Patterns of Trunk Diameter, Tree Height and Crown Depth in Crowded Abies Stands

The size structure of trees in crowded, even-aged Abies (fir)stands of ‘Shimagare’ or ‘wave-regenerated’sub-alpine forests is analyzed. Tree-height distributions showconsistently smaller variation and less positive skewness thanthe distributions of trunk diameter and crown depth (tree heightminus height of the lowest branch). This difference is associatedwith changes in the relationships between trunk diameter, treeheight and crown depth as stands age. These, in turn, resultfrom self-pruning of the lower foliage crown due to competitionfor light in crowded stands. Abies, diameter-height curve, competition, size distribution, stand development, tree geometry, wave-regeneration     

Effect of Method of Agar Addition on Post-autoclave pH of the Tissue Culture Media

Tissue culture media (MS, GB-5 and N6) were gelled with agarby employing different methods When agar was dissolved directlyin media by autoclaving at 120 °C for 1 mm followed by sterilization,the media pH dropped markedly — more so at the lower concentrationsof agar On the other hand, when agar was first dissolved indistilled water and added to the culture media the pH loss wasminimized considerably pH measurements carried out as a functionof time showed a gradual decline in media pH The media supplementedwith Panax ginseng callus became more acidic than the mediawith no callus Tentative reasons for the post autoclave pH fallassociated with various methods of agar addition are described Culture media, agar addition, post-autoclave pH, Panax gingseng     

Inhibition of Starfish Oocyte Maturation by Tumor-Promoting Phorbol Esters*

Effect of tumor promoters including phorbol esters and teleocidin on 1-methyladenine (1-MeAde)-induced oocyte maturation was studied in the starfish. When isolated immature oocytes were treated with 1-MeAde and 12-O-tetradecanoylphorbol-13-acetate (TPA), 1-MeAde-induced maturation was completely inhibited at more than 2.5 μg/ml. However, if TPA was added after the hormone-dependent period (the minimum period wherein 1-MeAde is required), such maturation-inhibiting effect was no longer observed. Pretreatment with TPA for 5 min showed that its inhibitory action is irreversible. However, when TPA-injected oocytes were treated with 1-MeAde, all oocytes underwent germinal vesicle breakdown (GVBD). GVBD was induced in TPA-treated oocytes upon injection of the cytoplasm of maturing oocytes containing maturation-promoting factor (MPF). These facts show that TPA acts on the oocyte surface to inhibit the production of MPF. Retinoids including retinal, retinol and retinoic acid reversed the inhibitory effect of TPA on 1-MeAde-induced maturation. Experiments with various phorbol esters showed a good correlation between their maturation-inhibiting activity and their known tumor-promoting activity. Further, telecoidin, which is structurally unrelated to phorbol esters, inhibited 1-MeAde action. Since both tumor-promoting phorbol esters and teleocidin are known to activate Ca²⁺ -activated, phospholipid-dependent protein kinase (protein kinase C) and their activation effect is inhibited by retinoids, it appears that the activation of protein kinase C by tumor promoters is involved in blocking of 1-MeAde action.     

Maintenance of species boundaries despite rampant hybridization between three species of reef fishes (Hexagrammidae): implications for the role of selection

Hybridization and introgression are antagonistic to the process of speciation. If hybrids are viable and backcross, introgression will slow or prevent the evolution of reproductive isolation between populations. If species hybridize upon secondary contact, introgression will ultimately erode species boundaries. If hybridization is rampant and gene flow is high, the proportion of hybrids will approach values expected with random mating, and introgression will overcome species boundaries, homogenizing populations. Alternatively, if species are genetically distinct, the proportion of hybrids would be significantly less than expected with random mating, gene flow would be interrupted by selection against hybrids, and inviability or sterility of F ₁ hybrids or backcrosses would be expected. Here, we investigate a system with characteristics expected by both of these opposing scenarios. Hybridization occurs between three species of reef fishes in the genus Hexagrammos at unexpected high frequencies in a zone of distributional overlap. Backcrossed individuals are detected, indicating F ₁ hybrids are viable and capable of reproducing. Yet, these species are genetically distinct at multiple loci. To study this apparent paradox, we estimate the relative proportions of hybrids, patterns of symmetry, inviability, and cytonuclear disequilibria using one mitochondrial and two nuclear markers. We invoke selection against hybrids, at various life history stages, in the maintenance of species boundaries in this system.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 135–147.     

Allometry and Competition between Saplings of Picea jezoensis and Abies sachalinensis in a Sub-boreal Coniferous Forest, northern Japan

The crown shape and the mode of competition between saplings(<2m in height) of the two conifers,Picea jezoensis andAbiessachalinensis, of a sub-boreal forest, northern Japan, wereinvestigated based on the diffusion model. A model for individualsapling growth considering both inter- and intraspecific competitionwas developed. The effect of species-specific crown shape onthe sapling growth and competition of the two species were examined.PiceajezoensisandAbies sachalinensissaplings had deep conic and shallowflat crowns, respectively.Picea jezoensishad more foliage massthanAbies sachalinensisof the same sapling mass. It was suggestedthat thePicea jezoensissapling has a high cost for assimilation–respirationbalance under dark conditions of closed canopies, whereas theAbiessachalinensissapling maintains effective assimilation even undersuppressed conditions. Widely spaced saplings, such as gap successors,ofPicea jezoensishad a greater relative growth rate (a₀) thanwidely spacedAbies sachalinensis. The crown shape of saplingsof the two species shows different adaptations for efficientpersistence in the sub-boreal forest. Saplings ofPicea jezoensisandAbies sachalinensiswere not uniformlydistributed, but aggregated in different sites as the saplingsgrew, indicating habitat segregation between the two speciesat the sapling stage. Intraspecific sapling competition wasone-sided in each of the two conifers. Interspecific saplingcompetition was one-sided in the direction only fromAbies sachalinensistoPiceajezoensis. Therefore, asymmetric competition prevailed at thesapling stage of the two species. These results contrast withweak symmetric competition or the almost absence of competitionbetween trees (2m in height) of the two species (Kubota andHara,Annals of Botany76: 503–512, 1995). The mode of competitionchanged with the life-history stage from the sapling (intenseand asymmetric) to the tree (weak and symmetric or almost absent). In conclusion (1) asymmetric and intense competition betweensaplings brought about habitat segregation between the dominantspecies,Picea jezoensisandAbies sachalinensis, in the earlystage of life-history; (2) therefore, the coexistence ofPiceajezoensisandAbies sachalinensisof the sub-boreal forest wasdetermined by the boundary conditions for the growth dynamicsof the trees, as segregation of establishment sites resultingfrom asymmetric and intense competition between saplings; (3)then the species composition of the forest was maintained byweak symmetric competition or the almost absence of competitionbetween trees. Crown shape; growth dynamics; species coexistence; habitat segregation; diffusion model     

CHANGES IN CALCIUM CONCENTRATIONS OF SERUM AND COELOMIC FLUID OF THE BULLFROG, RANA CATESBEIANA, DURING LARVAL DEVELOPMENT AND METAMORPHOSIS

The serum calcium levels of bullfrog tadpoles (stage 26 to 33) and adults are higher than those of the coelomic fluid. The serum levels increase gradually from stage 26 (7.6 mg/100 ml) to stage 30 (8.4 mg/100 ml), and then sharply to stage 33 (10.5 mg/100 ml), while the coelomic fluid levels increase from 7.1 to 8.7 mg/100 ml during this period. Only minor differences are found in serum and coelomic fluid sodium levels among larval stages with the exception of a temporary decrease during metamorphic climax.
These results suggest that the adult type of regulation of serum calcium concentrations is established during larval development and is fully achieved after the completion of metamorphosis. The control mechanism for serum calcium may be different from that for coelomic fluid.     

Distributional Change of Membrane-associated Calcium in Sea Urchin Eggs during Fertilization

The "source and sink" for the intracellular calcium released during fertilization were examined in sea urchin eggs, Hemicentrotus pulcherrimus , with chlortetracycline as a fluorescent chelate probe. In order to distinguish the differential distribution of membrane-associated calcium in various compartments in cytoplasm, eggs were stratified by centrifugation before or after fertilization. Only the layer containing mainly mitochondria exhibited the chlortetracycline-fluorescence in unfertilized eggs. After fertilization, a new fluorescent band emerged in the membrane-rich clear layer of stratified eggs. Chlortetracycline-fluorescence in the clear layer was gradually redistributed surrounding the prophase nucleus and then incorporated into the mitotic apparatus. From these observations, we postulate that the major source(s) of released free calcium ions at fertilization is in the mitochondira layer and membranes in the clear layer are newly activated as the calcium sequestering system after fertilization.     

老挝北部宾夕法尼亚纪的一个新(筳)类动物群

作者报道了一个小型■类动物群,包括Eostaffella? sp., Pseudoendothyra sp., Staffella pseudosphae-roidea Dutkevich, Neostaffella ( N.)sp ., Profusulinella bona Grozdilova et Lebedeva以及P.cf .prisca (Depart) ,此动物群是在老挝北部琅勃拉邦省西南部的Thong Phiang Vilay村附近的石灰岩山中发现的。根据Profusulinella bona和P.cf. prisca的出现,该动物群的时代可归到晚石炭世宾夕法尼亚纪巴什基尔期或莫斯科期最早期。这是在老挝北部对该时代■类动物群的首次报道。当前■类动物群证明琅勃拉邦地区和泰国北部的黎地区在地质上有重要的关系,表明老挝北部地区从地质构造上属于印度支那板块的边缘。