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.     

The Cell Cycle and Cell Population Kinetics in the Programmed Cell Death in the Limb-Buds of Normal and 5-Bromodeoxyuridine- Treated Chick Embryos

The cell cycle and cell population kinetics have been analyzed in the interdigital regions of chick limb-buds during the course of programmed cell death both in normal and the 5-bromodeoxyuridine (BrdU)-treated embryos. Our previous study has shown that a single administration of BrdU at day 6 1/3 inhibited the programmed cell death occurring in normal development of limb-buds.
Pulse- as well as continuous labelings with tritiated thymidine (³H-TdR) were used. The results obtained from the analyses made on both normal and experimental embryos have demonstrated the presence of a particular DNA-synthetic period, around day 6 1/3, closely related to the programmed death occurring on day 7 1/3. In normal embryos, new cell populations, which did not belong to any phases of normal cell cycle, made their appearances in the process of programmed cell death. A possible correlation between programmed cell death and the cell cycle has been discussed in relation to the morphogenesis of limbs in both normal and BrdU-treated embryos.     

The Effect of Hydrocortisone on the Epidermal Proliferation in an Organ Culture of Chick Embryonic Skin

Hydrocortisone is regarded as an initiator of keratinization in embryonic skin. The present investigation dealt with the effect of hydrocortisone on the proliferation of epidermal cells during early development: Cell kinetic analyses using ³H-thymidine autoradiography were applied to a skin organ culture prepared from a 13-day chick embryo.
Hydrocortisone at a concentration between 0.01 and 1.0 μg/ml was effective in initiating a morphological change leading to the epidermal keratinization in vitro and caused a marked decrease in the mitotic and labeling indices of epidermal basal cells, the decrease being maximum at 2 days of culture previous to the morphological change.
During continuous labeling with ³H-thymidine, the number of labeled basal cells reached 100% within 2 days in the control and 4 days in the culture treated with hydrocortisone. This confirmed that the growth fraction of epidermal basal cells was 1.0 even after the administration of hydrocortisone.
The duration of each cell cycle phase at 2 days of culture was determined by percent labeled mitoses and double-labeling analyses. It was concluded that hydrocortisone extended the generation time of epidermal basal cells at this time point about three fold over the control. This extension was mainly due to the elongation of the G ₁ phase.     

Studies on chloroplast development in Chlamydomonas reinhardtii I. Effect of brief illumination on chlorophyll synthesis

When dark grown cells of Chlamydomonas reinhardtii y-1 mutantwere exposed to continuous light, an immediate transformationof small amounts of protochlorophyll(ide), which had been presentin the dark grown cells, to chlorophyll was observed. Afterthis, there was a slow accumulation of chlorophyll lasting for2.5-3 hr before the start of exponential synthesis. Initialaccumulation of chlorophyll was distinctly slower at a highlight intensity (13,000 lux) than it was at moderate intensitiesof light (2,000–5,000 lux). However, the exponential synthesisof chlorophyll started after the same 2.5–3 hr of illumination. A brief pre-illumination of cells followed by incubation indarkness was effective in promoting chlorophyll synthesis undersubsequent continuous illumination at high, as well as moderatelight intensities. Pretreatment alleviated retardation of theinitial chlorophyll accumulation by light of high intensity.The promoting effect of preillumination on chlorophyll synthesiswas sufficient, even when a light impulse as short as 10 secwas given. However, the effect was dependent on length of thedark period after the short pre-illumination. The full extentof this effect was observed when the dark period was about 2.5–3hr long. Further dark incubation gradually decreased the effect. On the basis of these findings, it is assumed that a factor(s)responsible for promotion of chlorophyll (or chloroplast) synthesisin the process of greening of dark grown cells is produced duringthe dark period after a brief pre-illumination, and that thefactor is turned over at a relatively fast rate. The possiblenature of the presumed factor is discussed in relation to chloroplastdevelopment. ¹Present address: Department of Biology, Faculty of Science,Kobe University, Nada-ku, Kobe, Japan. (Received August 18, 1970; )     

Function of the <Emphasis Type="Italic">rel</Emphasis> Gene in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Sokawa et al. suggest that rel^- strains of Escherichia coli possess abnormal protein synthesizing machinery, which cannot carry out normal protein synthesis when the supply of amino-acids is limited.     

Effects of after-ripening and gibberellic acid on the thermoinduction of seed germination in Solarium melongena

Daily alternating temperatures or a short exposure to low orhigh temperatures were necessary for the germination of eggplantseeds at the initial stage of after-ripening. But requirementsbecame less strict with the progress of after-ripening, andafter 4 to 8 months of afterripening, germination occurred easilyboth at constant (20 and 25) and daily alternating temperatures(30 for 16hrs and then 20 for 8hrs). With further progress in after-ripening, however, daily alternatingtemperatures or a short exposure to low or high temperaturesbecame again indispensable for attaining a high percentage ofgermination. The progress of after-ripening was greatly influencedby the degree of seed ripening, that is, by the period beforethe seeds were sampled from fruits after anthesis (ripening). The effect of GA on the germination of egg plant seeds varieddepending on the concentration of GA, temperature and the degreeof maturity (ripening and after-ripening) of the seeds. (Received March 8, 1968; )     

EFFECT OF LIGHT ON THE CHLOROPHYLL FORMATION IN THE "GLUCOSE-BLEACHED" CELLS OF CHLORELLA PROTOTHECOIDES

1. Previous studies have shown that when Chlorella protothecoidesis grown in a medium rich in glucose and poor in nitrogen source(urea), apparently chlorophyll-less cells with profoundly degeneratedplastids—referred to as "glucose-bleached cells—areproduced either in the light or in darkness. When the glucose-bleachedcells are incubated in a medium enriched with the nitrogen sourcebut without added glucose, an active formation of chlorophylloccurs after a certain lag period under illumination, whilein darkness a very small amount of chlorophyll is formed atabout the same time as in the light. The stimulating effectof light on the chlorophyll formation is not appreciably affectedwhen the photosynthetic CO₂-fixation of greening algal cellsis blocked by the addition of CMU. In the present study, itwas further found that the light-enhanced chlorophyll formationproceeds, although at a somewhat lower rate, under aerationof CO₂-free air. All the experiments in this work were doneunder these non-photosynthetic conditions to exclude any influenceof photosynthates.
2. The effect of light (from daylight fluorescentlamps) on thechlorophyll formation in the glucose-bleachedalgal cells wassaturating at about 1,000 lux. Blue light wasfound to be mosteffective; yellow, green and red light followingin the orderof decreasing effectiveness.
3. When the bleachedalgal cells were illuminated for a short periodin the lag phaseof chlorophyll formation and subsequently incubatedin darkness,there occurred an appreciable enhancement of chlorophyllformationin the dark. When the short illumination was appliedat differenttimes of the lag phase, the enhancement was inducedto almostthe same extent. But the longer the duration of theilluminationduring the lag phase, the greater was the enhancementof chlorophyllformation in the subsequent dark incubation.In such experimentsblue light was most effective and red lightleast, as it wasthe case in the experiments of continuous illumination.An intervenientillumination of the bleached cells at lowertemperatures orunder the atmosphere of N2 produced little orno enhancementof the chlorophyll formation in the subsequentdark incubation.
4. Based on these results, it was concluded that the light enhancementof chlorophyll formation in the glucose-bleached algal cellsis mediated by a non-chlorophyllous photoreceptor(s), absorbingmaximally blue and yellow light, and that a light-induced changeof the photoreceptor is immediately followed by a certain dark(temperaturedependent and aerobic) process(es) which is connected,directly or indirectly, to the chlorophyll synthesis.

(Received August 10, 1967; )     

Role of Contents of the Germinal Vesicle in Male Pronuclear Development and Cleavage of Starfish Oocytes

During 1-methyladenine induced germinal vesicle breakdown, contents of the germinal vesicle of starfish oocytes are mixed with the surrounding cytoplasm. Upon injection of contents of the germinal vesicle from immature (fully grown) oocytes into enucleated and inseminated oocytes, incorporated spermatozoa were not observed to change structurally. Alternatively, after treatment of the above oocytes with 1-methyladenine, sperm asters and male pronuclei were developed and subsequent cleavage was also detected. From these results, it is concluded that both action of 1-methyladenine and participation of contents of the germinal vesicle are indispensable for male pronuclear development and subsequent cleavage.