Arbuscular mycorrhizal fungi colonize decomposing leaves of<Emphasis Type="Italic"> Myrica parvifolia</Emphasis>,<Emphasis Type="Italic"> M. pubescens</Emphasis> and<Emphasis Type="Italic"> Paepalanthus</Emphasis> sp.

Hyphae and vesicles of arbuscular mycorrhizal fungi (AMF) were found within the decomposing leaves of Myrica parvifolia, M. pubescens and Paepalanthus sp. at three montane sites in Colombia. Hyphae, vesicles, and arbuscule-like structures were also found within scale-like leaves of the rhizomes of Paepalanthus sp. The litter found in the vicinity of the roots was divided into three decomposition layers. The highest AMF colonization occurred in the most decomposed leaves, which were in close association with roots. In contrast, there were no differences in AMF colonization of roots present in the different decomposition layers. Colonization of decomposing leaves by AMF did not differ between the two closely related species M. parvifolia and M. pubescens, nor between two sites (Guatavita and Zipacón, Colombia) differing in soil fertility. Occurrence of vesicles in decomposing leaves was correlated with abundant AMF extraradical hyphae among the leaves. We propose that AMF enter decomposing leaves mechanically through vascular tissue. As a consequence, AMF are well positioned to obtain and efficiently recycle mineral nutrients released by decomposer microorganisms before their loss by leaching or immobilization in soil.     

An improved plant regeneration system and ex vitro acclimatization of <Emphasis Type="Italic">Ocimum </Emphasis><Emphasis Type="Italic">basilicum</Emphasis> L.

An efficient, rapid and large scale propagation of a multipurpose herb, Ocimum basilicum through in vitro culture of nodal segments with axillary buds from mature plants has been accomplished. Among the cytokinins, 6-benzyladenine (BA), thidiazuron (TDZ), kinetin (Kin) and 2-isopentenyl adenine (2-iP) tested as supplements to Murashige and Skoog (MS) medium, 5.0 μM BA was optimum in inducing bud break. The highest rate of shoot multiplication was achieved on half-strength MS medium supplemented with 2.5 μM BA and 0.5 μM indole-3-acetic acid (IAA) combination. The shoots regenerated from TDZ supplemented medium when subcultured to hormone-free MS medium considerably increased the rate of shoot multiplication and shoot length by the end of third subculture. For rooting, MS medium supplemented with 1.0 μM indole-3-butyric acid (IBA) proved to be better than that supplemented with IAA or α-naphthalene acetic acid (NAA). The in vitro raised plantlets with well developed shoots and roots were successfully established in earthen pots containing garden soil and were grown in greenhouse with 90% survival rate. Chlorophyll a and b, carotenoids and net photosynthetic rate were measured in leaves during ex vitro acclimatization at 0, 7, 14, 21 and 28 days. Firstly these parameters showed a decreasing trend but subsequently increased after 7 days of acclimatization. These findings indicate that the adaptation of micropropagated plants to ex vitro conditions is more extended in time than generally accepted.     

Tryptophan dimer produced by water-stressed bahia grass is an attractant for <Emphasis Type="Italic">Gigaspora margarita</Emphasis> and <Emphasis Type="Italic">Glomus caledonium</Emphasis>

We isolated and elucidated the structure of several stimulants for arbuscular mycorrhizal fungi (AMF) in water-stressed bahia grass roots. We could isolate some compounds that promoted the growth of Gigaspora margarita Becker and Hall and Glomus caledonium (Nicol. and Gerd.) Trappe and Gerd. In these compounds, tryptophan dimer (Trp–Trp) was elucidated the structure. Trp–Trp was abundantly produced in water-stressed bahia grass roots and exuded to the soil, although it was scarcely detected in non-stressed root exudates. Interestingly, this peptide strongly attracted the hyphae of Gi. margarita and G. caledonium and promoted their hyphal growth in vitro (1.8 × longer than the control). Tryptophan, however, had no effect on hyphal growth and attraction. Thus, Trp–Trp exuded from water-stressed roots would play an important role as a major signal for AMF. An erratum to this article can be found at     

Differential effects of <Emphasis Type="Italic">Paenibacillus</Emphasis> spp. on cucumber mycorrhizas

The effects of 17 Paenibacillus strains on root colonization by Glomus intraradices or Glomus mosseae and plant growth parameters (shoot and root weight) of mycorrhizal cucumber plants were examined. The Paenibacillus strains were originally isolated from mycorrhizal (G. intraradices) and non-mycorrhizal cucumber rhizosphere and/or hyphosphere, except for strain EJP73, which originated from a Pinus sylvestris-Lactarius rufus ectomycorrhiza. Root colonization of cucumber plants by G. intraradices or G. mosseae was unaffected by all seven strains of Paenibacillus polymyxa, but was decreased or increased by four strains of Paenibacillus macerans and strain EJP73 of Paenibacillus sp. Overall, shoot dry weight of cucumber grown in symbioses with either G intraradices or G. mosseae was unaffected by inoculation with all of the Paenibacillus strains, except for strain MB02-429 of P. macerans, which increased the shoot dry weight in the cucumber-G. mosseae symbiosis. On the other hand, several Paenibacillus strains caused altered root growth. Three strains of P. polymyxa and four strains of P. macerans increased the root fresh weight of the cucumber–G. intraradices symbiosis, whereas three strains of P. polymyxa and one strain of P. macerans as well as Paenibacillus sp. EJP73, decreased the root fresh weight of the cucumber–G. mosseae symbiosis. In conclusion, our results show that bacteria from several species of Paenibacillus differentially affect cucumber mycorrhizas.     

Morphology and colonization preference of arbuscular mycorrhizal fungi in <Emphasis Type="Italic">Clethra barbinervis</Emphasis>, <Emphasis Type="Italic">Cucumis sativus</Emphasis>, and <Emphasis Type="Italic">Lycopersicon esculentum</Emphasis>

Clethra barbinervis (Ericales), Cucumis sativus, and Lycopersicon esculentum were grown in soils collected from six different vegetation sites (cedar, cypress, larch, red pine, bamboo grass, and Italian ryegrass), and morphology and colonization preference of arbuscular mycorrhizal (AM) fungi were investigated by microscopic observation and PCR detection. C. barbinervis consistently formed Paris-type AM throughout the sites. C. sativus formed both Arum- and Paris-type AM with high occurrence of Arum-type AM. L. esculentum also formed both Arum- and Paris-type AM but with high occurrence of Paris-type AM. AM diversity within the same plant species was different among the sites. Detected AM diversity from AM spores in different site soils did not consistently reflect AM fungal diversity seen in test plants. Detected families were different, depending on test plants grown even in the same soil. AM fungi belonging to Glomaceae were consistently detected from roots of all test plants throughout the sites. Almost all the families were detected from roots of C. barbinervis and L. esculentum. On the other hand, only two or three families of AM fungi (Archaeosporaceae and/or Paraglomaceae and Glomaceae) but not two other families (Acaulosporaceae and Gigasporaceae) were detected from roots of C. sativus, indicating strong colonization preference of AM fungi to C. sativus among test plants. This study demonstrated that host plant species strongly influenced the colonization preference of AM fungi in the roots.     

Mycorrhizal status of <Emphasis Type="Italic">Eucalyptus</Emphasis> plantations in south China and implications for management

The aim of this study is to assess the mycorrhizal status of Eucalyptus plantations in south China and to determine the need for inoculation. In four provinces in south China, 155 plantations were sampled for sporocarps of ectomycorrhizal (ECM) fungi, spores of arbuscular mycorrhizal (AM) fungi, and mycorrhizas over 2 years. This study revealed a low above-ground diversity of ECM fungi consisting of 15 taxa fruiting beneath Eucalyptus plantations. The most common ECM genera were Scleroderma and Pisolithus, but they were infrequent. A total of 21 AM fungi, mostly Glomus species, were recognized from spores collected from eucalypt plantations. Four Glomus species were frequently present in soils, but spore density and relative abundance of AM fungi were generally low. Eucalypt roots from all plantation sites were poorly colonized by either ECM fungi or AM fungi. A bioassay with E. urophylla as a bait host, using soils collected from 11 eucalypt plantations, confirmed low levels of inoculum of both ECM and AM fungi in field soil. This is the first integrated study on the mycorrhizal status of eucalypt plantations in China. Findings from this research can be used to encourage adoption of mycorrhizal technology by eucalypt nurseries in the region. The potential of using spores of compatible ECM fungi or collections for forest nurseries is discussed.     

Plant growth promotion abilities and formulation of <Emphasis Type="Italic">Bacillus megaterium</Emphasis> strain B 388 (MTCC6521) isolated from a temperate Himalayan location

Bacillus megaterium strain B388, isolated from rhizosphere soil of pine belonging to a temperate Himalayan location has been characterized. The plant growth promotion and biocontrol properties of the bacterium have been evaluated through petridish and broth based assays. The isolate solubilized tricalcium phosphate under in vitro conditions; maximum activity (166 μg/ml) was recorded at 28°C after 15 days of incubation. Production of indole acetic acid demonstrated in broth assays was another important plant growth promoting character. The bacterium produced diffusible and volatile compounds that inhibited the growth of two phytopathogens viz. Alternaria alternata and Fusarium oxysporum. The carrier based formulations of the bacterium resulted in increased plant growth in bioassays. The rhizosphere colonization and the viability of the cells entrapped in alginate beads were greater in comparison to coal or broth based formulations. The bacterium showed maximum similarity with Bacillus megaterium by 16S rRNA analysis.     

Purification and properties of aminoaldehyde dehydrogenase from <Emphasis Type="Italic">Avena</Emphasis><Emphasis Type="Italic">sativa</Emphasis>

NAD-dependent aminoaldehyde dehydrogenase (AMADH, EC 1.2.1.-) from Avena shoots was purified by DEAE Sephacel, hydroxyapatite, 5′-AMP Sepharose 4B, Mono Q, and TSK-GEL column chromatographies to homogeneity by the criterion of native PAGE. SDS–PAGE yielded a single band at a molecular mass of 55 kDa. IEF studies showed a band with a pI value of 5.3. In contrast to AMADHs from other species, the TSK-GEL chromatography showed that Avena AMADH exists as a monomer in the native state. The purified enzyme catalyzed the oxidations of 3-aminopropionaldehyde (APAL), 4-aminobutyraldehyde (ABAL) N-(3-aminopropyl)-4-aminobutyraldehyde (APBAL), and 4-guanidinobutyraldehyde (GBAL), but not of betaine aldehyde or indoleacetaldehyde. The K _m values for APAL, ABAL, and GBAL were 1.5×10^–6, 2.2×10^–6, and 1.3×10^–5 M, respectively. Although N-terminal amino acid sequence of Avena AMADH could not be determined due to a modification of the amino residue, the sequence of the fragment of AMADH cleaved by V8 protease showed greater similarity to the barley BADH than to the pea AMADH. Electronic Publication     

Growth,fluorescence, photosynthetic O<Subscript>2</Subscript> production and pigment content of salt adapted cultures of <Emphasis Type="Italic">Arthrospira</Emphasis> (<Emphasis Type="Italic">Spirulina</Emphasis>) <Emphasis Type="Italic">platensis</Emphasis>

The effect of salt concentration (NaCl) on growth, fluorescence, photosynthetic activities and pigment content of the cyanobacterium Arthrospira platensis has been investigated over 15 days. It has been observed that high NaCl concentration induces an increase of the growth, photosynthetic efficiency (α), phycobilin/chlorophyll ratio and a slight decrease of dark respiration and compensation points. Moreover, high NaCl concentration enhances photosystem II (PSII) activity compared to photosystem I (PSI). Results show that the phycobilin-PSII energy transfer compared to the chlorophyll-PSII (F_695,600/F_695,440) increases. However, data obtained about the maximal efficiency of PSII photochemistry are controversial. Indeed, the Fv/Fm ratio decreases in salt adapted cultures, while at the same time the trapping flux per PSII reaction center (TR₀/RC) and the probability of electron transport beyond Q_A (₀) remain unchanged at the level of the donor and the acceptor sites of PSII. This effect can be attributed to the interference of phycobilin fluorescence with Chl a when performing polyphasic transient measurements.     

Diversity of arbuscular mycorrhizal fungi colonising roots of the grass species<Emphasis Type="Italic"> Agrostis capillaris</Emphasis> and<Emphasis Type="Italic"> Lolium perenne</Emphasis> in a field experiment

Analysis of arbuscular mycorrhizal (AM) fungal diversity through morphological characters of spores and intraradicular hyphae has suggested previously that preferential associations occur between plants and AM fungi. A field experiment was established to investigate whether AM fungal diversity is affected by different host plants in upland grasslands. Indigenous vegetation from plots in an unimproved pasture was replaced with monocultures of either Agrostis capillaris or Lolium perenne. Modification of the diversity of AM fungi in these plots was evaluated by analysis of partial sequences in the large subunit (LSU) ribosomal RNA (rDNA) genes. General primers for AM fungi were designed for the PCR amplification of partial sequences using DNA extracted from root tissues of A. capillaris and L. perenne. PCR products were used to construct LSU rDNA libraries. Sequencing of randomly selected clones indicated that plant roots were colonised by AM fungi belonging to the genera Glomus, Acaulospora and Scutellospora. There was a difference in the diversity of AM fungi colonising roots of A. capillaris and L. perenne that was confirmed by PCR using primers specific for each sequence group. These molecular data suggest the existence of a selection pressure of plants on AM fungal communities.     

Arbuscular mycorrhizal fungi may serve as another nutrient strategy for some hemiparasitic species of <Emphasis Type="Italic">Pedicularis</Emphasis> (Orobanchaceae)

As an important component of plant kingdom, parasitic plants have intrigued many scientists with their heterotrophic strategy. Numerous investigations have been carried out for a better understanding of interactions between parasitic plants and their hosts. Nevertheless, studies on parasitic plants from a mycorrhizal perspective are lacking, largely because of the notion that parasitic plants do not form mycorrhizal associations. Although long being regarded as nonmycorrhizal, some Pedicularis species are recently found to be heavily colonized by mycorrhizal fungi. Because the precise information about parasitism of Chinese Pedicularis has been lacking, we surveyed both the mycorrhizal status and parasitism of 29 Pedicularis species from the northwest of Yunnan Province, China, to test the hypothesis that some Pedicularis may be mycorrhizal and parasitic simultaneously. The majority of studied species were found to be parasitic as well as mycorrhizal. In some cases, parasitic organs and arbuscular mycorrhizal fungi (AMF) were detected in the same rootlets. The results suggest that some Pedicularis species may have another nutrient strategy (e.g., mycotrophy) besides being parasitic. Also, the findings indicate that host plants as well as AMF should be taken into account in cultivation of Pedicularis species.     

Ultrastructure of spore development in <Emphasis Type="Italic">Scutellospora heterogama</Emphasis>

The ultrastructural detail of spore development in Scutellospora heterogama is described. Although the main ontogenetic events are similar to those described from light microscopy, the complexity of wall layering is greater when examined at an ultrastructural level. The basic concept of a rigid spore wall enclosing two inner, flexible walls still holds true, but there are additional zones within these three walls distinguishable using electron microscopy, including an inner layer that is involved in the formation of the germination shield. The spore wall has three layers rather than the two reported previously. An outer, thin ornamented layer and an inner, thicker layer are both derived from the hyphal wall and present at all stages of development. These layers differentiate into the outer spore layer visible at the light microscope level. A third inner layer unique to the spore develops during spore swelling and rapidly expands before contracting back to form the second wall layer visible by light microscopy. The two inner flexible walls also are more complex than light microscopy suggests. The close association with the inner flexible walls with germination shield formation consolidates the preferred use of the term ‘germinal walls’ for these structures. A thin electron-dense layer separates the two germinal walls and is the region in which the germination shield forms. The inner germinal wall develops at least two sub-layers, one of which has an appearance similar to that of the expanding layer of the outer spore wall. An electron-dense layer is formed on the inner surface of the inner germinal wall as the germination shield develops, and this forms the wall surrounding the germination shield as well as the germination tube. At maturity, the outer germinal wall develops a thin, striate layer within its substructure.     

Four new species of <Emphasis Type="Italic">Phyllosticta</Emphasis>, one new species of <Emphasis Type="Italic">Pseudocercospora</Emphasis>, and one new combination in <Emphasis Type="Italic">Passalora</Emphasis> from Japan

During a survey of plant-inhabiting fungi in a botanical garden in Japan, some noteworthy fungi were collected from leaf spots of some herbal and arboreal plants. Among them, five new species are described, namely: Phyllosticta. ardisiicola on Ardisia crenata, Phy. aspidistricola on Aspidistra elatior, Phy. kerriae on Kerria japonica, Phy. fallopiae on Fallopia japonica, and Pseudocercospora davidiicola on Davidia involucrata. Passalora pyrrosiae, a new combination for Pseudocercospora pyrrosiae on Pyrrosia lingua, is proposed based on its morphological characteristics designating the neotype specimen.     

Antimicrobial activity of <Emphasis Type="Italic">Bacillus megaterium</Emphasis> strains

A bacterial strain with a high level of antimicrobial activity was isolated from soil and identified as Bacillus megaterium. Production of antibiotics by nine strains of this species from the collection of the State Research Institute for Genetics and Selection of Industrial Microorganisms was investigated. In submerged cultures, nine out of ten B. megaterium strains were found to produce antibacterial antibiotics differing in their spectra of action. Physicochemical characteristics of five compounds were described. Three of them belonged to peptide antibiotics. All five compounds were active against the methicillin-resistant strain Staphylococcus aureus INA 00761. Three of them were shown to be the previously undescribed compounds. Antibiotics produced by various B. megaterium strains were also active against the Leuconostoc mesenteroides VKPM B-4177 strain resistant to glycopeptide antibiotics and against gram-negative bacteria Pseudomonas aeruginosa ATCC 27853 and Escherichia coli ATCC 25922.     

Bio-resolution of glycidyl (<Emphasis Type="Italic">o</Emphasis>, <Emphasis Type="Italic">m</Emphasis>, <Emphasis Type="Italic">p</Emphasis>)-methylphenyl ethers by <Emphasis Type="Italic">Bacillus megaterium</Emphasis>

A newly isolated Bacillus megaterium with epoxide hydrolase activity resolved racemic glycidyl (o, m, p)-methylphenyl ethers to give enantiopure epoxides in 84–99% enantiomeric excess and with 21–73 enantiomeric ratios. The (S)-enantiomer was obtained from rac-glycidyl (o or m)-methylphenyl ether while the (R)-epoxides was obtained from glycidyl p-methylphenyl ether. The observations are explained at the level by enzyme-substrate docking studies.     

Osmotic solute responses of mycorrhizal citrus (<Emphasis Type="Italic">Poncirus trifoliata</Emphasis>) seedlings to drought stress

This study investigated the accumulation of osmotic solutes in citrus (Poncirus trifoliata) seedlings colonized by Glomus versiforme subjected to drought stress or kept well watered. Development of mycorrhizae was higher under well watered than under drought-stressed conditions. Arbuscular mycorrhizal (AM) seedlings accumulated more soluble sugars, soluble starch and total non-structural carbohydrates in leaves and roots than corresponding non-AM seedlings regardless of soil-water status. Glucose and sucrose contents of well-watered and drought-stressed roots, fructose contents of well-watered roots and sucrose contents of drought-stressed leaves were notably higher in AM than in non-AM seedlings. K⁺ and Ca²⁺ levels in AM leaves and roots were greater than those in non-AM leaves and roots, while AM symbiosis did not affect the Mg²⁺ level. AM seedlings accumulated less proline than non-AM seedlings. AM symbiosis altered both the allocation of carbohydrate to roots and the net osmotic solute accumulations in response to drought stress. It is concluded that AM colonization enhances osmotic solute accumulation of trifoliate orange seedlings, thus providing better osmotic adjustment in AM seedlings, which did not correlate with proline but with K⁺, Ca²⁺, Mg²⁺, glucose, fructose and sucrose accumulation.     

Thidiazuron-induced high-frequency direct shoot organogenesis of <Emphasis Type="Italic">Cannabis sativa</Emphasis> L.

Induction of high-frequency shoot regeneration using nodal segments containing axillary buds from a 1-yr-old mother plants of Cannabis sativa was achieved on Murashige and Skoog (MS) medium containing 0.05–5.0 μM thidiazuron. The quality and quantity of regenerants were better with thidiazuron (0.5 μM thidiazuron) than with benzyladenine or kinetin. Adding 7.0 μM of gibberellic acid into a medium containing 0.5 μM thidiazuron slightly increased shoot growth. Elongated shoots when transferred to half-strength MS medium supplemented with 500 mg l⁻¹ activated charcoal and 2.5 μM indole-3-butyric acid resulted in 95% rooting. The rooted plants were successfully acclimatized in soil. Following acclimatization, growth performance of 4-mo-old in vitro propagated plants was compared with ex vitro vegetatively grown plants of the same age. The photosynthesis and transpiration characteristics were studied under different light levels (0, 500, 1,000, 1,500, or 2,000 μmol m⁻² s⁻¹). An increase in photosynthesis was observed with increase in the light intensity up to 1,500 μmol m⁻² s⁻¹ and then decreased subsequently at higher light levels in both types of plants. However, the increase was more pronounced at lower light intensities below 500 μmol m⁻² s⁻¹. Stomatal conductance and transpiration increased with light intensity up to highest level (2000 μmol m⁻² s⁻¹) tested. Intercellular CO₂ concentration (C _i) and the ratio of intercellular CO₂ concentration to ambient CO₂ (C _i/C _a) decreased with the increase in light intensity in both in vitro as well as ex vitro raised plants. The results show that in vitro propagated and hardened plants were functionally comparable to ex vitro plants of same age in terms of gas and water vapor exchange characteristics, within the limits of this study.