Rhizobia in tropical legumes—VIII. Serological characteristics of Psophocarpus tetragonolobus (L.) DC. isolates

Antisera were prepared against six inoculant strains of rhizobia for Psophocarpus tetragonolobus, and used to react with 62 different strains in both agglutination and immunodiffusion systems. A wide array of reactions occurred, indicating the extent of heterogeneity amongst strains capable of nodulating the same host. In agglutination reactions, the heat-stable somatic antigens could be arranged in 25 serogroups. In gel diffusion, antigens which produced strong precipitin bands usually showed agglutination relationships, but the corollary was not true. The immunodiffusion technique easily distinguished homologous and cross-reacting reactions and could be reliably used in field experiments with P. tetragonolobus.     

Rhizobia in tropical legumes—IX. pot and field trials with inoculants for Psophocarpus tetragonolobus (L.) DC.

Antigenically identifiable inoculants for Psophocarpus tetragonolobus were evaluated in three non-sterile soils contained in pots (sandy-clay, Renggam series; a loamy-sand, Sungei Buloh series; silty-clay, Munchong series). Most-probable-numbers of indigenous rhizobia ranged from 4 (Renggam series) to 13 (Munchong series) g^?1. Only two (RRIM 56 and 968) of the eight rhizobia tested formed > 50% of the nodules in all soils. Recovery of two strains (RRIM 968 and UMKL 12) was significantly poorer from the Munchong series soil which had the most indigenous rhizobia and the highest silt plus clay content. In a field trial using a Sungei Buloh series soil containing 700 rhizobia g^?1 capable of nodulating P. tetragonolobus, none of the applied strains formed > 18% of the nodules; two formed no nodules. There were no significant increases in plant yield in response to inoculation in the field trial and in two soils in the pot trials. In Sungei Buloh series soil, RRIM 56 formed 90% of the nodules when the indigenous rhizobia were 5 cells g^?, and 14% when the population was 700 g^?1. This raises the question of the need to inoculate seed sown into soils with high indigenous rhizobial populations, but there was some indication of increasing representation of inoculant strains in nodules with time.     

Rhizobia in tropical legumes—VII. Effectiveness of different isolates on Psophocarpus tetragonolobus (L.) DC

Rhizobia isolated from fourteen different genera of legumes were tested for their N-fixing effectiveness with Psophocarpus tetragonolobus in standard Leonard jar trials. Isolates from all plants except Pithecellobium jiringa were able to form nodules with P. tetragonolobus although a wide range of effectiveness amongst the different rhizobia was demonstrated. Thus P. tetragonolobus may be considered promiscuous with respect to its rhizobial requirements. Based on this experiment, a group of rhizobia comprising three elite strains (RRIM 56 from P. tetragonolobus, UMKL 36 from Lablab purpureus and CB 756 from Macrotyloma africanum, a moderately effective strain (NGR 258 from P. tetragonolobus), and two strains of low effectivity (RRIM 968 from Centrosema pubescens and UMKL 12 from Phaselus angularis) were selected for further study. When these were used to inoculate P. tetragonolubus growing in soil taken from virgin jungle (less than 1.54 rhizobia g^?1 soil); RRIM 56 and UMKL 36 again performed well, but NGR 258 outperformed CB 756.     

印度芥菜(Brassica juncea L.)重金属耐性机理研究进展

印度芥菜可富集/忍耐Cd、Zn 等多种重金属, 是研究植物修复技术的一种模式植物。高浓度的重金属离子会改变植物的基因表达、细胞形态、细胞结构, 最终使植物生长受抑, 甚至死亡。印度芥菜高效的抗氧化系统、损伤修复系统以及对重金属的螯合、区域化可部分解除重金属的毒性, 缓解重金属离子的毒害作用。利用基因工程技术在印度芥菜中导入重金属耐性及运输相关基因可大幅度提高其重金属富集能力, 在重金属污染修复方面具有广阔的应用前景。     

Interactions between Escherichia coli and allophane—II. Metabolism

A purified allophane clay fraction increased the respiration of Escherichia coli (ATCC 11303B) by buffering the suspension against decreases in pH. Allophane had no significant effect on respiration in the presence of 0.02 M phosphate buffer. When E. coli was exposed to pH values below 5.0 in the presence of allophane, allophane supernatant (which contains soluble Al), or soluble Al. toxicity was evident even after raising the pH to 7.0.     

Drying-rewetting cycles and γ-irradiation effects on enzyme activities of distinct layers from a Quercus ilex L. litter

In a Mediterranean climate, water stress is one of the principal constraints on proper forest ecosystem functioning. Drought influences rates of organic matter degradation by affecting microbial growth and enzyme activities. The objectives of this study were: (i) to evaluate the effect of repeated drying-rewetting cycles on cellulase, alkaline phosphatase and fluorescein diacetate (FDA) hydrolase activities of three distinct Quercus ilex L. litter layers, and (ii) to investigate the effect of these cycles on γ-irradiated litters in order to distinguish the abiotic influence on the fluctuations observed. Results, for all three layers, showed high correlations between litter water content and enzyme activities. Under mesocosm conditions, and using non-sterilized litter samples, cellulase, alkaline phosphatase, and FDA activities significantly decreased or increased during drying or rewetting cycles respectively. Significant differences were also found when evaluating the effect of litter depth on enzyme activities, the intermediate depth (OLv layer) generally being the most active. For γ-sterilized samples, FDA activity still fluctuated with drying-rewetting cycles. Assays showed that pre-humidification of γ-irradiated litter increased FDA activity two-fold in the first 30 min. All these results have shown that, following drying-rewetting cycles, some of the fluctuations occur independently of microbial growth, suggesting abiotic interactions, such as desorption, in combination with both solvatation status and conformational changes of enzymes.     

Interactions between Escherichia coli and allophane—I. Adsorption

Sorptive interactions between Escherichia coli (ATCC 11303B) and a purified allophane clay fraction were studied quantitatively using electronic particle counting and electrophoresis. Adsorption was influenced by pH and ions present at the allophane surface. These effects could be rationalized by considering changes in the net surface charge of the components. Electronic particle counting studies at pH 5.5 and above gave adsorption isotherms that obeyed single-term Langmuir kinetics. At pH 4.5, a more complex two-step isotherm was obtained, which was attributed to aggregation of unadsorbed cells by Al solubilized from the allophane surface.     

Are forests potential landscape barriers for foraging bumblebees? Landscape scale experiments with Bombus terrestris agg. and Bombus pascuorum (Hymenoptera, Apidae)

Habitat fragmentation is generally considered to have detrimental effects on insect movement and associated pollen flow between plant populations. Against this background the role of forests as potential barriers for foraging bumblebees of the species Bombus terrestris agg. and Bombus pascuorum was studied in different experiments. Bombus terrestris agg. workers were found foraging at distances of up to 2.2 km from their nests. B. terrestris agg. as well as B. pascuorum individuals crossed 600 m of forestland between floral mass resources (Phacelia tanacetifolia, Helianthus annuus), although in general a high degree of site fidelity was observed. B. pascuorum workers accepted artificial floral resources within the forest, whereas the minor use of resources below forest canopy observed for B. terrestris agg. possibly indicates a preference for direct forage flights, probably leading above the forest canopy. Our results warn against experiments with genetically modified crop species with potential bumblebee pollination (e.g. Brassica napus), in which an isolating effect of forests is assumed.     

Die Scopolaminbildung in der ArtkreuzungDatura ferox L. ×Datura stramonium L.

Zusammenfassung Datura ferox enthält als Hauptalkaloid Scopolamin, da sie die Fähigkeit hat, während ihrer ganzen Lebensdauer in ihren oberirdischen Organen Hyoscyamin, das aus der Wurzel in den Sproß geleitet wird, in Scopolamin umzuwandeln. Diese Fähigkeit wird dominant vererbt, wennD. ferox mitDatura stramonium gekreuzt wird. Das Hauptalkaloid vonDatura stramonium ist Hyoscyamin, während Scopolamin nur in kleiner Menge enthalten ist. Die F₁-Bastarde sind ausgesprochene Scopolamin-Pflanzen; Hyoscyamin führen sie nur in geringer Menge. Die F₂-Generation besteht aus Individuen vom Scopolamin-Typ und solchen vom Hyoscyamin-Typ im Verhältnis 3:1.

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Summary The main alkaloid ofDatura ferox is hyoscine the plant being able to convert hyoscyamine into hyoscine in its overground organs. Hyoscyamine is formed in the roots and migrates to the aerial parts. The ability to convert hyoscyamine into hyoscine is dominant hereditary in hybrids betweenDatura ferox andDatura stramonium. The main alkaloid ofDatura stramonium is hyoscyamine,D. stramonium contains hyoscine only in a small amount. The F₁-hybrids are typical hyoscineplants, containing hyoscyamine in little amounts only. In the F₂-generation typical hyoscine plants and typical hyoscyamine plants are to be found at a rate 3:1.

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Datura ferox , ( ) . D. ferox c D. stramonium . D. stramonium , . F₁ . (F₂) ( 3:1) , , .

     

The re-establishment of the large copper butterfly Lycaena dispar batava obth. on Woodwalton Fen National Nature Reserve,Cambridgeshire, England, 1969–73

The Dutch race of the large copper butterfly (Lycaena dispar Haw.), was introduced to Woodwalton Fen in 1927 and with careful management survived until 1969, following an exceptional July flood in 1968 which submerged the food plants, greatly reducing oviposition. This paper records the re-establishment of the butterfly in 1970 from caged stock and the population growth in the following three years in relation to weather conditions and fen management. It is suggested that the insect is not perfectly adapted to a fen environment because it has specialised requirements in terms of size and situation of the food plant. It is at risk from drowning if floods occur before or after the hibernation period and slight changes in the growth form of fen plants, which may overshade the food plant, can influence egg production. Experimental work suggests that when the fen vegetation is modified by cattle-grazing during June and July egg production increases because the food plants are made more accessible to the female butterflies. The heaviest mortality occurs in the period from oviposition to the beginning of hibernation but there is no known management technique which will reduce this. However, after emergence in the spring, protection in muslin cages significantly increases the survival rate. It is estimated that only about 30 ha of the Fen can be maintained in a suitable condition for the butterfly to breed successfully. It seems likely that this is too small an area for the insect to maintain itself without artificial aid such as protection for some of the larvae, creation of germination conditions for the food plant, continuance of a controlled grazing regime and the maintenance of a reserve stock in case re-introduction becomes necessary.     

Age determination in the dugong, Dugong dugon (Müller)

Growth layers in the dentine of about 75 dugong, Dugong dugon (Müller), unworn permanent incisor teeth have been examined with a view to absolute age determination. Thirteen of these teeth come from complete skulls which had previously been allocated relative ages within three arbitrary life stage groups (Mitchell, 1973). The layer numbers found range from zero to $\text{57}\text{1}\text{2}$, with a continuous scatter between the two extremes. It appears that the layers are either annual or biannual, and it is suggested that the dugong can attain an age of just under 60 or just under 30 years and reaches sexual maturity at about 10 or 5 years. A full account of this work is in preparation.     

Genetic variation vis-à-vis molecular polymorphism in groundnut, Arachis hypogaea L.

Recent studies on the genus Arachis using molecular markers have revealed very little demonstrable polymorphism in the cultivated groundnut, A. hypogaea. This has led to the hasty generalization that the groundnut lacks genetic variation. However, this is in complete contradiction to the results of other lines of investigations into the origin and evolution of A. hypogaea. Further, a characterization of the world collection for various traits also shows significant levels of variation for almost all genetic traits. The literature review in this article suggests that the lack of genetic variation was inferred because of an inadequacy in the material studied, and the range of techniques used to study molecular polymorphism. A comprehensive and rigorous examination of the material available in the groundnut world collection, either by improving current techniques, or by using such advanced techniques as SSRs and AFLP could well reveal polymorphism at the molecular level.