Histochemical and histofluorescence tracing of chelatable zinc in the developing mouse.

Zinc is an essential element in mammalian development. However, little is known about concentrations of zinc in specific regions/organs in the embryo. We have employed selenite autometallography (AMG) and TSQ histofluoroscence to detect histochemically reactive (chelatable) zinc in whole midsagittal embryos and sections from neonatal mice. Chelatable zinc exhibited a broad distribution, being particularly localized to rapidly proliferating tissues, such as skin and gastrointestinal epithelium. Zinc was also observed in various types of tissues such as bone and liver. In the perinatal central nervous system, zinc was present almost exclusively in choroid plexus. The two methods used demonstrated generally similar distributions with some exceptions, e.g., in liver and blood. The ubiquity of zinc in the embryo, particularly in rapidly proliferating tissues, suggests a widespread role in fetal physiology.     

Application of complex conservation strategy to <Emphasis Type="Italic">Iris atrofusca</Emphasis> of the Northern Negev,Israel

We applied the quasi in situ conservation strategy, described in an accompanying paper, to a critically endangered plant species, Iris atrofusca from the Northern Negev, Israel. As the first steps of this strategy implementation we performed habitat and demographic observations; creation of two living collections outside the natural populations, but within the same ecological conditions; and relocation experiments. Plants in the living collections got established and showed high reproductive potential. In the relocation experiments, 3 years after introduction of rhizomes, no firm conclusions could be made about factors limiting species distribution at either large or small scale, but microhabitat was important for relocation success. We conclude that complex conservation approach that includes quasi in situ strategy should be useful for an endangered species that is distributed over variable ecological conditions.     

Symbiotic bacteria enable olive flies (Bactrocera oleae) to exploit intractable sources of nitrogen

Insects are often associated with symbiotic micro‐organisms, which allow them to utilize nutritionally marginal diets. Adult fruit flies (Diptera: Tephritidae) associate with extracellular bacteria (Enterobacteriaceae) that inhabit their digestive tract. These flies obtain nutrients by foraging for plant exudates, honeydew and bird droppings scattered on leaves and fruit – a nutritional niche which offers ample amounts of carbohydrates, but low quantities of available nitrogen. We identified the bacteria resident in the gut of the olive fly (Bactrocera oleae) – a worldwide pest of olives and examined their contribution to nitrogen metabolism in the adult insect. By suppressing bacteria in the gut and monitoring female fecundity, we demonstrate that bacteria contribute essential amino acids and metabolize urea into an available nitrogen source for the fly, thus significantly elevating egg production. In an ecological context, bacteria were found to be beneficial to females subsisting on bird droppings, but not on honeydew – two natural food sources. We suggest that a main gut bacterium (Candidatus Erwinia dacicola) forms an inseparable, essential part of this fly's nutritional ecology. The evolution of this symbiosis has allowed adult flies to utilize food substrates which are low or imbalanced in assimilable nitrogen and thereby to overcome the nitrogen limitations of their natural diet.     

Phosphonic acid derivatives of 1,3-dioxan: Potential plant growth regulators

A series of novel (0,0-dialkyl)phosphono derivatives of 1,3-dioxan was prepared, with various alkyl substituents on different positions on the ring carbon atoms. The compounds were obtained by an Arbuzov-type rearrangement of trialkyl phosphites either with halogenoacetals or with 2-alkoxy-1,3-dioxans. The products were tested as potential plant growth regulators, using as a primary screen the effect in a tissue culture of green and white cells, followed by algal growth experiments, green-house tests on barley and maize, and small scale field trials on cucumber, tomato and maize.