Aucuba Japonica Research Articles

The examination of the broadleaf evergreen ornamental shrub species in Keszthely

The examination of production possibilities of woody ornamental shrubs (originating from warmer regions than our country) commenced with the financial support of the INTERREG IIIA Slovenia – Hungary – Croatia programme at the Department of Horticulture of the University of Pannonia’s Georgikon Faculty in spring 2007. Our examinations focused on the appearance of species in our country as well as on their frost resistance abilities. The species participating in the experiment are as follows: Abelia grandiflora, Aucuba japonica ’Rozzanie’, Calycanthus floridus, Cotoneaster franchettii, Elaeagnus pungens ’MaculataAurea’, Ilex cornuta, Ligustrum sinense, Ligustrum texanum, Nandina domestica, Osmanthus heterophyllus, Perovskia atriplicifolia, Phyllyrea angustifolia, Photinia fraseri ’Red Robin’, Prunus lusitanica, Sarcococca hoockeriana, Spartium junceum, Teucrium fruticans, Viburnum cinnamonifolium, Viburnum tinus.

Botanical Transculturation: Japanese and British Knowledge and Understanding of Aucuba japonica and Larix leptolepis 1700-1920

Abstract Two species, Aucuba japonica and Larix leptolepis , introduced from Japan to Britain provide examples of different types of transculturation. We demonstrate the complexity of the interchange of Japanese and European knowledge of natural history in the late eighteenth and early nineteenth centuries. The importance of this exchange and interaction was consciously underplayed by those recounting the discovery of plants by European collectors. We identify different modes of transculturation. Initially, most introduced plants are celebrated as exotic but after a period of testing the most popular plants become culturally assimilated. Some plants may, at a later stage, become physically hybridised. The hardiness of the plants was a crucial factor for successful cultural assimilation. In Britain, Aucuba japonica was initially celebrated as an exotic but over time became culturally assimilated, particularly in town and city gardens. Larix leptolepis also became assimilated through its economic timber value and became physically hybridised with the European larch in Scotland to produce Larix eurolepis .

Morphology and taxonomy of five Cephaleuros species (Trentepohliaceae, Chlorophyta) from Japan, including three new species

Suto Y. and Ohtani S. 2009. Morphology and taxonomy of five Cephaleuros species (Trentepohliaceae, Chlorophyta) from Japan, including three new species. Phycologia 48: 213–236. DOI: 10.2216/07-31.1Five species of the genus Cephaleuros, including three new species, were collected on leaves, green twigs, and fruits of various woody plants from Japan. The three new species grow subcuticularly. Cephaleuros aucubae sp. nov. forms thalli in a thin layer or a raised spot showing open-filamentous growth, growing only on Aucuba japonica. Cephaleuros japonicus sp. nov. forms more or less a circular disk with pseudoparenchymatous growth in the central portion and open-filamentous growth in the marginal portion. It is one of the most common species in Japan, growing frequently on Camellia japonica, Cleyera japonica, Eurya japonica, and Symplocos lucida. Cephaleuros microcellularis sp. nov. forms a circular raised disk with pseudoparenchymatous growth, growing on Persea japonica and Symplocos lucida. Small filamentous and gametic cells and concentric zonal rings of gametangia and setae characterize the species. We present the first report of Cephaleuros biolophus in Japan. This species is characterized by subcuticular, subepidermal, and intramatrical growth, growing frequently on Castanopsis cupsidata var. sieboldii, Myrica rubra, and Quercus spp. The sporangiophores which project from the lower leaf surface, produce head cells and sporangiate-laterals terminally and laterally. Cephaleuros virescens, which so far has been the only known species in Japan, grows subcuticularly and forms a circular raised disk with pseoudoparenchymatous growth, inhabiting frequently Magnolia grandiflora and Persea thunbergii.

The leaf anatomy of a broad‐leaved evergreen allows an increase in leaf nitrogen content in winter

In temperate regions, evergreen species are exposed to large seasonal changes in air temperature and irradiance. They change photosynthetic characteristics of leaves responding to such environmental changes. Recent studies have suggested that photosynthetic acclimation is strongly constrained by leaf anatomy such as leaf thickness, mesophyll and chloroplast surface facing the intercellular space, and the chloroplast volume. We studied how these parameters of leaf anatomy are related with photosynthetic seasonal acclimation. We evaluated differential effects of winter and summer irradiance on leaf anatomy and photosynthesis. Using a broad-leaved evergreen Aucuba japonica, we performed a transfer experiment in which irradiance regimes were changed at the beginning of autumn and of spring. We found that a vacant space on mesophyll surface in summer enabled chloroplast volume to increase in winter. The leaf nitrogen and Rubisco content were higher in winter than in summer. They were correlated significantly with chloroplast volume and with chloroplast surface area facing the intercellular space. Thus, summer leaves were thicker than needed to accommodate mesophyll surface chloroplasts at this time of year but this allowed for increases in mesophyll surface chloroplasts in the winter. It appears that summer leaf anatomical characteristics help facilitate photosynthetic acclimation to winter conditions. Photosynthetic capacity and photosynthetic nitrogen use efficiency were lower in winter than in summer but it appears that these reductions were partially compensated by higher Rubisco contents and mesophyll surface chloroplast area in winter foliage.

A Mechanical Plant Defense Defines the Opening of a Phenological Window for Gall Induction byAsphondylia aucubae(Cecidomyiidae: Diptera)

Many insect herbivores can only use hosts during a specific phenological stage, i.e., a phenological window. Previous studies have primarily examined the effects of these windows on insect herbivores, but relatively little is known about the mechanisms controlling the phenological windows. In most gall insect systems, phenological windows have been attributed to the short duration of physiologically active plant tissues that induce gall formation (reactive plant tissue). In the fruit gall midge, Asphondylia aucubae Yukawa and Ohsaki, and the host plant (i.e., Aucuba japonica) system, the disappearance of reactive plant tissue closes the phenological window, but its presence does not define the opening of the window. The hard endocarp of the fruit covers most potential oviposition sites just before the midge emergence season, but decreases in proportional cover during the emergence season. We experimentally manipulated the timing of oviposition relative to fruit development. Midges that emerged earliest and attacked fruits during their earliest developmental stages were unable to oviposit because of intact, hard endocarps, whereas their counterparts that emerged later could oviposit more readily through cracks in the endocarp. We noted possible oviposition avoidance behavior and the necessity of more frequent (repeated) ovipositor insertions to intensively stimulate the decreased reactive tissues during the latter half of the emergence season. Overall, our results indicated that the fragmentation of the defensive, hard endocarp of the host plant defines the opening of the phenological window in this plant-herbivore system.

Development of SCAR markers for sex determination in the dioecious shrub Aucuba japonica (Cornaceae)

Two sex-linked fragments were identified by RAPD analyses in the dioecious diploid shrub Aucuba japonica var. ovoidea and were converted into markers of male-specific sequence characterized amplified region (SCAR) markers. PCRs using the primers designed in this study correctly discriminated 24 flowering males and 24 flowering females at higher annealing temperatures (SCAR markers OPA10-424 at 55 degrees C and OPN11-1095 at 65 degrees C), although at relatively low annealing temperatures, the fragments were amplified in both males and females. These SCAR primers were also tested to see whether they were applicable to sex identification in the conspecific tetraploid Aucuba japonica var. japonica. One set pf SCAR primers could be used for sex identification even in this tetraploid variety, although the other failed. The SCAR markers developed in this study will provide a powerful tool in identifying the sex of immature plants of dioecious A. japonica, which is a commercially valuable shrub due to its conspicuous fruits.

Habitat niche specialization in an understory species in a warm temperate forest

AbstractRelationships between microhabitat variables; understory light conditions in summer and winter, altitude, slope inclination and topographic categories (valley, ridge, and slope) and the distribution of Aucuba japonica Thunb. (Cornaceae), a common understory shrub species in Japan were examined using non‐contagious 66, 20 × 20 m2 quadrats. The Morishita's Iδ suggested that A. japonica distributions were strongly heterogeneous among the quadrats. Therefore positive spatial autocorrelation of A. japonica at a within‐quadrat level (≤20 m) was obvious. Moran's I statistics showed a significant positive spatial autocorrelation in A. japonica abundance within the distance shorter than 60 m. But the partial Mantel tests suggested that the mass effect from neighboring quadrats would little explain A. japonica abundance in a quadrat. The partial Mantel tests also clearly showed that A. japonica distributions were strongly structured by topography and understory light conditions. Using Monte Carlo randomization tests, we found that A. japonica was aggregately distributed in quadrats in valley which were covered by deciduous canopies. Better understory light conditions in winter together with valley edaphic conditions may increase the abundance of A. japonica there. It is concluded that habitat niche specialization is important in structuring distribution of A. japonica in this forest community.

Loss of Integument in Maturing Fruits Prevents Gall Induction by the Midge,Asphondylia aucubae(Cecidomyiidae: Diptera)

Gall-inducing insects require close phenological synchrony with their host plants. It has been hypothesized, but seldom shown, that this is because, to induce galls the insects require physiologically active plant tissue, which exists only during a limited stage of plant development, forming a phenological window for gall induction. We examined this hypothesis in the system of a shrub, Aucuba japonica Thunberg, and its specialist fruit gall midge Asphondylia aucubae Yukawa et Ohsaki. Female midges lay eggs into young host fruit and stimulate the integument, a reactive tissue in the fruit, to induce galls. Our results showed that the lifetime of the integument defines the end point of the phenological window. The integument was rapidly degenerated as fruit matured, and eventually disappeared. The degeneration of the integument began simultaneously with the adult emergence season of the midge, and was greatly accelerated in the latter half of the adult midge season, forming an apparent end point of the window. We experimentally caged host infructescences to keep them free from midge oviposition, and released one field collected ovipositing female into each cage. When the treatment was performed before the end point of the window, gall induction success of the midge was much higher. The integument, however, does not define the start point of the window because gall induction success was not lower when the midge was released very early in the adult emergence season. We suggest that the start point is defined by another factor, likely the hard endocarp of the fruit.

Density‐dependent egg mortality in early stages of gall induction by the fruit gall midge Asphondylia aucubae Yukawa and Ohsaki

AbstractDensity‐dependent mortality has been considered a symptom of intraspecific competition. We examined the occurrence of such mortality in the early stages of gall induction by the gall midge Asphondylia aucubae Yukawa et Ohsaki (Diptera: Cecidomyiidae). Female midges deposit eggs into young fruit of the dioecious shrub Aucuba japonica Thunberg to induce gall formation. Each host fruit received 0–67 eggs (mean 18.5 eggs) from multiple females, whereas established galls each contained one to ten larvae. Midges suffered intense mortality (65–90%) at the egg stage. Egg mortality occurred even in fruit in which no larvae had hatched, suggesting that this mortality cannot be wholly attributed to larval interference. Egg mortality was affected by fruit size, i.e., resource capacity. Midges distributed more eggs in larger fruit. Egg mortality increased as the per‐fruit density increased relative to fruit size. In contrast, the mortality of hatchlings was density‐independent. Our results suggest that A. aucubae intensely compete for gall‐induction substrates, which are spatiotemporally rare resources.

Anicemycin, a New Inhibitor of Anchorage‐Independent Growth of Tumor Cells from Streptomyces sp. TP‐A0648.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Shoot morphology of Aucuba japonica incurred by anisophylly: ecological implications

Anisophylly, having leaves different in size and/or shape, was quantified in adult Aucuba japonica and simulations were carried out to evaluate the effects of anisophylly on the extent of self-shading at the single-shoot level as well as at the whole-canopy level. Clear anisophylly was observed in the individual after switching from the single-stemmed juvenile stage to the multi-stemmed adult stage. In such plants, leaf area in the canopy abruptly increased. The effective display of adult foliage involved a variety of morphological changes in addition to anisophylly, most prominently reduction in leaf size compared to juveniles. The simulation results indicate that diversity of leaf size and shape is an effective means of minimizing self-shading as well as allowing the efficient exploitation of a larger canopy volume in adult plants. Anisophylly also increased the biomass use efficiency of individual plants at maturity. Taken together, having diverse leaf forms is superior to having a single leaf form for maximizing area acquisition and for efficiently filling the acquired area. We therefore conclude that the anisophylly expressed in A. japonica is adaptive.

Plasticity in leaf-area density within the crown of Aucuba japonica growing under different light levels

We assessed leaf-area density (LAD; m(2) m(-3)) within the crown of Aucuba japonica (Cornaceae) growing under different light regimes and analyzed the components of crown architecture that most influenced variation in LAD. At a whole-crown level, extension-unit (EU) density (EUs/m(3)) had the greatest impact on LAD. The number of leaves per unit EU length and EU length had a wide range of impacts depending on the degree of crowding of foliage on the EU. Leaf size had a lesser impact on LAD. LAD was higher in the uppermost crown and declined towards the base. The non-uniformity of LAD among crown layers was much greater under high irradiance. Individuals under high irradiance achieved greater LAD by increased branching, well-marked EU dimorphism and a larger number of leaves per unit EU length; the reverse was true for the individuals under low irradiance. We identified two distinct modes of growth response to light regime. Under high irradiance, individuals responded by differential growth between the layers of crowns with the lower crown suppressed and growth in the upper crown increased. Conversely, shaded individuals did not respond by differential growth between crown layers.

Anicemycin, a New Inhibitor of Anchorage-independent Growth of Tumor Cells from Streptomyces sp. TP-A0648

The anchorage-independence of cells is closely related to their tumorigenicity. In the screening of inhibitors of anchorage-independent growth of tumor cells, anicemycin was isolated from the fermentation broth of an actinomycete strain TP-A0648. The producing strain was isolated from a leaf of Aucuba japonica collected in Toyama, Japan and identified as Streptomyces sp. based on the taxonomic data. The structure of anicemycin was elucidated as a new analog of spicamycin by NMR and MS analysis. Anicemycin inhibited the anchorage-independent growth of the human ovary cancer SKOV-3 cells with an IC50 of 0.015 microM about three times more potently than their anchorage-dependent growth.

Seasonal changes in light and temperature affect the balance between light harvesting and light utilisation components of photosynthesis in an evergreen understory shrub

In a temperate climate, evergreen species in the understory are exposed to large changes in photosynthetic photon flux density (PPFD) and temperature over the year. We determined the photosynthetic traits of leaves of an evergreen understory shrub Aucuba japonica at three sites at monthly intervals: understorys of a deciduous forest; an evergreen forest; and a gap in a mixed forest. This set up enabled us to separate the effects of seasonal change in PPFD and temperature on photosynthetic acclimation under natural conditions. The effects of PPFD and temperature were analysed by simple and multiple regression analyses. The amounts of light utilisation components (LU), represented by nitrogen and rubisco contents per area, were higher in winter, when temperature was low and PPFD was high. The LU relative to the amount of light harvesting components (LH), represented by chlorophyll a/b and rubisco/chlorophyll ratios, and the inverse of chlorophyll/nitrogen ratio were also higher in winter. We quantified the effects of PPFD and temperature on the LU and LH components. Across sites PPFD had stronger effects than air temperature, while within a site temperature had stronger effects on photosynthetic acclimation. We concluded that the photosynthetic apparatus is strongly affected by the prevailing PPFD at the time of leaf development. Within a given light regime, however, plants acclimated by increasing LU relative to LH primarily in response to temperature and to a lesser extent to PPFD.

Anisophylly inAucuba japonica(Cornaceae): An outcome of spatial crowding in the bud

Anisophylly in Aucuba japonica Thunb. occurs exclusively in axillary buds on shoots of individuals that have reached reproductive maturity; juvenile plants or sprouts and shoots from terminal vegetative buds on adult plants are isophyllous. The initially smaller leaf primordium in each anisophyllous leaf pair gives rise to the larger final leaf size. Immediately before bud break, the size of the initially smaller primordium is already almost twice as large as the initially larger primordium, and the size differential is further amplified following bud break. The degree of aniso phylly, however, varies among the nodes of a shoot, depending on leaf pair orientation (tangential or parallel to the inflorescence axis) and nodal position. Paired leaves approach isophylly when they originate tangential to an inflorescence but become anisophyllous when originating parallel to an inflorescence. The degree of anisophylly depends on crown light conditions through effects on terminal bud size and foliage distribution on the shoot, but ultimately appears to arise from space limitations and crowding between the leaf primordia and the developing inflorescence in terminal reproductive buds.Key words: Aucuba, anisophylly, bud internal morphology, developmental anatomy, developmental constraints.

Internal structure of developing aucuba fruit as a defence increasing oviposition costs of its gall midges Asphondylia aucubae

Abstract. 1. Damage to juvenile plant tissues can cause reductions in fitness. Therefore, plants are expected to have evolved various defences for juvenile organs; however, so far, little attention has been paid to mechanical defence, as they have been considered to constrain the growth of juvenile organs. This study revealed that the dioecious tree Aucuba japonica uses mechanical defences to protect young developing fruit from the gall midge Asphondylia aucubae.2. Young fruit of A. japonica have a hard layer of endocarp covering the integument. Midges oviposit on the surface of the integument, where larval chambers are later formed. The endocarp gradually becomes cracked as the embryo sac develops.3. Oviposition by the midges is successful only when the ovipositors happen to pass through cracks in the endocarp. Thus, to successfully lay eggs, midges must insert the ovipositor repeatedly. This should decrease the fecundity of the midges, and subsequently their infectiousness, because their adult lifespan is short and they do not consume food during this time.4. Expansion of the cracks in the endocarp simplifies oviposition over time; however, the embryo sac continues to grow, increasing its volume relative to that of the ovule. This appears to deplete available space and tissue used in the construction of larval chambers, gradually making the fruit less susceptible to midge attacks.5. The temporary nature of this defence should prevent it from constricting the growth of young fruit. This exemplifies a novel strategy for a mechanical defence of young developing plant tissues.

Oviposition site of and gall formation by the fruit gall midge Asphondylia aucubae (Diptera: Cecidomyiidae) in relation to internal fruit structure

AbstractMost gall insects use young developing plant organs for gall formation; however, little information is available on the histological identification of such tissues or the changes in their availability with plant growth. We investigated the oviposition site of and the tissue used for gall formation by the midge Asphondylia aucubae Yukawa and Ohsaki, which is responsible for galls on the fruit of Aucuba japonica Thunb., by comparing the internal structures of young developing fruit, mature intact (uninfested) fruit, and galled fruit. The midge deposited eggs between the integument and the carpel of young fruit. Larval chambers were made of callus‐like tissue and were formed between the embryo sac and the carpel, where the integument was initially situated. The integument and part of the carpel were thus identified as critical plant tissues used by A. aucubae in forming galls. The integument degenerates in mature intact fruit; therefore, the season of emergence and oviposition by the midge may be determined by the timing of integument degeneration.

Distinct geographic structure as evidenced by chloroplast DNA haplotypes and ploidy level in Japanese Aucuba (Aucubaceae)

The geographic distribution of diploid and tetraploid cytotypes and cpDNA haplotypes throughout the entire range of Aucuba japonica was investigated. We measured relative genome size using flow cytometry and sequenced two cpDNA intergenic regions, atpB-rbcL and psbA-trnH (GUG). Two haplotypes include both diploids and tetraploids; four others are all tetraploids. Based on the combination of these haplotypes and cytotypes, eight "haplo-cytotypes" can be defined, which show a distinct geographic structure. Two diploid haplo-cytotypes are distributed in the southwestern part and six tetraploid ones in the northeastern part of the Japanese archipelago. Diploid and tetraploid haplo-cytotypes with the same haplotype are, in one case, disjunctively distributed, and in another case, in contact. The phylogenetic relationships of haplo-cytotypes indicate that the traditional circumscription of A. japonica is paraphyletic. One lineage consists of four tetraploid haplo-cytotypes and another of diploid and tetraploid haplo-cytotypes plus A. chinensis. Tetraploidization occurred independently at least three times, once at the base of the former lineage and twice in the latter. Taking the geographic, cytological, and phylogenetic evidence into account, the formation of the present geographic differentiation pattern of haplo-cytotypes through postglacial expansion from glacial refugia is discussed.

Two types of matter economy for the wintering of evergreen shrubs in regions of heavy snowfall.

Plant adaptation to an environment subject to heavy snowfalls was investigated in four species of evergreen shrubs growing in a Fagus crenata forest in an area of Honshu on the Sea of Japan. These shrubs stored carbohydrates in some organs before the snowy season and were covered with snow for 4-5 months. Aucuba japonica var. borealis, Camellia rusticana, and Ilex crenata var. paludosa maintained a reserve of carbohydrates during the snowy season. In Daphniphyllum macropodum var. humile, the reserve of carbohydrates decreased during winter. The respiration rates in the first three species decreased from autumn to winter, whereas the decrease in D. macropodum was slight. It was found that the first three species could use reserve carbohydrates for the growth of new shoots after the thaw, whereas in the last species the growth of new shoots depends on high photosynthetic activity in late spring. Our findings suggest some types of matter economy in evergreen shrubs for wintering in an environment of heavy snow.

樹木の発炎燃焼性に関連する未燃ガスの発生について

It was confirmed by the existing studies that, when it was exposed by only radiant heat, leaves of many species of trees ignited without flame but Juniperus chinensis cv. Kaizuka flamed lower than the tolerance limit of radiant heat. (It is said the lowest heat flux level of glowing as to coniferous trees was 13.95kW/m2.) The research on such danger is not progressing but which should be verified, for utilizing the fire prevention function of trees and for planning landscape in narrow residence, such as city. So, in this experiments, the concentration and transition of unburned combustible gas and the temperature under the leaves were measured about 23 species of trees, in this time the hydrocarbon was mainly measured as the unburned gas. The following results were obtained: (1) The states of hydrocarbon generating and temperature transition were obviously different depending on the species. (2) Three species of the family Cupressaceae discharged much hydrocarbon from the first stage of heating as well as J. chinensis cv. Kaizuka. (3) Aucuba japonica, Prunus mume, Phyllostachys bambusoides, and Pleioblastus chino generated hydrocarbon few from beginning to end. (4) Viburnum awabuki, Ginkgo biloba, and Hydrangea macrophylla generated few in first stage compared with the total quantity.