In vitro test of self-incompatibility in Malus domestica

Summary An in vitro assay in which self-incompatible pollen of Malus domestica is selectively inhibited is described. This assay involves heat-labile substances diffusing from the stylar tissues — in particular, glycoproteins found in the protein extract of styles. In the presence of the self-style extract, a dramatic decrease in total protein concentration in the culture medium was revealed at 30-min germination. Pretreatment of the self-pollen with 100 mM glucose prevented this drop in protein level; moreover, tube growth was entirely restored. A possible explanation in terms of protein-carbohydrate complementation is suggested.     

Sulphate reduction in oxic and sub-oxic North-East Atlantic sediments

Abstract Oxic and sub-oxic N.-E. Atlantic sediments were examined for sulphate-reducing activity. Oxygen and/or nitrate reduction are probably the dominant mineralisation processes in the abyssal plain sediment studied. A low rate of sulphate reduction (0.1 nmol SO²⁻₄/ml/day) was recorded in the surface 5 cm of the continental slope sediment, together with the presence of a range of sulphate-reducing bacteria (SRB). A higher activity of sulphate reduction (2.2 nmol SO²⁻₄/ml/day) occurred in the continental shelf sediment which led to a small decrease in pore water sulphate and an increase in titration alkalinity. This sediment contained approx. 10²–10³ acetate, lactate and propionate oxidising SRB/ml. No low- M _r organic acids were detected in these sediments. However, amendment with 75 μM acetate stimulated sulphate-reducing activity in the shelf sediment.     

Self-incompatibility (S) alleles of the rosaceae encode members of a distinct class of the T2/S ribonuclease superfamily

Stylar riboncleases (RNases) are associated with gametophytic self-incompatibility in two plant families, the Solanaceae and the Rosaceae. The self-incompatibility-associated RNases (S-RNases) of both the Solanaceae and the Rosaceae were recently reported to belong to the T2 RNase gene family, based on the presence of two well-conserved sequence motifs. Here, the cloning and characterization of S-RNase genes from two species of Rosaceae, apple (Malus × domestica) and Japanese pear (Pyrus serotina) is described and these sequences are compared with those of other T2-type RNases. The S-RNases of apple specifically accumulated in styles following maturation of the flower bud. Two cDNA clones for S-RNases from apple, and PCR clones encoding a further two apple S-RNases as well as two Japanese pear S-RNases were isolated and sequenced. The deduced amino acid sequences of the rosaceous S-RNases contained two conserved regions characteristic of the T2/S-type RNases. The sequences showed a high degree of diversity, with similarities ranging from 60.4% to 69.2%. Interestingly, some interspecific sequence similarities were higher than those within a species, possibly indicating that diversification of S-RNase alleles predated speciation in the Rosaceae. A phylogenetic tree of members of the T2/S-RNase superfamily in plants was obtained. The rosaceous S-RNases formed a new lineage in the tree that was distinct from those of the solanaceous S-RNases and the S-like RNases. The findings suggested that self-incompatibility mechanisms in Rosaceae and Solanaceae are similar but arose independently in the course of evolution.     

Distribution of unesterified and esterified pectins in cell walls of pollen tubes of flowering plants

Immunocytochemical localization of polygalacturonic acid (pectin) and methyl-esterified pectin in the walls of pollen tubes of 20 species of flowering plants grown in vitro was investigated by using monoclonal antibodies (MAbs) JIM5 and JIM7 and by means of confocal laser scanning microscopy (CLSM). In general, periodic annular deposits of pectins were found coating the tube wall in species possessing solid styles, and a more uniform pectin sheath in tube walls in species having hollow styles or no styles. We hypothesize that the periodic ring-like structure of the pectin sheath reinforces pollen tubes for passing through the transmitting tract in the style. Esterified pectin which prevents Ca²⁺-induced gelification of pectate is located predominantly at the apex. This implies that pectin esterification is related to tip wall loosening that is required for cell wall expansion during tip growth of pollen tubes. The occurrence of unesterified pectins in other areas of pollen tube walls suggests that de-esterification of pectin following tip expansion leads to a more rigid form of pectin that contributes to the construction of the pollen tube wall.     

Genotypic effects on the amino acid relationships in maize (Zea mays L.) pollen and style

Summary The free amino acid content of the pollen grains and the style from three single cross hybrids (Wf9 x H55, Ky49 x Ky27, K64 x K55) and two inbred lines (Oh43, H55) was determined. No tyrosine was detected in the pollen grains of any genotype. Significant differences between pollen genotypes were found for aspartic acid, threonine, serine, lysine and histidine with no effect resulting from the vigor of the pollen source. No proline was found in the style of any genotype. Significant differences between style genotypes were obtained for threonine, serine, glutamic acid, leucine, tyrosine, ethanolanine, aminobutyric acid and histidine with a relationship between vigor of the style genotype present for tyrosine, ethanolanine and aminobutyric acid. The relationship between the pollen and style level for each amino acid as influenced by genotype was analyzed. A significant negative correlation was found only for threonine. Apparently, a complementary relationship between the pollen and style exists for some amino acids. Proline and tyrosine are available only from the pollen and style respectively. Threonine levels are balanced with varying contributions from both pollen and style depending on the genotype.     

Les otolithes des Téléostéens du Plio-Pleistocène belge

The study of approximately twenty three thousand otoliths from Plio-Pleistocene sites in the harbour region of Antwerp, as well as a critical revision of already published material allowed us to identify a teleostean fauna with fourty seven species (including two subspecies and seven species in open nomenclature). Two of these, Ophidion springeri and Uranoscopus septentrionalis are new to science. The fauna is typical for coastal waters slightly warmer than those of the actual North Sea and caracterized by the predominance of Gadidae. Biostratigraphically this fauna is well individualized with respect to preceeding ones (only seven species in common with the Miocene fauna) and those following twenty-three species in common with the extant fauna). The following biostratigraphical subdivision has been recognized in the Upper Miocene and the Plio-Pleistocene of the Antwerp region: (1) an association with «genus? Macrouridarum labiatus, Trisopterus sculptus, Gadiculus benedeni and Trisopterus luscus spectabilis, in the Sands of Deurne (Upper Miocene); (2) an association with Gadiculus benedeni and Merlangius pseudaeglephinus, in the Formation of Kattendijk (Pliocene); (3) an association with Gadiculus verticalis and Merlangius pseudaeglefinus in the Formation of Lillo (Plio-Pleistocene); (4) an association with Gadus morhua and Merlangius pseudaeglefinus in the so called «Icenian deposits not present in Belgium but found in the Netherlands.     

Trophic niche partitioning of five skate species of genus Bathyraja in northern and central Patagonia,Argentina

Overexploitation of marine communities can lead to modifications in the structure of the food web and can force organisms like elasmobranchs to change their feeding habits. To evaluate the impact that fisheries have on food webs and on the interactions between species, it is necessary to describe and quantify the diet of the species involved and follow it through time. This study compares the diet of five skate species using the data obtained from the by-catch of the Argentine hake (Merluccius hubbsi) fishery in north and central Patagonia, Argentina. Diet composition was assessed by analysing the digestive tract contents and trophic overlapping between species of the genus Bathyraja: Bathyraja albomaculata, Bathyraja brachyurops, Bathyraja macloviana, Bathyraja magellanica and Bathyraja multispinis. A total of 184 stomachs were analysed. The diets of B. albomaculata and B. macloviana mainly comprised annelids, whereas that of B. brachyurops primarily comprised fish, including hake heads discarded by the fishery. The diets of B. magellanica and B. multispinis were largely based on crustaceans. Despite the morphological similarities and their shared preference for benthic habitats, no complete diet overlaps were found between the different species. These results suggest that these skate species have undergone a process of diet specialisation. This is a common feeding strategy that occurs to successfully eliminate competition when resources are limited, which corresponds to the conditions found in an environment being affected by the pressures of overfishing.     

Maritime Legislation of Mainland China and Taiwan: Developments,Comparison, Implications,and Potential Challenges for the United States

In January 1998, Taiwan promulgated the Law of the Republic of China (ROC) on the Territorial Sea and the Contiguous Zone and the Law of the Republic of China on the Exclusive Economic Zone (EEZ) and the Continental Shelf, both of which came into force on January 21, 1998. On June 26, 1998, China adopted the Law of the People's Republic of China on the Exclusive Economic Zone and the Continental Shelf, which is the most significant maritime legislation since its 1992 Law on the Territorial Sea and the Contiguous Zone. This article studies the recent maritime legislation developments in Mainland China and Taiwan, the differences and similarities between the two sets of laws, their implications for the Asia-Pacific region, and the potential challenges for the United States.     

Abundance and Distribution of Benthic Macroinvertebrates near Little Egg Inlet,New Jersey,from 1972 to 1974

Benthic collections taken during a 34 month period from Little Egg Inlet, New Jersey were dominated by haustoriid amphipods and collections from a nearshore ridge/swale formation were dominated by ampharetid and capitellid polychaetes. Polychaetes were most abundant at the swale station where density was 2.4 to 17.5 times higher than at other stations. Changes in species composition and density were influenced by increases in the silt/clay component of the sediment which was influenced by depth, bottom topography, and exposure to currents.     

A review of the chronostratigraphical ages of Middle Triassic to Late Jurassic dinoflagellate cyst biozones of the North West Shelf of Australia

The chronostratigraphical ages of the 20 dinoflagellate cyst zones and one dinoflagellate cyst assemblage for the Middle Triassic (Ladinian) to the Jurassic-Cretaceous transition of the North West Shelf of Australia are comprehensively reviewed. Evidence from macro- and micropalaeontology, palynology and strontium isotopes made available after the establishment of these biozones in the 1980s has been used to reassess the ages of this important zonal scheme and to calibrate it to the international stratigraphical stages. The Shublikodinium Superzone is renamed herein as the Rhaetogonyaulax Superzone, and based on conodont evidence is determined to span the Ladinian to Early Sinemurian. This is significantly shorter in duration than was originally envisaged (Late Anisian to Late Pliensbachian). The Luehndea Assemblage is a low diversity dinoflagellate cyst association which marks a eustatic rise; it is subdivided into two subzones. It is of latest Pliensbachian to Early Toarcian age, based largely on palynological evidence. The Bajocian to earliest Oxfordian Pareodinia ceratophora Superzone represents the inception of a continuous Mesozoic-Cenozoic dinoflagellate cyst record in Australia. It comprises seven zones, which are considered to be slightly older than originally interpreted. The overlying Pyxidiella Superzone is characterised by diverse dinoflagellate cyst associations. It is Early Oxfordian to Kimmeridgian in age, and comprises three zones. The bases of the Wanaea spectabilis and Wanaea clathrata zones are reinterpreted as being slightly older than originally proposed. The superjacent Fromea cylindrica Superzone is Tithonian to earliest Valanginian and modified ages are indicated for four of the nine zones. This unit is dominated by endemic dinoflagellate cysts, reflecting a global trend towards provincialism at this time due to a regressive eustatic regime.