A SUCTION TRAP FOR SMALL AIRBORNE INSECTS WHICH AUTOMATICALLY SEGREGATES THE CATCH INTO SUCCESSIVE HOURLY SAMPLES

This paper describes the design and operation of a suction trap which takes in air at a constant rate in winds up to 12 m.p.h. The catch is deposited in a collecting tube into which closely fitting disks fall, one every hour, thus segregating the catch into successive hourly samples. The trap is electrically driven; it operates in all weathers and heavy rain does not disorganize the catch.     

The influence of leaf‐atmosphere NH3(g) exchange on the isotopic composition of nitrogen in plants and the atmosphere

The distribution of nitrogen isotopes in the biosphere has the potential to offer insights into the past, present and future of the nitrogen cycle, but it is challenging to unravel the processes controlling patterns of mixing and fractionation. We present a mathematical model describing a previously overlooked process: nitrogen isotope fractionation during leaf‐atmosphere NH_3(g) exchange. The model predicts that when leaf‐atmosphere exchange of NH_3(g) occurs in a closed system, the atmospheric reservoir of NH_3(g) equilibrates at a concentration equal to the ammonia compensation point and an isotopic composition 8.1‰ lighter than nitrogen in protein. In an open system, when atmospheric concentrations of NH_3(g) fall below or rise above the compensation point, protein can be isotopically enriched by net efflux of NH_3(g) or depleted by net uptake. Comparison of model output with existing measurements in the literature suggests that this process contributes to variation in the isotopic composition of nitrogen in plants as well as NH_3(g) in the atmosphere, and should be considered in future analyses of nitrogen isotope circulation. The matrix‐based modelling approach that is introduced may be useful for quantifying isotope dynamics in other complex systems that can be described by first‐order kinetics.     

Glycoconjugate Synthesis During Gastrulation in Xenopus laevis

Xenopus laevis gastrulae show more incorporation of isotopicallyabelled glucosamine and galactose into TCA-insoluble materialsthan blastulae. These materials are high molecular weight anddegraded by pronase as judged by their behavior in various gelfiltration media. Labelled materials migrate slowly on celluloseacetate electrophoresis, bind to DEAE—cellulose and eluteat low ionic strength, but are not precipitated by cetyl pyridiniumchloride (CPC) in the presence of added carrier hyaluronic acid. Pulse—chase labelling experiments and light microscopicautoradiography were used to examine secretion and depositionof glucosamine and galactose—labelled materials in differentstages of developing Xenopus laeins embryos. After a 30-minpulse, grains are predominantly over cytoplasmic structures.After a 30-min pulse and a 60-min pulse chase, grains are commonlyencountered over cytoplasmic structures but are predominantlylocalized over extracellular materials. Scanning electron microscopic studies show that extracellularfibrillar materials increase in number during gastrulation inXenopus laevis. Increasing numbers of extracellular fibrillarstructures occur in the blastocoel cavity and along the inneraspect of the roof of the lastocoel (Nakatsuji and Johnson,1983).     

Cellular Differentiation in a Highly Specialized Insect Secretory Organ

The colleterial glands of insects are accessory reproductive structures which produce secretions that are applied to eggs after fertilization and which serve a number of protective functions. The colleterial glands of lepidoptera are of particular interest in the study of the events of cellular differentiation because they undergo rapid development, generally during the pupal adult transformation, and contain highly specialized cells which produce large amounts of a restricted variety of secretory products. The extreme specialization of these organs facilitates parallel studies of differentiation at the biochemical and morphological level. This communication describes the changes in the ultrastructure of cells which will form the protein-secreting segment of the colleterial gland of the moth Actias luna during the period of transition from the undifferentiated state to the acquisition of secretory ability.
An initial stage of general cellular proliferation by mitosis in the presumptive colleterial tissue mass is followed by differentiation of the cells in the absence of further mitosis. Four distinctive cell types are recognized during the phase of differentiation. These types include a chitogenous cell which forms the chitin lining of the main duct, and three cells which cooperate in the formation of a secretory apparatus. Cell A forms two temporary flagella-like structures which assist in the formation of a ductule, which eventually leads from the secretory cell to the main duct. Near the end of the differentiative phase, Cell A degenerates and is phagocitized by Cell B. Cell B becomes the actual secretory element, and acquires cytoplasmic features such as extensive rough endoplasmic reticulum and Golgi apparatus which are associated with synthesis and secretion of protein. The final element, Cell C, remains associated with the ductule which it helps to construct and which traverses its cytoplasm.     

Biochemical Changes Associated with Zygotic Pine Embryo Development

Johnson, M. A., Carlson, J. A., Conkey, J. H. and Noland, T.L. 1987. Biochemical changes associated with zygotic pine embryodevelopment.—J. exp. Bot. 38: 518–524. At intervals during the period from pre-fertilization to nearmaturation, pine (Pinus resinosa Ait. and Pinus strobus L.)ovules were analysed for several biochemical constituents, andthe results were expressed on a fresh weight basis. Lipid accumulatedin parallel with the growth of the developing seeds. Solubleprotein also accumulated but only in the initial stages of development.ATP content peaked approximately 2 weeks after fertilization,followed about one week later by the energy charge; these peakswere associated with maximal growth stages of the developingembryos. Likewise, peaks of glutathione (GSH) and ascorbic acid(AA), two water-soluble reductants, preceded or coincided withthe ATP maximum. At late stages of seed development, dissectionof the more mature ovules into embryos and gametophytes foranalysis revealed that the ATP, GSH, and AA were more concentratedin the embryonic tissue. On the other hand, this segregationshowed that virtually no proanthocyanidin was located in thedeveloping embryos proper, although they contained other reductants,some of which were probably phenolics. Also, general stainingwith reagents for phenolics and thiols indicated that the formeroccurred primarily in non-embryonic tissue, whereas GSH wasin the embryo per se. These findings are consistent with rolesfor ATP, GSH, and AA in the growth and development of zygoticpine embryos; however, it would appear that lipid and proteinare being stored for subsequent germination events and thatmuch of the phenolic component is segregated from the developingembryo. Key words: Pine, embryogenesis, biochemistry