Coexistence of two congeneric tree species of Lauraceae in a secondary warm‐temperate forest on Miyajima Island,south‐western Japan

We analyzed the spatial distributions of two congeneric tree species, Neolistea aciculata and Neolistea sericea (Lauraceae), in a warm‐temperate forest on Miyajima Island, south‐western Japan. Both species were mainly found in valley sites on the island. Hence, these species shared the same topographic habitat niche. However, we found a clear difference between the spatial distributions of the two species in relation to the light environment. Neolistea aciculata was predominantly found in stands with low light, such as beneath the canopy of dense evergreen broadleaved forest. In contrast, N. sericea was predominantly associated with ample light, such as in secondary Pinus densiflora forest. In stands with moderate light conditions, both species were found. This habitat niche segregation in relation to light conditions presumably allows the coexistence of these two species in the predominantly successional forest on Miyajima Island.     

Leaf Anatomy and Carbon Discrimination in NAD-malic Enzyme Panicum Species and their Hybrids Differing in Bundle Sheath Cell Ultrastructure

The relationship between leaf anatomy, ultrastructure and carbondiscrimination was investigated in leaves of two F₁hybrids (F₁-1and F₁-2) between two different types of the grassPanicum [anNAD-malic enzyme (ME) C₄species], which differ in bundle sheathultrastructure. The female parent was Kabulabula grass, whichhas centrifugal chloroplasts in bundle sheath cells and is designatedan NAD-ME(F) species, while the male parent was Makarikari grass,which has centripetal chloroplasts in the bundle sheath cellsand is designated an NAD-ME(P) species. Suberin lamellae arepresent in Kabulabula grass but are lacking in Makarikari grass.Both F₁hybrids had the same chromosome number (2n =36) as theparents but exhibited both univalent (about 45%) and bivalent(about 55%) chromosome pairing which was the major basis forthe identification of F₁hybrids. In F₁-1, elongated bundle sheathcell chloroplasts are arranged mainly in a centripetal position,similar to those in the male parent, Makarikari grass. In contrast,most of the bundle sheath cells in F₁-2 are packed with starch-containingchloroplasts, although in some cells chloroplasts tended tobe centripetally arranged. In both F₁hybrids, suberin lamellaewere found in the bundle sheath cell walls, similar to the femaleparent, Kabulabula grass. The ¹³C values of both F₁hybrids were-11.4 to -11.7, almost the same as those of Kabulabula grass(-11.4), but significantly higher than those of Makarikari grass(-12.7). These results indicate that the chloroplast orientationin the bundle sheath cells and the presence of suberin lamellaeare not obligatorily linked in their expression and suggestthat suberin lamellae may play an important role in discriminationagainst¹³C. Panicum ; NAD-malic enzyme species; hybrid; chloroplast position; ¹³C discrimination; suberin lamellae     

Parasitoid aggregation and interference in host–parasitoid dynamics

1. Parasitoids do not distribute themselves evenly among available patches, which has an important bearing on the dynamics of host–parasitoid interactions. This study examined the density‐dependent nature of aggregation of the parasitoid Dirhinus giffardii Silvestri on the oriental fruit fly host, Bactrocera dorsalis (Hendel) distributed among discrete patches. 2. Four artificial patches were created in a cage, and the number of hosts in each patch was manipulated. Parasitoids were released into the cage, and whether parasitoid density and host density influence the degree of parasitoid aggregation was examined. 3. Parasitoid aggregation became stronger (e.g. uneven distribution among patches) as the parasitoid density decreased and also as the host density increased. The index of parasitoid aggregation was not influenced by the distribution of hosts among patches. 4. The empirically characterised aggregation pattern was incorporated in a host–parasitoid model that consists of one host and one parasitoid species. The analysis of the model shows that an unstable system (i.e. the coexistence of the host and parasitoid is impossible) can be stabilised (i.e. coexistence is possible) when the parasitoid aggregates in a way that is consistent with the pattern found in the experiment.     

Studies on chlorophyll formation in Chlorella protothecoides I. Enhancing effects of light and added {delta}-aminoIevulinic acid, and suppressive effect of glucose on chlorophyll formation

Light-induced formation of chlorophyll in "etiolated" cellsof Chlorella protothecoides was studied under various experimentalconditions, (i) Two different types of enhancing effect of lightwere demonstrated: a "long-term" effect lasting for many hoursafter a relatively short illumination of etiolated cells anda "short-term" effect disappearing in a few hours after illumination,(ii) Addition of ALA caused enhancement of chlorophyll synthesisin etiolated cells in darkness as well as in light; the ALA-enhancedrate of dark chlorophyll synthesis, however, was much lowerthan the rate in light without added ALA. ALA was replaceablewith succinic acid plus glycine in light, but not in the dark,for enhancement of chlorophyll formation, (iii) Adding glucose,fructose, galactose, glycerol or acetate—at concentrationsmuch lower than those previously shown to induce "bleaching"of green algal cells-caused a more or less marked suppressionof light-induced greening in etiolated cells, (iv) Added glucosealmost instantaneously and completely stopped chlorophyll synthesisin light as well as in darkness either with or without addedALA. On the basis of these and other results, a tentative schemeis presented for the enhancing effects of light and the suppressiveeffects of glucose on chlorophyll formation in algal cells. (Received April 1, 1970; )     

Distribution,Molecular Structure and Functional Analysis of Carnitine Transporter (SLC22A5) in Canine Lens Epithelial Cells

While carnitine has been reported to have an anti-oxidative role on the ocular surface, there has been no report on the existence of a carnitine transporter (SLC22A5) in the lens. Therefore, we investigated the carnitine transport activity of canine lens epithelial cells (LEC) and determined the molecular structure of canine SLC22A5. The carnitine transport activity was 7.16 ± 0.48 pmol/mg protein/30 min. Butyrobetaine, the analogue of carnitine, reduced 30% of the activity at 50 µM. A coding sequence of canine carnitine transporter was 1694 bp long and was predicted to encode 557 amino acid polypeptides. The deduced amino acid sequence of canine carnitine transporter showed >80% similarity to that of mouse and human. Western blot analysis detected the band at 60 kDa in the membrane of lens epithelial cells. The high content of carnitine in the lens is possibly transported from aqueous humor by SLC22A5.     

Hysteresis of Contraction-Extension Cycle of Glycerinated Vorticella

SYNOPSIS. The helical coiling state of a glycerinated stalk in the family Vorticellidae had been regarded, without any evidence, as a reversible and completely equilibrated mechano-chemical system regulated by the external free Ca²⁺ concentration. Our present detailed observations of many individual stalks of glycerinated Vorticella convallaria revealed that the contraction-extension cycle of the helical stalks caused by increasing and decreasing free Ca²⁺ concentrations in the medium represents a kind of hysteresis. This phenomenon was observed in extensively glycerinated Vorticella in a medium of very low or physiological ionic strength, as well as in briefly glycerinated ciliates. With regard to the configurational change in various parts of a glycerinated stalk during the contraction-extension cycle, it was found that the initial bending of the stalk caused by increasing free Ca²⁺ concentration begins to take place near the zooid (head) while the initial reextension of the stalk with decreasing free Ca²⁺ concentration begins to take place near the zooid (head) while the initial reextension of the stalk with decreasing free Ca²⁺ concentration takes place simultaneously throughout the entire stalk. The Ca²⁺ threshold for complete reextension of the part of the stalk near the rootlet was found to be much higher than that near the zooid.     

Seedling Establishment of a Canopy Tree Species in Malaysian Tropical Rain Forests

Abstract Unlike many other canopy tree species in tropical rain forests, Dryobalanops aromatica (Dipterocar-paceae, local name: Kapur) establishes monospecific dominant (monodominant) forests in Peninsular Malaysia. In natural conditions, monodominance of Kapur does not necessarily mean low species diversity of the Kapur forests. While the emergent canopy layer is occupied by Kapur, many other plant species, which are common to lowland dipterocarp primary forests in the same region, are found in lower canopy layer and understory.
To understand the ecological implications of the monodominance of Kapur, we monitored post dispersal survival and seedling establishment in a pure stand of Kapur in a plantation in Kepong, near Kuala Lumpur. Immediately after seed fall, seeds and cotyledon-stage seedlings suffered high predation by vertebrates such as rodents. The predation pressure was higher in a more general fruiting year (1991) than in a sporadic fruiting year (1992). In contrast to the high mortality of seeds and newly emerged seedlings, seedlings surviving to the six-leaf stage showed low mortality, which allowed the establishment of a sapling bank.
The occurrence of saplings of Kapur with a wide range of size classes in natural forests indicates that this species is more shade tolerant than other dipterocarp species such as the Shorea group and that it could well respond to enhanced light conditions caused by canopy opening. These characteristics may partly contribute to maintaining monodominance of Kapur.     

Estimation of the Outcrossing Rate on Dryobalanops aromatica Gaertn. f. in Primary and Secondary Forests in Brunei, Borneo, Southeast Asia

Abstract Dryobalanops aromatica is an emergent canopy tree species with hermaphroditic bee-pollinated flowers. This species is distributed in the lowland dipterocarp forests of Malaya, Sumatra, Rhio Archipelago and Borneo. The flowering of many different dipterocarp species was observed in some parts of Brunei in 1991, and all over Brunei in 1992. The outcrossing rates of D, aromatica were estimated in 1991 and 1992 in the secondary forest, and in 1992 in the primary forest. Selective harvesting of D. aromatica has occurred in the secondary forest about 20 years ago. Four enzyme systems with a total of six isozyme loci were used to estimate the single locus and the multilocus outcrossing rates. The multilocus outcrossing estimates ranged from 0.794 to 0.856, with a mean of 0.816. These estimates are similar to those for other tropical tree species. Although the flowering density of D. aromatica in the secondary forest was lower than in the primary forest, the multilocus outcrossing estimates were not significantly different. The variation between years in the secondary forest was also not significant. These findings may be largely the result of the high flowering tree density of this species, even in the secondary forest. In this study, the outcrossing rates of D. aromatica were maintained by high flowering density regardless of the size structure or the topography of the habitat.