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1.
The present work investigates the impact of phosphorus (P) starvation on plant growth, symbiotic nitrogen fixation, and internal P status (determined as extracted P fractions) of leaves, roots, and nodules of 27-days–old pea (Pisum sativum L) plants inoculated with Rhizobium leguminosarum bv viciae strain D293. The procedure of separation of organic and inorganic P compounds in 10% perchloric acid (HCLO4) and the absorption of nucleotides in active charcoal gave several fractions, containing different phosphorus compounds, which were extracted and determined as inorganic phosphate after combustion. These are acid soluble and insoluble P, sugar P, nucleotide P, and inorganic P. The P starvation of plants inhibited significantly plant dry mass accumulation, nodulation rate and specific nitrogenase activity of nodules. These results were accompanied with lower quantities of total P per plant, acid soluble and acid non-soluble P fractions in all plant organs. The inhibited accumulation of P in the acid soluble P fraction was associated with decrease of sugar, nucleotide and inorganic P in all plant organs. The most negatively affected were all P fractions extracted from nodules and leaves. The low content of inorganic P in the stressed plant tissues was regarded as primary reason for induced alterations in the content of analyzed P fractions.  相似文献   

2.
The impact of phosphorus (P) deficiency on response of symbiotic N2 fixation and carbohydrate accumulation in soybean (Glycine max [L.] Merr.) to atmospheric CO2 enrichment was examined. Plants inoculated with Bradyrhizobium japonicum MN 110 were grown in growth chambers with controlled atmospheres of 400 and 800 μL CO2 L‐1 and supplied either 1.0 mM‐P (P‐sufficient) or 0.05 mM‐P (P‐deficient) nitrogen (N)‐free nutrient solution. When plants were supplied with sufficient P, CO2 enrichment significantly increased whole plant dry mass (83%), nodule mass (67%), total nitrogenase activity (58%), and N (35%) and P (47%) accumulation at 35 days after transplanting (DAT). Under sufficient P supply, CO2 enrichment significantly increased starch concentrations in nodules compared to the normal atmospheric CO2 treatment. Under normal CO2 levels (400 μL L‐1) nonstructural carbohydrate concentration (starch plus soluble sugar) was significantly higher in leaves of P‐deficient plants than in leaves of P‐sufficient plants in which nonstructural carbohydrate concentration exhibited a strong diurnal pattern. Under deficient P supply whole plant dry mass, symbiotic N2‐fixation parameters, and N and P accumulation were not enhanced by atmospheric CO2 enrichment. Phosphorus deficiency decreased nonstructural carbohydrate accumulation in nodules at the end of a 10‐day period in which functional activity was developing by 86% relative to P‐sufficient controls. While P deficiency elicited significant increases in the nonstructural carbohydrate concentration in leaves, it caused significant decreases in the nonstructural carbohydrate concentration in nodules over the diurnal cycle from 30 to 31 DAT. Collectively, these results indicate that the lack of a symbiotic N2‐fixation response to atmospheric CO2 enrichment by P‐deficient plants may be related to the decreased carbohydrate status of nodules.  相似文献   

3.
Drought in soybean [Glycine max (L.) Merr.] decreases yield‐related processes and N2 fixation is more sensitive to drought than are many other of these processes. Therefore, application of nitrogen (N) fertilizer may increase drought tolerance over those plants primarily dependent on N2 fixation. In a field experiment, NH4NO3 applications (+N) to drought‐stressed soybean resulted in biomass and N accumulation rates similar to those rates for an irrigated treatment without N fertilizer (‐N). In contrast, biomass and N accumulation rates were decreased for the ‐N treatment. N fertilization increased seed growth rate and decreased seed fill duration for irrigated and drought treatments. In the drought treatment, N application increased seed number per unit area, which resulted in higher yields. In a greenhouse experiment, fertilization with either KN03 or NH4C1 increased biomass and N accumulation rates during drought over those of plants dependent solely on N2 fixation. It was concluded that application of N fertilizer to soybean increases drought tolerance because of the extreme sensitivity of N2 fixation to drought.  相似文献   

4.
Phosphorus (P) is a major nutrient factor influencing nitrogen (N) accumulation and partitioning of photosynthates in plants, especially the symbiotic N2‐fixation in legumes. This study was conducted to investigate how P application (0, 20, 40, and 60 kg P2O5/ha) affects symbiotic N2‐fixation of three cultivars (C 235, Pusa 408, and Pusa 417) of chickpea (Cicer arietinum L.). Application of P in general significantly increased leaf area, shoot dry weight, and the rate of acetylene (C2H2) reduction. Phosphorus concentration of shoots and roots, soluble sugar content of nodules, and shoot N accumulation were also significantly increased, especially by P at the 40 kg P2O5/ha rate. The P concentration in nodules was, however, not affected by different levels of P. The Pusa 417 cultivar responded better than the others to the P treatments. Phosphorus‐deficient plants accumulated sugar in their leaves. The interaction effect was found significant on leaf area, shoot dry weight, nodule number, and shoot N accumulation. Pusa 417 gave greatest response to 40 kg P2O5/ha but Pusa 408 and C 235 interacted best with the 20 kg P2O5/ha rate only. The increased nodulation and symbiotic N2‐fixation on P application seem to be the result of morphologically advanced shoots which are making more photosynthates for transport to nodules and not the direct effect of P on the nodules.  相似文献   

5.
Siratro (Macroptilium atropurpureum) and soybean (Glycine max) were grown in pots with or without irrigation for 3 weeks at the vegetative stage to examine the effect of water stress on plant biomass production, biological N2 fixation, CO2 assimilation rate, stomatal conductance, leaf water potential, and the partition of 14CO2 to plant parts. Biomass production decreased by water stress and the decrease was less conspicuous in siratro, mainly due to the maintenance of a relatively higher growth rate in stem plus petioles and roots. Siratro maintained a higher stomatal conductance and CO2 assimilation rate at a lower leaf water potential compared to soybean. Water stress decreased the biological N2 fixation in both species, and the decrease was more appreciable in siratro than in soybean under stress conditions. Water stress affected the export of photoassimilates from leaves in both species. The translocation of 14CO2 photoassimilates to nodules and roots was less substantial in siratro than in soybean under water stress conditions. Translocation of photoassimilates from leaves to stem plus petioles in siratro enables the maintenance of growth of stem and petioles under water stress conditions.  相似文献   

6.
The objective of this study was to establish whether the iron‐stress responses observed in T203 soybean (Fe‐inefficient) with active nodules are products of the nodules or of the entire root system. A split‐root system was used in which half the roots of each plant were inoculated and actively fixing nitrogen and the other half were not. Soybean cultivar T203 is normally Fe‐inefficient and does not exhibit the Fe‐stress responses, however an iron‐stress response did occur during active N2 fixation in earlier studies. This implies that the active nodules influenced the plant's ability to respond to Fe‐deficiency stress. In this study, the Fe‐stress response (H+ and reductant release) observed in T203 soybean was limited to the inoculated side of the split‐root system. The severe Fe chlorosis which developed in these plants was overcome in a manner similar to Fe‐efficient cultivars undergoing normal Fe‐stress response and the T203 plants completely regreened. Exudation of H+ ions was similar in both the presence and absence of Fe, and was generally limited to inoculated roots. Reductant release was nearly nonexistent from the non‐inoculated roots and was greater for the Fe‐stressed (‐Fe) plants than for non‐stressed (+Fe) plants. Thus, the response observed, which alleviated Fe chlorosis, appeared to be associated with N2 fixation of the active nodules.  相似文献   

7.
在短期无氮营养液栽培(28天)条件下,研究缺硼和正常供硼处理对Bragg大豆品种及不结瘤突变体nod49和超结瘤突变体nts382生长、矿质元素吸收与分布及固氮量的影响。试验结果表明:1.在正常供硼的条件下,不结瘤突变体nod的植株生长量,株高、主根生长均高于超结瘤突变体及其亲本。缺硼处理时三种基因型大豆的生长均受到明显的抑制作用。无论是正常供硼还是缺硼处理,超结瘤突变体nts382根系的生长量均明显小于其它基因型。2.正常供硼处理时三种基因型大豆地上部、根及nts382的根瘤中硼的浓度和积累量均高于缺硼处理。缺硼处理,超结瘤突变体及其亲本地上部和根中大部分矿质元素浓度高于正常供硼处理,但积累总量低于正常供硼处理或变化不大。施硼处理的nts382和Bragg,根和根瘤中钙的浓度和积累量明显降低,而地上部变化不大,同时在nts382根瘤中,锌、锰、铁、铜浓度和含量也下降,而钼含量增加。3.施硼处理和Bragg和nts382地上部、根及根瘤中氮的浓度和含量均显著高于缺硼处理,其中超结瘤突变体中氮浓度和总量最高。在缺硼条件下,Bragg和超结瘤突变体能够结瘤,但是Bragg大豆根瘤的固氮作用完全受到抑制,而nts382根瘤还能保持较强的固氮能力。  相似文献   

8.
Salt stress can affect alfalfa growth directly by adversely affecting metabolism, or indirectly by its effect on Rhizobium capacity for symbiotic N2 fixation. Growth and carbohydrate metabolism in leaves, roots and nodules of two alfalfa cultivars (Medicago sativa cv Apica and salt-tolerant cv Halo) in association with two rhizobial strains (A2 and salt-tolerant Rm1521) exposed to different levels of NaCl (0, 20, 40, 80 or 160 mM NaCl) were assessed under controlled conditions. For both cultivars, shoot and root biomasses and shoot to root ratio significantly declined with increasing NaCl concentrations. Under 80 mM NaCl, Halo plants yielded 20% more fresh shoot biomass than Apica while plants inoculated with Rm1521 allocated more biomass to the roots than to the shoots compared to A2. Halo plants maintained a steady shoot water content (about 80%) under the entire range of NaCl concentrations. Shoot water content was more variable in Apica. Apica in association with salt-tolerant strain Rm1521 maintained a better water status than with strain A2, as indicated by the higher shoot water content at 80 mM NaCl. Under salt stress, two major compatible sugars involved in plant osmoregulation, sucrose and pinitol, increased in leaves while a large accumulation of starch was observed in roots. In nodules, pinitol, sucrose and starch increased under salt stress and were much more abundant with strain Rm1521 than with A2. This suggests that there could be an active transport from the shoot to the nodules to help maintain nodule activity under NaCl stress and that strain Rm1521 increases the sink strength toward nodules. Our results show that combining cultivars and rhizobial strains with superior salt tolerance is an effective strategy to improve alfalfa productivity in salinity affected areas.  相似文献   

9.
Sulfur (S) and Nitrogen (N) metabolisms in plants are interacted and it is known that S deficiency decrease N absorption and metabolism. In leguminous plants S deficiency also decreases N2 fixation by rhizobia in the nodules. Deep placement of a controlled-release N fertilizer is a good method to provide nitrogen to soybean without inhibiting N2 fixation; thus, it was hypothesized that this method is able to provide nitrogen effectively to sulfur-deficient soybean plants. In this study effects of deep placement of coated urea on S-N physicological interaction, growth and productivity in soybean plants were examined using pot experiments. Soybean plants were grown with sulfate concentrations of 30, 100, or 1000 μM, with or without deep placement of coated urea. Shoot weights at the developing stage were not affected by S deficiency. SPAD values of leaves during the flowering stage decreased with S deficiency and increased with the deep placement of coated urea. S deficiency decreased seed weight per plant at the harvesting stage, but this decrease was attenuated by the deep placement of coated urea. N and S content in shoots at the developing stage increased with the deep placement of coated urea, whereas in seeds, only the N content increased. N2 fixation activity based on the relative ureide-N content in xylem sap indicated that the deep placement of coated urea did not inhibit N2 fixation activity at the early flowering stage. Without deep placement of coated urea, the relative ureide-N content decreased under S deficiency at the seed filling stage. These results suggest that the deep placement of coated urea is an efficient method to supply N to support soybean yield under S deficiency.

Abbreviations: Deep+: with deep placement of coated urea; Deep–: without deep placement of coated urea  相似文献   

10.
Abstract

Sowing on elevated ridges is effective in reducing wet injury of soybean plants cultivated in upland fields converted from rice paddy fields. Therefore, we investigated the effect of ridge tillage (RT) on soybean N accumulation properties. We compared the amounts of plant N associated with N2 fixation of nodules and from soil and fertilizer in the RT treatment with amounts in conventional tillage (CT) in two fields in 2002–2003. Both fields were upland fields converted from rice paddy fields (Typic Hydraquents). The main difference between the fields was the presence of a field underdrain. The amounts of Rb and K accumulated in the shoots were also determined to estimate soybean root distribution. The grain yields with RT increased in both fields from 106% to 129% compared with CT. Increased pod number and seed weight were the major factors responsible for the yield increase. anova indicated that RT significantly increased the activities of both N2 fixation of nodules and N absorption by roots until R1 (flowering stage). The ratio of Rb and K accumulated in the shoots indicated that with RT, the root distribution was more abundant in the superficial layers compared with CT. Thus, RT reduced wet injury during the rainy season that overlapped the flowering stage. Nitrogen accumulation from N2 fixation until the R7 stage with RT was significantly higher than that with CT. We concluded that RT was effective in increasing N2 fixation of nodules in poorly drained upland fields converted from rice paddy fields.  相似文献   

11.
A field experiment was conducted to study the effect of adding different phosphorus (P) fertilizer levels [0, 40, and 80 kg phosphorus pentoxide (P2O5) ha?1 (abbreviated as P0, P1, and P2, respectively)] and rates of sheep manure (M) [0, 20, and 40 ton ha?1 (abbreviated as M0, M1, and M2, respectively)] on growth and nitrogen (N2) fixation of soybean (Glycine max L.). Sorghum bicolor L. was employed as a reference crop to evaluate N2 fixation using the 15N-isotpic dilution technique. Results showed that addition of P fertilizer or sheep manure had positive effects on dry-matter production, N accumulation, and seed yield. Such effects were more pronounced when adding sheep manure and P together than adding separately. Solely P fertilizer had a small impact on N2 fixation. A tangible increase in the amounts of N2 fixed due to manure addition occurred. The efficient use of N fertilizer (%NUE) increased significantly as the result of adding a high level of P fertilizer. However, a drastic decrease in %NUE was observed when sheep manure was added solely or in combination with P fertilizer. From productivity and ecological standpoints, P2M1 and P2M2 surpassed the other treatments in showing greater grain yield and greater N2 fixation. However, considering the high cost of sheep manure, P2M1 was the optimal treatment for improving growth and N2 fixation in soybean plants with minimal manure consumption. In conclusion, the integrated use of manure and P fertilizer could be considered a useful agricultural practice for improving the performance of soybean plants grown in an Aridisol. Their beneficial effects were mainly attributed to the enhancement of N2 fixation through root growth and soil property improvements besides being a source of P and other nutrients that are essential for N2-fixation process.  相似文献   

12.
Exposing 12‐day‐old soybean plants to 0.2 ppm nitrogen dioxide (NO2) for four weeks increased the nitrite concentration and acidity, and decreased the Leghemoglobin (LHb) concentration and the nitrogenase activity of root nodules. The supply of 1 mol.m‐3 nitrate to the roots intensified the nitrite accumulation, decreased the acidity of the nodules, and alleviated the inhibition of nitrogenase activity by NO2 fumigation. These results suggested that the inhibition of nitrogen (N2) fixation by N fertilizer supply might relate to the acid‐alkali balance in nodules.  相似文献   

13.
Effects of phosphorus (P) deficiency on nodulation were examined in soybean grown in nutrient solution for 7 weeks. Increasing P supply increased shoot growth of nitrogen (N2)-fixing plants from week 5 and that of nitrate-fed plant from week 4 after treatment. Nitrogen (N2)-fixing plants had a greater P requirement for maximum growth at week 5. Increasing P supply from 1 to 16 μ M increased N concentration in N2-fixing plants at week 4 but did not affect it from week 5. By contrast, P deficiency increased N concentration in nitrate-fed plants. Increasing P supply improved nodule formation from week 3. Nodule mass was affected more by P supply than nodule number, which, in turn, was affected more than plant growth. However, P supply did not decrease nodule specific N2 fixation from week 5. The results suggest that P deficiency impaired symbiotic N2 fixation through delaying onset of nodule function and decreasing nodule development.  相似文献   

14.
We studied the effect of the soil physical properties on soybean nodulation and N2 fixation in the heavy soil of an upland field (UF) and an upland field converted from a paddy field (UCPF) in the Hachirougata polder, Japan. Seeds of the soybean cultivar Ryuho were sown in each field with or without inoculation of Bradyrhizobium japonicum A1017. The soybean plants were sampled at 35 (V3) and 65 (Rl) d after sowing (DAS), and then nodulation and the percentage of N derived from N2 fixation in the xylem sap were determined. The soil physical properties were different between UF and UCPF, especially the air permeability and soil water regime. Nodule growth was restricted in UCPF irrespective of rhizobial inoculation, though rhizobial infection was not inhibited by the unfavorable soil physical conditions. Soybean plant growth was closely related to the nodule mass and N2 fixation activity, and the inoculation of a superior rhizobium strain was effective only at 35 DAS. These results indicate that soybean nodulation and N2 fixation was considerably affected by the physical properties of heavy soil, and that it is important to maintain the N2 fixation activity and inoculate the soybean plants with a superior rhizobium strain at a later growth stage in order to increase soybean production in heavy soil fields.  相似文献   

15.
We investigated the effects of applying hairy vetch foliage on nodulation and atmospheric nitrogen (N2) fixation in soybean cultivated in three soil types in pot experiments. Soybean plants were grown in Gley Lowland soil (GLS), Non-allophanic Andosol (NAS), and Sand-dune Regosol (SDR) with hairy vetch foliage application in a greenhouse for 45 days. In GLS, the nodule number was not influenced by the application, however, nodule dry weight and N2 fixation activity tended to increase. In NAS and SDR, nodule formation was depressed by foliage application. Soybean plant growth was promoted in GLS and SDR but not in NAS. These promotive effects of hairy vetch foliage application on soybean plant growth in GLS were considered to be mainly caused by the increase in N2 fixation activity of the nodules, whereas it was considered to be mainly caused by the increase in nitrogen uptake activity of the roots in SDR. The varying effects of hairy vetch foliage application on soybean nodulation may be due to soil chemical properties such as pH and cation exchange capacity, which are related to soil texture. Therefore, we conclude that it is important to use hairy vetch for soybean cultivation based on the different effects of hairy vetch on soybean plant growth in different soil types.  相似文献   

16.
Prolonged flooding of soybean [Glycine max(L.) Merrill] reduce yields. One explanation for lower yields in legumes has been the reduction in N fixation associated with the reduction in 02 supply in the flooded soil. This work investigated the effects of prolonged flooding at the initiation of reproductive growth on the dry matter and N and P accumulation in soybean. The field study was conducted on a Crowley silt loam (Typic Albaquaif). Forrest soybean were flooded at R2 for 7 consecutive days at a flood height of 2.5 cm. Dry matter accumulation and concentrations of N and P of the stems, leaves, branches, and pods were determined by nodes on both flooded and non‐flooded plants for six sampling periods of 0, 7, 14, 21, 36, and 62 days after flooding. The results showed that, in terms of concentration and total amounts accumulated, flooding at R2 adversely affected N nutrition in soybean. The soybean recovered from this effect two weeks after the flood was removed. As compared to the non‐flooded soybean, flooding improved P nutrition. The flooded soybean had greater P concentrations and total amounts of P accumulated. Flooding also prolonged vegetative growth in the upper portion of the canopy.  相似文献   

17.
The effect of ammonium nitrate fertilization on ureide synthesis, xylem transport and assimilation was examined in four week old nodulated soybean plants. In nodules the activity of 5‐phosphoribosylpyrophosphate amidotransferase, a key enzyme of ureide biosynthesis, declined 75%, while enzymes of purine oxidation (xanthine dehydrogenase and uricase) showed no response to nitrogen treatment. Xylem sap concentrations of allantoin and allantoate, as compared to untreated controls, were reduced by about 85% and 65%, respectively. Despite the substantial decline in ureide synthesis and transport, allantoate concentration in leaves of ammonium nitrate treated plants increased by about three‐fold. No ureide accumulation was observed in leaf tissue following a suppression of ureide formation in nodules by allopurinol, an inhibitor of xanthine dehydrogenase. In the pathway of ureide assimilation in leaves, application of inorganic nitrogen had no effect on activity of allantoinase, but caused a 50% drop in activity of allantoate amidohydrolase. Therefore, the observed accumulation of allantoate in soybean leaves in response to nitrogen fertilization was due to new ureide synthesis in plant tissues other than nodules, or to retardation of ureide degradation in leaves caused by the alternative source of nitrogen.  相似文献   

18.
Summary A field study carried out in a sandy, relatively acid Senegalese soil with a low soluble P content (7 ppm) and low vesicular-arbuscular mycorrhizal (VAM) populations showed that soybean responded toGlomus mosseae inoculation when the soluble P level in the soil had been raised by the addition of 22 kg P ha–1. In P-fertilized plots, N2 fixation of soybean, assessed by the A value method, was 109 kg N2 fixed hat when plants were inoculated withRhizobium alone and it reached 139 kg N2 fixed ha–1 when plants were dually inoculated withRhizobium andGlomus mosseae using an alginate bead inoculum. In addition to this N2 fixation increase (+28%),Glomus mosseae inoculation significantly improved grain yield (+13%) and total N content of grains (+16%). This success was attributed mainly to the low infection potential of the native VAM populations in the experimental site. In treatments without solubleP or with rock phosphate, no effect of VAM inoculation was observed.  相似文献   

19.
The influence of three sulphur application rates in combination with two nitrogen application rates on N2 fixation and growth of different legumes was investigated. N was applied as N-labelled 15NH4 15NO3. The 15N isotope dilution technique was used to estimate N2 fixation. At both N increments dry matter yield was highest with high S supply. Independently of the N supply, the high S application rate resulted in a significantly higher N accumulation, which was mainly caused by a higher N2 fixation rate. With the grain legumes the weight of nodules was increased by the high S application rate. The higher number of nodules per pot with optimum S supply was the result of a better root growth. Rates of acetylene reduction correlated significantly with S supply.  相似文献   

20.
Soybean plants (Glycine max L. cv. Akisengoku) were grown in water culture in a greenhouse. At the pod-setting and pod-filling stages, plants were subjected to stem-ringing or treated with high concentration of nitrate. Respiration and N2 fixation (acetylene reducing activity) were studied in individual nodules along with the concentrations of ATP and magnesium.

There was a high positive correlation between respiration activity and acetylene reduction in soybean nodules. The maintenance respiration in mature nodules corresponded to a CO2 evolution of 5.5 µmol/g F.W., and the respiratory cost for nitrogen fixation was estimated at 2 mg C liberated/mg N fixed, though this value was probably underestimated due to CO2 fixation by the nodules. For the nitrogenase activity there was a threshold value of ATP concentration at around 0.15 µmol/g F.W., and the activity increased up to around 0.35 µmol/g F.W., beyond which the ATP concentration did not increase unlike the nitrogenase activity. The values for the magnesium concentration in the nodules detected in the present experiments were above the optimum level.  相似文献   

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