Symbiotic Characteristics and Rhizobium Requirements of a Leucaena leucocephala x Leucaena diversifolia Hybrid and Its Parental Genotypes

In 56-day-old plants, Leucaena leucocephala and its hybrid with L. diversifolia showed 100% more total N than did L. diversifolia. Significant (P < 0.01) host-inoculation interaction in total N was 14.4% of the total phenotypic variation. The most effective and competitive Rhizobium sp. for the leucaenas was TAL 1145. Three-strain mixed inoculation was inferior to TAL 1145 alone.     

Segmental allopolyploidy and paleopolyploidy in species of Leucaena benth: evidence from meiotic behaviour analysis

In this paper we report meiotic behaviour in 28 accessions of the tetraploid (2n = 4x = 104 or 112) Leucaena confertiflora, L. diversifolia, L. involucrata, L. leucocephala, L. x spontanea and the diploid (2n = 2x = 52 or 56) L. shannonii and L. macrophylla. We compare and discuss our data with that on literature about polyploidy in the genus. Despite the general predominance of bivalent formation, quadrivalents and other associations were found in all the taxa analysed. In the diploid species. multiple associations were found in up to 62% of the cells in L. shannonii and 97.6% in L. macrophylla. In the tetraploid taxa irregularities such as univalents, trivalents and other multivalents were observed in varying proportions, up to 55% in L. involucrata. Mean meiotic indexes per accession in the diploids and tetraploids were over or near 90%, but pollen fertility varied from 54.2% to 87.3%. The rather frequent presence of quadrivalents in the diploid species supports a paleopolyploid origin. For the tetraploid taxa, the presence of quadrivalents reflect chromosomal homology due to polyploid origin. Even if an autotetraploid origin cannot be ruled out by cytological data alone, considering other existing evidence, it is probable that L. confertiflora, L. pallida, L. leucocephala and L. involucrata are segmental allopolyploids. However, an autopolyploid origin for L. diversifolia cannot be ruled out nor cytologically nor by other existing data.     

The use of Tagasaste (Chamaecytisus proliferus) from different origins for biomass and paper production

In order to identify faster-growing non-woody species usable for biomass and paper production, four Tagasastes (Chamaecytisus proliferus) from different origins are tested. All the Tagasaste species (T. Huelva, T. Australia, T. New Zealand and T. La Palma island) show a good soil and climatic adaptation to Southwest Spain. The studied Tagasaste provenances shows biomass productivity ranges from 1.0 t ha(-1)yr(-1) to 3.4 th a(-1)yr(-1) (o.d.b.) and 25.3 t ha(-1)yr(-1) to 49.4 t ha(-1)yr(-1) under Mediterranean conditions for first and second year sprouts, respectively. The quantity of solubles and extractives shows similar values when compared with wood materials. A relatively lower lignin content in Tagasaste (from 13.7% to 17.1%) species has been found with respect to other vegetal species. The alpha-celullose contents (43.6-45.3%) were in the range of the normal values expected for the other non-wood raw materials. The study confirms the feasibility of the organocell yield pulping process to Tagasaste provenances. Organocell processes provide an efficient delignification (kappa index from 7.2 to 10.9 and pulp yield from 43.6% to 54.1%). The best results are obtained for the physical properties of paper sheets for Tagasaste from Australia in the second year, with values of tensile index of 16.0 kNm/kg, burst index of 1.12 MPa m2/kg and tear index of 0.55 Nm2/kg.     

银合欢叶作氮源栽培食用菌研究

以银合欢叶作氮源全部或部分取代基质中米糠或麸皮,栽培毛木耳、凤尾菇、金针菇、黑木耳、香菇和佛罗里达侧耳6种食用菌。结果表明,银合欢叶能促进菌丝生长。栽培中发现,含10%银合欢叶和17%麸皮的基质能使金针菇获得增产,而含10%或20%银合欢叶的基质可使其它5种食用菌产量提高11.4%~39.1%。     

Integral valorization of two legumes by autohydrolysis and organosolv delignification

Two woody legumes species (Chamaecytisus proliferus L.F. ssp. palmensis and Leucaena diversifolia) were evaluated for integrally exploitation. The raw material was subjected to autohydrolysis under variable operating conditions which provided a liquid phase rich in hemicellulose oligomers and a solid phase that was used to obtain cellulose pulp and paper sheets by using organosolv procedures. The chemical properties of both C. proliferus and L. diversifolia allow their integral exploitation by using a hydrothermal treatment prior to their organosolv pulping with ethanol. The pulp yields obtained are quite high (40.3% for L. diversifolia and 58.2% for C. proliferus), and so are the sugar concentrations in the liquors from the thermal pretreatment (viz. 16.1 and 20.0 g oligomers/l in C. proliferus and L. diversifolia, respectively, and 1.5 and 1.1g xylose/l, respectively, in the two raw materials). The strength-related properties of the paper sheets obtained are acceptable (tensile index 7.76 and 10.77 kN m/kg for C. proliferus and L. diversifolia, respectively and kappa index 31 and 12.5 for C. proliferus and L. diversifolia, respectively), but somewhat worse than those provided by other raw materials such as eucalyptus; however, they can be improved by mechanical refining of the pulp.     

干旱胁迫下坡柳等幼苗质膜相对透性和脯氨酸含量的变化

以金沙江干热河谷主要树种坡柳、银合欢和山毛豆幼苗为材料,通过盆栽苗自然干旱胁迫,同时以浇水处理为对照,探讨了干旱胁迫下三树种幼苗叶片的相对含水量、质膜透性以及脯氨酸含量的变化情况。结果表明,干旱胁迫后三树种叶片的相对含水量、质膜相对透性以及脯氨酸含量都发生了变化,只是变化的幅度和进程不同。三项生理指标的综合分析及结合其自然表现,坡柳具有较强的抗旱能力,其次为银合欢,最后是山毛豆。     

Nutritive value and qualitative assessment of secondary compounds in seeds of eight tropical browse, shrub and pulse legumes

Seeds of four tropical multipurpose trees (Albizia saman, Albizia lebbeck, Albizia rhizonse, Leucaena leucocephala), two shrubs (Tephrosia candida, Tephrosia bracteolata) and two pulse legume (Lablab purpureus, Canavalia ensiformis) were chemically analysed for dry matter (DM), ash, crude protein (CP), neutral detergent fibre (NDF) and ether extract (EE). Qualitative evaluation of secondary metabolites (saponins, phenols, steroids, and alkaloids) was elucidated. The DM, ash, CP, NDF and EE ranged between 88.9-93.6 %, 3.0-5.4 %, 24.8-38.2 %, 22.1-46.9 % and 2.0-17.0 % respectively. All seed species contained at least one group of secondary plant metabolites and steroids were common to all except C. ensiformis that was not implicated for any. A. lebbeck and A. rhizonse showed low saponin content. Indications for water soluble tannins were reported for L. leucocephala while the two species of Tephrosia contained flavonoids or condensed tannins. The study suggested the potentials of the legumes seed species as a feed source for ruminants.     

元谋干热河谷不同人工林中鞘翅目甲虫多样性比较

在元谋干热河谷采用网扫法调查了云南松林、桉树林、新银合欢林、桉树＋新银合欢林、印楝林及多树种混交的人工林鞘翅目昆虫多样性。结果表明,鞘翅目甲虫标本925号,计71种,分属18个科,其中叶甲科种类最丰富,象甲科数量最丰富。人工林鞘翅目昆虫群落物种丰富度在7～23,Shannon—Wiener多样性指数在1．249～2．562,昆虫多样性总体较低。各样地鞘翅目群落之间为不相似水平。云南松林鞘翅目昆虫群落物种丰富度、Shannon—Wiener指数、Simpson指数及Pielou指数分别为20、2．562、0．104和0．855,其多样性最高,多树种混交林较高,印楝林较低,而桉树林、新银合欢林、桉树＋新银合欢林多样性极低。多树种混交的恢复对昆虫多样性提高有显著促进作用。     

A novel host shift and invaded range of a seed predator, Acanthoscelides macrophthalmus (Coleoptera: Chrysomelidae: Bruchinae), of an invasive weed, Leucaena leucocephala

An endophagous seed predator, Acanthoscelides macrophthalmus (Coleoptera: Chrysomelidae: Bruchinae), utilizes Neotropical Leucaena (Fabaceae: Mimosoideae). One of its hosts, Leucaena leucocephala , is a fast-growing nitrogen-fixing tree that serves as a multipurpose beneficial plant but eventually becomes an aggressive invader where it was introduced. Herein, we report A. macrophthalmus invasion of the Far East, South Asian tropics and subtropics (Japanese Pacific Islands, Taiwan, Southern China, Northern Thailand and Southern India). Of other field-collected mimosoid legumes, an introduced tree, Falcataria moluccana , in Taiwan was found to be used by the seed predator. Conversely, our published work review revealed that the seed predator had retained high host specificity to Leucaena species in its native and introduced regions. Acanthoscelides macrophthalmus was able to utilize aphagously postharvest mature seeds for oviposition and larval development, which is a trait of post-dispersal seed predators. We confirmed that A. macrophthalmus that was reared on L. leucocephala was able to utilize F. moluccana as well. Although the relatively high host specificity of the oligophagous beetle is suitable for controlling the weedy L. leucocephala , the potential host range expansion confirmed by this study must be cautioned.     

The archaeological remains of leucaena (Fabaceae) revised

Archaeological specimens of Leucaena (Fabaceae; Mimosoideae) previously published (Tamaulipas, Tehuacan Valley, and Oaxaca Valley) which are housed at the Departmento de Prehistoria, Instituto Nacional de Antropología e Historia, Mexico City, were reexamined. Selected remains from Tehuacan were observed with scanning electron microscopy and ultrastructural features were compared to material from herbarium specimens. External epidermis near margins of legume valves provided identification characteristics (stomata abundance and morphology, texture, pubescence). In Tehuacan, L. leucocephala subsp. glabrata was found in addition to two previously reported taxa—L. esculenta and L. diversifolia subsp. stenocarpa (L. pueblana). Acacia sericea, a wild tree with edible legumes, was frequently misidentified as Leucaena. In Guilá Naquitz, Oaxaca, all samples reported as L. esculenta were identified as another edible, wild legume tree, Conzatia multiflora. Chronology was assigned following published reports and, also for Tehuacan, the field catalogue. Possible use was assigned based upon evidence of chewing and insect damage, indicating ripeness of legumes. No direct evidence of cultivation was found. However, the presence of L. esculenta in Tehuacan (since ca. 4000-1000 B.C.) and of L. I. glabrata (since ca. 300 B.C.-A.D. 780) suggests their introduction there as a cultivated plant.     

干旱胁迫对坡柳等抗旱树种幼苗膜脂过氧化及保护酶活性的影响

以金沙江干热河谷主要树种坡柳、银合欢、山毛豆实生幼苗为材料,通过盆栽苗自然干旱胁迫,同时以浇水处理为对照,研究了干旱胁迫对坡柳、银合欢、山毛豆3个树种丙二醛含量、膜相对透性及保护酶活性的影响。结果表明,干旱胁迫下3个树种幼苗的细胞膜透性、MDA及SOD, POD酶活性都发生了变化,只是变化的幅度和进程不同。干旱胁迫对银合欢膜系统损伤生成的主要降解产物不是MDA;山毛豆清除活性氧毒害作用主要不是通过SOD和POD的作用;通过叶片相对保水力测定及膜透性、MDA相对含量、酶活性变化情况的分析,3个树种中坡柳耐旱性最强,其次为银合欢,山毛豆居后。     

Construction of Genomic Library for Leucaena Leacocephala and Isolation of a Gene Enco ding Seed Storage Protein

Leucaena leucocephala (Mimosaceae), a tropical plant, has been a very important forage for livestock in tropical area. The leaves and seeds contain proteins up to 30% and 33% of the dry weight respectively. We have been interested in studying these proteins and expression of genes encoding these proteins and constructed the genomic library. Total DNA from leaves of L. leucocephala was isolated and digested partially with Sau3A. Bacterophage lambda EMBL3 was used as a cloning vector. Recombinant molecules were packaged into viable phage particles in vitro and the yield of recombinant phages was 3.5×106 pfu. In order to understand the homology between genes encoding seed storage protein from L. leucocephala and soybean, the library was amplified and screened with a gene encoding the α'-subunit of the soybean 7S storage protein. Four positive clones were obtained and three of them were chosen for further analysis. Physical mapping and partial DNA sequence have revealed the homology between genes encoding storage proteins of L. leucocephala and soybean.     

Leaf-closing substance in Leucaena leucocephala

Potassium (2R,3R)-2,3,4-trihydroxy-2-methylbutanoate (1) was identified as a leaf-closing substance in the nyctinastic plant, Leucaena leucocephala. Compound 1 showed strong leaf-closing activity toward L. leucocephala and was not effective against other nyctinastic plants. The potassium ion was indispensable for the bioactivity of 1. Compound 1 gradually lost its bioactivity because of the exchange of the counter cation during isolation. A leaf-opening substance was also observed in the same plant.     

Phytostabilization of a Pb-contaminated mine tailing by various tree species in pot and field trial experiments

The potential of 6 tree species (Leucaena leucocephala, Acacia mangium, Peltophorum pterocarpum, Pterocarpus macrocarpus, Lagerstroemia floribunda, Eucalyptus camaldulensis) for phytoremediation of Pb in sand tailings (total Pb >9850 mg kg(-1)) from KEMCO Pb mine in Kanchanaburi province, Thailand, were investigated employing a pot experiment (3 months) and field trial experiment (12 months). In pot study E. camaldulensis treated with Osmocote fertilizer attained the highest total biomass (15.3 g plant(-1)) followed by P. pterocarpum (12.6 g plant(-1)) and A. mangium (10.8 g plant(-1)) both treated with cow manure. Cow manure application resulted in the highest root Pb accumulation (>10000 mg kg(-1)) in L. floribunda and P. macrocarpus. These two species also exhibited the highest Pb uptake (85-88 mg plant(-1)). Results from field trial also showed that Osmocote promoted the best growth performance in E. camaldulensis (biomass 385.7 g plant(-1), height 141.7 cm) followed by A. mangium (biomass 215.9 g plant(-1), height 102.7 cm), and they also exhibited the highest Pb uptake (600-800 microg plant(-1)). A. mangium with the addition of organic fertilizer was the best option for phytostabilization of Pb-contaminated mine tailing because it retained higher Pb concentration in the roots.     

Vesicular arbuscular mycorrhizal fungi improves establishment of micropropagated Leucaena leucocephala plantlets

Investigations were carried out to achieve cent per cent transplantation success of micropropagated Leucaena leucocephala (a fast growing multipurpose leguminous tree species) plantlets using two vesicular arbuscular mycorrhizal fungi, Glomus fasciculatum and Glomus macrocarpum. Plantlets were obtained by rooting the shoots [obtained through; hypocotyl callus in presence of 10^-5M BAP + 10^-6M NAA; and axillary bud sprouting from cotyledonary and other nodes in presence of 10^-5M BAP, on Gamborg's B5 medium], on half strength B5 medium supplemented with 5×10^-6M IBA. Subsequent to the nodulation of their roots with Rhizobium (strain PRGL 001)in soilrite, these plantlets were tranferred to sterilized garden soil by laying inoculum of either Glomus fasciculatum or Glomus macrocarpum around their roots. Only 20% of the plantlets survived in soils lacking VAM fungus. In contrast, cent per cent of the plantlets of Leucaena leucocephala established very well and showed good growth in VAM inoculated soil. Roots of the later plantlets showed presence of both external and internal hyphae with well formed arbuscules and vesicles confirming the establishment of good mycorrhizal association. These studies convincingly demonstrate that the mycorrhizal association help in successful establishment of tissue culture raised plantlets of Leucaena leucocephala in the field conditions by alleviating the transplantation shock. This revised version was published online in June 2006 with corrections to the Cover Date.     

Prospective application of Leucaena leucocephala for phytoextraction of Cd and Zn and nitrogen fixation in metal polluted soils

The study deals with phytoextraction of Zn and Cd by Leucaena leucocephala grown on effluent fed and low nitrogen soils collected from S1, S2, and S3 sites, representing decreasing metal content with increasing distance from the effluent drain. Plant nitrogen fixation potential and soil micro-biochemical attributes against metal stress were also assessed. Increasing soil metal content and plant growth enhanced metal accumulation. Relatively greater amount of Zn than Cd was accumulated by L. leucocephala, which exceeded in roots with that of other parts. Remediation factor for Cd was maximum (3.6%) in S2 grown plant. Nodule numbers, their biomass, nitrogenase activity, and leghaemoglobin content were maximum in plants grown in S3 and minimum in S1 soil having maximum metals. Maximum soil organic C, total N, C(mic), and N(mic), respiration rate, ATP content, and enzymatic activities in response to phytoremediation was recorded in S3 followed by S2 and S1. Phytoremediation for a year enhanced extractable Zn and Cd by 36% and 45%, and their total removal by 20% and 30%, respectively from S2, which suggests the possible application of L. leucocephala for the remediation of metal contaminated sites and their fertility restoration by improving microbial functionalities and N-pool.     

Genetic diversity of rhizobia from Leucaena leucocephala nodules in Mexican soils

Leucaena species are leguminous plants native to Mexico. Using two L. leucocephala cultivars grown in different soils, we obtained 150 isolates from the nodules. Twelve rDNA types were identified which clustered into groups corresponding to Mesorhizobium, Rhizobium , and Sinorhizobium by restriction fragment length polymorphism (RFLP) of amplified 16S rRNA genes. Types 2, 4, 5, 6, 10, 11, and 12 were distinct from all the defined species. Others had patterns indistinguishable from some recognized species. Most of the isolates corresponded to Sinorhizobium . Forty-one electrophoretic types (ETs) were identified among the isolates based on the different combinations of electrophoretic patterns of 13 metabolic enzymes. ETs were clustered into groups in general agreement with the rDNA types. Diverse plasmid patterns were obtained among the isolates, but common plasmids were observed among most isolates within rDNA types 5, 10, and 11. The symbiotic plasmids were identified among most of the isolates, except for the Mesorhizobium isolates. The affinities of host cultivars for different rhizobial groups and the impact of soil cultivation on the soil populations of rhizobia were analysed from the estimation of isolation frequencies and diversity. The results showed differences in rhizobial populations in cultivated and uncultivated soils and also differences in rhizobia trapped by L. leucocephala cv. Cunningham or Peruvian.     

元谋干热河谷生态恢复区昆虫多样性研究

以元谋退化生态系统初始生态恢复中人工构建植被为研究对象,在样地调查的基础上,对比分析了退化生态系统和恢复生态系统昆虫群落多样性组成与结构的恢复状况及其对人工群落类型的生态响应。结果表明,植物群落组成是影响昆虫群落多样性的关键因子。与天然植被相比,混交林促进了昆虫在退化地的扩散和定居,物种多样性明显增加。主成分分析排序将6种生境分为两大类:第Ⅰ类为赤桉纯林,代表物种单一、林下空旷、环境干燥为特点的植被;第Ⅱ类为扭黄茅草坡、车桑子灌丛及赤桉 银合欢、赤桉 相思、相思 银合欢3种混交林,代表物种相对复杂,生境偏向湿润的植被。不同生境的特有昆虫和优势昆虫种类和数量分析表明,在3种混交林中,相思 合欢恢复的效果较赤桉 相思与赤桉 合欢显著,是最好的先锋群落植物混交模式,能够较快改良生境,提高其物种多样性。但由于造林面积较小,植被恢复时间短,受人为干扰较大,昆虫多样性恢复的效果还不明显。     

The effect of plant succession on slope stability

The aim of this field investigation was to study the enrichment of biodiversity of the slope at an early phase of succession, initiated by selected pioneers, and to study how this enrichment related to enhancement of the slope stability. Four experimental plots, with differing plant pioneers and number of species (diversity), were designed in order to assess the effects of plant succession on slope stability. Plant growth pattern was assessed by observing the increment in species diversity (number), species frequency and plant biomass. Higher vegetation biomass in a mixed culture situation (LLSS) in the field with Leucaena leucocephala as a pioneer, marked an increase in species diversity after 24 months of observation. In contrast, G (grasses and legume creepers) plot revealed the slowest rate of succession and the lowest above-ground biomass amongst the plots. The mixed-culture plot without L. leucocephala (SS) had also shown a lower biomass, a similar phenomenon observed in a plot grown by L. leucocephala (LL) with low plant diversity. Consequently, these plant growth patterns gave a positive effect on slope stability where the regression study showed that the shear strength was much affected by plant biomass. Meanwhile, throughout the succession process in LLSS plot, root length density reached the highest value amongst the plots, 23 Km m^?3. In relation to this, the saturation level of the slope indicates the unsaturated condition of the soil which resulted in the enhancement of both soil penetrability and soil shear strength of the plot. These attributes reveal a strong positive relationship between the process of natural succession and the stability of slopes.