCHI具有典型的Chalcone结构域，其二级结构与苜蓿CHI蛋白十分相似，7个α-螺旋与8个延伸链由随机结构联系起来。但其活性中心的第三个关键氨基酸残基N115为M115所取代，这一取代可能导致该蛋白无生物活性，也可能使它具有一般CHI不同的功能。构建Smchi正义、反义真核表达载体，通过农杆菌介导导入烟草，获得转正义、反义Smchi基因的烟草。转基因烟草花色未改变，但叶片总黄酮发生了显著的变化，50%转正义基因烟草总黄酮含量显著提高，最高比对照提高6倍，70%转反义基因烟草总黄酮含量显著下降，最多达85.1%，初步证明Smchi具有功能，并能有效调控烟草类黄酮次生代谢。因此，SmCHI可能是不同于已知CHI的一类新的CHI蛋白，它催化的反应可能与花色素合成无关，其反应机制也可能有所不同。 3. 伴随Smchi的克隆获得了一个黄烷酮3-羟化酶类似基因Smf3h的cDNA，全长1334bp，编码一个343aa的蛋白。根据这一cDNA序列克隆了Smf3h DNA序列，全长1630bp，结果表明该基因由4个外显子和3个内含子组成。Smf3h mRNA具有十分复杂的二级结构。 推测蛋白氨基酸同源性分析表明，SmF3H属于2OG-FeII_Oxy家族，与同一家族的的颠茄H6H的同源性为45%，与拟南芥F3H的同源性为40%，但对SmF3H、典型F3H及典型H6H推测蛋白二级结构、活性中心关键氨基酸残基的位置与相对距离、软件进行功能预测分析，发现SmF3H与F3H更相似。构建Smf3h的正义与反义真核表达载体，通过农杆菌介导导入烟草，但只获得一批转正义基因的烟草，反义基因导致烟草不能再生而未获得转反义基因烟草。转基因烟草花色未改变，叶片总黄酮也与对照相似，初步确认Smf3h与烟草类黄酮生物合成无关，而是一个既不属于f3h也不属于h6h的功能未确定的新基因。 4. 采用与克隆Smchi基因相似的方法，从cDNA文库中克隆了SmP基因cDNA，全长969bp，编码一个256 aa的蛋白质。根据cDNA序列克隆了SmP基因的DNA序列，结果表明，SmP基因无内含子。SmP基因cDNA 一级结构及mRNA二级结构预测分析表明，该基因A+T含量很高（63%），所形成二级结构以A-T配对为主，其稳定性可能较差。SmP推测蛋白序列具有R2R3-Myb转录因子的典型特征，在N-端具有两个Myb DNA-binding Domain，其二级结构与鸡Myb转录因子1A5J十分相似，与其他基因如水稻OsMYB、番茄ThMYB的同源区域主要集中在这一结构域，分别为71.3%和70.8%;C-端富含丝氨酸，与烟草NtMYB、葡萄VlMYB等类黄酮调控因子相似，都呈寡聚体分布，并具有相同的保守磷酸化位点S170与S206。构建SmP基因真核表达载体，通过农杆菌介导导入烟草，获得大量转基因烟草。转基因烟草花色未发生改变，但51%的转基因烟草叶片总黄酮含量都显著提高（0.5-6倍），表明SmP具有促进烟草类黄酮生物合成的功能，但所调控的支路与花色素合成无关。初步试验结果表明，转SmP基因烟草对蚜虫具有很高的抗性，可有效地抑制蚜虫在烟草上的生长，抑制率最高可达92%-100%。这一抗性与烟草中类黄酮的积累可能具有直接的联系，但还需要进一步的试验证明。 5. 与美国俄亥俄州立大学Erich Grotewold 博士实验室合作，完成了微型EST库50个克隆的测序并进行了分析，从中获得了水母雪莲花色素合酶基因SmANS及醛脱氢酶基因SmALDH的特异探针。根据SmANS特异探针设计引物，采用PCR从这50个克隆中筛选获得了SmANS的cDNA序列，全长1229bp，编码一个356aa的蛋白质。SmANS在cDNA水平上与同属的翠菊ANS基因高度同源，但同源区域集中在ORF区域，达到80%，mRNA 预测二级结构十分复杂;推测氨基酸序列与翠菊ANS同源性达到82.9%。SmANS属于2OG-FeII_Oxy家族，在2OG-FeII_Oxy结构域高度保守，与翠菊、甜橙ANS保守结构域同源性达到94%。预测蛋白二级结构以α-螺旋-β-折叠为主，由7个主螺旋和11个主β-折叠及随机结构连接而成，并具有2OG-FeII_Oxy家族活性中心的三个保守的组氨酸残基（His84、His235、His291）和一个天冬氨酸残基（Asp237）。 6. 根据微型EST库中获得的SmALDH特异探针设计引物，采用PCR从这50个克隆中筛选获得了SmALDH基因cDNA 序列，全长1664bp，编码一个491aa的蛋白质。SmALDH基因cDNA具有独特的碱基组成，3/-UTR富含A+T，占该区域碱基总量的80%，5/-UTR的A+T和G+C各占50%，比ORF区域（52%）还低，因此其mRNA二级结构中5/-UTR可以单独形成自身二级结构并且十分稳定，这可能影响基因的表达。这一现象在水稻、玉米等植物中也存在。SmALDH在cDNA水平上在ORF区域与拟南芥、藏红花、水稻等具有较高同源性，分别为64.03%、63.89%、63.72%，但在推测蛋白氨基酸序列水平上同源性反而较低，分别为54.9%、54.3%、54.0%。SmALDH缺少线粒体定位信号，为胞质醛脱氢酶，具有一个Aldedh 保守结构域，还具有与1OF7-H相似的以α-螺旋-β-折叠为主的二级结构，由10个主螺旋和15个主β-折叠及随机结构连接而成。由于ALDH在植物细胞乙醇发酵中具有解除醛类物质毒害的功能，因此SmALDH基因的克隆为改造细胞自身以适应发酵培养条件，解决水母雪莲细胞大规模培养中需氧问题提供了可能。

拟南芥有性生殖模式和叶片特性对大气CO2浓度变化的响应

预计到本世纪末，大气CO2浓度将会增加到540～970ppm，大气CO2浓度升高所引起的全球气候变化已经受到广泛的关注。植物生长依赖CO2，并且对大气CO2浓度升高在结构和生理上产生响应。目前已有大量报道，从生态系统、群落、种群、个体、器官、组织、生理以及生化等水平上研究高浓度CO2所对植物产生的影响。但是有关高浓度CO2对植物有性生殖影响的报道却很少，同时多数实验均建立在短期的生殖响应，忽视了植物在长期高CO2浓度下具有的反馈作用和CO2浓度变化对植物的驯化作用。植物有性生殖与其生态适应性和农作物籽粒产量的关系极为密切;同时，植物有性生殖特性的变化，也可作为预测植物对全球气候变化响应的重要指标之一。为此，利用高浓度CO2对植物进行长期选择实验将很有必要。研究结果将为预测未来大气CO2浓度增加的条件下陆地生态系统的演变趋势、全球变化对植物有性生殖响应的方式和机制提供新的思路和有效方法。 　　在本研究中，我们以模式植物拟南芥(Arabidopsis thaliana)作为实验材料，利用370和700ppm CO2对其进行连续8个世代处理，首先研究高浓度CO2对每一个世代的拟南芥有性生殖特性的影响，然后比较各个世代中各种生殖特性指标变化的规律，从细胞、组织和个体尺度上揭示拟南芥有性生殖对全球变化的响应模式。此外，在700ppm CO2处理下，我们对拟南芥叶片生理、生化以及结构的变化进行了相关研究。两部分研究结果及主要结论如下： 　　首先，在每一个世代中，与370ppm CO2相比较，700ppm CO2处理显著促进了拟南芥开花，缩短生长周期，增加花、角果及种子等生殖的产量，降低种子N含量，提高种子C/N比、种子千粒重以及生殖生物量所占总生物量的比例等，而对种子萌发率、角果所含种子数目以及角果长度则无显著影响。但是， 通过对相同CO2浓度处理条件下，不同世代之间的研究结果比较发现，不同世代之间相关的生殖生物学指标并无显著差异。 　　其次，高浓度CO2显著降低叶片气孔密度、气孔指数、气孔导度以及蒸腾速率。在高浓度CO2处理下，叶肉细胞中叶绿体数目、叶绿体宽度和表观面积、淀粉粒大小和数量、叶片和细胞壁厚度等都显著增加，但是基粒内囊体膜的数量却显著下降。叶片中碳水化合物如可溶性总糖、淀粉以及纤维素含量在高浓度CO2下分别显著增加71.9%、78.7% 和 22.3%。此外，在高浓度CO2处理下，叶片中多数激素如如吲哚乙酸(indole-3-acetic acid, IAA)、赤霉素(gibberellin, GA)、玉米素核苷(zeatin riboside, ZR)、二氢玉米素核苷(dihydrozeatin riboside, DHZR)和异戊烯基腺苷(isopentenyl adenosine, iPA)均都显著地增加，而脱落酸(abscisic acid, ABA)含量却有所下降。最后，叶片中各种矿物质元素含量如N、P、K、Ca和Mg等含量在高浓度CO2处理下也都显著下降，而C/N比增加24.8％。 　　以上结果表明： 　　(1) 在每一个世代中，700ppm CO2处理对拟南芥各种有性生殖特性具有显著的影响，但是高浓度CO2处理对植物所引起的效应在多个世代以内并不能够传递给后代，所以在多个有性生殖世代内，高浓度CO2处理对植物生长、生殖没有驯化作用。 　　(2) 在高浓度CO2处理下，拟南芥叶片中叶绿体超微结构的变化，可能主要是由于叶绿体中淀粉粒数量和体积大小显著增加而引起。 　　(3) 在高浓度CO2处理下，由于拟南芥叶片内与促进细胞分裂与伸长的激素含量显著增加，从而对拟南芥植株生长发育速率的提高起了重要的作用。 　　(4) 拟南芥生长在高浓度CO2条件下，其叶片中各种矿质元素含量（如N、P、K、Ca和Mg）均显著降低，究其原因可能是，第一由于叶片中碳水化合物含量的显著增加而对矿物质元素具有稀释作用;第二由于蒸腾速率下降，引起矿质元素从根部随着蒸腾流运输到地上部分的含量相应减少。