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51.
Pirrone F Albertini M Clement MG Lafortuna CL 《Veterinary journal (London, England : 1997)》2007,173(1):144-150
The aim of this study was to investigate and quantify respiratory mechanical dysfunctions in Standardbred horses with both poor performance and bronchoalveolar lavage fluid cytology characteristic of inflammatory airway disease (IAD). A control group of healthy Standardbred horses was compared. Respiratory mechanics and breathing pattern were examined at rest and during hyperventilation induced using a rebreathing method. At rest, respiratory mechanics and breathing pattern were superimposable in both groups. In IAD horses, rebreathing increased ventilation, with larger tidal volumes and lower respiratory frequencies. During hyperventilation, IAD animals showed frequency-dependent dynamic lung compliance, and had greater viscous lung resistance and rate of dynamic work of breathing. As IAD alters pulmonary mechanics, the ventilatory load increases and horses requiring significantly higher energy for breathing may suffer restrictions in their athletic performance. This rebreathing method permits early evaluation of respiratory mechanical dysfunction in poorly performing horses with sub-clinical IAD. 相似文献
52.
Maria de Fátima Loureiro Glaciela Kaschuk Odair Alberton Mariangela Hungria 《Biology and Fertility of Soils》2007,43(6):665-674
In this study, soybean nodules were collected from 12 sites in the State of Mato Grosso, in the Brazilian Cerrados, where
both exotic soybean [Glycine max (L.) Merrill] and bradyrhizobial strains have been introduced from 1 to 18 years before. All soils were originally devoid
of rhizobia capable of effectively nodulating soybean and varied in terms of chemical and physical properties, inoculation
procedures, and cropping systems. Rhizobial genetic diversity was assessed on 240 isolates by rep-PCR fingerprinting with BOX primer, and indices of diversity (abundance-based coverage estimator and traditional and modified
Shannon indices) were applied to the profiles obtained. The genetic diversity was much greater than expected, as after the
introduction of a maximum of four strains, up to 13 profiles were identified, some sharing many similar bands with the inoculant
strains, but others quite distinct from the putative parental genotypes. The increase in the number of rep-PCR profiles could be attributed to genetic variability due to the stressful tropical environmental conditions, but also
might indicate that indigenous rhizobia become capable of nodulating the host legume. After the third year of cropping with
the host legume, inoculation did not affect rhizobial diversity. A high content of clay decreased diversity in comparison
with that seen in a sandy soil, probably due to reduced aeration. Diversity was higher under the no-tillage system when compared
to the conventional tillage management, highlighting the importance of maintaining crop residues in tropical soils. Understanding
the ecology of exotic rhizobia after being introduced into new cropping areas represents a first step towards the establishment
of better strategies of inoculation, which in turn may result in sustainability and higher plant yields. 相似文献
53.
54.
Diogo Fernando Saturno Paula Cerezini Pedro Moreira da Silva Arnold Barbosa de Oliveira Maria Cristina Neves de Oliveira Mariangela Hungria 《Journal of plant nutrition》2017,40(12):1690-1701
Soybean (Glycine max Merrill) crop production in Brazil relies mainly on biological nitrogen fixation (BNF) for nitrogen (N) supply. Recent adoption of indeterminate growth-type genotypes has raised doubts on the need for supplemental mineral N that might negatively affect the BNF. We assessed the effects of mineral N on BNF attributes of soybean genotypes grown in central and southern Brazil. Genotypes were inoculated with Bradyrhizobium sp. and/or received mineral N in three sets of experiments. In the first set, two genotypes received increasing rates of mineral N in nutrient solution, which consistently reduced the BNF. In the second set, mineral N applied at sowing and/or topdressing reduced nodulation and ureides-N in determinate and indeterminate growth-type genotypes. In the third set, mineral N applied at R5.3 stage, foliar or as topdressing, did not increase grain yield in four field experiments. Mineral N impaired BNF irrespective of the growth type and had no effect on grain yield. 相似文献
55.
In order to identify soybean cultivars with higher biological N2 fixation capacities, North American and Brazilian soybean [Glycine max (L.) Merrill] cultivars, belonging to maturity groups VI–VIII, were evaluated for nodulation parameters and N2 fixation rates. The symbiotic performance of 152 cultivars was evaluated in pots containing 4 kg soil with an established
population of the three Bradyrhizobium elkanii strains [29w (SEMIA 5019):SEMIA 566 : SEMIA 587, 22%:36%:34%] which are established in most Brazilian soils cultivated with
soybean. Differences were verified among cultivars, with some accumulating up to twice as much nodule dry weight and N in
tissues as others. The variability among cultivars was also confirmed when six of them were used in a field experiment, resulting
in differences in nodulation, yield and total N accumulated in grains. The analysis of nodule occupancy in 12 cultivars grown
either under sterile conditions and receiving a double inoculum and N-free nutrient solution, or in pots containing soil with
an established population of bradyrhizobia, showed the preference of cultivars for specific strains.
Received: 7 December 1998 相似文献
56.
M. Hungria L. H. Boddey M. A. Santos M. A. T. Vargas 《Biology and Fertility of Soils》1998,27(4):393-399
In a previous study soybean Bradyrhizobium strains, used in Brazilian studies and inoculants over the last 30 years, and strains adapted to the Brazilian Cerrados, a
region frequently submitted to environmental and nutritional stresses, were analyzed for 32 morphological and physiological
parameters in vivo and in vitro. A cluster analysis allowed the subdivision of these strains into species Bradyrhizobium japonicum, Bradyrhizobium elkanii and a mixed genotype. In this study, the bacteria were analyzed for nodulation, N2 fixation capacity, nodule occupancy and the ability to increase yield. The goal was to find a relationship between the strain
groups and the symbiotic performance. Two strains of Brazilian B. japonicum showed higher rates of N2 fixation and nodule efficiency (mg of N mg–1 of nodules) under axenic conditions. These strains also showed greater yield increases in field experiments when compared
to B. elkanii strains. However, no differences were detected between B. japonicum and B. elkanii strains when comparing nodule occupancy capacity. The adapted strains belonging to the serogroup B. elkanii SEMIA 566, most clustered in a mixed genotype, were more competitive than the parental strain, and some showed a higher capacity
of N2 fixation. Some of the adapted strains, such as S-370 and S-372, have shown similar N2 fixation rates and nodulation competitiveness to two Brazilian strains of B. japonicum. This similarity demonstrates the possibility of enhancing N2 fixing ability, after local adaptation, even within B. elkanii species. Differences in the DNA profiles were also detected between the parental SEMIA 566 and the adapted strains by analyses
with the ERIC and REP-PCR techniques. Consequently, genetic, morphological and physiological changes can be a result of adaptation
of rhizobia to the soil. This variability can be used to select strains capable of increasing the contribution of N2 fixation to soybean nutrition.
Received: 28 May 1997 相似文献