Cobalt and nitrogen fixation in Lupinus angustifolius L. II. nodule formation and function

The effects of cobalt deficiency on nodule formation and function in sweet lupin (Lupinus angustifotius L. cv. Unicrop) were studied in cobalt‐deficient Lancelin sand in the glasshouse. Bacteroid densities in cobalt‐deficient nodules were lower than in normal nodules. Recovery from cobalt deficiency in inoculated treatments was associated with increases in bacteroid density and cobalt accumulation in lateral nodules. Such changes did not occur in treatments infected with rhizobia from the soil. Acetylene‐reducing activity of cobalt‐deficient plants was not initiated until plants were nearly 6 weeks old, at which time cobalt‐treated plants were at their peak of activity. Specific activities of cobalt‐deficient nodules remained very low even when nitrogenase did develop. Their large mass of nodules allowed cobalt‐deficient plants to reach 20 to 50 % of the normal activity per plant, but specific activities were only 5 to 13 % of peak activities in cobalt‐treated nodules. Nodule bacteroid content and leghaemoglobin content were linearly related to cobalamin content, each with a single relationship. Plotting acetylene‐reducing activity against cobalamin content or leghaemoglobin content generated two different linear response curves in each case; the slopes of the lines were different, depending on the presence or absence of cobalt. It is suggested that there may be a function in N, fixation in legume nodules for a non‐cobalamin form of cobalt

The effect of copper on nitrogen fixation in subterranean clover (Trifolium subterraneum)

Copper deficiency decreased nitrogen fixation in subterranean clover. Three lines of evidence support this conclusion. Firstly, while both copper and nitrogen application increased the growth of the legume the interaction between copper and nitrogen on growth was negative. Secondly, the application of copper increased the concentrations of both total and protein nitrogen in the plant. Lastly, nitrogen fixation as measured by the acetylene reduction assay increased with copper application to the soil

Which stage of nodule initiation in Lupinus angustifolius L. is sensitive to iron deficiency?

Transfer experiments in solution culture were conducted to establish the stage of nodulation in lupins (Lupinus angustifolius L. cv. Yandee) most sensitive to iron deficiency. In all experiments, iron deficiency had a much greater effect on nodule number than on host plant growth. Irrespective of the iron treatment of either the Bradyrhizobium or the lupin plant prior to inoculation, plants receiving 2.5 μM iron after inoculation successfully formed nodule initials and nodules while those receiving 0.05 μM iron almost completely failed to initiate nodules. Thus, the prevention of nodulation by iron deficiency is not a consequence of either an inadequate number of infective bradyrhizobia surviving in the solution or an alteration in the iron status of the host root. Supply of 2.5 μM iron for 4 d or more after inoculation produced a similar number of nodule initials and nodules as did continuous supply of 2.5 μMiron. Delaying supply of 2.5 μM iron for 3 d or less after inoculation did not delay or prevent nodule initiation and formation. One‐day exposure of plants to 2.5μM iron on day 4 after inoculation induced the highest number of nodules of any 1 d treatment although this short exposure was not enough to allow the full complement of nodules to form. Hence, the impairment of the nodulation process by iron deficiency can be attributed to the prevention of a step at day 4, the stage just before nodule initials are formed. A further study was conducted to examine the effect of iron on nodule formation by using a vertical split‐root technique in which Bradyrhizobium sp. (Lupinus) was added to the upper compartment. Compared to plants receiving 0.05 μM iron in both compartments, plants receiving 0.05 μM in the upper and 5 5 μM iron in the lower compartments had only a slightly higher concentration of iron in the cortex of the upper part of the root. Furthermore, supplying 5 μM iron to the lower part of a root did not permit nodulation on the upper part of the root receiving 0.05 μMiron. Low concentration of iron in the cortex of roots may limit nodule formation

The role of iron in nodulation and nitrogen fixation in Lupinus angustifolius L

The effects of iron concentration in solution on nodulation and symbiotic N2 fixation in lupins (Lupinus angustifolius L. ev. Yandee) were studied in solution culture in the glasshouse by comparing plants supplied with NH4NO3 with those reliant on N2 fixation. At very low iron supply, adding NH4NO2 did not increase shoot growth. Under moderate iron deficiency, where plants were pale green, adding NH4NO3 increased shoot growth, implying that moderate iron deficiency was, operationally, nitrogen deficiency. Higher iron concentrations in solution were required for maximum growth of plants reliant on symbiotic N2 fixation than for those supplied with NH4NO3 Iron deficiency depressed nodule initiation earlier than host plant growth, resulting in decreased nodule number and mass. Alleviating iron deficiency enhanced leghaemoglobin production in nodules and increased nitrogen concentrations in the shoots. Iron concentration in the youngest fully expanded leaves provided a good indication of the severity of iron deficiency‐caused chlorosis. The results suggest that iron is involved in symbiotic N2 fixation through effects on both nodule initiation and nodule function, and that the symbiosis has a higher iron requirement than that needed for host plant growth

Cobalt and nitrogen fixation in Lupinus angustifolius L. I. Growth, nitrogen concentrations and cobalt distribution

Cobalt application markedly increased the growth of and nitrogen concentrations in tops of Lupinus angustifolius irrespective of inoculation with an effective strain of Rhizobium. Cobalt‐deficient plants produced a greater weight of lateral nodules and total nodule weight than cobalt‐adequate plants. Cobalt‐sufficient plants produced more crown nodule weight than cobalt‐deficient plants. Cobalt concentrations were higher in roots and nodules than in tops irrespective of cobalt application. In plant tops cobalt concentrations in young leaves were considerably lower than those in old leaves at both cobalt levels. Cobalt concentrations and contents increased in old leaves throughout the experiment. Under cobalt deficiency cobalt appeared to be preferentially distributed to nodules. Six weeks after sowing cobalt contents of nodules of cobalt‐deficient plants were similar to those in whole tops. By contrast at this time cobalt contents of nodules of cobalt‐adequate plants were only approximately one‐third those of whole tops

The market for modern art in New York in the nineteen forties and nineteen fifties: a structural and historical survey

The nineteen forties and nineteen fifties, acknowledged as the decades in which New York first emerged as a locus for modern art production of international stature (particularly the so-called 'New York School '), also witnessed its development into a market for modern art, both European and American, and it is upon this that this study focuses. A modern art market is a 'support-system' which consists of not only the producer-artists and consumer-collectors but also of a number of 'intermediaries'. This complex, in addition to the actual purchase of art works, serves, for instance: to disseminate a knowledge about modern art in general; to select particular artists and promote their work in the public eye; to support contemporary artists financially; and to enhance the sphere of collecting activity. The groups or institutions involved in these functions vary according to historical circumstances, and the first part of this study identifies the key constituents of the 'support-system' in the New York art market in this period as: New York museums concerned with modern and contemporary art, both foreign and native, private dealer-galleries, and collectors; and examines what parts each played in the structure of the art market as a whole, paying particular attention to the influence of wider socio-economic factors upon this. This 'support-system' structure discussed in the first part may be considered as synchronic. The second part of this study, however, concentrates upon an examination of changing trends in prices and in collectors' preferences for different artistic expressions (particularly the relative status of American as against European modern art). Emphasis is placed in this upon demonstrating where possible how such developments were related to the functioning of the support system as discussed; and to situating the behaviour of the New York art market of the period into a wider national socio-economic context

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Exponential Time Complexity of Weighted Counting of Independent Sets

We consider weighted counting of independent sets using a rational weight x: Given a graph with n vertices, count its independent sets such that each set of size k contributes x^k. This is equivalent to computation of the partition function of the lattice gas with hard-core self-repulsion and hard-core pair interaction. We show the following conditional lower bounds: If counting the satisfying assignments of a 3-CNF formula in n variables (#3SAT) needs time 2^{\Omega(n)} (i.e. there is a c>0 such that no algorithm can solve #3SAT in time 2^{cn}), counting the independent sets of size n/3 of an n-vertex graph needs time 2^{\Omega(n)} and weighted counting of independent sets needs time 2^{\Omega(n/log^3 n)} for all rational weights x\neq 0. We have two technical ingredients: The first is a reduction from 3SAT to independent sets that preserves the number of solutions and increases the instance size only by a constant factor. Second, we devise a combination of vertex cloning and path addition. This graph transformation allows us to adapt a recent technique by Dell, Husfeldt, and Wahlen which enables interpolation by a family of reductions, each of which increases the instance size only polylogarithmically.Comment: Introduction revised, differences between versions of counting independent sets stated more precisely, minor improvements. 14 page

The Frailty In Residential Sector over Time (FIRST) study: methods and baseline cohort description

Published online: 03 February 2021Background: The Frailty In Residential Sector over Time (FIRST) Study is a 3-year prospective cohort study investigating the health of residents living in residential aged care services (RACS) in South Australia. The study aims to examine the change in frailty status and associated health outcomes. Methods: This interim report presents data from March 2019–October 2020. The study setting is 12 RACS from one organisation across metropolitan and rural South Australia involving 1243 residents. All permanent (i.e. respite or transition care program excluded) residents living in the RACS for at least 8 weeks were invited to participate. Residents who were deemed to be medically unstable (e.g. experiencing delirium), have less than 3 months to live, or not fluent in English were excluded. Data collected included frailty status, medical diagnoses, medicines, pain, nutrition, sarcopenia, falls, dementia, anxiety and depression, sleep quality, quality of life, satisfaction with care, activities of daily living, and life space use at baseline and 12-months. Data Linkage will occur over the 3 years from baseline. Results: A total of 561 permanent residents (mean age 87.69 ± 7.25) were included. The majority of residents were female (n = 411, 73.3%) with 95.3% (n = 527) being classified as either frail (n = 377, 68.2%) or most-frail (n = 150, 27.1%) according to the Frailty Index (FI). Most residents were severely impaired in their basic activities of daily living (n = 554, 98.8%), and were at-risk of malnutrition (n = 305, 55.0%) and at-risk of sarcopenia (n = 492, 89.5%). Most residents did not experience pain (n = 475, 85.4%), had normal daytime sleepiness (n = 385, 69.7%), and low anxiety and depression scores (n = 327, 58.9%). Conclusion: This study provides valuable information on the health and frailty levels of residents living in RACS in South Australia. The results will assist in developing interventions that can help to improve the health and wellbeing of residents in aged care services. Trial registration: Prospectively registered with the Australian New Zealand Clinical Trials Registry (ACTRN1261 9000500156).Agathe Daria Jadczak, Leonie Robson, Tina Cooper, J. Simon Bell, Renuka Visvanathan, on behalf of the FIRST Study Collaborator