Fire Tolerance and the Fire-related Sprouting Characteristics of Two Cool-temperate Broad-leaved Tree Species

This study was conducted in a secondary broad-leaved forestin northern Hokkaido, Japan, which burned on 20–21 April1998. The study plot, set up on 13 July 1998, contained Quercusmongolica var. grosseserrata and Betula platyphylla var. japonicatrees. The latter were more severely damaged by the fire. Size-dependentsurvivorship was observed in both species with larger treesbeing more likely to survive the fire. However, many largeBetulatrees were completely destroyed. Both species developed abundantroot collar sprouts immediately after the fire. The number ofsprouts ranged from 0 to 296 in Betula and from 0 to 34 in Quercus.Trees with no sprouts were not necessarily dead. The frequencydistribution of the sprouting pattern in Betula was bimodal.This was related to damage severity, with the most abundantsprouting manifest in the most severely damaged trees. Thispattern was not observed inQuercus . Stem diameter also appearedto influence the extent of sprouting in Betula, while in Quercusthere was no distinct correlation between basal area and thenumber of sprouts. In Betula, the relationship between the numberof sprouts and the damage severity suggests a trade-off in resourceallocation for sprouting vs. shoot flushing in the crown. Copyright2000 Annals of Botany Company Betula platyphylla var. japonica, fire, fire tolerance, Quercus mongolica var.grosseserrata , resource allocation, root collar sprouting, stem diameter size.     

Effects of chloride ion on HILL reactions in Euglena chloroplasts

Effects of Cl^– and other anions on the rate of HILL reactionin Euglena chloroplasts were investigated. Cl^– acceleratedthe reaction rate with ferricyanide as HILL oxidant; Br^–,F^– and I^– were also effective; NO₃^–, PO₄^2–and SO₄^2– were less effective. Divalent cations, Ca²⁺and Mg²⁺, were also highly effective. The promoting effectsof these ions were highly dependent on pH and the nature andconcentration of the HILL oxidant used. Accelerating effectsof the ion increased with decreasing concentrations of ferricyanide.Generally, the stimulating effect of Cl^– was much moremarked at pH 7–7.5, with little effect at pH 5. Thus,the pH-activity relationship in the HILL reaction is more orless markedly modified by addition of ions. Cl^–, and other anions, accelerated the reaction by affectingonly the dark rate-limiting portion of the HILL reaction; thelight reaction constant remained uninfluenced. We inferred thatsome reaction step, at which ferricyanide receives electronfrom photosystem 2, is accelerated by Cl^– and other ions.Cl^– effects were rather small, or undetectable, with DPIPor p-benzoquinone as oxidants. (Received January 8, 1970; )     

Fractionation and Partial Characterization of Pectic Polysaccharides in Cell Walls from Liverwort (Marchantia polymorph) Cell Cultures

Konno, H., Yamasalu, Y. and Katoh, K. 1987. Fractionation andpartial characterization of pectic polysaccharides in cell wallsfrom liverwort (Marchantia polymorpha) cell cultures.—Jexp. Bot. 38: 711–722. Pectic polysaccharides were extracted from the starch-free cellwall preparation of cell suspension cultures of Marchantia polymorpha.The polysaccharides were fractionated by DEAE-Sephadex A-50ion-exchange chromatography yielding the five fractions, andthe degree of polymerization and glycosyl composition determinedfor each fraction. The neutral rich and acidic pectic polymerswere depolymerized by purified endoglucanase (l,4-ß-D-glucan4-glucanohydrolase, E.C. 3.2.1.4 [EC] .) and endopolygalacturonase(poly-l,4--Dgalacturonide glycanohydrolase, E.C. 3.2.1.15 [EC] ),respectively. The degraded pectic fractions were fractionatedby gel filtration chromatography on Bio-Gel A-5m and Bio-GelP-2, and glycosyl composition determined for each fraction.The results indicate that pectic polysaccharides contain glucose-richpolymer, rhamnogalacturonan and homogalacturonan in a ratioof 1:4:0–6. In addition, pectic polysaccharides were releasedas five pectic fragments from the cell walls by purified endopectatelyase (poly-l,4--D-galacturonide lyase, E.C. 4.2.2.2 [EC] ). Basedon the analysis of glycosyl composition of each fragment, thepectic polysaccharides of Marchantia cell walls are characterized Key words: Cell suspension culture, cell wall, liverwort, Marchantia polymorpha, pectic polysaccharides     

Effects of Extracellular Potassium on Acid Release and Motility Initiation in Toxoplasma gondii

The internal pH (pH_i) of Toxoplasma gondii was estimated by measuring the accumulation of the weak base 9-aminoacridine in buffers with various ionic compositions. The pH_i of the metabolizing parasite increased when the extracellular K⁺ was elevated in alkaline medium or when the external pH (pH_c) was substantially increased in medium employing high external K⁺ (90 mM). The parasite in mouse peritoneal fluid, or in potassium sulfate buffer (pH 8.2), where the pH_i was demonstrated to be increased to 7.9, became motile when acidic buffer was substituted for the original suspension medium. This acid-induced independent movement subsided within 5 min but was repeatedly induced if the pH_c was serially lowered to 6.0. Basic buffers, on the other hand, abolished motility when applied to the moving parasites. Nigericin, which is known to collapse pH gradients across the membrane, also abolished motility.     

Restriction Enzyme Analysis of Mitochondrial DNA of Acanthamoeba Strains in Japan

ABSTRACT. Eight isolates, identified as either Acanthamoeba castellanii or A. polyphaga from human eye infections, contact lens containers, and soil in Japan, were characterized by restriction fragment length polymorphisms (RFLP) of mitochondrial DNA (mtDNA). Mitochondrial DNA was digested with either Bgl II, Eco R I, Hind III, Hpa I, Sca I or Xba I, electrophoresed in agarose gels, and stained with ethidium bromide. Four distinct RFLP phenotypes that refer to the collection of six fragment size patterns obtained for a single strain with six enzymes, were discovered among the eight strains used in this study. Three strains morphologically classified as A. polyphaga share a single RFLP phenotype with the Ma strain of A. castellanii. The interspecific sequence differences of 7.06–12.74% in DNA nucleotide were estimated from the proportion of DNA fragments shared by each pair of mtDNA.     

Partial Synchronization of Carrot Cell Culture by Auxin Deprivation

A strain of carrot cells (Daucus carota cv. Kintoki) grew exponentially in the presence of 2,4-dichlorophenoxyacetic acid (2,4-D, 1 mg/1) with a doubling time of about 2 days. When those cells were transferred to a medium lacking 2,4-D, they continued to grow at almost the same rate for about a week. When the cells were again transferred to the auxin-free medium, the rate of cell division gradually decreased. After the cell division had ceased, cells were returned to the ordinary 2,4-D medium. A burst of cell divisions occurred after about 2 days. Timing of DNA synthesis and of mitosis suggested that the cells had been arrested at G₁ phase. In a medium containing indoleacetic acid instead of 2,4-D, the auxin was rapidly degraded and the culture was similarly synchronized as in the auxin-omitted medium.     

Different Growth Responses of Hamster Dermal Fibroblasts and Chondrocytes to Platelet–derived Growth Facter in Cell Culture

The growth responses of dermal fibroblasts and chondrocytes obtained from 1-week-old hamsters to a growth factor from platelets [platelet-derived growth factor (PDGF)] were compared. Autoradiography showed that most of the whole nuclei of dermal fibroblasts were labeled with ³H-thymidine in 5% whole blood serum (WBS), which contains platelet releasate, but only a few percent were labeled in 5% plasma-derived serum (PDS), which is free of platelet releasate. Addition of platelet releasate to PDS restored the growth stimulatory activity of the serum for dermal fibroblasts. In contrast, most of the nuclei of chondrocytes were labeled with ³H-thymidine both in 5% WBS and 5% PDS. Dermal fibroblasts grew in 5% WBS, but not in 5% PDS, whereas chondrocytes grew in both 5% WBS and 5% PDS. Partially purified PDGF added to the medium with 0.5% fetal calf serum stimulated DNA synthesis in dermal fibroblasts, but not in chondrocytes.     

EPIDERMAL METAPLASIA OF THE CORNEAL ANTERIOR EPITHELIUM IN THE CHICK EMBRYO

The corneal anterior epithelium of younger chick embryos can be changed into a keratinized epidermis, when it is cultured in vitro combined with 6 1/2-day dorsal dermis. Even if a Millipore filter is inserted between the corneal anterior epithelium and underlying dorsal dermis, the epithelium undergoes similar metaplastic changes. In older embryos, however, the epithelium gradually loses the competence for the keratinization. Cultivation of cornea (anterior epithelium, stroma and endothelium) of 6 1/2- or 10-day embryos results in maintenance of its original pattern, and the epithelium fails to differentiate into a keratinized epidermis. The dermis isolated from 8 1/2-day dorsal or 12 1/2-day tarsometatarsal skin is not so effective in inducing the epidermal metaplasia. The mesenchyme of 5 1/2-day proventriculus or 5 1/2-day gizzard fails to bring about any endodermal metaplasia of the corneal epithelium. The corneal stroma, on the other hand, has no inhibitory action on the keratinization of the epidermis obtained from 6 1/2-day dorsal skin.     

呼伦贝尔典型退化草原土壤理化与微生物性状

以内蒙古克鲁伦河流域呼伦贝尔典型草原为对象,设置了轻度、中度和重度退化3种类型样地,研究不同程度退化草原的物种组成、地上生物量、土壤理化性状、土壤微生物数量和酶活性,以及微生物生物量的变化.结果表明: 中度退化样地的群落物种丰富度最大,轻度退化样地的地上生物量显著高于重度退化样地.退化样地的土壤水分、养分(有机质、全氮),微生物量碳、氮,以及微生物数量和酶活性显著下降,土壤容重显著增加.退化样地的土壤微生物生物量碳、氮在128～185和5.6～13.6 g·kg^-1,土壤脱氢酶和脲酶活性均与土壤容重呈显著负相关,与土壤全氮、有机质、微生物数量以及微生物生物量碳、氮呈显著正相关,地上生物量与土壤细菌和真菌数量呈不同程度的正相关.