长喙田菁-Azorhizobium caulinodans共生固氮体系在华南地区的生长、结瘤、固氮和种子生产

研究了长喙田菁－Ａｚｏｒｈｉｚｏｂｉｕｍｃａｕｌｉｎｏｄａｎｓ共生固氮体系在华南地区的生长、结瘤、固氮和种子生产．结果表明,长喙田菁－Ａ．ｃａｕｌｉｎｏｄａｎｓ共生固氮体系在华南地区生长正常,并具旺盛的茎根瘤结瘤作用．经６５天的生长,其在湛江地区的单位面积生物量（干物质）和单位面积Ｎ产量分别为２８７５２和６８１ｋｇ·ｈｍ－２,远优于普通田菁的１６５２０和３５２ｋｇ·ｈｍ－２;茎瘤菌Ａ．ｃａｕｌｉｎｏｄａｎｓ品系ＡＲ１１１和ＡＲ５６在华南地区混合接种效果良好,植株茎瘤结瘤率达到１００％,平均单株茎瘤个数为１８２个,单株茎瘤鲜重约为１．２ｇ,茎瘤生物量在茎根瘤总生物量中所占比重为７０％,而其根瘤生物量略高于普通田菁;长喙田菁在华南地区能够正常开花结实,在栽植密度为４×１０４株·ｈｍ－２的条件下,其种子产量达３２００ｋｇ·ｈｍ－２．     

从田菁胶工业下脚料生产田菁蛋白胨的研究——[Ⅰ]田菁蛋白胨化学成份的研究

本文首次研究了田菁蛋白胨一般化学成份、氨基酸组份、肽链平均长度、微量元素、维生素以及红外、紫外光谱等。本文还将田菁蛋白胨氨基酸、红外光谱等和英国大豆蛋白胨作了比较。研究结果附图表于后。     

Stem Nodulation in Legumes: Diversity,Mechanisms, and Unusual Characteristics

Rhizobia can establish a nitrogen-fixing symbiosis with plants of the Leguminosae family. They elicit on their host plant the formation of new organs, called nodules, which develop on the roots. A few aquatic legumes, however, can form nodules on their stem at dormant root primordia. The stem-nodulating legumes described so far are all members of the genera Aeschynomene, Sesbania, Neptunia, and Discolobium. Their rhizobial symbionts belong to four genera already described: Rhizobium, Bradyrhizobium, Sinorhizobium, and Azorhizobium. This review summarizes our current knowledge on most aspects of stem nodulation in legumes, the infection process and nodule development, the characterization and unusual features of the associated bacteria, and the molecular genetics of nodulation. Potential use as green manure in lowland rice of these stem-nodulating legumes, giving them agronomical importance, is also discussed.     

田菁根际促生菌的筛选及其促生耐盐效果

【目的】为探究盐生植物田菁及其根际功能微生物改良盐碱地的效果,本研究从黄河三角洲盐碱区田菁根际土壤中分离促生菌,并明确其耐盐促生效果。【方法】采用选择培养方法从田菁根际土壤中分离固氮菌、解磷菌以及解钾菌,并进行16S rRNA分子生物学鉴定。之后对菌株的耐盐及促生特性进行测定,筛选性状优良菌株进行玉米促生作用研究。【结果】共分离得到105株根际促生菌,其中N102兼具多种促生特性且耐盐性达15%。田菁种子发芽试验表明,N102可显著提高田菁发芽率(47%,P<0.05)、芽长(48.5%,P<0.05)和根长(60%,P<0.05);玉米盆栽试验结果表明,N102对盐胁迫下玉米的株高、根长、叶绿素含量、地上部干重以及根干重具有显著的促进作用。经系统发育分析,N102与Enterobacter soli ATCC BAA-2102 (NR117547)序列相似度为99.30%,鉴定属于Enterobacter属。【结论】菌株N102具有多种植物促生耐盐特性,具有开发成有效促进盐碱地作物生长的微生物肥的良好前景。     

American eels produce and release bile acid profiles that vary across life stage

The American eel (Anguilla rostrata) is an imperilled fish hypothesized to use conspecific cues, in part, to coordinate long-distance migration during their multistage life history. Here, holding water and tissue from multiple American eel life stages was collected and analysed for the presence, profile and concentration of bile acids. Distinct bile acid profiles were identified in glass, elver, yellow eel and silver eel holding waters using ultraperformance liquid chromatography high-resolution mass spectrometry and principal component analysis. Taurochenodeoxycholic acid, taurodeoxycholic acid, cholic acid, deoxycholic acid, taurolithocholic acid and taurocholic acid were detected in whole tissue of American glass eels and elvers, and in liver, intestine and gallbladder samples of late-stage yellow eels. Bile acids were not a major component of silver eel washings or tissue. This study is novel because little was previously known about bile acids produced and emitted into the environment by American eels. Future behavioural studies could evaluate whether any bile acids produced by American eels influence conspecific migratory behaviour.     

Rhizome phyllosphere oxygenation in Phragmites and other species in relation to redox potential, convective gas flow, submergence and aeration pathways

Underground rhizomes of emergent aquatic macrophytes are important for perennation, vegetative spread, competition and anchorage. In four species we examined the potential for the development of oxidized phyllospheres around rhizome apical buds, similar to the protective oxygenated rhizospheres around roots. Redox potentials and polarographic measurements of radial oxygen loss were recorded using platinum cathodes around the apical buds. The aeration pathway from atmosphere to phyllosphere was investigated anatomically and by applied pressurized gas flow. Redox potentials increased by +400, +45, +200 and +340 mV around rhizome apices of Phragmites australis, Oryza rhizomatis, Carex rostrata and Glyceria maxima, respectively. Radial oxygen loss from rhizome apices of Phragmites was increased by convective gas flow through the rhizome and by shoot de-submergence, and decreased by resistances applied within the aeration pathway and by shoot submergence. We conclude that oxygen passes via internal gas-space connections between aerial shoot, rhizome and underground buds and into the phyllosphere regions via scale-leaf stomata and surfaces on the buds. We suggest that oxidized phyllospheres may protect rhizome apices against phytotoxins in waterlogged soils, just as oxidized rhizospheres protect roots.     

Survival for specific life intervals of smallmouth bass, Micropterus dolomieu, during parental care

We tested whether daily mortality rates (DMR) of smallmouth bass offspring were influenced by life interval, offspring density and growth, parental male attributes, and selected mortality factors during parental care in a regulated Virginia stream. Mortality averaged 9.5% per day (range 5.2–13.9%) and 94.1% total (range 80.9–99.5%) from egg deposition to the juvenile period (29–36 d) for individual broods. Offspring losses were primarily attributed to fungus (Saprolegnia parasitica) infection of eggs and to American eel, Anguilla rostrata, predation. DMR were significantly higher for the interval from swim-up of larvae to metamorphosis relative to earlier and later intervals. There was no significant autocorrelation of DMR among life intervals for individual broods, indicating that relative mortality rates were inconsistent among broods through time. DMR were also uncorrelated with the number of offspring per brood, offspring growth rates, and parental male attributes, except during egg and embryo intervals. Daily egg mortality was negatively related to male size and positively related to the number of eggs per nest, suggesting that density-dependent egg mortality may have been partially offset in nests of larger males. Larger males received more eggs, tended to maintain larger broods throughout parental care, and contributed a high proportion of the total number of juveniles reared. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of abscisic acid on galactomannan degradation and endo-β-mannanase activity in seeds of Sesbania virgata (Cav.) Pers. (Leguminosae)

Seeds of Sesbania virgata (Cav.) Pers. (Leguminosae) have an endosperm which accumulates galactomannan as a storage polysaccharide in the cell walls. After germination, it is hydrolysed by three enzymes: α-galactosidase (EC 3.2.1.22), endo-β-mannanase (EC 3.2.1.78) and β-mannosidase (EC 3.2.1.25). This work aimed at studying the effect of abscisic acid (ABA) on galactomannan degradation during and after germination. Seeds were imbibed in water or in 10⁻⁴ M ABA, and used to evaluate the effect of exogenous and endogenous ABA. Tissue printing was used to follow biochemical events by detecting and localising endo-β-mannanase in different tissues of the seed. The presence of exogenous ABA provoked a delay in the cellular disassembly of the endosperm and disappearance of endo-β-mannanase in the tissue. This led to a delay in galactomannan degradation. The testa (seed coat) of S. virgata contains endogenous ABA, which decreases ca. fourfold during storage mobilisation after germination, permitting the galactomannan degradation in the endosperm. Furthermore, endo-β-mannanase was immunolocalised in the testa, which has a living cell layer. The ABA appears to modulate storage mobilisation in the legume seed of S. virgata, and a cause–effect relationship between ABA (probably through testa) and activities of hydrolases is proposed.     

Predators of Mesoplatys ochroptera in sesbania planted-fallows in eastern Zambia

Mesoplatys ochroptera Stål (Coleoptera: Chrysomelidae) is a serious pest of the tropical legume sesbania (Sesbania sesban (L.) Merrill) widely used for soil fertility improvement in southern Africa. Surveys were conducted between October 1997 and June 1999 in order to identify the predators of M. ochroptera in sesbania fallows in eastern Zambia. The Heteroptera Afrius yolofa (Guérin-Méneville), Glypsus conspicuus (Westwood), Macrorhaphis acuta Dallas, Mecosoma mensor (Germar), Rhinocoris segmentarius (Germar), and Deraeocoris ostentans (Stål), the carabid beetle Cyaneodinodes fasciger (Chaudoir), the ants Tetramorium sericeiventre Emery and Pheidole sp., and the lacewing Mallada sp. were recorded as predators of M. ochroptera for the first time. The pentatomid bugs G. conspicuus, M. acuta and M. mensor were the most common predators in sesbania fallows. Adults and the different nymphal stages of the three species preyed on larvae, adults and occasionally on eggs of the beetle. In the insectary, the adults of G. conspicuus, M. acuta and M. mensor consumed a significantly higher number of larvae (p < 0.001) compared to adults of M. ochroptera under both free-choice and no-choice conditions. The voracity of the three species showed a positive response to prey density. The fifth instar nymphs showed variation in daily consumption of larvae, the highest number of prey being consumed two to three days after the fourth molt. These predators also attacked other pests associated with sesbania and crop plants. The potential role of the predators in the natural control of pests in agroforestry systems is discussed, with a review of their prey species.