Joo Young Cha

Arbuscular mycorrhizal colonization of tree species grown in peat swamp forests of Central Kalimantan, Indonesia

Abstract Arbuscular mycorrhizas improve the growth and nutrient uptake of plants and are formed in 80% of all land plants. Little information is available on the status of arbuscular mycorrhizas in tropical soils. The objective of this study was to clarify mycorrhizal colonization of tree species grown in tropical peat soils. Seedlings of 22 tree species in 14 families grown in a peat swamp forest of Central Kalimantan, Indonesia were collected in 2000 and 2001. Roots were stained with 0.05% aniline blue and arbuscules, vesicles and internal hyphae were observed under a compound microscope. Seventeen of 22 species showed arbuscular mycorrhizal colonization. Arbuscular mycorrhizal colonization was observed for the first time in roots of Shorea teysmanniana, Shorea balangeran, Shorea uliginosa (Dipterocarpaceae), Calophyllum sclerophyllum, Calophyllum soulattri (Guttiferae), Cratoxylum arborescens (Guttiferae), Tetramerista glabra (Tetrameristaceae), Palaquium gutta (Sapotaceae), Melastoma melabathricum (Melastomataceae), Gonystylus bancanus (Thymelaeaceae), Hevea brasiliensis (Euphorbiaceae) and Campnosperma auriculatum (Anacardiaceae). C. soulattri, C. arborescens, G. bancanus, Acacia mangium, M. melabathricum and H. brasiliensis showed a percentage mycorrhizal colonization of 50% or higher. No arbuscular mycorrhizal colonization was found in Hopea mengarawan (Dipterocarpaceae), Koompassia malacensis (Caesalpiniaceae), Tristaniopsis whiteana (Myrtaceae), Combretocapus rotundatus (Rhizophoraceae) and Dyera costulata (Apocynaceae). It is suggested that inoculation of arbuscular mycorrhizal fungi can improve the early growth of some tree species grown in peat swamp forests and this will be expected as a key technology to rehabilitate disturbed peatlands.

The dextromethorphan analog dimemorfan attenuates kainate‐induced seizures via σ1 receptor activation: comparison with the effects of dextromethorphan

1 In a previous study, we demonstrated that a dextromethorphan analog, dimemorfan, has neuroprotective effects. 2 Dextromethorphan and dimemorfan are high‐affinity ligands at σ1 receptors. Dextromethorphan has moderate affinities for phencyclidine sites, while dimemorfan has very low affinities for such sites, suggesting that these sites are not essential for the anticonvulsant actions of dimemorfan. 3 Kainate (KA) administration (10 mg kg−1, i.p.) produced robust convulsions lasting 4–6 h in rats. Pre‐treatment with dimemorfan (12 or 24 mg kg−1) reduced seizures in a dose‐dependent manner. Dimemorfan pre‐treatment also attenuated the KA‐induced increases in c‐fos/c‐jun expression, activator protein (AP)‐1 DNA‐binding activity, and loss of cells in the CA1 and CA3 fields of the hippocampus. These effects of dimemorfan were comparable to those of dextromethorphan. 4 The anticonvulsant action of dextromethorphan or dimemorfan was significantly counteracted by a selective σ1 receptor antagonist BD 1047, suggesting that the anticonvulsant action of dextromethorphan or dimemorfan is, at least in part, related to σ1 receptor‐activated modulation of AP‐1 transcription factors. 5 We asked whether dimemorfan produces the behavioral side effects seen with dextromethorphan or dextrorphan (a phencyclidine‐like metabolite of dextromethorphan). Conditioned place preference and circling behaviors were significantly increased in mice treated with phencyclidine, dextrorphan or dextromethorphan, while mice treated with dimemorfan showed no behavioral side effects. 6 Our results suggest that dimemorfan is equipotent to dextromethorphan in preventing KA‐induced seizures, while it may lack behavioral effects, such as psychotomimetic reactions.

Inoculation with the ectomycorrhizal fungi Pisolithus arhizus and Scleroderma sp. improves early growth of Shorea pinanga nursery seedlings

Abstract.Trees of the family Dipterocarpaceae are the dominant trees in Southeast Asian tropical forests where they play an important ecological role and are also important commercially. An experiment was conducted to determine the effect of ectomycorrhizal fungi on the growth of dipterocarp species in peat soils. Seedlings of Shorea pinanga were inoculated with spores of two ectomycorrhizal fungi, Pisolithus arhizus and Scleroderma sp. were grown in pots containing sterilized peat soil for 7 months. The percentage of ectomycorrhizal colonization on S. pinanga exceeded 86%. Colonization of S. pinanga roots by ectomycorrhizal fungi resulted in increased shoot height, stem diameter, number of leaves, and shoot fresh and dry weight. Survival rates of S. pinanga were greater for inoculated seedlings than control seedlings. These results suggest that inoculation of ectomycorrhizal fungi can improve the early growth of S. pinanga grown in tropical forests and that this technique will accelerate the rehabilitation of degraded dipterocarp forests.

Biological species and morphological characteristics of Armillaria mellea complex in Hokkaido: A. sinapina and two new species, A. jezoensis and A. singula.

Three intersterility groups ofArmillaria mellea sensu lato were discovered by examining all pairwise combinations of monosporous isolates of basidiomes collected in Hokkaido. One of them, group IV, was identified asA. sinapina by mating it with tester strains. Two new species, groups III and V, were namedA. jezoensis andA. singula, respectively. Their morphological forms and the ecology of their basidiomes are described.

A note on Armillaria mellea subsp. nipponica subsp. nov. in Japan

Basidiomes of homothallicArmillaria mellea complex were discovered in the forests of Hokkaido. Their monosporous isolates showed partial compatibility with North AmericanA. mellea s. str. haploid testers. The morphological characteristics of basidiomes differed from other temperateA. mellea s. str. in several aspects. Here, JapaneseA. mellea s. str. is reclassified asA. mellea subsp.nipponica and its basidiome morphologies and habitats are described.

The occurrence and diversity of ectomycorrhizas of Larix kaempferi seedlings on a volcanic mountain in Japan

Larix kaempferi seedlings, in the process of becoming established during the revegetation process following a volcanic eruption, were assessed for the types, occurrence patterns and diversity of their ectomycorrhizas along an elevation gradient. On the basis of macro- and microscopic characteristics, 12 types of ectomycorrhizas were classified. In general, ectomycorrhizal types differed more by site than by seedling age. The majority of root systems of seedlings with an age ranging from 1 to 5 years were colonized by 1 or 2 types of mycorrhizal fungi at low and intermediate elevations, 2 or 3 types at a higher elevation. Under the more stressed environments of high and intermediate elevations, the mean d.w. of 1 yr old seedlings, 40% of which were colonized by 3 or 4 mycorrhizal fungi, was double the weight of the same aged seedlings at lower elevation sites, only 10% of which were colonized by 3 or 4 mycorrhizal fungi. The correspondence between the type and frequency of mycorrhizas, the elevation gradient and litter accumulation suggests that change in litter accumulation along gradient may influence not only mycorrhizal types and their occurrence, but also the diversity of mycorrhizas on one seedling. Diversity of mycorrhizas on the same seedling is assumed to be critical for the establishment of seedlings from the very beginning on stressed sites, and may also be influenced by the availability of nutrients. The more intensive competition between mycorrhizas that occurs due to a reduction in the food source (tip roots) shared by the mycorrhizal fungi with similar resource requirements, results in frequent co-occurrence of mycorrhizas in the same root system or even the same root tip. As a result, the diversity of mycorrhizal types seems to become simplified as the seedlings age.

Armillaria jezoensis, a new symbiont of Galeola septentrionalis (Orchidaceae)in Hokkaido

NineArmillaria isolates obtained from the roots ofGaleola septentrionalis in Hokkaido were identified asA. jezoensis by means of mating tests. Cultures of these isolates were similar in colony morphology, mycelial growth and rhizomorph formation on each of malt extract-dextrose agar (MDA), potato-dextrose agar (PDA), andG. septentrionalis root extractdextrose agar (GDA) media, showing better mycelial growth and rhizomorph formation on GDA medium.

Dimemorfan prevents seizures induced by the L-type calcium channel activator BAY k-8644 in mice

A dextromethorphan (3-methoxy-17-methylmorphinan) analog, dimemorfan (3-methyl-N-methylmorphinan) that is not metabolized to dextrorphan [3-hydroxy-17-methylmorphinan, which induces phencyclidine (PCP)-like behavioral effects], attenuates maximal electroshock seizures. However, the pharmacological mechanism of action of dimemorfan remains to be determined. In this study, we assessed the locomotor activity mediated by these morphinans. Circling behavior was pronounced in mice treated with PCP or dextrorphan, while animals treated with dextromethorphan exhibited moderate behaviors. Dimemorfan did not show any significant behavioral effects. We used BAY k-8644 (an L-type Ca2+ channel agonist in the dihydropyridine class) to explore the effects of dextromethorphan and dimemorfan on the convulsant activity regulated by calcium channels. Intracerebroventricular injection of BAY k-8644 (37.5 microg) significantly induced seizures in mice. As with dextromethorphan (6.25 or 12.5 mg/kg), dimemorfan (6.25 or 12.5 mg/kg) pretreatment significantly attenuated BAY k-8644-induced seizures in a dose-dependent manner. BAY k-8644-induced seizure activity paralleled increased expression of c-fos and c-jun, AP-1 DNA binding activity, and fos-related antigen immunoreactivity. Pretreatment with dextromethorphan or dimemorfan significantly attenuated the expression induced by BAY k-8644. Therefore, our results suggest that the anticonvulsant effects of dextromethorphan and dimemorfan are mediated, at least in part, via L-type calcium channel, and that dimemorfan is equipotent to dextromethorphan in preventing BAY k-8644-induced seizures, while it lacks behavioral side effects related to psychotomimetic reactions.

Identification of Armillaria species from Hokkaido by analysis of the intergenic spacer (IGS) region of ribosomal DNA using PCR-RFLP.

The intergenic spacer (IGS) region, which is located between the 3′ end of 26S ribosomal DNA (rDNA) and the 5′ end of 5S rDNA, of sixArmillaria species from Hokkaido was investigated using polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP). Restriction with onlyAlu I could distinguishA. mellea subsp.nipponica from the other species. WithAlu I andDde I,A. ostoyae andA. gallica could be distinguished from the other species. Digestion withAlu I resulted in two patterns (types A and B) ofA. singula and three patterns (types A, B, and C) ofA. jezoensis. One pattern (type B) of the former species and two patterns (types B and C) of the latter species were each different from those of the other species.Armillaria sinapina gave only oneAlu I digestion pattern, which was identical to that ofA. jezoensis (type A) andA. singula (type A). However, by digestion withDde I,A. singula (type A) could be distinguished fromA. jezoensis (type A) andA. sinapina.

Genetic variation in Armillaria mellea subsp. nipponica estimated using IGS-RFLP and AFLP analyses

In this study, genetic variation of Armillaria mellea subsp. nipponica was estimated using intergenic spacer-restriction fragment length polymorphism (IGS-RFLP) and amplified fragment length polymorphism (AFLP) analyses. Four IGS-RFLP phenotypes were produced, of which two have never been reported. AFLP analysis suggested that the 11 isolates used could be divided into five subgroups, and the isolates within the same subgroup were distributed throughout a relatively large area in Japan. A parental isolate and its offspring (single-spore isolates) showed an almost identical AFLP profile to each other. These results suggest that the large distribution of the isolates within the same subgroup were established via the basidiospore from a common parental strain.