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141.
Summary Differences between isogenic uptake hydrogenase (HUP) mutants of Bradyrhizobium japonicum in terms of nodule efficiency, N2 fixation and N incorporation into various plant parts were studied in a monoxenic greenhouse experiment in order to confirm previous results with soybeans and beans inoculated with various HUP+ and HUP– strains. The HUP+ revertant PJ17-1 of a HUP– mutant (PJ17) of strain USDA DES 122 showed a completely restored relative efficiency (100% versus 78±2% for the HUP– mutant), higher nodule efficiency (N2 fixed per g nodules), higher ureide-N transport rates, higher N contents in pods and higher N harvest indices. All these observations confirm previous experiments with HUP+ and HUP– strains. 相似文献
142.
Cyanobacteria are important for global nitrogen cycle and often form complex associations referred to as cyanobacterial mats
or periphyton that are common in tropical, limestone-based wetlands. The objective of this study was to monitor the nitrogen
fixation rate using the acetylene reduction assay of these cyanobacterial mats in a tropical, unfertilized, and protected
wetland. To account for temporal and spatial variation of nitrogenase activity, we were interested in seasons in a hydrological
cycle (dry, rains, and end of rains), sites with different vascular vegetation, and rates of nitrogenase activity in a 24-h
cycle. The annual average of nitrogenase activity was 22 nmol C2H4 cm−2 h−1, with a range of <6 to 35 nmol C2H4 cm−2 h−1, and the annual nitrogen fixation rate of our study site (9.0 g N m−2 year−1) is higher than similar estimates from other freshwater wetlands. There was a clear temporal pattern in nitrogenase activity
with a maximum rate occurring during the rainy season (August) and a maximum nitrogenase activity occurring between 0600 and
1200 hours. We found spatial differences in nitrogenase activity among the four sites that could be attributed to variations
in species composition within the periphyton. 相似文献
143.
Hongjie Li Robert L. Conner Qin Chen Robert J. Graf André Laroche F. Ahmad A. D. Kuzyk 《Genetic Resources and Crop Evolution》2005,51(8):827-835
Wheat streak mosaic virus (WSMV), vectored by the wheat curl mite (WCM),Aceria tosichella Keifer, is one of the most destructive viral diseases of wheat found in many wheat producing areas of the world. Host resistance is the most effective method for controlling this disease and its vector. Symptomatological analysis and enzyme-linked immunosorbent assay (ELISA) were used to characterize WSMV-resistance in wheat-alien partial amphiploid lines and their derivatives. The results showed that most of partial amphiploids derived fromThinopyrum ponticum andTh. intermedium were free of systemic symptoms with very low ELISA readings that were similar to that of the non-inoculated Chinese Spring control. While the partial amphiploid lines 693 and PWM706 were identified as new genetic resources of resistance to WSMV. The present study demonstrated that both symptomatological and ELISA methods efficiently assessed WSMV-resistance in the wheat-alien hybrids and systemic symptom incidence and ELISA absorbance readings were highly correlated (r
2 = 0.8658–0.9323) over time following inoculation. The ELISA results also indicated that the virus did not buildup in the plant tissues of these virus-resistant partial amphiploids. Similar results were observed in chromosome translocation and substitution lines that have the geneWsm1 conferring WSMV resistance. However, the lines containing the geneWsm1 and all the partial amphiploid lines, except Agrotana, were susceptible to the WCM. One line derived from a cross of wheat and Agrotana, was effective in controlling the spread of WSMV and was highly resistant to the WCM. Another line and an accession ofTriticum dicoccoides (Koern.) Schweinf. were highly susceptible to WSMV and WCM. Early disease development was delayed in a new hard red winter cultivar McClintock. The partial WSMV-resistance of McClintock was demonstrated by initially low ELISA readings, and a lower percentage of infected plants than other WSMV-susceptible wheat. The use of the identified promising sources of resistance to WSMV and the WCM in wheat breeding is discussed.LRC Contribution No. 387-01061. 相似文献
144.
Application of an augmented nitrification assay to elucidate the effects of a spring barley crop and manures on temporal variations in rates 总被引:1,自引:0,他引:1
The effects of crop plants and farmyard or poultry manure applications on temporal variations in nitrification rates were
measured in a field experiment. In order to elucidate factors which may have been governing such rates, an augmented nitrification
assay was applied. The basis of the assay was to measure nitrification rates under circumstances where substrate, i.e. ammonium-ion,
and water and spatial constraints had been removed. Nitrification rates showed marked temporal variation, of over one order
of magnitude, throughout the growing season. Nitrification rates were also similarly increased when substrate and spatial
constraints were removed, but distinct temporal variations still persisted. The pattern of such variations varied according
to assay conditions in the augmented nitrification assay. Barley plants had a statistically significant effect on nitrification
rates, positive early in the growing season and negative at the end. Manures stimulated nitrification, with poultry manure
having a greater effect than farmyard manure, and there was evidence for a relationship between heterotrophic and autotrophic
activity. Factors other than ammonium-ion concentration and water or spatial restrictions must also regulate nitrification
rates in mineral soils; these could include population size or interactions.
Received: 7 January 1996 相似文献
145.
Summary In three field trials conducted during the summer season of 1986, 1987 and 1989 in an alkaline soil, 17 accessions of annual Sesbania spp. were evaluated for nodulation, N2 fixation (acetylene reduction assay), dry weight of roots and shoots, woody biomass production, and nutrient uptake. At 50 days after sowing all the accessions were effectively nodulated (average 36.4 root nodules plant-1) with a high nodule score (3.4). There was a lot of variation in nodule volume and mass and in acetylene reduction activity but not in N content (5.2%). N uptake in shoots, roots and nodules averaged 639, 31, and 13 mg plant-1, respectively, and much of the fixed N remained in shoots. Accessions of S. cannabina complex performed better than others. S. rostrata had poor root nodulation but exhibited excellent stem nodulation (300 nodules plant-1) even though not inoculated with Azorhizobium sp. Average concentrations of N, P, K, S, Ca, and Mg in the shoots were high, at 3.2, 0.28, 1.5, 0.28, 1.5, and 0.4% respectively, and Na was low (0.15%), reflecting the usefulness of Sesbania spp. as an integrated biofertilizer source. Green matter production was 26.0 Mg ha-1 (5.9 Mg dry matter) and N uptake was 158 kg ha-1, 54 days after sowing. Average woody biomass of six accessions at maturity, 200 days after sowing, was high (19.9 Mg ha-1), showing its potential for shortterm firewood production. Total nutrient uptake for production of woody biomass (200 days of growth) was no more demanding than growing the plant to the green-manuring stage of 50–60 days' growth. 相似文献
146.
Raman Rai 《Biology and Fertility of Soils》1992,14(4):293-299
Summary Following screening, selection, characterization, and symbiotic N2 fixation with 12,5, 25.0, and 40.0 mg N kg–1 in normal and saline-sodic soils, only two Phaseolus vulgaris genotypes (HUR 137 and VL 63) and two Rhizobium spp. strains (ND 1 and ND 2) produced maximum nodulation, nitrogenase activity, plant N contents, and grain yields in saline-sodic soil, with 12.5 mg N kg–1, compared with the other strains. However, interactions between strains (USDA 2689, USDA 2674, and ND 5) and genotypes (PDR 14, HUR 15, and HUR 138) were significant and resulted in more nodulation, and greater plant N contents, nitrogenase activity, and grain yields in normal soils with 12.5 mg N kg–1 compared with salt-tolerant strains. Higher levels of N inhibited nodulation and nitrogenase activity without affecting grain yields. To achieve high crop yields from saline-sodic and normal soils in the plains area, simultaneous selection of favourably interacting symbionts is necessary for N economy, so that bean yields can be increased by the application of an active symbiotic system. 相似文献
147.
Summary Nitrogenase activity associated with earthworms, their faeces and activity in soil was measured by the acetylene reduction technique. A clear increase in nitrogenase activity was found in field-deposited casts of Aporrectodea caliginosa in comparison with surrounding soil, although potential nitrogenase activity was significantly higher in soil than in casts. Nitrogenase activity associated directly with earthworms (Lumbricus rubellus ) was detected, indicating the presence of active N2-fixing bacteria on the body surface and/or in the gut. Laboratory experiments showed that nitrogenase activity in the casts of L. rubellus was higher than in unmodified soil, and that nitrogenase activity in soil was significantly increased by the burrowing and feeding activity of these worms. This paper discusses the possible causes of these earthworm effects on soil nitrogenase activity and some methodological problems of determining the nitrogenase activity. 相似文献
148.
在水稻基因组芯片分析的基础上,克隆到一个在水稻中高水平表达基因OsSG15'末端启动子区域1.6-kb的DNA片断,即Ospz1启动子,构建了由Ospz1启动子引导的GUS重组基因,并经农杆菌介导将重组基因导入到水稻中.对转基因水稻植株中GUS活性的定性测定结果表明,Ospz1启动子可驱动GUS报告基因在转基因水稻植株叶片、芽和根中高效表达,而在其它器官中不表达或表达活性极弱,表现出组织特异性.Ospz1启动子可用于农作物生物技术的遗传改良. 相似文献
149.
应用间接酶联免疫吸附试验(ELISA),检测了山羊关节炎-脑炎病毒(CAEV)试验感染山羊和自然感染山羊的血清抗体,确定了最适宜的反应条件。CAEV感染山羊血清终点滴度结果表明:ELISA比琼脂扩散试验(ID)敏感性高,对自然感染山羊检出率比ID高3%左右。CAE标准阳性血清和自然感染阳性血清预先被特异性抗原中和后的ELISA反应均呈阴性,从而证实了本方法的特异性。因此,本方法适于CAE的流行病学调查和监测工作。 相似文献
150.