Biochemical and ecological characterization of two peroxidase isoenzymes from the mangrove, Rhizophora mangle

This study examines phenolic peroxidase (POX) in Rhizophora mangle L. leaves in order to assess its role in phenolic manipulation and H₂O₂ scavenging. Sun-exposed and understorey leaves experiencing varying degrees of nutrient stress were analysed from an oligotrophic cay off the coast of Belize. POX activity was unaffected by growth environment, but increased throughout leaf development and persisted through senescence and after abscission. Histochemical analyses indicated POX activity throughout leaf tissues, especially in the apoplast. Phenolics were similarly broadly distributed. Two isoenzymes of POX were partially characterized with pIs of 4.1 and 6.3 and masses of 65.5 and 54.3 kDa, respectively. The larger, more acidic isoenzyme showed especially high heat stability, showing no reduced activity after 24 h at 60 °C. Rhizophora mangle POX oxidized quercetin preferentially, and, to a lesser extent, coniferyl alcohol, caffeic acid, chlorogenic acid, and p-coumaric acid. It did not oxidize ascorbate, but ascorbate could act as a secondary electron donor in the presence of a phenolic substrate and H₂O₂. However, because quercetin and other aglycones were not present in R. mangle leaves, and because POX showed no activity with the most abundant leaf flavonoid, rutin, it was concluded that detoxification of H₂O₂ is secondary to the other roles of POX in manipulation of phenolics.     

Studies in the Physiology of the Onion Plant: V. AN INVESTIGATION INTO THE GROWTH SUBSTANCE CONTENT OF BULBING ONIONS

Extracts have been prepared from induced and non-induced onionplants. These extracts have been fractionated and the ether-soluble,acidic components investigated using the wheat coleoptile straight-growthassay, colorimetric determination of 3-indolylacetic acid (IAA),and a new bioassay which has been introduced and modified togive reproducible results. This last is an assay of substanceswhich will cause ‘bulbing’ (swelling of the leafbases) of onion plants, and it has been used to demonstratea number of factors which influence the initiation of bulbingin the onion. It has been shown that substances are presentin extracts of onion tissue which will cause an increase inthe ‘bulbing ratio’ of test onion seedling sections. Results indicate that there is an increase in the IAA contentto a very high level during the first week following induction—beforethere is any visible sign of swelling of the leaf bases—butthat this falls off rapidly after 5–7 days and eventuallyfalls below the level found in non-induced plants.     

Colony size, reproductive success, and colony choice in Cave Swallows Petrochelidon fulva

We investigated how annual reproductive success, as measured by the number of nestlings surviving to day 10 and the percentage of nests that were successful, varied with colony size of the Cave Swallow Petrochelidon fulva in south central Texas. We also studied whether Cave Swallows chose colonies, in part, on the basis of reproductive success at a site the previous year. Neither measure of reproductive success varied significantly with colony size for either first-wave or second-wave nestings. Mean clutch size per colony did not vary significantly with colony size. Mean nestling body mass, an index of parental foraging efficiency, was unrelated to colony size, except for broods of five, in which nestling mass declined significantly with colony size. Colony size was not significantly affected by reproductive success at the site the previous year, although sites with more successful nests during the first wave declined less in size during the second wave within the same season than did sites that had fewer successful first-wave nests. Unlike the closely related Cliff Swallow Petrochelidon pyrrhonota , Cave Swallows did not use breeding performance of conspecifics in choosing nest-sites, because they did not preferentially aggregate at sites that were the most successful the previous year. Coloniality in Cave Swallows did not appear to have a net negative effect on annual fitness, suggesting that colonial nesting was not solely a response to nest-site limitation, but the benefits of breeding colonially (if any) were unclear.     

DNA microsatellites in the neon damselfish (Pomacentrus coelestis)

To determine the degree of genetic exchange between populations of the neon damselfish, Pomacentrus coelestis, among different reefs of the Great Barrier Reef, Australia, we characterized seven polymorphic microsatellite loci.     

Sex, diet and feeding method-related differences in body condition in the Oystercatcher Haematopus ostralegus

Measurements were made of Oystercatcher corpses to find the most reliable measure of body condition in live birds. Total body weight was as accurate as muscle thickness in assessing the weight of the pectoral muscles, a major store of protein reserves. Total body weight was also a good indicator of fat reserves. Wing‐length was the most reliable measure of body size. Body condition in live birds was measured as an individual's residual weight derived from a general linear model of (loge) body weight against age, month, (loge) wing‐length and time since capture. On the Exe estuary in autumn, there was no significant difference in body condition between same‐age Oystercatchers of different diets and feeding methods. In the winter months, however, body condition differed significantly between mussel feeders using different feeding methods, and between mussel feeders and birds that fed on worms and clams. Differences between diet/feeding methods were not the same for each age group. Birds with the highest mean body condition index in adults were mussel hammerers, in immatures mussel stabbers and in juveniles, worm/clam feeders. No significant difference in body condition was found between the sexes in any age group in autumn. In winter, when birds with the same diet/feeding method were considered, females were significantly heavier than males. However, when birds of all diets and feeding methods were combined, weight differences between the sexes were not apparent. We examine reasons why birds with certain diets and feeding methods may be heavier than others in winter, and why females are sometimes heavier than males. We conclude that, in most cases, it is due to differences between birds in their ability to achieve a common target weight. However, we conclude that adult females try to achieve a higher target weight than males, probably as a premigratory and prebreeding strategy. In the light of this, we consider the consequences for adult females, in terms of reproductive success and survival, of specializing in diets and feeding methods associated with lower body weights in winter.     

Sex-ratio differences in Mnium hornum Hedw. and M. undulatum Sw. in relation to spore germination and vegetative regeneration

As Mnium undulatum was shown to be homosporous, it was concludedthat neither male nor female derived an advantage from sporesize that might be related to the observed excess of femaleplants. The rate of germination was greater at 20 °C thanat 10 °C in M. hornum and M. undulatum, and was also reducedin short days (7.25 hours) at both temperatures. Spores of M.undulatum germinated more slowly than those of M. hornum undereach of the environmental regimes used. Isolated spores of M.undulatum showed a ratio of 1: 4.1 compared with 1: 0.89 inM. hornum. The excess of female plants of M. undulatum thathad been established by the end of germination, was maintainedamongst the first protonemal buds produced (1: 3.5), whereasan excess of male M. hornum was observed in the first protonemalbuds (1: 0.45). Frost reduced the rate of germination in M.undulatum, but unlike desiccation did not affect the final percentage.Male and female were amongst the spores which survived desiccationat 10 °C. Regeneration of detached leaves occurred more rapidly in M.undulatum than in M. hornum, and no difference between maleand female was detected. It was found that frost prior to orduring regeneration did not produce long-term harmful effectsin M. undulatum. None of the young male gametophytes producedby regeneration from leaves survived desiccation, compared with77 per cent of similarly produced female gametophytes.