Regulation of Growth in Avena (Oat) Stem Segments by Gibberellic Acid and Abscisic Acid

The purpose of this study was to analyze the nature of the interaction between gibberellic acid (GA₃) and abscisic acid (ABA) in the regulation of growth in excised Avena (oat) stem segments. Growth, compared to sucrose controls, was inhibited by ABA in the range of 10^?4 to 10^?6M. GA₃-promoted growth was also inhibited by ABA in the same concentration range. A Lineweaver-Burk analysis of the interaction between GA₃ and ABA indicated that ABA acts in a non-competitive fashion with GA₃. This same result was obtained previously with GA₃-indoleacetic acid (IAA) and GA₃-kinetin interactions with Avena stem sections. Our results indicate that ABA can inhibit GA₃-promoted growth within physiological concentrations, and that it is probably acting at a different physiological site from that for GA₃.     

Transfer of Immunity to Tumour Isografts by the Systemic Administration of Xenogeneic “Immune” RNA

SPECIFIC immunoreactivity can be conferred on lymphoid cells by incubation with RNA-rich extracts prepared from lymphoid tissues exposed to specific antigens in vivo¹ and in vitro^2,3. We have shown transfer of immunity to tumour specific antigens in vivo⁴ and in vitro⁵ by incubation of syngeneic spleen cells in vitro with RNA extracted from the lymphoid tissues of xenogeneic or syngeneic animals immunized with the tumour to be treated. Administration of these spleen cells to normal animals decreased the development and growth of isografts of the same tumour.     

Distribution, production and role of aquatic macrophytes in a southern Michigan marl lake

A typical marl lake of the Upper Great Lakes region has very few quantitatively important aquatic macrophytes. The macrophytes, however, dominate the total primary production of the lake. Submersed vegetation is extremely sparse on the shallow (less than I m) marl bench that characterizes the littoral of these lakes, and is completely dominated by one. little-known species (Scirpus subterminalis Torr.) between 1 and 7 m. A detailed investigation of the spatial and seasonal distribution of macrophytic species and biomass showed that S. subterminalis strongly dominated the lake (79% of total biomass). S. suhterminalis represented an almost pure stand (to 200 g m^?2 mean annual ash-free dry weight) at all times of the year at intermediate depths of macrophytic growth (1–6 m). Two species of Chara (of eight varieties and forms) were present in significant quantities (12% of total biomass; to 100 g m^?2) but were severely limited to shallow depths (0-S-l m) and protected areas. Several annual submersed angiosperms were present (9% of total biomass), but only two species were quantitatively important. Potamogeton illinoensis Morong. and P. praelongus Wulfen formed brief summer peaks (less than 100 g m^?2) at 3 and 4–6 m, respectively. A striking feature of the seasonal biomass distribution of Scirpus subterminalis was the higher, viable biomass (to 150g m^?2) throughout the winter under ice cover. Cyclic fluctuations of the S. subterminalis populations were discerned at different depths, each with different periodicities. The population at 2 m exhibited a fall peak; that at 4 m had a summer maximum. The lowest overall biomass of S. subterminalis occurred in the 2 m population in June. Chara populations at 0–2 m also exhibited a relatively constant biomass throughout the year. The appearance of Nitella at 7 m in July-October and of Chara at 5 m in September-October was interpreted as an interaction between light, thermal, and carbon stratification. Estimates of macrophytic productivity of perennial (‘evergreen’) species populations whose biomass remains relatively constant throughout the year were made employing several different methods of calculation and turnover factors. All methods resulted in productivity estimates in good agreement with the conservative value of 178 g m^?2 year^?1 for the entire lake. In comparison to the other components (phyto-planktonic, epiphytic and epipelic algae) of the primary production of Lawrence Lake, the aquatic macrophytes constituted a major portion (anuual mean 82·77 g C m^?2 year^?1 or 48·3 %) of the total production of the lake. The low diversity but relatively high quantitative importance of macrophytes in marl lakes is attributed to an adverse dissolved inorganic and organic chemical milieu which inhibits phytoplanktonic production and allows only certain adapted macrophytes to develop strongly. The phenomenon of perennial biomass levels throughout the year is believed to be much more common than previously suspected and has iikely resulted from adaptations of submersed macrophytes to ameliorated conditions of water and temperatures relative to the terrestrial situation in winter.     

The relation of Late Ordovician glaciation to the Ordovician-Silurian changeover in North American brachiopod faunas

Sheehan, P. M.: The relation of Late Ordovician glaciation to the Ordovician-Silurian changeover in North American brachiopod faunas.
The Ordovician-Silurian changeover of brachiopod faunas in North American epicontinental seas involved the abrupt extinction of endemic Late Ordovician stocks and subsequent repopulation of North American seas by Old World taxa. The Late Ordovician Gondwanaland glaciation may have lowered sea levels sufficiently to place severe stress on the widespread shallow marine faunas in North America, resulting in their eventual extinction. The Late Ordovician depositional history in North America is not well enough known to establish the presence of a latest Ordovician regression, but the earliest Silurian was an interval of off-lap in North America. Therefore, the glacial lowering of sea level is considered to be the most likely cause of the faunal changeover.     

Pantothenic Acid Metabolism During Avian Malaria Infection: Pantothenate Kinase Activity in Duck Erythrocytes and in Plasmodium lophurae*

SYNOPSIS. The initial enzymatic reaction in the pathway of coenzyme A genesis from pantothenic acid, i.e., the conversion of pantothenic acid to phosphopantothenic acid catalyzed by pantothenic acid kinase, was found in extracts of avian erythrocytes but not in extracts of Plasmodium lophurae or intact parasites. The activity of the kinase was significantly higher in extracts prepared from normal duck erythrocytes than those infected with P. lophurae. The apparent absence of pantothenic acid kinase in P. lophurae is corroborative support for nutritional studies(7,9) which suggest that the avian malarial parasite is dependent for its supply of coenzyme A on the host cell.     

Responses of tree sap-feeding herbivores to elevated CO2

Five species of sap-feeding homoptera were studied on Fagus sylvatica and Acer pseudoplatanus and exposed to elevated concentrations of carbon dioxide (600 μL L^–1). The concentration of total soluble amino acids in foliage of F. sylvatica was unaffected by growing saplings in elevated atmospheric CO₂ concentrations. Although experiments on individual aphids indicated poorer performance of Phyllaphis fagi (fewer, smaller nymphs produced), resultant populations did not differ from those in ambient (350 μL L^–1) conditions. The area of beech foliage stippled by the leafhopper Fagocyba cruenta was similar at ambient and elevated CO₂ concentrations. The concentration of total amino acids and that of serine of A. pseudoplatanus foliage were significantly lower at elevated CO₂ concentrations. However, the relative growth rates of two aphid species Drepanosiphum platanoidis and Periphyllus testudinaceus and one leafhopper Ossiannilssonola callosa were not significantly different in elevated CO₂. No evidence was found that, under the conditions of these experiments, populations of aphids and leafhoppers will change as concentrations of CO₂ increase.     

Phylogenetic Position of Psalteriomonas lanterna Deduced from the SSU rDNA Sequence

ABSTRACT. The small subunit ribosomal DNA sequence (SSU rDNA) of the microaerophilic free-living amoeboflagellate Psalteriomonas lanterna has been sequenced and analyzed. The gene is 1,945 bp long and has a G + C content of 33.4%. Based upon ultrastructural studies, P. lanterna has been placed in the class Lyromonadea within the phylum Percolozoa Cavalier-Smith, 1991. However, based upon cytological characteristics, this microaerophilic free-living amoeboflagellate appears to be very primitive. It shares certain characteristics in common with some archezoans, i.e. it lacks mitochondria and dictyosomes but contains hydrogenosomes. Despite sharing these characteristics with the amitochondriate taxa, P. lanterna is not related to any of these taxa but instead to the Vahlkampfiidae. Therefore, we used primary sequence data and the secondary structure of the SSU rDNA gene to determine the placement P. lanterna in the phylogenetic tree. Our analyses showed that P. lanterna groups as a sister taxon to the Vahlkampfiidae but probably diverged from them quite early.     

New fossil paussids from Dominican amber with notes on the phylogenetic systematics of the paussine complex (Coleoptera: Carabidae)

The first fossil representative of the Protopaussinae and the second fossil Eohomopterus (Paussinae) are described from amber inclusions of Tertiary age collected in the Dominican Republic on the West Indian island of Hispaniola ( Protopaussus pristinus sp.n., Eohomopterus poinari sp.n.). These finds increase the total number of paussids present in Dominican amber to four species in three genera ( Protopaussus , Eohomopterus , Homopterus ). A key is provided for the identification of the New World genera of Protopaussinae and Paussinae and for the species of Eohomopterus . Based on synapomorphic character states, the paussid beetles are split into two subfamilies, the monobasic Protopaussinae and the more inclusive Paussinae (the twenty-three genera are placed into two supertribes: the Carabidomemnitae comprising two tribes and the Paussitae comprising eight tribes. The extant congeners of Eohomopterus and Homopterus live in the Neotropical Region, while the extant members of Protopaussus are known only from the Oriental Region. This record of New World Tertiary Protopaussus adds another example of the Old World relationships of taxa from Dominican amber. The temporal and geographical distribution of Protopaussus indicates that its present zoogeographical range may represent the relict of a wide Laurasian distribution in the past. It does not support the previously suspected Oriental centre of origin for the ancestral stock of {Protopaussinae + Paussinae}.     

Gynoecium diversity and systematics of the Magnoliales and winteroids

Carpel and ovule structure was compared in representatives of all 11 families of the Magnoliales (Annonaceae, Canellaceae, Degeneriaceae, Eupomatiaccae, Himantandraceae, Magnoliaceae, Myristicaceae) and winteroids (Austrobaileyaceae, Illiciaceae, Sehisandraceae, Winteraceae). Special attention was paid to features that are constant at family level. Bisexual flowers are always protogynous. In all representatives studied the carpels are closed at anthesis. Caipel closure is attained in three different ways: (1) postgenital fusion of inner surfaces (Degeneriaceae, Eupomatiaccae. Winteraceae), or (2) occlusion by secretion (Austrobaileyaceae, Sehisandraceae), or (3) a combination of (1) and (2): in Annonaceae, Canellaceae, Myristicaceae there is a conspicuous secretory canal in the innermost part of the ventral slit; in Illiciaceae and Magnoliaceae there is a narrow canal in the innermost part of the ventral slit; and in Himantandraceae the ventral slit is postgenilally fused in the style but completely open in the ovary. In most families the carpels have a double stigmalic crest or they have two tips in the transversal symmetry plane (i.e. at right angles to the median plane). Stigmas are unicellular papillate in most families but the papillae are bi-to multicellular (uniseriate) in Degeneriaceae and Eupomatiaceae. An unusual cryptic exlracarpellary compitum was found in Himantandraceae and Sehisandraceae. Intrusive oil cells were found in the carpel epidermis of Illiciaceae and Sehisandraceae. Mature ovules vary in length between 0.15 and 1.1 mm. The outer integument is fully annular (not semiannular) in Degeneriaceae, Himantandraceae, Canellaceae, Myristicaceae, and Illiciaceae. A rudimentary aril occurs in Canellaceae, and originates at the same site as in arillate Annonaceae and Myristicaceae. The results most strongly support an Annonaceae-Myristicaceae-Canellaceae alliance, to some degree also an Eupomatiaccac-Degeneriaceae-Himantandraceae-Magnoliaceae alliance, and an Illiciaceae-Schisandraceae-Winteraccae-Austrobaileyaceae alliance.     

The anatomy and systematics of the New Caledonian land snail genus Draparnaudia Montrouzier, 1859 (Pulmonata: Orthurethra)

A comprehensive study of the anatomy, ecology and distribution of the orthurethran genus Draparnaudia confirms its family-group status, and suggests a probable sister-group relationship with another Pacific family, the Partulidae; its previous position as a subfamily of the Enidae is refuted. Draparnaudia is endemic to New Caledonia, but records from the New Hebrides are thought to result from introductions. A total of six species are recognized in the taxonomic revision, including two new species. Spermatophores are recorded for the first time.