Genotypic Variation for Nitrogen Fixation in Soybean

Twenty soybean cultivars from maturity groups IV, V, VI, VII and VIII were screened in the growth chamber study to determine their response to two Rhizobium strains through N-fixation rates. Cultivars Lee 74, Essex and Bay showed high nitrogenase activities of 201.00, 93.75 and 74.86 nM C₂H₂/pl/hr, respectively. Braxton, Hutton and Bragg showed low nitrogenase activity rates of 4.73, 4.20 and 3.0 nM C₂H₂/pl/hr, respectively. A range of variation was found among the cultivars in shoot fresh and dry weights, nodule number and nodule weight.     

Nitrogen Fixation and Nitrate Assimilation of Determinate, Semi-determinate and Undeterminate Soybeans (Glycine max L.)

Soybean ( Glycine max L.) nitrogen nutrition is ensured by both symbiotic nitrogen fixation and mineral nitrogen assimilation. The relationship between these two modes of N nutrition was analysed in 3 growth types (determinate, semi-determinate and undeterminate) of soybean. The nitrate reductase activity and nitrogenase activity (acetylene reduction) of plants grown in the field and greenhouse showed that these enzymatic activity acted simultaneously or successively during the growth cycle, depending on the availability of inorganic nitrogen in the growing medium. Undeterminate soybean types had a higher potential nitrate reductase activities than determinate types.
The proportion of N₂ fixed as measured by ¹⁵N labelling or stem ureide content indicated that determinate soybeans derived a higher proportion of their N from N₂ fixation than the undeterminates.     

Nitrogen Fixation by Hybrids of White Clover (Trifolium repens L.) and Trifolium nigrescens

Development of hybrids between white clover ( Trifolium repens L.) and Trifolium nigrescens provides a novel route for genetically improving the reproductive capacity of white clover, provided the hybrids are agronomically viable, particularly with respect to N₂ fixation. A comparative study of growth and rates of N₂ fixation over 21 days was conducted with the parental species, F ₁ hybrids and backcross hybrids, in flowing solution culture, without a supply of mineral N to the plants. T. nigrescens was unable to fix N₂ in association with the strains of Rhizobium leguminosarum biovar. trifolii selected for inoculation. Rates of N₂ fixation per plant increased in the order T. nigrescens < F ₁ hybrid < T. repens < backcross 1. Specific rates of N₂ fixation (days 0–21) increased in the order T. nigrescens < F ₁ hybrid < backcross 1 <  T. repens . Dry matter production and nodule biomass per plant increased at a higher rate in backcross 1 hybrids than in T. repens. The results suggest that the potential for N₂ fixation by backcross 1 hybrids is at least as great as that by T. repens .     

Einfluß des Lichtangebotes auf das Wachstum und die biologische Stickstoff-Fixierung von Weißklee (Trifolium repens L.)

Influence of light quantity on growth and biological nitrogen fixation of white clover ( Trifolium repens L.)
The influence of photon irradiance (E_p; 100 to 500 μmol m⁻² s⁻¹) and of the photoperiod (16 or 11 h) on growth and nitrogenase activity of nodulated white clover plants was studied in growth chambers at two nitrate levels (1.0 and 7.5 mM NO₃⁻).
Total dry mass production, the root proportion and nitrogenase activity increased with increasing E_p and photoperiod. Nitrogenase activity generally increased proportionally to root mass. Only at low E_p (100 μmol m⁻² s⁻¹) and under a short photoperiod (11 h) was the specific nitrogenase activity per unit root mass reduced. An abrupt change in E_p led to a rapid and parallel change in nitrogenase activity and relative growth rate.
A higher NO₃⁻ concentration in the nutrient solution (7.5 mM) led to a marked decrease in specific nitrogenase activity, but increased growth between 200 and 500 μmol m⁻² s⁻¹ during early development only. At 100 μmol m⁻² s⁻¹, there was no growth response to nitrate, although its effect on nitrogenase activity was more marked than at a higher E_p.
The results show that with changing light quantity, biological nitrogen fixation of white clover adapts to the existing demand for nitrogen and does not limit growth except during early development, even when light supply is low.     

The Performance of Pea (Pisum sativum L.) and its Role in Determining Yield Advantages in Mixed Stands of Pea and Oat (Avena sativa L.)

On a brown warp soil (Fluventic Eutrochrept) near Goettingen, Germany, conventional leafed pea ( Pisum sativum L. cvs Messire and Bohatyr) and semileafless types (cvs Profi, Juno and Azur) were grown in mixed stands together with oat ( Avena sativa cvs Alf and Lutz) in substitutively designed experiments from 1995 to 1997. Oat was the dominant component. Crowding coefficients for oat averaged 7.4. No relationship could be detected between the crowding coefficient of oat and any yield advantage from the mixture. Crowding coefficients for pea varied substantially, between 0.1002 (Juno and Alf in 1996) and 0.2979 (Bohatyr and Alf in 1996). Crowding coefficients for semileafless pea cultivars were smaller than for conventional leafed types. The yield advantage of the mixture increased as the crowding coefficient of pea increased. The maximum yield increase for the mixture was achieved when the relative yield total (RYT)=1.17 or + 11 dt grain DM ha^–1 for mixtures of the long-strawed conventional leafed cultivars Bohatyr and Alf (in 1996). The crowding coefficients of pea were positively correlated with the level of symbiotically fixed N₂ in the mixed stands. When N₂ fixation with mixed cropping was about 30 kg N ha^–1, RYT was unity. Increasing symbiotic N₂ in the mixtures resulted in increasing yield advantages in the mixture. Short-strawed pea cultivars seem unsuitable for mixing with oat. Plant height of pea appeared to be more important than plant leaf type. Accordingly, mixtures containing the long-strawed semileafless pea cultivars Profi and Alf were more successful. It is concluded that increased competitiveness of the pea component in the mixture with oat entails increasing the level of symbiotic N₂ fixation including resource complementarity and thus yield advantage in the mixed stands.     

Response of Soybean [Glycine max (L.) Merr.] Cultivars to Genistein-Preincubated Bradyrhizobium japonicum: Nodulation and Dry Matter Accumulation under Canadian Short-Season Conditions

The addition of genistein, a plant-to-bacteria signal molecule, to Bradyrhizobium japonicum cells prior to use as inocula has been shown to increase nodule number and promote soybean N₂ fixation at low root zone temperatures. Previous greenhouse and field experiments involving only two cultivars have indicated that soybean [ Glycine max (L.) Merr.] cultivars can vary in their response to genistein application. The objective of this study was to evaluate a range of soybean cultivars for response to genistein application under short-season cool-spring Canadian conditions. A 2-year field study was conducted in 1997 and 1998 with a range of soybean cultivars recommended for Quebec. The 11 cultivars tested represented a range of yield potentials and maturity groups. They were inoculated with genistein-preincubated B. japonicum inocula or regular inocula, applied into the furrow at the time of planting. The results of these experiments indicated that neither maturity nor yield was correlated with increases in nodulation, biomass, and plant total nitrogen content resulting from genistein treatment and that all maturity groups responded to genistein application in essentially the same way. Thus, response of soybean cultivars to genistein addition is regulated by genotype characteristics other than maturity or yield level.     

Nitrogen Fixation, Growth and Yield of Intercropped Mungbean (yigna radiata L.) and Groundnut (Aracbis bypogaea L.) as Affected by the Genotype

¹⁵N-aided investigations were conducted to ascertain the Nj fixation and the nitrogen (N) contribution by mungbean ( Vigna radiata L.) and groundnut ( Aracbis hypogaea L.) when intercropped with maize ( Zea mays ). The study involved growing seven genotypes of the above legumes with maize in alternate rows in two separate experiments. A sole crop of maize was used as the reference crop to determine N2 fixation by the ¹⁵N methodology. Significant genotypic differences in pod yield and stover N content were observed in intercropped mungbean and groundnut. The percentage N derived from the atmosphere showed a genotypic variation of 31 to 45 % (7 to 10 kg N₂ fixed ha⁻¹O in mungbean and 47 to 69 % (9 to 18 kg N₂ fixed ha⁻¹) in groundnut. Harvest index for N varied from 58 to 77 % in mungbean and 55 to 75 % in groundnut. In groundnut, the uptake of soil N was significantly affected by the genotype. Assuming that the N contribution to the soil by the helow-ground plant parts was negligible, the removal of seeds at maturity resulted in a negative N balance in the soil in all the genotypes of mungbean. In groundnut, some genotypes produced a positive N balance in the soil. Owing to high N₂ fixation capacity and low harvest index for N, groundnut showed a greater N supplementing ability than mungbean.     

Seasonal Changes in the Photosynthetic Capacity of Winter Rape Plants under Different Nitrogen Regimes Measured in the Field

Winter rape (cv.'Falcon') grown under different nitrogen regimes (N₀, N₁₂₀; 0 and 120 kg.ha⁻¹, respectively) in northern Germany was investigated over the 1996 spring–summer season. Using a CO₂, H₂O diffusion porometer, diurnal courses or net photosynthesis and respiration were measured in situ and were related to microclimatic conditions and leaf water relations. Photosynthesis was modelled and daily CO₂ gain was calculated. In contrast to the N₁₂₀ plants, plants of the low nitrogen plot (N₀) grew less densely and their leaves behaved more like sun leaves. Increased nitrogen supply had little influence on photosynthetic capacity but it increased productivity through higher leaf area index and an extended period of photosynthetic activity. N₁₂₀ plants also appeared to be better acclimated to hot, summer conditions. Higher nitrogen supply substantially increased seed production with the yield of the N₁₂₀ plants being 16% of the N₀ plants.     

N2-Fixierung und Ertragsstruktur der Weißen Lupine (Lupinus albus L.) im Vergleich zu Vicia faba L. und Glycine max (L.) Merr. auf verschiedenen Standorten

N₂-Fixation and Yield Structure of White Lupin ( Lupinus albus L.) in Comparison to Vicia faba L. and Glycine max (L.) Merr. on Different Sites
In field studies white lupin ( Lupinus albus L., Eldo ) was compared with faba bean ( Vicia faba L., Herz Freya ) in 1986 and soybean ( Glycine max [L.] Merr., Gambit ) in 1988 on five sites respectively. Total N₂-fixation, which was determined by the extended difference method, and yield components were correlated to weather and soil conditions:
1. While faba bean responded to low pH with delayed nodulation, white lupin showed no decrease in N₂-fixation at pH less than 5.5 as far as soil was not calcareous.
2. The white lupin developed its root system most quickly into further soil depths and produced a root dry weight six times as large as that of faba bean in the soil layer 60-90 cm until the end of July (Bayreuth).
3. Despite on the calcareous sites the white lupin showed the highest total-N₂-fixation (max. 36 g N/m²) throughout, the N-gain for the succeeding crop was up to 8 g N/m² for white lupin and faba bean as well. In contrast the N-balance of soybean was mostly negative.
4. Seed yields of white lupin (48-450 g/m²) ranged between those of faba bean (145-549 g/m²) and of soybean (89-290 g/m²); its raw protein yields were the highest found (max. 158 g/m²) though.     

Diallel analysis of sugar composition of 10 vegetable soybean lines

Few studies have evaluated vegetable soybean for sugar content at the green pod stage. Information on combining ability and type of gene action that governs inheritance of seed traits can help breeders to select suitable parents and devise an appropriate breeding strategy. Ten vegetable soybean accessions were crossed in a complete diallel mating design. Parent lines and F₂ and F₃ progenies were evaluated for two nutritional components. In this study, both general and specific combining ability and reciprocal effects were significant for sucrose and total sugar. Cultivars 'Kanrich', 'Pella', 'Verde' and V81-1603 had good general combining ability for high sucrose. In general, high sucrose content was observed in progeny of the early maturity group genotypes 'Kanrich', 'Pella' and 'Verde'. The best combiners for high total sugar content were 'Verde', V81-1603 and PI 399055. These genotypes could serve as genetic sources in a vegetable soybean breeding programme.     

Sensitivity of Corn, Oats, Peanuts, Rice, Rye, Sorghum, Soybean and Tobacco to UV-B Radiation under Growth Chamber Conditions

Sensitivity of different agronomic crops to UV-B radiation was studied under environmentally controlled conditions. UV-B radiation reduced plant height, fresh weight, dry weight and ash contents. The reduction varied among the different species tested. Narrow-leaved plants (mainly C₄) were less sensitive to UV-B than broad-leaved plants (mainly C₃).     

减量施氮对带状套作大豆土壤通气环境及结瘤固氮的影响

为研究种植模式和施氮量对大豆土壤通气环境及结瘤固氮的影响,本研究采用二因素裂区试验设计,主区为种植模式:大豆单作(SS)、玉米/大豆带状套作(MS),副区为不同施氮量:不施氮(NN:0 kg hm^-2)、减量施氮(RN:45kghm^-2)和常量施氮(CN:60kghm^-2),监测了大豆生育期内土壤的O₂含量和土壤呼吸速率的动态变化规律,分析了各处理的土壤水稳性团聚体、容重和孔隙度差异,探讨了大豆生育期内结瘤量、固氮能力的变化特征。2年数据结果表明,与单作大豆相比,带状套作大豆可提高土壤O₂含量、>2 mm粒径团聚体的百分含量、显著增加土壤孔隙度、显著增强后期土壤呼吸的速率,显著降低<1mm粒径团聚体百分含量与土壤孔隙度;R5期根瘤干重差异不显著,但结瘤数量显著增加39.9%,固氮酶活性与固氮潜力也在此时显著高于单作大豆。各施氮量间,土壤O₂含量、0.25～1.00mm粒径的百分含量、带状套作大豆的土壤呼吸速率以RN处理最高,施氮能降低<0...     

Effect of Gibberellic Acid Spray and Basal Nitrogen and Phosphorus on Productivity and Fatty Acid Composition of Rapeseed-Mustard

Two field experiments were conducted during] 994-95 to study the effect of spray of 10⁻⁵ M GA3 at 40 days after sowing on mustard ( Brassica juncea (L.) Czern & Coss.) cv. Varuna grown with basally applied 0, 40, 80 and 120 kg N ha⁻¹ (Expt. 1) and 0,15, 30 and 45 kg P ha⁻¹ (Expt. 2) on pod number per plant, seeds per pod, 1000 seed weight, seed yield, biological yield, harvest index and fatty acid composition of oil. No significant difference between water and GA3 spray was found when basally applied nitrogen was 0 or 40 kg N ha⁻¹. N₈₀ proved to be the best for yield characteristics. In another experiment on phosphorus, GA₃ and 30 kg P ha⁻¹ individually enhanced the yield, but interaction of GA₃ and P remained non-significant. The fatty acid composition of oil in both experiments was significantly affected only by nitrogen and phosphorus treatments for oleic acid and erucic acid. It was found that return in the form of yield was more for every kg applied fertilizer under GA, spray treatment. The response was more for N fertilizer in comparison to P. GA₃ at a low level of fertilization significantly increased the return from fertilization.     

Transpiration Dynamics in Cadmium-Treated Soybean (Glycine max L.) Plants

Soybean ( Glycine max L.) plants, cv Richland, were grown during 30 days in a nutrient solution. After this period the plants were treated with a 50 μM Cd(NO₃)₂ solution. Sap flow rate and stomatal conductance were monitored during 4 consecutive days; at the end of this period relative water content and stomatal width and length were determined on fully expanded leaves. On the second day from the Cd treatment sap, flow rate and stomatal conductance in the treated plants were reduced to 60% of the control plants. Stomatal conductance kept on decreasing up to the fourth day. Cadmium decreased the leaf relative water content and the reduction in the stomatal closure was supported by an increase in the L/W ratio of the stomata. Root water uptake should be the primary mechanism reduced by Cd stress in soybean, and this reduction is consistent with the decrease in transpiration rate and with the stomatal closure.     

Untersuchungen über die Wirkung von Ammonium- und Nitrat-Ernährung auf die Ertrags- und Proteinbildung bei Hafergenotypen

Investigations about the effect of ammonium- and nitrate nutrition on the formation of yield and protein of oats genotypes
The formation of yield and proteins of three different oats genotypes (cv. Gambo, Flämingskrone, Caesar ) in dependence on ammonium or nitrate nutrition was investigated in pot trials over 2 years (from 1982 to 1983). On oats the NH₄-nutrition showed in comparison to NO₃ nutrition increases in grain yield up to 20 % due to a favourable influence on the number of panicles per pot (s. Fig. 1).
Protein content and protein yield increased particularly by high fertilizing with NH₄-N (N₃- and Invariant); the best effect was ascertained by the N₄-variant increase of 4 % (D.M.). Among the protein fractions (albumins, globulins, prolamins, glutelins) the albumin- and prolamin-proteins increased after NH₄-fertilizing by 1–2 %, whereas at the same time the glutelins decreased by 1–4 %; the globulins showed no differences.     

Allometric Relationships of Growth Components in Maize (Zen mays L.) Cultivars

Allometric relationship (W₁=αW₂^β, where α and β are the parameters) was fitted among growth components in two maize cultivars viz., Decani hybrid and Deccan 101 in order to obtain estimates of other components of the plant system which are time consuming measurements. The results of the agronomic field trial conducted at the University of Agricultural Sciences, Bangalore were used. This model's predictability was compared with linear regression model. In both the cultivars, allometric model using leaf area (LA - W₂.) and leaf dry matter (LDM - W₂) simulated total dry matter production (DMP - W₂) by 79 to 98 % of actual values. Further allometric model fitted well to predict stem dry matter by 91 to 93 % using LDM and LA 89 to 92 % using LDW. Whereas linear regression model estimated total DMP by 95 to 96 % using cob dry matter. In case of LDM - LA association, linear regression model was found to be the best than other model. The leaf area decreased after silking in both the cultivars and the ratio of growth rates of DMP – LA ( β ₂) was negative. Between cultivars, cv. Deccan 101 had higher R² values in most of the relationships than cv. Deccan hybrid indicating the varietal difference.     

The Effects of Intercrop Spacing Patterns on the Silage Yield of Maize and Soybean

The effects of intercrop spacing patterns on the silage yields of both maize (lea mays L.) and soybean (Glycine max [L.] Merr.) were examined from 1985 to 1987. Dwarf maize was intercropped with nonnodulatmg or nodulating soybean in the spacing patterns, S_40same (two crops in the same row, 40 cm row width) and S_20ait or S_40ak (two crops in alternate rows, 20 cm or 40 cm row width, respectively). Tall maize was intercropped with nodulating soybean in S_40sames S_40alt and S_40pair (maize in 40 cm paired rows, soybean rows 20 cm outside each maize row and 80 cm from the next set of four rows) at 0 or 60 kg N ha⁻¹ and at population densities of 67% maize: 67% soybean or 50 % maize: 50% soybean. Maize and soybean were also intercropped and stripcropped on a farm-scale. The only difference between intercrops arranged in the same rows versus those in alternate rows was that the average soybean protein yields were higher in S_40same than in S_40alt. In 1986, the S_40alt maize-soybean intercrops produced higher maize yields, total biomass yields and Land Equivalent Ratios (LERs) than in S_40pirs, and in 1987, these responses were higher in intercrops than in stripcrops. In 1986, at 0 kg N ha⁻¹, the soybean biomass and protein yields were lower in S_40alt, than in S_40pairs and in 1987, these responses were lower in intercrops than in stripcrops.     

A Rapid Method for Measuring Freezing Resistance in Crop Plants

The objective of this study was to develop a technique based on chlorophyll fluorescence to assess freezing injury and resistance of leaves. Optimization was done with faba bean leaves and applicability to other crops was examined at winter and spring with types of barley, oats, rape and faba beans. Selected leaves from young hardened beans were subjected to standardized freezing tests with different minimum temperatures ( T _min) and fluorescence was monitored. After a dark period basic fluorescence ( F _O was induced by 0.2 μmol m⁻² s⁻¹ pulsed red light and maximum fluorescence ( F _m) was assayed at different light intensities. 1500 μmol m⁻² s⁻¹ rendered to give the maximum possible output of Fm and best differentiation of differently damaged leaves by F _n= F _m - F _O. Leaf temperature during measurement and during a short storage (± 2 h) should be kept at about 0°C to avoid biases between differently damaged leaves. The measuring spot on the leaf must be standardized since fluorescence response differed at the tip and base of a leaflet, but not between the two leaflets of a faba bean leaf. The applicability of F _rr (ratio of F _r of stressed to unstressed leaves) as a measure of resistance was demonstrated by comparison of winter hardiness of cultivars with freezing resistance calculated from the relationship of F _vr and the T _min used in freezing tests.     

The Effect of Nitrogen Fertilization and Population Density of the Field Bean (Vicia faba L. minor) of Indeterminate and Determinate Growth Habit on the Symbiosis with Root Nodule Bacteria and on the Seed Yield

Field beans of indeterminate (cv. Nadwiślański) and determinate (cv. Tibo) growth habits were grown on field plots with a density of 20, 40 and 80 plants m⁻² at two levels of nitrogen fertilization: low (20 kg N ha⁻¹) and very high (150 kg N ha⁻¹). At the phase of intense pod growth the number and the dry matter weight of root nodules as well as their nitrogenase activity and some features of the plants growth were determined, and in the period of ripeness the components of seed yield were established.
It was found that increased density of sowing as well as the high level of nitrogen fertilization inhibited the growth and development of root nodules and limited their nitrogenase activity in both cultivars. Plants of both varieties were characterized by a similar potential of forming the root nodules, however, in plants of the cv. Tibo the nitrogenase activity of nodules was much lower than in the cv. Nadwiślański.
Increased population density of the plants has in both varieties given increased seed yield when calculated per m² of the soil, compensating in excess the depression of the seed yield from one plant. Such compensation did not occur in the case of the depression of nitrogen fixation under intense nitrogen fertilization.     

Differential Nitrogen Uptake, Utilization and Biomass Accumulation by Some Sorghum Cultivars

Five cultivars of sorghum viz: PU-7, Sarokartuho, Bagdar, Redjanpur and Potobar 4–8 were studied for their growth, N uptake and utilization efficiency at 5 mM N in solution culture. These cultivars differed significantly in their dry matter accumulation and relative growth rate of shoot. Differences in shoot/root of the cultivars were also notable. Markedly different mean N intake rate among the sorghum cultivars was 108 μmol g⁻¹ root dry wt. hr⁻¹ in Bagdar and 53 μmol g⁻¹ root dry wt. hr⁻¹ in PU-7 and Redjanpur. Both relative accumulation rate of N and efficiency of biomass accumulation per unit N absorbed also differed appreciably among the cultivars.