• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.4
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• pp.316-324
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• 2004

Sinorhizobium sp. strain MUS10 forms nitrogen-fixing stem nodules on Sesbania rostrata, a tropical green manure crop. In this study, the ultrastructural events associated with the formation of stem nodules were investigated. Sinorhizobium sp. strain MUS10 entered the host tissue through cracks created by the emerging adventitious root primordia and multiplied within the intercellular spaces. During early phases of infection, host cells adjacent to invading bacteria revealed cellular damage that is typical of hypersensitive reactions, while the cells at the inner cortex exhibited meristematic activity. Infection threads were numerous in S-day-old nodules and often were associated with the host cell wall. In several cases, more than one infection thread was found in individual cells. The junction at which the host cell walls converged was often enlarged due to fusion of intracellular branches of infection threads resulting in large infection pockets. The infection threads were made up of a homogeneous, amorphous matrix that enclosed the bacteria. Several finger-like projections were seen radiating from these enlarged infection threads and were delineated from the host cytoplasm by the plasma membrane. As in Azorhizobium caulinodans induced root nodules, the release of Sinorhizobia from the infection threads into the plant cells appears to be mediated by 'infection droplets'. A 15-day­old Sesbania stem nodule revealed typical ultrastructure features of a determinate nodule, containing several bacterioids within symbiosomes.

• Applied Biological Chemistry
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• v.35 no.6
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• pp.449-456
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• 1992

Expermient were conducted to determine the effect of phosphorus stress on bacteroid content and energy status of soybean (Glycine max [L.] Merr.) nodules. Plants inoculated with Bradyrhizobium japonicum MN 110 were grown with P-stressed (0.05 mM-P) and control (1 mM-P) treatment in the greenhouse. Phosphorus stress decreased nodule mass per plant and nodule mass to whole plant mass ratio. Phosphorus concentration in leaf, stem and root tissues were reduced by 75% but in nodule tissue was reduced only by 40% under phosphorus stress during 3 week experimental period. The bacteroid content per unit nodule mass and the distribution of total nitrogen and total phosphorus among the bacteroid and plant cell fractions of nodule were not affected significantly by phosphorus stress. Regardless of phosphorus treatment, 22% of the nitrogen and 27% of the phosphorus in whole nodules were associated with the bacteroid fraction. The ATP and total adenylate concentrations in and energy charge of whole nodule were decreased 77%, 46% and 37%, respectively, by phosphorus stress. The ATP concentration in and energy charge of the host plant cell fraction of nodules were decreased 86% and 59%, respectively, but these parametres in bacteroid in nodules were not affected by phosphorus stress. These results indicated that nodule is a strong phosphorus sink and that nodule growth and development are regulated to maintain a high phosphorus and energy content in bacteroid even when the host plant is subjected to phosphorus deficiency.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.23 no.2
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• pp.105-112
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• 1978

Earliness of the nodule formation was significantly different among soybean varieties. The numbers of the nodules were much various due to the origins of the soybean varieties and the date of observation. The significant positive correlations were shown between the weight of nodule and soybean yield and also between the weight of nodules and number of nodules but the correlations among the other characters were not significant.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.5
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• pp.594-599
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• 1995

Generally, excessive soil water stress in vegetative growth stage inhibits the growth of soybeans. Leaf area expansion of the plant during excessive soil water stress was only half and the respiration of roots was much diminished compared with the plant none water stress. When excessive soil water stress to the soybeans was continued for 7 days, outer epidermis and vascular system of tap root were severely cracked, more than thirty-five percent of nodule was died and the bacteroid layers of alive nodule were disintegrated.

• Molecules and Cells
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• v.24 no.2
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• pp.185-193
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• 2007

Symbiotic nitrogen fixation with nitrogen-fixing bacteria in the root nodules is a distinctly beneficial metabolic process in legume plants. Legumes control the nodule number and nodulation zone through a systemic negative regulatory system between shoot and root. Mutation in the soybean NTS gene encoding GmNARK, a CLAVATA1-like serine/threonine receptor-like kinase, causes excessive nodule development called hypernodulation. To examine the effect of nts mutation on the gene expression profile in the leaves, suppression subtractive hybridization was performed with the trifoliate leaves of nts mutant 'SS2-2' and the wild-type (WT) parent 'Sinpaldalkong2', and 75 EST clones that were highly expressed in the leaves of the SS2-2 mutant were identified. Interestingly, the expression of jasmonate (JA)-responsive genes such as vspA, vspB, and Lox2 were upregulated, whereas that of a salicylate-responsive gene PR1a was suppressed in the SS2-2 mutant. In addition, the level of JA was about two-fold higher in the leaves of the SS2-2 mutant than in those of the WT under natural growth conditions. Moreover, the JA-responsive gene expression persists in the leaves of SS2-2 mutant without rhizobia infection in the roots. Taken together, our results suggest that the nts mutation increases JA synthesis in mature leaves and consequently leads to constitutive expression of JA-responsive genes which is irrelevant to hypernodulation in the root.

• Applied Biological Chemistry
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• v.40 no.2
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• pp.134-138
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• 1997

The objective of this study was to examine the effect of phosphorus deficiency on nitrogen fixation and photosynthesis of nitrogen fixing soybean plant under $CO_2$ enrichment condition. The soybean plants(Glycine max [L.] Merr.) inoculated with Bradyrhizobium japonicum MN 110 were grown with P-stressed(0.05 mM-P) and control(1 mM-P) treatment under control$(400\;{\mu}l/L\;CO_2)$ and enrichment$(800\;{\mu}l/L\;CO_2)$ enviromental condition in the phytotron equipped with high density lamp$(1000\;{\mu}Em^{-2}S^{-1})$ and $28/22^{\circ}C$ temperature cycle for 35 days after transplanting(DAT). At 35 DAT, phosphorus deficiency decreased total dry mass by 64% in $CO_2$ enrichment condition, and 51% in control $CO_2$ condition. Total leaf area was reduced significantly by phosphorus deficiency in control and enriched $CO_2$ condition but specific leaf weight was increased by P deficiency. Phosphorus deficiency significantly reduced photosynthetic rate(carbon exchange rate) and internal $CO_2$ concentration in leaf in both $CO_2$ treatments, but the degree of stress was more severe under $CO_2$ enrichment condition than under control $CO_2$ environmental condition. In phosphorus sufficient plants, $CO_2$ enrichment increased nodule fresh weight and total nitrogenase activity(acetylene reduction) of nodule by 30% and 41% respectively, but specific nitrogenase activity of nodule and nodule fresh weight was not affected by $CO_2$ enrichment in phosphorus deficient plant at 35 DAT. Total nitrogen concentrations in stem, root and nodule tissue were significantly higher in phosphorus sufficient plant grown under $CO_2$ enrichment, but nitrogen concentration in leaf was reduced by 30% under $CO_2$ enrichment. These results indicate that increasing $CO_2$ concentration does not affect plant growth under phosphorus deficient condition and phosphorus stress might inhibit carbohydrate utilization in whole plant and that $CO_2$ enrichment could not increase nodule formation and functioning under phosphorus deficient conditions and phosphorus has more important roles in nodule growth and functioning under $CO_2$ enrichment environments than under ambient condition.

• The Korean Journal of Ecology
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• v.18 no.1
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• pp.43-54
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• 1995

Effects of environmental factors of N, P, pH, moisture, temperature and oxygen on growth and nitrogen fixation activity of kummerowia striate (Thunb.) Schindler seedling, bearing symbiotic root nodules, were quantitatively analyzed during the growing period. The specific nitrogenase activity (ARA) of nodules showed the maximum value of 187 μmol C₂H₄g fr wt-1 h-1 6 weeks after seeds were germinated. The total nitrogenase activities per plant attained as 1.56, 0.85, 0.09 and 4.0, 1.11, 0.04 μmol C₂H₄hr-1, respectively for the treatments of 1, 3 and 5 mM NO₃￣and NH₄＋ on the 60th day. While the plant grown in N-free media for 20 days after treatments of 5 mM NH₄+for 40 days resulted in 30 mg fr wt of nodule formation and exhibited the relative activities of 152％ and 162％ for total and specific ARA in comparison with those of control plant grown with N-free for 60 days. Total biomass and ARA was by 70％ and 86％ lower in N and P deficiency, respectively. The N and P deficient plot showed 70％ and 86％ decreases of total biomass and ARA in comparison with those of control. The plant grown with N-free for 20 days after pretreatment with N and P free media for 40 days showed the relative values of 77％, 118％ and 150％, respectively for nodule biomass, total and specific ARA in comparison with those of control. The treatment with acid or alkali gradients resulted in significant decreases of nodule biomass and ARA. The optimum temperature and pO₂for ARA were 30°C and 40 kPa, respectively. Two peaks of diurnal variation appeared at 11:00 and 23:00 o'clocks by the continuous light condition. The plants with water stress by temporary wilting point rsulted in 95~97％ inhibition for nodule respiration, transpiration and specific ARA. Transpiration and ARA ware recovered to 88％ and 38％ of those of water unstressed plants, respectively, 6 hours after the plants were rewatered from water stressed condition.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.4
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• pp.389-396
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• 1994

Poor establishment of white dover (Trifolium repens L.) into grass-dominant pastures has been limited its availability. The experiment was done to clarify the effects of timing of initial defoliation, defoliation frequency on the regrowth and nodule formation of the clover cultivars during 28-day regrowing period. Individual plants of cv. Regal, Louisiana S-1 (La. S-1), Grasslands Huia (Huia) and Aberystwyth S184 (S184) were grown in containers until grown to unifoliolate, 1, 2, 4, or 8 trifoliolate stage, and then clipped to 1cm in height every 7 or 28 day for 28 days. To measure the effects, plants were sampled immediately after final harvest, and 1, 3, 7, 14 and 28 days after the harvest. Shoot, root dry weight and biomass were reduced with earlier, more frequent defoliation or shorter regrowing period. In frequent defoliation shoot dry weight and biomass were increased with delayed initial defoliation while in less frequent defoliation steeply done when initial defoliation was delayed to 4 trifoliolate stage. Shoot /Root ratio inclined with more frequent defoliation or lengthened regrowing period, and was greater in initial defoliation of unifoliolate to 2 trifoliolate than the others. Although nodules no. per plant declined with earlier or more frequent defoliation, the effect disappeared to some extent after 14-day regrowth. In comparison with the others, Regal had the highest shoot. dry weight and biomass to 2 trifoliolate stage while S184 did the most nodules regardless of defoliation timing. On 7-day after last defoliation nodule formation of Regal, Huia and S184 but on 28-day after last defoliation that of La. S-1, Huia and S184 was positively correlated to shoot and root dry weights upto 2 trifoliolate stage. On the former day, however, that was negatively correlated to Shoot /Root ratio upto 1 trifoliolate stage although on the latter day it was not, meaning that in addition to more frequent defoliation earlier defoliation was harmful in nodule formation of white clover.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.25 no.2
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• pp.38-48
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• 1980

To evaluate Rhizobium meliloti BALSAC, a strain selected from Canada as an acid tolerant one, and ordinary lucerne inoculant in acid condition, lucerne (Medicago sativa L. cv. Wairau) was inoculated and/or pelleted in the laboratory, and grown for two months in an acid soil (Lismore silt loam, pH 5.4) with three levels of lime in the, glasshouse. The results of controlled (noninoculated), nitrogen fertilized, laboratorial and commercial inoculated seeds were compared to give the following conclusions: 1. There was no significant difference in the top and root dry matter yields between two Rhizobium strains. However, Balsac inoculant showed higher single nodule dry matter weight and relatively higher number of larger nodules than the ordinary inoculant. 2. Lime application increased dry matter yields of plants and nodules, and the number of nodules per pot and the increase of nodules on the lateral roots in both inoculants. Lime application also caused an evenly distribution of nodules on the root by showing an increase of nodules mainly on the lateral roots. 3. Fertilizer nitrogen without inoculant slightly increased the nodulation percentage, the nodule dry matter weight per nodule and the relative proportion of larger nodules. 4. Commercially inoculated and pelleted seed showed less consistent results. 5. Relatively larger variations in measuring nodule characteristics was discussed and concluded that extreme cares should be given to reduce the variation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.4
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• pp.308-315
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• 2003

A field experiment was conducted to investigate the performance of three legume species in a zero-tillage, non-fertilized rice field in a temperate zone. Before the experiment for 5 years, from 1995 to 1999, plant growth patterns of three legume species grown as over-wintering (October-May) cover crops on a paddy field were maintained to study N balance and $\textrm{N}_2$ fixation. Decrease in plant density accelerated from after winter to flowering from 1,090, 320, and 5 to 732, 232, and 6 plants $\textrm{m}^{-2}$ in Chinese milk vetch (CMV), white clover (WC), and hairy vetch (HV), respectively. Total dry weights of plants above-ground level were 0.05, 0.11, and 2.43 g $\textrm{plant}^{-1}$. in WC, CMV and HV respectively but steeply increased at ripening up to 0.77, 2.33, and 26 g $\textrm{plant}^{-1}$. The root dry weight of HV and CMV rapidly increased while in WC, root dry weight increased slightly towards flowering. The highest nodule numbers were recorded in CMV to April thereafter WC produced the highest. Nodule size was distributed within 7mm in CMV but it was larger in HV varying from 1 to 10mm. Shoot N (g $\textrm{m}^{-2}$) greatly increased from over-wintering to flowering in CMV, HV and WC and it ranged from 1.66, 0.5 and 1.92 to 12.6, 3.1 and 13.02 g $\textrm{m}^{-2}$, respectively. After wintering, the initial shoot N content (%) was more in CMV. Root N content (%) was constant or slightly decreased in HV and WC. Soil total N in the control plot (clean fallow) was the highest on Mar. 2 then decreased rapidly to flowering. Soil N content was constant in HV plots whereas it was low in WC plots for the entire growth period except just after winter. Maximum nitrogenase activities were 9, 37.8, and 131 mol $\textrm{C}_2\textrm{H}_4$ $\textrm{plant}^{-1}$ $\textrm{hour}^{-1}$. in CMV, HV, and WC, respectively. Nitrogenase activity showed a direct correlation with nodule number, size and fresh weight. As a cover crop preceding a rice crop, CMV is more suited to colder regions due to its earlier ripening characteristics. Hairy vetch and WC are recommended for regions with a mild winter and a long summer owing to their late ripening and great N fixation activity.