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.     

Leaf expansion of four sunflower (Helianthus annuus L) cultivars in relation to water deficits. I. Patterns during plant development

Abstract. The influence of a slow stress and recovery cycle on the pattern of leaf expansion in four diverse sunflower cultivars ( Helianthus annuus L. cvs. Hysun 31, Havasupai, Hopi and Seneca) was studied in a glasshouse. Stress had no significant effect on the time of flower bud emergence and anthesis, or on final leaf number, but delayed the appearance of leaves at high insertions in all cultivars except Hysun 31.
Leaf expansion was markedly reduced as the predawn leaf water potential decreased from −0.35 to −0.60 MPa, and the predawn turgor pressure decreased from 0.3 to 0.2 MPa, and expansion ceased at a predawn leaf water potential of about −1.0 MPa, i.e. when the predawn turgor pressure reached zero.
The leaves most reduced in final size when water was withheld were those at the insertions which grew the most rapidly in unstressed plants. The maximum reduction in final leaf size of 25–35% was similar in all cultivars and was due to retardation of the rate of leaf expansion: the duration of leaf expansion was actually increased by stress. However, leaves that were initiated during stress, but emerged after rewatering, had final leaf areas at least equal to those in the unstressed plants: in the cultivar Seneca, the final size of leaves of high insertion was significantly greater in stressed than unstressed plants, whereas in the three other cultivars the final leaf sizes were similar in both treatments. All four cultivars examined adjusted osmotically to the same degree, but leaf water potentials in one, Seneca, increased more rapidly after rewatering than in the other three, and this may have contributed to the greater relative leaf size in the leaves of high insertion in this cultivar.     

STAGING OF NEWT BLASTULA EMBRYOS AND FIRST APPEARANCE OF PRIMARY MESODERMAL COMPETENCE

Using the swimbladder of the crusian carp ( Carrasius auratus ) as an inductor, the first appearance of mesodermal competence in the presumptive ectoderm of the newt ( Triturus pyrrhogaster ) blastula was investigated. The time course of embryonic development before the gastrula stage was determined by counting the number of surface cells on a 0.25 mm line at the animal pole. Pregastrula embryos with 2–3, 4–5, 6–7 and 7–8 cells roughly correspond to those at 14, 14–12, 8–6 and 4–0 hr before the beginning of gastrulation. Using presumptive ectoderm of the early gastrula stage, 15 min was found to be the minimum time of contact necessary for the realization of induction. The reactivity of the presumptive ectoderm from pregastrula embryos was tested by 30 min contact. Presumptive ectoderm up to the 4–5 cell stage did not react to the inductor. It may become competent within the next 4–8 hr, since the ectoderm from embryos in the 6–7 cell stage was reactive.     

The ultrastructure of anionic sites in rat articular cartilage as revealed by different preparation methods and polyethyleneimine staining

The ultrastructure of anionic sites in the middle layer of rat articular cartilages was studied by two methods, the quick-freezing and deep-etching method, and the quick-freezing and freeze-substitution method. The anionic sites were visualized with a cationic tracer, polyethyleneimine. They were also compared with those revealed in tissues subjected to conventional fixation, such as pre-embedding or post-embedding. With the deep-etching method, three-dimensional meshwork structures were observed more clearly in the extracellular matrix compared with those seen in conventional ultrathin sections. In combination with polyethyleneimine staining, in which no chemical contrast was needed for visualization of anionic sites, numerous stained particles were detected around filaments in the extracellular matrix, indicating that they were anionic sites consisting mainly of proteoglycans. With the pre-embedding method and polyethyleneimine staining, the shapes of aggregated stained particles varied with different preparation procedures, including chemical fixation and contrasting. The fine meshworks were also observed with the post-embedding method and polyethyleneimine staining. It is suggested that such images of anionic sites, as revealed by the deep-etching method and the post-embedding polyethyleneimine-staining method with low-temperature dehydration, are probably closer to native states than those revealed by the conventional pre-embedding polyethyleneimine-staining method. © 1998 Chapman & Hall     

The influence of male age on within‐pair and extra‐pair paternity in passerines

Although male age has often been found to predict success in gaining extra‐pair paternity, it is unclear whether this gain is associated with an individual’s success in avoiding cuckoldry. We examined the relationship between male age and both within‐ and extra‐pair paternity in passerines using a meta‐analytical approach. There was a positive correlation between male age and success in extra‐pair paternity but little evidence for an association between male age and within‐pair paternity. In addition, effect sizes for male within‐pair paternity and male extra‐pair paternity were not significantly correlated. Thus, factors that predict success in obtaining extra‐pair paternity, such as male age, may not necessarily predict success in avoiding cuckoldry.     

Quantitative trait loci controlling aluminium tolerance in two accessions of Arabidopsis thaliana (Landsberg erecta and Cape Verde Islands)

Quantitative trait loci (QTL) analysis of aluminium (Al) tolerance was performed using Ler/Cvi recombinant inbred (RI) lines of Arabidopsis thaliana. Relative root length (RRL) (root length with 4 µm Al/root length with no Al at pH 5.0) on day 5 was used as the Al tolerance index for QTL analysis. Al tolerance judged by RRL was well correlated to tolerance judged by other indexes, including accumulation of callose, reactive oxygen species in the root apex and growth performance on acid soil containing a large amount of exchangeable Al. Using data sets with an h_b² of 0.91, two QTLs were detected at the top of chromosome 1 and bottom of chromosome 3. These QTLs explained 40 and 16% of the phenotypic variation of Al tolerance, respectively, and the positive effect of the Cvi allele. The QTL on chromosome 1 overlapped with a major QTL in another recombinant inbred population, and is possibly related to malate excretion. A complete pair-wise search revealed 11 sets of epistatic interacting loci pairs, which accounted for the transgressive segregation among the RI population. Several epistatic interactions shared the same chromosomal region, indicating the possible involvement of regulatory proteins in Al tolerance in Arabidopsis.