The role of seed reserves in arbuscular mycorrhizal formation and growth of Leucaena leucocephala (Lam.) de Wit. and Zea mays L.

We show here that seed reserves in Leucaena leucocephala (Lam.) de Wit. and Zea mays L. (maize) are important for mycorrhizal formation and seedling growth. Seed reserve removal reduced mycorrhizal formation markedly in Leucaena but not in maize, except at 15 and 45 days after seed reserve removal. Partial or total removal of seed reserves decreased plant growth and tissue nutrient concentrations in both hosts. Nodule number in Leucaena, which was related positively to plant biomass and mycorrhizal infection levels, was reduced when one or both cotyledons were severed. Leucaena seedlings without or with partial seed reserves had higher nutrient use efficiencies throughout seedling growth. But such an effect was observed only initially in maize. Seed reserve removal increased the specific absorption rates of nutrients in both hosts. Phosphorus absorption rate was significantly and positively related to root infection levels in both Leuceana and maize. Though the growth rates of plants without seed reserves were low initially, these plants had higher growth rates during later stages. We conclude that seed reserves are not only important for seedling growth, but also for mycorrhizal formation and nodulation. Received: 15 July 1999 / Accepted: 6 December 1999     

Nodulation and growth ofLeucaena leucocephala (Lam.) de Wit as affected by inoculation and N fertilizer

Leonard jar, pot and field experiments examined the effects of inoculation and the influence of nitrogen fertilizer on nodulation, nitrogen fixation and growth ofLeucaena leucocephala (Lam.) de Wit at IITA, Ibadan, Nigeria. Leucaena responded to both inoculation and/or nitrogen application. Shoot growth and total N and P of inoculated plants were comparable to those of the highest N treatment, and the values were about 55% greater than those of uninoculated ones. Field data indicated that toal N yields of inoculated leucaena were increased by 50% with 40 or 80 kg ha^–1 of N fertilizer. However, N fertilizer depressed N fixation by 56% as was expected from nodule mass data. N-fixation was delayed for about 8 weeks in the plots without N. Application of small amounts of N starter (20 ppm) proved to be beneficial to satisfy the plant need during the early stage of leucaena growth. The rhizobial strains IRc 1045 and IRc 1050 were effective, competitive and survived well in the field one year after their establishment.     

Testa Structure and Histochemistry Related to Water Uptake in Leucaena leucocephala Lam. (De Wit)

The testa structure and histochemistry of Leucaena leucocephalaLam. (De Wit) seed were investigated by bright-field and fluorescencelight microscopy, and scanning electron microscopy. The testaconsisted of several separate layers. Externally there was anon-cellular layer made up of two parts differing in histochemicalcharacteristics: an "outer strip" rich in hydrophilic substances,and a "thicker part" showing the occurrence of phenolics, involvedin water impermeability control. A second underlying thin layerwas formed by the palisade cell caps, joined one to another.This layer, which we called the "cap film ", became metachromaticreddish-blue with Toluidine O pH 4·4 and reacted positivelywith Alcian blue pH 2·5, revealing the presence of polysaccharidehydrophilic material. The palisade cells consisted of two parts,having different structures and histochemical features. Thefurrowed upper part revealed the simultaneous presence of hydrophilicand hydrophobic substances in the furrows and in the ribs respectively.The corresponding periclinal section showed a central daisy-likepattern (made up of hydrophilic material) with a small chainof tiny spots (made up of hydrophobic material) all around it.The inner part of the palisade cells was also furrowed, butshowed only hydrophobic substances of lipidic nature, detectedby Auramine O and Phosphine 3R. The light line was found tobe rich in callose as shown by the strong fluorescence inducedby Aniline Blue. These findings add supporting evidence of thecomplex structure and composition of the Leucaena leucocephalatesta.Copyright 1994, 1999 Academic Press Leucaena leucocephala, testa, structure, histochemistry, water entry     

Stigmatic inhibition of pollen grain germination-its implication for frequency distribution of seed number in pods of Leucaena leucocephala (Lam) de Wit

Summary Seed number per pod is negatively skewed in Leucaena leucocephala. Post-fertilisation abortion of pods does not completely explain the skewed distribution. It is shown that a pre-fertilisation regulation effectively restricts the formation of pods with less than a certain number of seeds. The regulation is rendered through the inhibition of pollen grain germination by the stigmatic fluid when the pollen grain is less than a certain critical load in the stigma. Such a control is shown to have implications in the evolution of pollen package units, generation of male gametophytic competition and the economy of packing seeds in pods.     

Nitrogen fixation of field-inoculatedLeucaena leucocephala (Lam.) de Wit estimated by the15N and the difference methods

The amount of nitrogen fixed byLeucaena leucocephala (Lam.) de Wit was assessed on an Alfisol at the International Institute of Tropical Agriculture located in southwestern Nigeria. Estimated by the difference method, nitrogen fixation of leucaena inoculated with Rhizobium strain IRc 1045 was 133 kg ha^–1 in six months. Inoculation with Rhizobium strain IRc 1050 gave a lower nitrogen fixation of 76 kg ha^–1. Fertilization with 40 and 80 kg N ha^–1 inhibited nitrogen fixation by 43–76% and 49–71%, respectively. Estimates with the¹⁵N dilution method gave nitrogen fixation of 134 kg ha^–1 in six months when leucaena was inoculated with Rhizobium strain IRc 1045 and 98 kg ha^–1 for leucaena inoculated with Rhizobium strain IRc 1050. This nitrogen fixation represented 34–39% of the plant nitrogen. Inoculated leucaena derived 5–6% of its nitrogen from applied fertilizer and 56–54% from soil.     

Cloning,expression, and characterization of an antifungal chitinase from Leucaena leucocephala de Wit

Chitinase cDNAs from Leucaena leucocephala seedlings were cloned by PCR amplification with degenerate primers based on conserved class I chitinase sequences and cDNA library screening. Two closely related chitinase cDNAs were sequenced and inferred to encode precursor proteins of 323 (KB1) and 326 (KB2) amino acids. Expression of the KB2 chitinase from a pET32a plasmid in Origami (DE3) Escherichia coli produced high chitinase activity in the cell lysate. The recombinant thioredoxin fusion protein was purified and cleaved to yield a 32-kDa chitinase. The recombinant chitinase hydrolyzed colloidal chitin with endochitinase-type activity. It also inhibited growth of 13 of the 14 fungal strains tested.     

Effects of drought stress and arbuscular mycorrhiza on the growth of Gliricidia sepium (Jacq). Walp, and Leucaena leucocephala (Lam.) de Wit. in simulated eroded soil conditions

A greenhouse investigation was conducted to determine the effect of arbuscular mycorrhiza and drought on the growth of two tropical hedgerow legume trees (Gliricidia sepium and Leucaena leucocephala) under simulated eroded soil conditions. It was a factorial design with two levels of watering regime (adequate watering and drought), inoculation with Glomus deserticola (with and without), and two soil types (0-30 cm topsoil and 30-60 cm subsoil). Each treatment was replicated 3 times. After ten drought cycles, the growth of Gliricidia sepium in the subsoil was enhanced by mycorrhizal inoculation under both watering regimes whereas there was no significant contribution of mycorrhizal inoculation to the growth of L. leucocephala in both soil types under the two watering regimes. Drought stress significantly reduced most growth parameters for the two tree species in both soils with or without fungal inoculation. The N-fixing activity of Gliricidia sepium benefited from Glomus deserticola inoculation while that of L. leucocephala was not significantly affected in the topsoil. Mycorrhizal colonization was reduced for both tree species in the subsoil compared to the topsoil while it was significantly increased for both species in the subsoil when compared to the uninoculated subsoil counterpart. In the subsoil, inoculation of Gliricidia sepium with the mycorrhizal fungus increased root colonization by 89% and 73% under adequate watering and drought, respectively, whereas L. leucocephala had only a 38% and 42% increase in root colonization under comparative conditions in the subsoil. Thus Glomus deserticola inoculation may be beneficial to the growth of Gliricidia sepium in a badly eroded site where topsoil is missing.     

Influence of exogenous ethylene on cambial activity,xylogenesis and ray initiation in young shoots of Leucaena leucocephala (lam.) de Wit

The effect of exogenous ethephon on cambial activity, xylem production and ray population in young shoots of Leucaena leucocephala was investigated anatomically. The application of ethephon showed a diphasic effect on cambial activity and xylogenesis in a dose dependent manner. Lower concentration of ethephon enhanced cambial activity while high concentrations reduced cambial cell divisions and daughter-cell differentiation. High ethephon concentration also resulted in shorter vessel elements, thick walled fibers and phenolic accumulation in ray cells and vessel elements, whereas low concentration allowed elongation of fibers and vessel elements. The density of rays increased significantly with increase in ethylene concentration. The evaluation of longitudinal sections of cambial zone in ethephon treated plants showed high frequency of transformation of fusiform initials into ray initials through divisions and segmentation, resulting in high ray frequency in both xylem and phloem. The present study demonstrates that ethylene plays an important role in regulating secondary vascular tissue composition by reducing the population of fusiform initials in the cambium.     

In vitro plantlet regeneration from cotyledons of the tree-legume Leucaena leucocephala

Two plant regeneration methods applicable to Leucaenaleucocephala were developed. In the first method, involvingorganogenesis via callus formation, cotyledon, hypocotyl and root segments wereinitiated on MS medium containing different concentrations ofN⁶-benzyladenine (BA), 2,4-dichlorophenoxyacetic acid (2,4-D), andnaphthaleneacetic acid (NAA). Both compact (type I) and friable (type II) calliwere obtained from the cotyledon and hypocotyl explants treated with differentconcentrations of the growth regulators. Shoots were generated only from thefriable calli formed from the cotyledon explants. The calli formed from thehypocotyl explants did not generate shoots and the root explants died withoutforming callus. Cotyledon explants from 3–4 day old seedlings showedmaximum callus induction compared to those from older seedlings. In a secondmethod involving direct organogenesis, excised cotyledons were cultured on 1/2MS medium containing 10–35 mg l^–1N⁶-benzyladenine (BA) for 7–14 days. Transfer of thecotyledonsto regeneration medium containing low BA resulted in callus formation andsubsequent shoot regeneration from the base of the excised cotyledon explants,with up to 100% frequency. Regenerated shoots rooted best on a basal mediumcontaining no growth regulators.     

Characterization of Serine Proteinase Inhibitor from Subabul (Leucaena leucocephala Lam) Seeds

Partially purified subabul trypsin inhibitor (STI) showed high level of thermotolerance and pH stability with a molecular weight of -15 kD. Bioassay results showed that STI is a strong inhibitor of Helicoverpa armigera larval gut proteinases. In vitro feeding experiments revealed 40% mortality in inhibitor fed larvae followed by 12 days extension in larval growth period and significant reduction in pupal weight. Differential activity staining for the larval gut proteolytic enzymes did not show any difference in the isoprotease pattern between the control and the larvae fed with STI.     

Effect of Exogenously Applied 24-Epibrassinolide and Brassinazole on Xylogenesis and Microdistribution of Cell Wall Polymers in Leucaena leucocephala (Lam) De Wit

Journal of Plant Growth Regulation - Plant growth regulators play a key role in cell wall structure and chemistry of woody plants. Understanding of these regulatory signals is important in advanced...     

Competitiveness of Rhizobium sp. [Leucaena leucocephala (Lam.) Dewit] strains and their genetically marked derivatives

D.M. SWELIM, L.D. KUYKENDALL, F.M. HASHEM, S.M. ABDEL-WAHAB AND N.I. HEGAZI. 1996. The competitiveness of wild-type strains of Rhizobium sp. ( Leucaena ) and their genetically marked double mutants was examined in mixed infection experiments in the greenhouse. Antibiotic resistance markers were selected for use in strain identification, but these genetic markers apparently lowered both competitiveness and effectiveness, except in the case of strain DS 144/2 where the genetically marked derivative was evidently superior to the wild-type parent strain in effectiveness. Four wild-type strains and their genetically marked derivatives were carefully evaluated using double reciprocal pairs, the results of which nevertheless allowed the formulation of some conclusions. Strains DS 65 and DS 78 were more competitive than strain DS 144/2; only strain DS 78 was more competitive than DS 158; and strains DS 158 and DS 65 were equally competitive. There was no correlation between nodule number and competitiveness. Shoot dry weight and nitrogen mass, as well as nitrogenase activity, decreased with some strain mixtures indicating that relatively ineffective symbioses had formed, as compared with single-strain inoculations using symbiotically competent strains.     

The Hilar Region in Leucaena leucocephala Lam. (De Wit) Seed: Structure, Histochemistry and the Role of the Lens in Germination

Structural and histochemical features of the hilar region inthe seed of Leucaena leucocephala Lam. (De Wit) were investigatedby bright-field and fluorescence light microscopy and scanningelectron microscopy. In the dry seeds the lens appeared as anelliptical depression prevailing in size over the hilum andmicropyle. In the imbibed seeds, both naturally softened seedand those requiring softening with boiling water, the lens rosegradually to form a cavity between the palisade layer and themesophyll below. This apoplastic pathway was traced using RutheniumRed dye. In place of the hour-glass cells, the hilar regioncontained abnormal cells, called 'white cells' because theyremained unstained by Toluidine Blue O at pH 4·4. Theapparently opposing characteristics of the lens are discussed.It is hypothesized that the lens acts as a valve. By remainingclosed it hinders the entry of water because of the presenceof a high light-line rich in callose and in lipid-like substancesand to the almost total lack of hydrophilic polysaccharide material.Under favourable conditions for germination, the lens opens,allowing water to enter, through a thin palisade layer and withthe probable intervention of the 'white cells'.Copyright 1995,1999 Academic Press Seed germination, Leucaena leucocephala, hilar region, lens, structure, histochemistry     

Hardening in vitro and morpho-physiological changes in the leaves during acclimatization of micropropagated plants of Leucaena leucocephala (LAM.) de wit

A protocol for hardening of microprogated plants of Leucaena leucocephala in vitro is described which ensures up to 85% survival of plants following their transfer to pots or garden beds. Morpho-physiological studies confirm the earlier reports that cultured plants have poor control of water loss. Their leaves had very little epicuticular wax and lacked starch grains in their cells. Interestingly, the leaf cells at the shoot multiplication stage appeared normal. Reduction in their size and abnormality of shape appeared first during the rooting stage in vitro. During hardening the appearance of starch grains preceded the normalization of mesophyll cells.     

In vitro vegetative propagation of Chinese cabbage

Explants from cotyledons, axillary buds, inflorescence stems and flower buds of Brassica campestris ssp. pekinensis (Lour.) Olsson (Chinese cabbage, cv. Wongbok) were cultured on MS medium with growth regulators. Multiple shoots were obtained from cotyledons, axillary buds and flower buds but not from inflorescence stems. Propagation of shoots from cotyledons was more successful than from axillary buds and flower buds. The vegetative propagation rates varied amongst clones derived from cotyledons of the same cultivar and seed lot. The propagation rates of the cotyledon-derived material followed a normal distribution with an average propagation rate of 2.6 shoots per two weeks subculture when cultured on MS media plus 44.4 m benzyladenine (BA) and 14.8 m -indolebutyric acid (IBA). Shoots from three clones were cultured on MS medium with nine different concentrations of BA. The concentration of BA which promoted the highest rate of shoot propagation varied for the three clones and was in the range 44.4 to 177.6 m.     

Symbiotic competence, genetic diversity and plasmid profiles of Egyptian isolates of a Rhizobium species from Leucaena leucocephala (Lam.) Dewit

L.D. KUYKENDALL, D.M. SWELIM, F.M. HASHEM, S.M. ABDEL-WAHAB AND N.I. HEGAZI. 1996. There is considerable interest in improving nitrogen fixation in tropical legume trees to increase soil fertility, particularly in developing countries. To provide information needed for the development of improved strains, characterization of strains of Leucaena -nodulating Rhizobium was performed. Thirteen strains were isolated from root nodules of Leucaena leucocephala grown in different geographical regions in Egypt. Plasmid DNA profile groups, including identification of symbiosis-controlling plasmids, were defined. Symbiotic competence was determined in plant tests and some strains were perhaps more symbiotically proficient at fixing nitrogen with L. leucocephala than were reference strains. The genetic diversity of these strains was determined by RFLP analysis of total DNAs using, as probes, six arbitrarily selected cosmid clones from a gene library of strain TAL 1145, a well-characterized reference strain. There were four plasmid profile groups which did not correlate with either symbiotic competence or RFLP analysis. RFLP analysis, unlike plasmid profiles, permitted a determination that all 13 Egyptian strains were evidently homogeneous and quite distinct from previously studied Leucaena -nodulating Rhizobium as represented by reference strains.     

地宝兰的离体快速繁殖

1植物名称地宝兰[Geodorum densiflorum (Lam.)Schltr.]。2材料类别种子。3培养条件种子萌发培养基:(1)MS;(2)MS 6-BA1.0mg·L-1(单位下同) NAA0.5;(3)1/2MS;(4)1/2MS 6-BA1.0 NAA0.5;(5)KC(Kundson     

Fluctuation of Endogenous Levels of Free and Conjugated Gibberellins throughout Seed Maturation in Leucaena leucocephala (Lmk) De Wit

Combined gas chromatography-selected ion monitoring (GC-SIM)analysis of a purified extract from seeds of Leucaena leucocephalashowed the presence of GA₁, GA₈, GA₁₇, GA₁₉, GA₂₀, GA₂₃, GA₂₉and GA₅₃. GA₁, GA₈ and GA₂₉ were also found both as glucosylester-like and glucosyl ether-like conjugates, and GA₂₀ as aglucosyl ester-like conjugate; these conjugates were analyzedas free GAs after enzyme hydrolysis. GA₂₃ was shown to be themain free gibberellin in immature seeds (268 ng/seed), thoughits level drastically decreased during their maturation. GA₁was the main free C₁₉-gibbercllin and GA₁ glucosyl ester-likeand glucosyl ether-like conjugates were found at the highestlevels in the seeds prior to maturation. Fluctuation of endogenouslevels of gibberellins is discussed in terms of seed development. (Received May 9, 1984; Accepted August 25, 1984)     

In vitro propagation of the endangered orchid,Geodorum densiflorum (Lam.) Schltr. through rhizome section culture

Micropropagation of the endangered terrestrial orchid, Geodorum densiflorum (Lam.) Schltr. was achieved through rhizome section culture from in vitro seed- derived rhizomes. Rhizome sections were cultured on Murashige and Skoog (MS) and Knudson C(KC) media supplemented with various growth regulators and 0.1% activated charcoal. The rhizome sections responded on MS medium. Naphthaleneacetic acid (NAA) at 2.0 μM stimulated rhizome growth. However, benzyladenine (BA) at 5.0 μM induced multiple shoots within four weeks of culture and inhibited rhizome growth. The regenerated shoots rooted on MS only or with NAA at 1.0 μM. Well-developed plantlets were transferred to community pots and then to a greenhouse where the plants have been acclimatised. This revised version was published online in June 2006 with corrections to the Cover Date.