Sequential Analysis of the Organogenesis of Lucerne (Medicago sativa) Root Nodules Using Symbiotically-Defective Mutants of Rhizobium meliloti

Legume root-nodules are differentiated organs composed of peripheral tissue containing vascular bundles, and a central tissue in which are located the nitrogen-fixing bacteroids. The morphogenesis of these eukaryotic organs is induced by a prokaryotic organism, Rhizobium , which is amenable to genetic analysis. Inoculation of lucerne seedlings with leucine-requiring (Leu⁻) mutants of R. meliloti resulted in the formation of ineffective nodules. In these nodules, bacteria were not released from the infection threads into the host cytoplasm. When urea was provided as a nitrogen source to compensate for the defect in nitrogen fixation, the nodules became anatomically similar to those of effective nodules induced by the wild-type strain. The fact that these nodules were induced by bacteria which remained sequestered in infection threads indicates that nodule morphogenesis can be triggered from a distance. We hypothesize the existence of a bacterial nodule organogenesis-inducing principle (NOIP) which can cross the plant cell wall and plasmalemma.
In nitrogen-fixing nodules the central tissue exhibited a ploidy gradient, while in ineffective Leu⁻ nodules it was found to be monosomatic. The initiation of nodule formation is therefore independent of polyploidy. Supplying the defective plant-bacterial system with l -leucine or one of its precursors, α-ketoisovalerate or α-ketoisocaproate, caused the release of rhizobia into the plant cytoplasm and a restoration of nitrogen fixation. In the central tissue infected cells were polyploid and enlarged, and uninfected cells remained small and contained small nuclei. Therefore induction of differentiation of the central tissue requires the presence of bacteria in the cytoplasm. We hypothesize the role of a bacterial central tissue differentiation inducing principle (CTDIP) which cannot pass from cell to cell.     

The effect of a long-term water stress on the metabolism and emission of terpenes of the foliage of Cupressus sempervirens

The effects of long-term water stress on water and terpene contents of the foliage of Cupressus sempervirens were studied. A great deal of water was lost over 2 months before a remarkable stabilization. A strong decrease of all the classes of terpenes accompanied this dehydration. Mono- and sesquiterpene hydrocarbons and free terpenols were almost entirely metabolized, whereas esters and terpene glycosides rose slightly and remained at a constant level when the water content had stabilized. Although a significant part of the mono- and sesquiterpene hydrocarbons was emitted in the early stage of stress application, the major part was used by the plant in response to the drought conditions.     

GROWTH AND DEMOGRAPHY OF POPULATIONS OF BIOMPHALARIA PFEIFFERI (GASTROPODA, PLANORBIDAE) IN THE LABORATORY

The growth and demography of the freshwater snail Biomphalariapfeifferi, an intermediate host of the parasitic worm Schistosomamansoni in Eastern Zaire, were investigated in the laboratoryunder two conditions of crowding. Both individual and populationgrowth were depressed by crowding. Crowding reduced growth rateand all the variables and parameters related to reproduction(fecundity, instantaneous birth rate, net reproduction rate),but did not affect maximum size, survivorship, instantaneousdeath rate and life expectancy. The mechanism involved in theseeffects is likely to be exploitation competition for especiallyprofitable food items such as diatoms. (Received 10 November 1986;     

Adipokinetic hormone of the true armyworm, Pseudaletia unipuncta: immunohistochemistry, amino acid analysis, quantification and bioassay

Abstract A cluster of five to seven AKH-like immunoreactive cells lie in each lobe of the paired corpora cardiaca of the true armyworm, Pseudaletia unipuncta. These cells form a mesh work of immunoreactive processes within the corpora cardiaca, and immunoreactive tracts projecting posteriorly over the aorta.
Reversed-phase high performance liquid chromatography of extracts of the corpora cardiaca of P.unipuncta revealed a single large U.V. absorbent peak with a retention time identical to synthetic Manduca- AKH. Amino acid analysis of the contents of this peak yielded a composition identical to that of synthetic Manduca-AKH which was analysed in a parallel manner. Furthermore the material within the peak possessed adipokinetic activity when bioassayed in day 2 adult male P. unipuncta. The corpora cardiaca of similar individuals were found to contain approximately 17.6ng (17.6pmol) of Manduca-AKH equivalents per pair.
Injection of Manduca-AKH into 2-day-old adult male P.unipuncta resulted in a dose-dependent elevation in haemolymph lipid levels with a maximum level of 80–90μmg/μl obtained with 5–10 ng of Manduca-AKH. Continuous flight also elevated haemolymph lipid levels in day 4 adult males with a significant elevation evident in the first samples taken after 15 min of flight and lipid levels plateauing at approximately 100 μg/μl by about 60 min of flight.     

A comparative study of sex pheromone reception in the Hadeninae (Lepidoptera: Noctuidae)

Abstract A comparative study of the olfactory responses to pheromone compounds was performed in twenty-four species of Hadeninae. Electroantennograms (EAG) were recorded on male moths in response to thirty compounds and the response profiles of each species were analysed by factorial correspondence analysis. A limited number of molecules were found active and the most effective stimuli were Z9 tetradecenes and Z11 hexadecenes. The species of the Mythimna genus were most sensitive to aldehydes. Tholera decimalis did not respond to any of the molecules tested. The species belonging to the Mamestra and the Orthosia genera responded to a variety of molecules and no simple correlation was found between the genus and the EAG sensibility. Pheromone reception is discussed in relation to the taxonomy and the evolution of olfactory communication in Hadeninae.     

In Vitro Culture of Phytomonas Sp. Isolated from Euphorbia characias. Metabolic Studies by 1H NMR

ABSTRACT. We describe the in vitro culture of Phytomonas species isolated from Euphorbia characias . The best choice between tested media was SDM-79, in which promastigotes, after 6 days of culture, reached cell densities as high as 4 × 10⁷ cells/ml. Cells growing in LIT or MTL medium showed longer division times and lower cell densities. We succeeded in obtaining Phytomonas sp. amastigote and spheromastigote forms in modified GRACE's medium, yielding transformation rates of up to 70%. Electron microscopy studies were performed in order to characterize the ultrastructural features of these forms obtained in vitro. On the other hand, metabolic studies based on qualitative (nuclear magnetic resonance spectroscopy) and quantitative metabolic methods (enzymatic assays) showed that promastigote forms secreted mainly ethanol, acetate, glycine, glycerol, piruvate and succinate in SDM-79 medium, whereas the major metabolites found after transformation in modified Grace's medium were ethanol, acetate, glycine, piruvate and smaller amounts of glycerol.