Wetland development in early stages of volcanic succession

Abstract. Wetland vegetation developed in the crater of Mount Usu, northern Japan, soon after the 1977–1978 eruptions which destroyed the vegetation. The cover of each species was measured in 1994 in 118 50 cm × 50 cm plots situated in transects and related to environmental factors (elevation, water depth, soil texture, soil compaction, soil organic matter, and soil pH) to clarify vegetation development. Five vegetation types were recognized dominated by Eleocharis kamtschatica, Equisetum arvense, Lythrum salicaria, Juncus fauriensis and Phragmites australis respectively. Sedge/grass marsh and reed swamp dominated deep-water sites; willow swamp and wet meadow vegetation characterized shallow-water sites, indicating that vegetation zonation developed soon after the eruption. Since those wetland plants were derived neither from seed banks nor from vegetative propagules, they had to immigrate from outside the summit areas. However, except for willows, most species lack the ability for long-distance dispersal. Late successional species, such as P. australis established in the early stages of the primary succession. The water depth varied by 27.5 cm among the plots. Coarse soil particles accumulated, and pH (5.22–6.55) was low on the elevated sites. Organic matter ranged from 2.8 % to 19.1 %, and was high on the elevated sites. Water depth was responsible for the establishment of large-scale vegetation patterns, while edaphic factors, i.e. soil compaction, pH, and organic matter, were determinants of small-scale vegetation patterns. Among the edaphic factors, soil compaction appeared to have a strong influence on vegetation development.     

Population dynamics of four understorey shrub species during a 7‐yr period in a primary beech forest

Abstract. Shrubs persist in the understorey layer of forests throughout their lives, while tall trees remain there only during the juvenile stage and then grow into the canopy layer. Thus demographic parameters (recruitment‐, mortality‐, and growth‐rates) of shrub species are expected to differ from those of tall tree species. We investigated aspects of the demography of four dominant deciduous‐shrub species (Viburnum furcatum, Lindera umbellata var. membranacea, Magnolia salicifolia, and Hydrangea paniculata) in Fagus crenata forests at the beginning and at the end of a 7‐yr period in a 1‐ha permanent plot. For each species, the number of stems changed little (within ± 10%) during the study period, while total basal area increased markedly (11.7–33.8%), because (1) new stems continuously recruited by vegetative growth replaced the substantial number of dead stems, and (2) vegetative stems grew vigorously, probably due to nutrient support from parents. The results indicate that these four understorey shrub species have high ability to maintain their population size in the shaded forest understorey. While in each species more than half of the dead stems were standing dead, a substantial proportion of the dead stems (9.0–38.5%) showed signs of mechanical damage, such as stem breakage and suppression by fallen branches or trees. Snow pressure that resulted in decumbent stems was also an important mortality agent for V. furcatum (20.7%) and L. umbellata var. membranacea (5.6%). Probability of damage was constant across all DBH‐classes for all study species. In each species, newly recruited stems and dead stems were spatially aggregated, largely due to habits of vegetative growth and mechanical damage, respectively. This study revealed that several demographic traits, resulting from recruitment by vegetative growth and death by mechanical damage, were shrub‐species specific and markedly different from those of tall tree species.     

Impact of site‐induced mouse caching and transport behaviour on regeneration in Castanea crenata

Abstract. Dispersal and retrieval site selection by mice, transport distance, cache depth, and emergence and survival of seedlings of Castanea crenata (Japanese chestnut) were investigated by a magnet‐locating experiment in two habitat conditions (gap vs. forest understorey). Magnets were inserted into nuts (n= 450) and the nuts placed in the edge of forest gaps. Although wood mice (Apodemus speciosus and A. argenteus) initially buried nuts singly in shallow surface caches near the nut source, by the following spring these cached nuts were retrieved and re‐cached in larger, deeper caches farther from the source, particularly in forest understories, probably to reduce the threat of pilferage. All the nuts cached in the forest understories were consumed, but 4 seedlings emerged in gaps, apparently because of lower foraging activity in the gaps by the mice. Seed size was not correlated with cache depth or cache site selection. With increasing seed size, transport distance increased, particularly in gaps, possibly due to a greater potential energy gain (relative to handling cost to the cacher), or to attempts to prevent density‐ or mass‐dependent loss of caches by other foragers. Variable seed dispersal behaviour based on variation in seed size may influence the chances of colonization and distribution of the light‐demanding Castanea trees in mosaic landscapes and may play an important role in community organization and dynamics.     

野葛离体培养生产异黄酮类化合物研究进展

野葛含有大量的异黄酮类化合物,其中葛根素是葛属植物特有药用成分。该文综述了野葛细胞和器官培养生产异黄酮类化合物的研究现状以及各种影响葛根素等异黄酮类化合物产生的因素,并评述葛根素的应用前景。     

Exogenous auxin effects on growth and phenotype of normal and hairy roots of Pueraria lobata (Willd.) Ohwi

Pueraria lobata hairy roots have faster elongationand more branches than normal roots. The responses of hairy roots and normalroots to treatment with three auxins, indole-3-acetic acid (IAA),indole-3-butyric acid (IBA), and naphthalene acetic acid (NAA) were different.In normal roots, all three auxins strongly stimulated lateral root formation atall tested concentrations. Responses to IAA and IBA in primary root growth andlateral root elongation were similar and depended on concentration; promotionat0.1 M, no effect at 1.0 M, and inhibition at2.5 M. In hairy roots, lateral root formation varied inresponseto the different auxins, i.e. depressed by NAA, unaffected by IAA, and promotedby IBA. Primary root growth was slightly inhibited by IBA and was unaffected byIAA. However, mean lateral root length was reduced in response to IAA and IBA.Only NAA exerted strong inhibition on primary and lateral root elongation inboth root types. The similar free IAA and conjugated IAA content but quitedifferent basal ethylene production and biosynthesis in hairy and normal rootssuggested different mechanisms of response to exogenous auxins in the two roottypes.     

Succession of secondary forests affected by pine wilt disease in western Japan followed on vegetation maps

Abstract. Succession, changes in the distribution pattern of forest vegetation, and Pinus forest survival following pine wilt disease were clarified based on phytosociological analysis and vegetation maps. Survival of Pinus forests was restricted to the early successional stages, which were located on ridges and the upper part of slopes. Subsequent to pine wilt disease, the succession progressed from early to late substages of Pinus forest, mixed deciduous and evergreen Quercus, to evergreen Quercus forest. Succession occurs in abandoned pine forests which apparently are in a bad state and are vulnerable to attacks by pine wilt disease.     

Spatial distribution of Eurya japonica in an old-growth evergreen broad-leaved forest,SW Japan

Abstract. The spatial distribution of Eurya japonica, an evergreen understorey species, was studied on a 4-ha permanent plot in an old-growth, temperate, evergreen broad-leaved forest in southwestern Japan. The pattern of spatial dispersion varied with size class, the environmental heterogeneity produced by tree-fall gaps and microtopography and the scale of observation. Seedlings (0.05 to < 0.5 m high) had the most clumped distributions, followed by saplings (0.5 to 1.3 m high) and adults (> 1.3 m). Individuals were more clumped at the smallest grid size, 1.56m × 1.56 m, and became less clumped as grid size increased for all size classes. On grids of less than 6.25 m × 6.25 m, no spatial correlations were found between seedlings and larger size classes; positive spatial correlations were found between saplings and adults at this scale. Abundant seedlings appeared in tree-fall gaps formed by uprooted trees, but seedlings were frequent on ridge tops and upper slopes. Saplings and adults also occurred on upper slopes, but their spatial distribution had little relation to current tree-fall gaps. The spatial distribution of E. japonica individuals was largely attributed to the distribution of tree-fall gaps and the differential responses to microtopographic variation by individuals at different size classes.     

三齿草藤(Vicia bungei Ohwi)凝集素的亲和层析纯化及其部分性质的研究

用Sephadex G-100或猪甲状腺球蛋白-对氨基苯砜乙基-交联琼脂作亲和吸附剂,均可从三齿草藤(Vicia Bungei Ohwi)的种子中分离纯化出三齿草藤凝集素。该凝集素经连续或不连续系统聚丙烯酰胺凝胶电泳均显示出单一蛋白带;糖蛋白染色法证实为糖蛋白;SDS-聚丙烯酰胺凝胶电泳测定其分子量为24,600,凝集素浓度为1.95微克/毫升时就能凝集兔红细胞;但对人ABO型血细胞不发生凝集作用;其对兔红细胞的凝集作用可被D-Man、D-GlcNA和D-GIC所抑制;它也是一种促有丝分裂原。     

Isoprene emission by plants is affected by transmissible wound signals

Isoprene (2-methyl 1,3-butadiene) is emitted from many plants, but the signals regulating isoprene emission are unknown. Mounting leaves in a gas exchange chamber or taking small leaf punches for biochemical analysis was found to reduce the rate of isoprene emission (Loreto & Sharkey 1993). This phenomenon was investigated by putting terminal leaflets of velvet bean (Mucuna deeringeniana L.) and kudzu [Pueraria lobaia (Willd) Ohwi.] into a gas exchange chamber and monitoring isoprene emission and photosynthesis. Lateral leaflets or remote leaves were then wounded or mechanically stimulated. The rate of isoprene emission was reduced after 1 min by up to 75% by burning a lateral leaflet with a match. Even a 7 ms^?1 (25km h^?1) wind imposed on a lateral leaflet reduced isoprene emission from the terminal leaflet by 18%. Photosynthesis rates were either unaffected by these treatments or reduced more slowly than isoprene emission rates, indicating that the effect of isoprene emission rates was not a consequence of changes in photosynthetic activity. Isoprene emission from a terminal leaflet was reduced by burning leaves above and below the monitored leaflet when on the same stem. The effect was much reduced if the burned leaf (all three leaflets) was on a different stem from the monitored leaflet. Reduction of the rate of isoprene emission was observed even when the burned leaf was 52 cm distant from the measured leaflet. Increasing the distance between the stressed leaf and the monitored leaf caused the effect to be slower and smaller. It is speculated that a signal is generated by wounding which propagates through the plant at 1.3 mm s^?1. This velocity was consistent throughout the measurements and is similar to the rate of propagation of electrical signals such as action potentials and variation potentials. The effect of the environmental stress, and particularly the wind effect, can be frequent in nature and should be considered when estimating local and regional emission of isoprene for modelling atmospheric chemistry. If leaf samples used for isoprene determination are exposed to the type of stress we investigated, isoprene emission inventories based on leaf level measurements will be underestimated.