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.     

Diamondback moth females oviposit more on plants infested by non‐parasitised than by parasitised conspecifics

Abstract 1. When offered a choice, female diamondback moths (Plutella xylostella) oviposited more eggs on plants with non‐parasitised conspecific larvae than on plants with parasitised larvae. 2. The leaf area consumed by parasitised larvae was significantly lower than that by non‐parasitised larvae. However, this quantitative difference in larval damage did not explain the female’s ability to discriminate between plants with parasitised and non‐parasitised larvae, as females showed an equal oviposition preference for plants infested by higher or lower densities of non‐parasitised larvae. 3. Pupal weight and duration of the larval stage of P. xylostella were independent of whether larvae were reared on plants that were previously infested by either non‐parasitised or parasitised larvae. 4. The larval parasitoid Cotesia vestalis did not distinguish between plants infested by non‐parasitised larvae and plants infested by larvae that had already been parasitised by conspecific wasps. 5. Based on these data, it can be concluded that the moth oviposition preference for plants infested by non‐parasitised conspecifics relative to plants infested by parasitised conspecifics was not explained by plant quality or by the attractiveness of plants towards wasps. It is hypothesised that one of the reasons for this preference is avoidance of plants where a relatively high risk of parasitism is expected due to the emergence of parasitoids from the parasitised host larvae.     

Oxidative phosphorylation and the electron transport system of castor bean mitochondria

The difference spectrum (reduced minus oxidized) of castor bean(Ricinus communis L.) mitochondria showed the presence of cytochromeoxidase (cytochromes a+a₃), b-type cytochromes and cytochromec. The mitochondria actively oxidized succinate, -ketoglutarate,pyruvate and exogenous NADH, and oxidations of these substrateswere stimulated by added ADP, as in mammalian mitochondria.Values for the P/O ratio obtained for succinate, pyruvate and-ketoglutarate were the same as those reported for mammalianmitochondria, indicating that theoretical values are 2, 3 and4, respectively. The theoretical P/O ratio for exogenous NADHseemed to be 2. Oxidations of succinate and exogenous NADH instate 3 were almost completely inhibited by 0.3 mM cyanide and10 µM its antimycin A, while those of NAD⁺-linked substratesin state 3 were not completely suppressed even by excess concentrationsof these inhibitors. There seem to be two types of pathway forelectron transfer in the oxidation of NAD⁺-linked substratesin castor bean mitochondria, i.e. pathways which are sensitiveand insensitive to these inhibitors. Oxidation of exogenousNADH in state 3 was not inhibited by rotenone. Transitions of redox levels of the respiratory components fromstate 4 to state 3 on addition of ADP and from state 3 to state4 on exhaustion of added ADP were observed with a dual-wavelengthspectrophotometer. Effects of inhibitors on redox levels ofthe respiratory components in state 3 were investigated. Cytochromesof b-type and cytochrome c were fully reduced on addition ofcyanide. Cytochromes of b-type were also fully reduced on additionof antimycin A, but cytochrome oxidase (cytochromes a + a₃)and cytochrome c changed to the oxidized forms. The redox levelof the component(s) with an absorption maximum at 465 mµshifted further, but not completely, to the reduced side onaddition of antimycin A. However, this component(s) was oxidizedon addition of cyanide. Cyanide-, or antimycin A-resistant oxidationof NAD⁺-linked substrates seems to occur via an alternate electrontransfer pathway branching from NAD⁺-linked flavoprotein(s)in the mitochondria, not via the normal pathway through thecytochromes-cytochrome oxidase system. (Received June 8, 1970; )     

Inter-and intraspecific differences in fatty acid composition of freshwater crustacean zooplankton

1. The composition of fatty acids (FA) from C14 to C18 was measured for edible seston and for individual Daphnia galeata , Diaphanosoma brachyurum and Eodiaptomus japonicus from Lake Biwa using a pyrolysis–gas chromatography (Py–GC) method. Based on the relative abundance of the FA, inter-and intraspecific differences in composition were examined.
2. Among the FA, C16 : 0 was the most abundant, both in the three zooplankton species and in edible seston smaller than 20 μm, suggesting that the composition of the zooplankton was roughly reflected by their diet. However, the abundance of C18 : 1 relative to C16 : 1 and C18 : 0 was much higher in each zooplankton species than in the diet.
3. Comparison of the relative abundance of FA among the three zooplankton species revealed that intraspecific differences in FA composition are greater than interspecific differences. These results indicate that variability in FA composition is not necessarily species-specific, and can be obscured by variation in composition between individuals.     

Biological response to experimental damage of the phragmocone and siphuncle in Nautilus pompilius Linnaeus

Tsujino, Y & Shigeta, Y. 2012: Biological response to experimental damage of the phragmocone and siphuncle in Nautilus pompilius Linnaeus. Lethaia, Vol. 45, pp. 443–449. Three adult specimens of Nautilus pomplilius Linnaeus from the Philippines were experimented on to estimate the biological response to damage of the phragmocone and siphuncle in this cephalopod mollusc. In addition, the data obtained from the experiments were used for discussion of shell damage in ammonoids and in other extinct cephalopods. Specimen’s phragmocone and siphuncle were perforated and severed artificially, followed by observations in the laboratory tank during periods of 75 and 132 days. For at least 2 or 3 months, all individuals survived after damage to the phragmocone and siphuncle despite loss of neutral buoyancy. Based on our observations after completion of the experiments, the severed adoral remaining part of siphuncle healed by the siphunclar epithelium. In addition, perforation of the phragmocone was partly repaired by shell secretion from the dorsally extending mantle due to subsequent volution of shell growth. Our experiments revealed that damage to the phragmocone and siphuncle in Nautilus was not necessarily a lethal injury. It may be possible that such biological response also applies to extinct ammonoids and nautiloids. In a similar case of extinct ammonoids and nautiloids, damage to their phragmocone and siphuncle may also not have been a lethal injury as with Nautilus. However, some factors leading to death are likely to be dependent on the degree of damage to the phragmocone and siphuncle and influence of hydraulic pressure. □Ammonoids, injury, nautiloids, Nautilus, phragmocone, repair, siphuncle.     

Airborne‐pollen pool and mating pattern in a hybrid zone between Pinus pumila and P. parviflora var. pentaphylla

The reproductive isolation barriers and the mating patterns among Pinus pumila, P. parviflora var. pentaphylla and their hybrids were examined by flowering phenology and genetic assays of three life stages: airborne‐pollen grains, adults and seeds, in a hybrid zone on Mount Apoi, Hokkaido, Japan. Chloroplast DNA composition of the airborne‐pollen was determined by single‐pollen polymerase chain reaction. Mating patterns were analysed by estimating the molecular hybrid index of the seed parent, their seed embryos and pollen parents. The observation of flowering phenology showed that the flowering of P. pumila precedes that of P. parviflora var. pentaphylla by about 6 to 10 days within the same altitudinal ranges. Although this prezygotic isolation barrier is effective, the genetic assay of airborne‐pollen showed that the two pine species, particularly P. pumila, still have chances to form F₁ hybrid seeds. Both parental species showed a strong assortative mating pattern; F₁ seeds were found in only 1.4% of seeds from P. pumila mother trees and not at all in P. parviflora var. pentaphylla. The assortative mating was concluded as the combined result of flowering time differentiation and cross‐incompatibility. In contrast to the parental species, hybrids were fertilized evenly by the two parental species and themselves. The breakdown of prezygotic barriers (intermediate flowering phenology) and cross‐incompatibility may account for the unselective mating. It is suggested that introgression is ongoing on Mount Apoi through backcrossing between hybrids and parental species, despite strong isolation barriers between the parental species.     

Induction of DNA synthesis by 2,4-dichlorophenoxyacetic acid during callus induction in Jerusalem artichoke tuber tissues

During the induction of DNA synthesis in Jerusalem artichoke (Helianthus tuberosus L.) tuber by 2,4-D, the 2-¹⁴C-2, 4-D from the agar medium rapidly incorporated into the ethanol soluble and insoluble fractions. Although the 2,4-D level in the ethanol soluble fraction decreased on transplantation of the tissue from the 2-¹⁴C-2,4-D medium to medium without the auxin, its level in the buffer-soluble and -insoluble macromolecular fractions increased. The purified, buffer-insoluble macromolecules were chromatin. The 2,4-D binding to chromatin particularly increased during DNA synthesis. The histone contents of chromatin decreased as DNA synthesis progressed. The polyacrylamide gel electrophoretic patterns of the histones showed a decrease in the moderately lysine-rich histone fraction as compared to other fractions. Thus, the decrease in the histone level caused by 2,4-D and the presence of the 2,4-D moderately lysine-rich histone complex may be closely related to the induction of DNA synthesis by 2,4-D in cells.     

DEVELOPMENT OF THE EMBRYONIC CHICKEN THYMUS III. UNEQUAL DIVISION OF LYMPHOID CELLS

Cell division of thymus lymphoid cells from 11- to 17-day old embryonic chickens, as well as chickens just after hatch was investigated on cell smears stained with Giemsa. Unequally dividing cells were observed in the developmental stage of thymocytes. At the telophase of such cells, the cytoplasm of one of two future daughter cells was apparently larger in amount and was sometimes stained deeper than the cytoplasm of its counterpart. Unequal division was also observed in pro-, meta- and anaphase; sometimes a dividing cell had a large cytoplasmic process belonging to one hemisphere, suggesting that only one of the two daughter cells would receive the cytoplasmic process through cell division.
The incidence of unequal division calculated by a rough estimation was around 10% of the total cell division between 11 and 13 days of embryonic development, and decreased progressively thereafter.     

Role of male‐biased dispersal in inbreeding avoidance in the grey‐sided vole (Myodes rufocanus)

Effects of male‐biased dispersal on inbreeding avoidance were investigated in a semi‐natural population of Myodes (formerly Clethrionomys) rufocanus using a large outdoor enclosure (3 ha). Parentage of 918 voles weaned from 215 litters and relatedness of mates were analysed using microsatellite loci, and dispersal distances were obtained from mark–recapture live‐trapping data. Natal and breeding male‐biased dispersal was observed. There remained, however, chances that incestuous mating could occur, because not all males dispersed from their natal site, and 51 matings occurred between relatives (relatedness r > 0). The number of weaned juveniles from inbred litters was significantly smaller than that from non‐inbred litters. Fourteen incestuous matings occurred between close relatives (r ≥ 0.25), most of which were those between non‐littermate maternal half siblings (four cases) and those between paternal half siblings (seven cases). When comparing the observed frequencies to the expected ones generated by combining every oestrous female with a male randomly chosen from her surroundings, the observed values for inbreeding of r ≥ 0.25 were significantly smaller than the expectations, while no difference was observed for inbreeding of 0 < r < 0.25. These results suggest that male‐biased dispersal is partly effective to avoid incestuous mating, but it does not provide complete separation of male and female close relatives. Additional mechanisms such as kin discrimination based on familiarity may work in inbreeding avoidance of the vole.