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11.
The expression of a lectin gene in pea (Pisum sativum L.) roots has been investigated using the copy DNA of a pea seed lectin as a probe. An mRNA which has the same size as the seed mRNA but which is about 4000 times less abundant has been detected in 21-d-old roots. The probe detected lectin expression as early as 4 d after sowing, with the highest level being reached at 10 d, i.e. just before nodulation. In later stages (16-d- and 21-d-old roots), expression was substantially decreased. The correlation between infection by Rhizobium leguminosarum and lectin expression in pea roots has been investigated by comparing root lectin mRNA levels in inoculated plants and in plants grown under conditions preventing nodulation. Neither growth in a nitrate concentration which inhibited nodulation nor growth in the absence of Rhizobium appreciably affected lectin expression in roots.Abbreviation cDNA copy DNA - poly(A)+RNA polyadenylated RNA  相似文献   
12.
Similar ranges of gibberellins (GAs) were detected by high-performance liquid chromatography (HPLC)-immunoassay procedures in ten cultures of wild-type and mutant strains of Rhizobium phaseoli. The major GAs excreted into the culture medium were GA1 and GA4. These identifications were confirmed by combined gas chromatographymass spectrometry. The HPLC-immunoassays also detected smaller amounts of GA9- as well as GA20-like compounds, the latter being present in some but not all cultures. In addition to GAs, all strains excreted indole-3-acetic acid (IAA) but there was no obvious relationship between the amounts of GA and IAA that accumulated. The Rhizobium strains studied included nod and fix mutants, making it unlikely that the IAA- and GA-biosynthesis genes are closely linked to the genes for nodulation and nitrogen fixation.The HPLC-immunoassay analyses showed also that nodules and non-nodulated roots of Phaseolus vulgaris L. contained similar spectra of GAs to R. phaseoli culture media. The GA pools in roots and nodules were of similar size, indicating that Rhizobium does not make a major contribution to the GA content of the infected tissue.Abbreviations EIA enzyme immunoassay - GAn gibberellin An - GC-MS gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - IAA indole-3-acetic acid - Me methyl ester - RIA radioimmunoassay - TLC thin-layer chromatography  相似文献   
13.
14.
Air dry soil samples stored at room temperature for more than one and a half years, were used as inocula for actinorhizal plants. Seedlings of Colletia paradoxa, Discaria americana, D. articulata and D. trinervis (Rhamnaceae) cultivated in nitrogen-free nutrient solution, were inoculated by adding dry soil to the solution. All the soil samples tested were able to induce nodulation, showing the presence of infective propagules of Frankia. Healthy growth of nodulated plants suggested the occurrence of nitrogen fixation.  相似文献   
15.
The effects of inoculum level and lime-pelleting were studied in an acid soil with respect to the nodulation and growth of lucerne (Medicago sativa cv Resis) and the population dynamics of Rhizobium meliloti. In small root-boxes (rhizotrons), the in-situ survival of inoculated rhizobia was studied in the micro-environment around the seed for a period of 12 days after sowing. During the initial 24 hours, a strong increase in rhizobial numbers was measured, concomitantly with the development of roots. As a result of lime-pelleting, rhizobial numbers were higher only at 3 days after sowing (P<0.05). Later, this difference diminished steadily. Addition of lime did not increase the adhesion of the rhizobia to the seedling tap root. Plant responses to inoculation were studied in pots. To obtain optimal nodulation, the soil had to be neutralized around the seed with lime and at least 105 cells of R. meliloti were required. With more than 105 rhizobia per seed, lime-pelleting increased the number of crown-nodulated seedlings from 24% to 77%. Higher numbers of rhizobia could not compensate the effect of lime. A strong correlation was found between crown nodulation, nitrogen content and dry weight of the shoots.  相似文献   
16.
影响根瘤菌竞争结瘤的生态学因素分析   总被引:7,自引:0,他引:7  
丁武 《生态学杂志》1992,11(4):50-54
根瘤菌的发现并确证其共生固氮作用已逾100年,根瘤菌剂的制备和应用也已超过半个世纪,实践效果有目共睹。如美国对豌豆根瘤菌、三叶草根瘤菌和大豆根瘤菌的应用以及澳大利亚对三叶草根瘤菌的应用都取得显著成绩。我国在豆科作物和豆科绿肥上应用根瘤菌接种措施已有30余年历史,采用筛选的优良菌  相似文献   
17.
The lectin on the surface of 4- and 5-dold pea roots was located by the use of indirect immunofluorescence. Specific antibodies raised in rabbits against pea seed isolectin 2, which crossreact with root lectins, were used as primary immunoglobulins and were visualized with fluorescein- or tetramethylrhodamine-isothiocyanate-labeled goat antirabbit immunoglobulin G. Lectin was observed on the tips of newly formed, growing root hairs and on epidermal cells located just below the young hairs. On both types of cells, lectin was concentrated in dense small patches rather than uniformly distributed. Lectin-positive young hairs were grouped opposite the (proto)xylematic poles. Older but still-elongating root hairs presented only traces of lectin or none at all. A similar pattern of distribution was found in different pea cultivars, as well as in a supernodulating and a non-nodulating pea mutant. Growth in a nitrate concentration which inhibits nodulation did not affect lectin distribution on the surface of pea roots of this age. We tested whether or not the root zones where lectin was observed were susceptible to infection by Rhizobium leguminosarum. When low inoculum doses (consisting of less than 106 bacteria·ml-1) were placed next to lectin-positive epidermal cells and on newly formed root hairs, nodules on the primary roots were formed in 73% and 90% of the plants, respectively. Only a few plants showed primary root nodulation when the inoculum was placed on the root zone where lectin was scarce or absent. These results show that lectin is present at those sites on the pea root that are susceptible to infection by the bacterial symbiont.Abbreviations FITC fluorescein isothiocyanate - TRIC tetramethylrhodamine isothiocyanate  相似文献   
18.
用植物试管玻片培养技术研究NH_4~ 对细枝木麻黄及Frankia菌株Co01共生体系建立过程的影响。NH_4~ (100,150ppm(NH_4)_2SO_4)通过阻止菌株Cc01与其宿主细枝木麻黄根毛壁的亲和作用来影响结瘤。但NH_4~ 不能阻抑菌株Cc01中结瘤基因pel和cel的表达及纤维素酶和果胶酶活性,且菌丝一旦侵入宿主皮层细胞,并形成根瘤原基及前根瘤,则NH_4~ (250ppm(NH_4)_2SO_4)就不再阻止原基进一步发育为成熟的根瘤。但在这种情况下,NH_4~ 能抑制根瘤的固氮活性。  相似文献   
19.
Nitrogen fixed in 13 provenances of Acacia albida and 11 isolines of Leucaena leucocephala inoculated with effective Rhizobium strains was measured by 15N techniques and the total N difference method. In the test soil, on the average, L. leucocephala derived about 65% of its total N from atmospheric N2 fixation compared to about 20% by A. albida. Significant differences in the percentage of N derived from atmospheric N2 (% Ndfa) occurred, between provenances or isolines within species. The % Ndfa ranged from 37 to 74% within L. leucocephala and from 6 to 37 within A. albida; (equivalent to 20–50 mg N plant–1 and 4–37 mg N plant–1 for the two species over three months, respectively) and was correlated with the nodule mass (r=0.91). The time course of N2 fixation of three selected provenances (low, intermediate and good fixers) was followed at 12 weekly intervals over a 36 week period. The % Ndfa of all provenances and isolines increased with time; and except for one of the L. leucocephala provenances, % Ndfa was similar within species at the 36 weeks harvest. There was a significant correlation between % Ndfa and the amount of N2 fixed (r=0.96). Significant interactions occurred between provenances and N treatments and often growth of uninoculated but N fertilized plants was less variable than for inoculated unfertilized plants.  相似文献   
20.
Solarization of soil was found beneficial for plant growth in cowpea under field conditions. Root nodulation, infection by mycorrhizal fungi and yield were higher in plants grown in solarized soil. These increases were to the extent of 104.7, 20.0 and 23.7 per cent respectively when compared to control treatment without solarization.  相似文献   
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