A bacteriological survey of an oyster-growing area: The Oualidia Lagoon,Morocco

A 3-year bacteriological survey of an oyster-growing area in Morocco, where the Japanese oyster (Crassostrea gigas) is grown, showed that the contamination of this lagunar ecosystem was not continuous but intermittent and that animal manure and human recreational activities were important sources of pollution. The major source of contamination was of animal origin, except during the summer, when human contamination prevailed.     

Phosphorus deficiency induced by nitrogen input in Douglas fir in the Netherlands

Summary A re-examination of earlier NPK fertilization experiments in Douglas fir stands on sandy soils shows the effects of high nitrogen input by air pollution during the last 10–15 years on plant nutrition at these sites. In 1960, experimental plots showed a positive growth reaction to nitrogen, phosphorus, and potassium fertilization. All suffered from severe phosphorus deficiency in 1984, low phosphorus in the needles was invariably accompanied by a high nitrogen content, with all N/P ratios between 20 and 30. The same conclusion emerges from an independent investigation of nutrient status of a selection of Douglas fir stands. Hence, if stand productivity and a balanced nutrient status of the trees is to be maintained, the increase in atmospheric input of nitrogen calls for supplementary fertilization. Given the current N/P ratios in the needles, a positive growth response to phosphorus fertilization is to be expected.     

Nitrogen fixation in coniferous bark litter

Summary Non-symbiotic heterotrophic N₂ fixation in coniferous bark litter was investigated with the acetylene reduction assay under aerobic and anaerobic conditions. The litter studied was composed essentially of bark, of pH 5 and a C/N ratio of 101; the ratio of available C to available N, which governs N₂ fixation, was considerably higher. The rate of N₂ fixation was estimated as 2.5–4.4 g N. g^–1 dry wt. day^–1. Nitrogenase activity was still evident after seven months of incubation under aerobic conditions. The N₂-ase activity was O₂ dependent: under anaerobic conditions no N₂-ase activity was found unless a fermentable C source was added. The importance of N₂ fixation in N-poor litter for the maintenance of soil fertility is emphasized.     

Figs (Ficus spp.) and fig wasps (Chalcidoidea, Agaonidae): hypotheses for an ancient symbiosis

Figs and their pollinating fig wasps are dependent on one another for propagation of their own kinds. The wasps reproduce by ovipositing through the styles of female flowers within the closed fig receptacles (syconia). About half of the female flowers within the syconia of monoecious figs have styles which are longer than the ovipositors of the wasp, and they will therefore produce seeds rather than wasp larvae. Since a longer ovipositor would enable a wasp to reach more ovules and deposit more eggs, the question arises at to why longer ovipositors have not evolved.
In an attempt to answer this question, four seemingly plausible hypotheses are examined but each is shown to be problematical in some way. Consideration is then given to a fifth hypothesis which proposes that ovipositor length is constrained by abortion of syconia with relatively few seed embryos and many agaonid larvae. It is argued first that this pattern of abortion will be selected during a sustained period of heavy wasp infestation because seeds will then become scarce relative to pollen-carrying wasps. Increased expenditure by the fig on seed production would therefore be favoured by natural selection. A greater expenditure on seeds would occur if young syconia with exceptionally heavy wasp infestations were dropped and the saved nutrients invested in syconia of a subsequent crop containing average levels of wasp larvae and seeds. Provided that the energy and nutrient cost of dropping young syconia is small, the selective advantage to the wasp of longer ovipositors is eliminated in this way. A stable coexistence of figs and wasps is therefore possible. The paper concludes by discussing two general predictions of the abortion hypothesis, and how these may be tested.     

Effects of intravenous epinephrine on macaque platelets

Blood was obtained from three species of macaques for a study of platelets. A rapidly mobilizable platelet pool was demonstrated in rhesus macaques given intravenous epinephrine. The number of platelets/ml of blood increased about 30% 3 to 5 min after epinephrine was given. The size distributions of the platelets were similar before and after injection. Platelet aggregability was increased after injection. Basal platelet aggregabilities, as measured by platelet aggregate ratios, were similar in rhesus macaques. Celebes black macaques, and human subjects, but were significantly greater in cynomolgus macaques than in the other three species.     

Relationship between chloroplast structure and O2 evolution rate of leaf discs in plants from different biotopes in South Finland

Abstract The chloroplast ultrastructure, especially the thylakoid organization, the polypeptide composition of the thylakoid membranes and photosynthetic O₂ evolution rate, chlorophyll (Chl) content and Chi a/b ratio were studied in leaves of nine plants growing in contrasting biotopes in the wild in South Finland. All the measurements were made at the beginning of the period of main growth on leaves approaching full expansion, when the CO₂-saturated O₂ evolution rate (measured at 20°C and 1500 μmol photons m^?2s^?1) was at a maximum, ranging from 19.2 to 6.9 μmol O₂ cm^?2 h^?1. Among the species, the Chi a/b ratio varied between 3.75 and 2.71. In the mesophyll chloroplasts, the ratio of the total length of appressed to non-appressed thylakoid membranes varied between 1.07 and 1.79, the number of partitions per granum varied between 2.8 and 12.0 and the grana area between 21 and 42% of the chloroplast area. There was a significant relationship between the rate of O₂ evolution of the leaf discs and the thylakoid organization in the mesophyll chloroplasts. The higher the O₂ evolution rate, the lower was the ratio of the total length of appressed to non-appressed thylakoid membranes and also the lower the grana area. Although the relationship of the photosynthetic rate with the Chi content and the Chi a/b ratio of the leaves was not as clear, a significant negative correlation existed between the Chi a/b ratio and the ratio of appressed to non-appressed thylakoid membranes, indicating lateral heterogeneity in the distribution of different Chl- protein complexes.     

Study on growth and biomass of underground organs ofTypha angustata Bory & Chaub

Underground and aboveground biomass and their ratios at flowering time in different natural stands of Typha angustata near Jaipur, India were studied in the field and experimentally over a period of eleven months (June to April). The underground biomass was 40–50% of the aboveground biomass in both natural and experimental conditions.     

Is male back space limiting? An investigation into the reproductive demography of the giant water bug,Abedus indentatus (Heteroptera: Belostomatidae)

Because male giant water bugs in the subfamily Belostomatinae provide parental care by brooding eggs on their back, an accurate assessment can be made of both the actual and potential reproductive capacity of males. Two operational sex-ratio (OSR) indices were developed and empirically measured for a population of giant water bug, Abedus indentatus,in California. One index was based on reproductive rates measured in the laboratory; the other index was based on reproductive resources observed in the field. Both OSR indices suggest that the operational sex ratio fluctuates between maleskewed ratios in the summer and femaleskewed ratios in the winter. This pattern appears to be the consequence of two factors. First, the adult sex ratio is significantly female biased. Second, although males can outreproduce females at high ambient temperatures, the reverse is true at low temperatures. Possible reasons for the female-skewed adult sex ratio are examined, including differential recruitment, differential mortality, and sampling bias.