上海市园林绿地共生固氮植物资源调查

对上海市固氮植物的结瘤状况和固氮效果进行调查分析,采集根瘤寄主分属5科37属,共83种,其中非豆科植物有4科4属12种,豆科植物33属71种。结果表明,有93%的根瘤着生于寄主侧根,大小一般在1～10mm。形状以球形、近球形、柱形为主,颜色多为白色、黄褐色。固氮酶活性为0～10μmol/(g.h)。     

不同环境条件下联合共生固氮菌对小麦种子生长的影响

从13株小麦根际筛选得到3种联合共生固氮菌,通过单因素批次试验确定了不同菌种的培养时间、温度、pH、葡萄糖浓度及氮素浓度的适宜范围,得出单个菌株和组合菌组生长效果最佳的实验条件,并进一步测定单个菌株和组合菌组对小麦种子生长状况的影响。研究显示,在pH 7,温度35 ℃,NaCl浓度5%,葡萄糖浓度10%,氮素浓度3 g·L^-1的条件下培养36 h时,组合菌组作用于小麦种子的效果优于单个菌株的作用效果,相较于空白组,发芽率平均提高了4%,发芽势、发芽指数也均有所提高。组合菌组能更好地适应多变的环境,稳定发挥作用,有利于获得高产。     

Glycerol excretion by symbiotic algae from corals and tridacna and its control by the host

Zooxanthellae isolated from reef corals and Tridacna crocea incorporate labeled carbon dioxide photosynthetically. In the presence of some component of the host tissue, up to 40 percent of the labeled algal photosynthate is liberated primarily as glycerol. Excretion of glycerol by the algae in situ and its control and utilization by the host may represent a mechanism by which zooxanthellae contribute to produtctivity of coral reefs.     

贵州固氮蓝藻室内培养及固氮力研究

为初步筛选出适合贵州气候特点的具有较高生物量和固氮力的蓝藻品系,以中国淡水藻种库(OCCFA)引进的鱼腥藻112、118、1017、1105、1042、HBl3和中华植生藻800,采用室内继代培养后制成的混合藻种A、B,经改进后的水生111无氮培养基,通过室内开放式通气培养和静置培养,测定不同水深条件下的生长率、固氮力。结果表明,固氮蓝藻的生长能改变环境pH值,使之适应藻种的生长;水深条件>10cm 有利于提高鲜藻产量;固氮蓝藻A组固氮力为7215kg·hm     

秸秆还田条件下固氮蓝藻复合菌剂与促生细菌SM13对水稻产量及稻米品质的影响

【目的】研究秸秆还田条件下施用固氮蓝藻复合菌剂和促生细菌SM13对水稻产量及品质的影响,为2种微生物肥料在秸秆还田中的应用提供实践经验和理论依据。【方法】以水稻品种龙粳31为试验材料,设常规施肥（CK）、施用固氮蓝藻复合菌剂（LZ）、施用促生细菌SM13（SM）及混施固氮蓝藻复合菌剂和促生细菌SM13（SL）共4个处理。测定水稻主要生育期的叶面积及干物质质量,在水稻成熟后考察水稻穗部性状和产量,在稻米理化性质稳定后测定稻米加工、外观、营养和食味品质,对比分析不同处理对水稻产量及稻米品质的影响。【结果】与CK相比,LZ处理的水稻灌浆期干物质质量显著增加26.40%（P<0.05,下同）;SL处理显著降低了一次枝梗结实率,LZ处理显著降低了二次枝梗的千粒重;SM、SL和LZ处理的产量分别增加10.00%、9.80%和8.78%。单施固氮蓝藻复合菌剂或促生细菌SM13及二者混施对稻米加工、外观和营养品质无显著影响（P>0.05）,但SM和SL处理显著改善了稻米食味品质,其口感值和食味值较CK分别提高7.23%、4.87%和7.22%、5.74%。相关分析结果表明,产量及其构成与水稻穗部性状存在不同程度的相关性,其中产量与穗质量呈极显著正相关（P<0.01）,与二次枝梗枝梗数呈显著正相关。【结论】在秸秆还田条件下固氮蓝藻复合菌剂和促生细菌SM13具备提高水稻产量的潜力,且促生细菌SM13能在一定程度上改善稻米食味品质。     

Herbivory in asymbiotic soft corals

A zooxanthellae-free soft coral from the Red Sea feeds almost exclusively on phytoplankton, a mode of nutrition so far unknown for corals. Herbivory was also found in three other azooxanthellate soft corals. In tropical oligotrophic waters, phytoplankton biomass density may be an order of magnitude higher than that of zooplankton. Use of this resource allows these azooxanthellate cnidarians to be highly productive in flow-exposed oligotrophic reef waters.     

Long-term region-wide declines in Caribbean corals

We report a massive region-wide decline of corals across the entire Caribbean basin, with the average hard coral cover on reefs being reduced by 80%, from about 50% to 10% cover, in three decades. Our meta-analysis shows that patterns of change in coral cover are variable across time periods but largely consistent across subregions, suggesting that local causes have operated with some degree of synchrony on a region-wide scale. Although the rate of coral loss has slowed in the past decade compared to the 1980s, significant declines are persisting. The ability of Caribbean coral reefs to cope with future local and global environmental change may be irretrievably compromised.     

Mass spawning in tropical reef corals

Synchronous multispecific spawning by a total of 32 coral species occurred a few nights after late spring full moons in 1981 and 1982 at three locations on the Great Barrier Reef, Australia. The data invalidate the generalization that most corals have internally fertilized, brooded planula larvae. In every species observed, gametes were released; external fertilization and development then followed. The developmental rates of externally fertilized eggs and longevities of planulae indicate that planulae may be dispersed between reefs.     

Growth of Western Australian corals in the anthropocene

Anthropogenic increases of atmospheric carbon dioxide lead to warmer sea surface temperatures and altered ocean chemistry. Experimental evidence suggests that coral calcification decreases as aragonite saturation drops but increases as temperatures rise toward thresholds optimal for coral growth. In situ studies have documented alarming recent declines in calcification rates on several tropical coral reef ecosystems. We show there is no widespread pattern of consistent decline in calcification rates of massive Porites during the 20th century on reefs spanning an 11° latitudinal range in the southeast Indian Ocean off Western Australia. Increasing calcification rates on the high-latitude reefs contrast with the downward trajectory reported for corals on Australia's Great Barrier Reef and provide additional evidence that recent changes in coral calcification are responses to temperature rather than ocean acidification.     

Skeletal low-magnesium calcite in living scleractinian corals

The skeletons of living specimens of the scleractinian coral Porites lobata have been found to contain up to 46 +/- 5 percent low-magnesium calcite even though free of gross detrital inclusions and boring or encrusting organisms. The calcite crystals occur in the interior of skeletal structures, have dimensions of 20 micrometers or less, and are surrounded by typical aragonite needles. Biogenic deposition seems to be the most likely source of the calcite, although the evidence does not rule out diagenesis of metastable.     

The tricarboxylic acid cycle in cyanobacteria

It is generally accepted that cyanobacteria have an incomplete tricarboxylic acid (TCA) cycle because they lack 2-oxoglutarate dehydrogenase and thus cannot convert 2-oxoglutarate to succinyl-coenzyme A (CoA). Genes encoding a novel 2-oxoglutarate decarboxylase and succinic semialdehyde dehydrogenase were identified in the cyanobacterium Synechococcus sp. PCC 7002. Together, these two enzymes convert 2-oxoglutarate to succinate and thus functionally replace 2-oxoglutarate dehydrogenase and succinyl-CoA synthetase. These genes are present in all cyanobacterial genomes except those of Prochlorococcus and marine Synechococcus species. Closely related genes occur in the genomes of some methanogens and other anaerobic bacteria, which are also thought to have incomplete TCA cycles.     

固氮菌的筛选及其对菜场垃圾堆肥化的影响

分别以可溶性淀粉、鼠李糖、蔗糖为唯一碳源的无氮培养基,从校园土壤中分离到褐球固氮菌(Azotobacter chroococcum)、维涅兰得固氮菌(A.vinelandii)和拜氏固氮菌(A.beijerinckii)三种菌种各2株菌株。将3种菌种单独及混合分别投加到菜场垃圾堆肥装置中。结果表明,接种混合固氮菌的菜场垃圾废物堆肥的全氮、铵态氮、硝态氮的含量最高,堆肥化所用的时间最短。接种一种固氮菌(褐球固氮菌、拜氏固氮菌或维涅兰得固氮菌)的也有所提高。     

Role of chemotaxis in establishing a specific nitrogen-fixing cyanobacterial-bacterial association

A specific association with the cyanobacterium Anabaena oscillarioides was established by positive bacterial (pseudomonad) chemotaxis to Anabaena oscillarioides heterocysts. This association enhanced nitrogen fixation in A. oscillarioides, and positive chemotaxis was particularly strong during periods of active nitrogen fixation. Addition of compounds known to elicit positive chemotaxis in pseudomonads interfered with the establishment of the association, while removal of these compounds led to reestablishment of the association. Anabaena oscillarioides excretion products, some of which are exuded from heterocyst-vegetative cell junctions, are likely to be responsible for positive chemotactic responses. Chemotaxis-controlled associations such as this one explain in part why aquatic bacterial-algal and bacterial-particle associations occur sporadically and are heterogeneously distributed in time and space.     

玉米内生联合固氮菌的分离与鉴定

试验对玉米内生固氮菌进行分离、鉴定,并研究内生细菌与玉米的联合固氮活性。结果表明,从玉米中分离出5株具有联合固氮活性的菌株,分别为1株弯曲假单胞菌NFR19(Pseudomonas geniculata),2株产酸克雷伯氏菌NFL28与NFSt18(Klebsiella oxytoca),1株节杆菌NFR7(Arthrobacter sp.),1株纤维化纤维菌NFR10(Cellulosimicrobium cellulans)。研究首次分离出具有固氮活性的纤维化纤维菌,并证实节杆菌具有固氮活性。从环境中筛选新的玉米内生固氮菌资源,促进玉米生长,为玉米内生联合固氮细菌的应用奠定基础。     

Flexibility in algal endosymbioses shapes growth in reef corals

The relation between corals and their algal endosymbionts has been a key to the success of scleractinian (stony) corals as modern reef-builders, but little is known about early stages in the establishment of the symbiosis. Here, we show that initial uptake of zooxanthellae by juvenile corals during natural infection is nonspecific (a potentially adaptive trait); the association is flexible and characterized by a change in (dominant) zooxanthella strains over time; and growth rates of experimentally infected coral holobionts are partly contingent on the zooxanthella strain harbored, with clade C-infected juveniles growing two to three times as fast as those infected with clade D.     

豆科植物固氮根瘤衰老过程中的代谢调控研究进展

衰老是影响豆科植物根瘤固氮效率的主要因素之一,深入探究根瘤的衰老调控机制具有重要意义。本文从衰老根瘤的形态特征和生理生化变化、衰老的途径以及物质代谢调控等方面综述根瘤衰老的研究进展,总结了豆科植物和根瘤菌中与衰老相关基因在共生固氮过程中的功能。开发新的研究方法和技术能够更全面地揭示衰老根瘤中关键物质代谢的分子机制。深入了解根瘤衰老的分子机制有助于通过遗传改造延缓根瘤衰老,提高豆科植物的固氮效率,促进农业生产的可持续发展。