Symbiotic Parameters Research Articles

Correction to: Symbiotic Parameters, Productivity and Profitability in Kabuli Chickpea (Cicer arietinum L.) as Influenced by Application of Phosphorus and Biofertilizers

There were the following errors in this article as originally published.

Symbiotic Parameters, Productivity and Profitability in Kabuli Chickpea (Cicer arietinum L.) as Influenced by Application of Phosphorus and Biofertilizers

The present investigation was undertaken with objectives of studying the effect of phosphorus and biofertilizer treatments on symbiotic parameters, productivity and profitability of kabuli chickpea. The field experiment was conducted during 2017–2018 and 2018–2019 with five phosphorus levels (0, 20, 30, 40 and 50 kg P2O5 ha−1) and three biofertilizer treatments (uninoculated control, Mesorhizobium + RB-1 [Pseudomonas argentinensis] and Mesorhizobium + PSB-18 [Bacillus cereus]). Biofertilizers were used for inoculation of seed prior to sowing. Chlorophyll content index, number of nodules, nodule dry weight, leghaemoglobin content and nitrogen and phosphorus concentrations in shoot were recorded the highest with application of 50 kg P2O5 ha−1. The highest grain yield (2059 and 2196 kg ha−1 in 2017–2018 and 2018–2019, respectively) was obtained with the application of 50 kg P2O5 ha−1 which was statistically at par with 40 kg P2O5 ha−1 (2045 and 2183 kg ha−1). However, the highest net returns and benefit-cost ratio were obtained with the application of 40 kg P2O5 ha−1. Inoculations with Mesorhizobium + RB-1 and Mesorhizobium + PSB-18 proved superior over uninoculated control with respect to all parameters studied. Mesorhizobium + RB-1 and Mesorhizobium + PSB-18 enhanced the grain yield by 15.33 and 15.52% in 2017–2018 and by 13.82 and 14.27% in 2018–2019, respectively, over uninoculated control. For obtaining high productivity and net returns of kabuli chickpea, 40 kg P2O5 ha−1 and seed inoculation with Mesorhizobium + RB-1 (Pseudomonas argentinensis) or Mesorhizobium + PSB-18 (Bacillus cereus) are found to be the most efficient.

Influence of herbicides on symbiotic parameters, growth, yield and nutrient uptake in mungbean [Vigna radiata (L.) Wilczek

ABSTRACT Effects of various herbicides applied at different rates as pre-emergence or as post-emergence were studied on symbiotic parameters, growth, productivity and nutrient accumulation in mungbean. Pre-emergence application of pendimethalin 30 EC at 0.75 kg ha−1, pendimethalin 30 EC at 0.45 kg ha−1 + hand weeding (HW) at 4 weeks after sowing (WAS) and pendimethalin 30 EC + imazethapyr 2 SL (pre-mix) at 0.45 kg ha−1 + HW at 4 WAS had no/little inhibitory effect on symbiotic parameters (nodule number, nodule dry weight and leghaemoglobin content). Among herbicide treatments, pendimethalin 30 EC at 0.45 kg ha−1 + HW proved to be the best in influencing grain yield (1574 and 1246 kg ha−1 in 2016 and 2017, respectively) and nutrient uptake by crop (130.0–150.9 kg nitrogen, 13.6–16.4 kg phosphorus and 75.9–87.9 kg potassium ha−1) followed by pendimethalin 30 EC + imazethapyr 2 SL (pre-mix) at 0.45 kg ha−1 + HW (1528 and 1177 kg ha−1 grain yield, 123.9–140.9 kg nitrogen, 12.8–15.2 kg phosphorus and 71.5–81.5 kg potassium ha−1). Application of imazethapyr at 50 or 75 g ha−1 at 15 or 25 DAS had adverse effect on symbiotic parameters, grain yield and nutrient uptake.

Symbiotic Parameters, Growth, Productivity and Profitability of Chickpea as Influenced by Zinc Sulphate and Urea Application

The present investigation was undertaken with objectives of studying the effect of soil and foliar applied zinc sulphate (ZnSO4) and foliar application of urea on symbiotic characters, growth parameters, yield attributes, grain yield and economics in chickpea. A 2-year field experiment was conducted with six zinc sulphate and three urea application treatments. In the case of foliar applications, both ZnSO4 (0.5%) and urea (2%) were sprayed to foliage at flowering and flowering + pod formation stages. The maximum plant height, number of branches, chlorophyll content, number and dry weight of nodules, leghaemoglobin content, yield attributes, grain yield (1935 and 1955 kg ha−1 in first and second year of study), net returns (US$ 722.71 and 855.71 ha−1) and benefit cost ratio (1.40 and 1.63) were recorded with soil application of ZnSO4 (25 kg ha−1) at sowing + foliar spray of ZnSO4 (0.5%) at flowering and pod formation stages. Foliar spray of ZnSO4 (0.5%) alone at flowering + pod formation stages was also equally effective in improving these parameters. Urea spray (2%) at flowering + pod formation stages resulted in the highest symbiotic parameters, growth attributes, yield attributes, grain yield (1920 and 1939 kg ha−1), net returns (US$ 720.22 and 851.59 ha−1) and B/C ratio (1.41 and 1.65) which remained statistically similar with foliar spray of urea (2%) at flowering stage alone. The application of zinc sulphate and urea deserves a special attention for increasing productivity and profitability of chickpea.

Two Broad Host Range Rhizobial Strains Isolated From Relict Legumes Have Various Complementary Effects on Symbiotic Parameters of Co-inoculated Plants.

Two bacterial strains Ach-343 and Opo-235 were isolated, respectively from nodules of Miocene-Pliocene relict legumes Astragalus chorinensis Bunge and Oxytropis popoviana Peschkova originated from Buryatia (Baikal Lake region, Russia). For identification of these strains the sequencing of 16S rRNA (rrs) gene was used. Strain Opo-235 belonged to the species Mesorhizobium japonicum, while the strain Ach-343 was identified as M. kowhaii (100 and 99.9% rrs similarity with the type strains MAFF 303099T and ICMP 19512T, respectively). Symbiotic genes of these strains as well as some genes that promote plant growth (acdS, gibberellin- and auxin-synthesis related genes) were searched throughout the whole genome sequences. The sets of plant growth-promoting genes found were almost identical in both strains, whereas the sets of symbiotic genes were different and complemented each other with several nod, nif, and fix genes. Effects of mono- and co-inoculation of Astragalus sericeocanus, Oxytropis caespitosa, Glycyrrhiza uralensis, Medicago sativa, and Trifolium pratense plants with the strains M. kowhaii Ach-343 and M. japonicum Opo-235 expressing fluorescent proteins mCherry (red) and EGFP (green) were studied in the gnotobiotic plant nodulation assay. It was shown that both strains had a wide range of host specificity, including species of different legume genera from two tribes (Galegeae and Trifolieae). The effects of co-microsymbionts on plants depended on the plant species and varied from decrease, no effect, to increase in the number of nodules, nitrogen-fixing activity and plant biomass. One of the reasons for this phenomenon may be the discovered complementarity in co-microsymbionts of symbiotic genes responsible for the specific modification of Nod-factors and nitrogenase activity. Localization and co-localization of the strains in nodules was confirmed by the confocal microscopy. Analysis of histological and ultrastructural organization of A. chorinensis and O. popoviana root nodules was performed. It can be concluded that the strains M. kowhaii Ach-343 and M. japonicum Opo-235 demonstrate lack of high symbiotic specificity that is characteristic for primitive legume-rhizobia systems. Further study of the root nodule bacteria having complementary sets of symbiotic genes will contribute to clarify the evolutionary paths of legume-rhizobia relationships and the mechanisms of effective integration between partners.

Influence of inoculation on photosynthesis and symbiotic parameters of pea and its crop yield in the conditions of the southern forest steppe of Western Siberia

The paper highlights the effect of inoculation by means of biological specimens on formation of photosynthetic parameters, nodule-forming capacities and yield of pea grain. The authors reveal the varieties which mostly respond to the tillage, effective specimens and methods of their application. The researchers explored two varieties of pea as Omskiy 9 and Omskiy 18 and two biological specimens (risotorphine and ruminatine). The study was conducted in the experimental fields of Omsk agricultural research center in 2016-2017 in the following variants: control (without inoculation), inoculation by means of risotorphine, inoculation by ruminatine and combined tillage. The researchers observed different meteorological conditions during the research. The experiments and calculations of the experimental data were carried out by means of general methodics. The positive effect of inoculation on increasing of such parameters as leaf surface index and photosynthetic potential is observed. Active symbiotic potential, number and weight of nodules rhizosphere of pea had a maximum value when being treated by biospecimen ruminatine and combined inoculation of seeds by risotorphine and ruminatine. The authors highlight significant positive relationship between photosynthetic and active symbiotic potential. Inoculation influenced the yield of pea varieties in a different way in the years of research. The results of variance analysis showed that conditions of experiment influenced the yield of varieties – 34.4 %, the proportion of inoculation effect was 25.0 % and genotype – 17,3 %. Omsk 18 variety was characterized by the highest rates of photosynthetic and symbiotic activity. Seed treatment with ruminatine and combined inoculation with risotorphine and ruminatine have impact when growing pea in the conditions of southern forest-steppe of Western Siberia.

Symbiotic parameters, growth, nutrient accumulation, productivity and profitability as influenced by integrated nutrient management in lentil (Lens culinaris)

ABSTRACTField experiments evaluated the effects of integrated nutrient management on symbiotic parameters, growth, nutrient accumulation, productivity and profitability of lentil (Lens culinaris Medikus). Application of recommended dose of nutrients (RDN, 12.5 kg N ha−1 + 40 kg P2O5 ha−1) + 25 kg ZnSO4 ha−1 + seed inoculation with biofertilizers [Rhizobium + phosphate solubilizing bacteria (PSB) + plant growth promoting rhizobacteria (PGPR)] + 1.0 g ammonium molybdate kg−1 seed recorded the highest number & dry weight of nodules, leghaemoglobin content, root & shoot dry weight, plant height, number of pods plant−1 and 100-seed weight. The next best treatment was RDN + seed inoculation with biofertilizers + 1.0 g ammonium molybdate kg−1 seed. On the basis of mean of three-year data, the treatment of RDN + 25 kg ZnSO4 ha−1 + seed inoculation with biofertilizers + 1.0 g ammonium molybdate kg−1 seed proved the best in realizing the highest grain yield (34.0%), gross returns (34.0%) and net returns (54.8% higher over control). Nitrogen, phosphorus and potassium in the grains and straw were significantly improved where RDN was applied in combination with seed inoculation, basal application of ZnSO4 and seed treatment with 1 g ammonium molybdate than their single applications.

Growth, symbiosis, productivity, and profitability of soybean at varying planting methods and nitrogen levels

ABSTRACTA field experiment was conducted to study the effect of different planting methods (Happy Seeder sowing, Straw Chopper + Zero Tillage sowing, and conventional sowing) and nitrogen (N) levels (0%, 75%, 100%, and 125% of recommended N) on the emergence, growth, symbiotic parameters, productivity, and profitability of soybean sown after wheat harvest. Growth and symbiotic parameters were significantly better under Happy Seeder sowing and Straw Chopper + Zero Tillage sowing than conventional sowing. The seed yield, nutrient uptake, and economic returns were significantly higher under Happy Seeder sowing than other methods. The growth parameters, symbiotic parameters, biological, straw, and seed yields were increased significantly up to 100% recommended N level. The nutrient uptake increased significantly up to 100% recommended N level. Therefore, sowing with Happy Seeder after combine harvested wheat along with 100% recommended N would best optimize soybean yield and profitability.

Evaluation of thermotolerant rhizobacteria for multiple plant growth promoting traits from pigeonpea rhizosphere

In pigeonpea due to the prevailing high temperature, poor nodulation have usually been observed as a limiting factor in its productivity. Plant growth promoting traits of 5 pigeonpea rhizobacterial isolates out of 32, selected on the basis of maximum growth at 30, 40 and 50°C, were evaluated for their potential application in enhancing symbiosis and plant growth of pigeonpea. The level of IAA at 30, 40 and 50°C varied from 0.95-20.96 ?g/ml, 1.21- 34.82 ?g/ml and 0.16-17.34 ?g/ml in the presence of tryptophan respectively. Maximum flavonoid production and siderophore production was recorded bacterial isolates with S12p6 (6.68 ?g/ml) at 30°C and S1p1 (4.2 cm) at 40°C respectively. Isolates S1p1 and S12p6 showed relatively superior production of growth hormone, flavonoid-like compounds and siderophores can further be tested as co-inoculant with recommended Rhizobium for studying their efficacy under field conditions for symbiotic parameters and growth of pigeonpea.

Evaluation of microbiological management strategy of herbicide toxicity to greengram plants

Abstract In order to circumvent the problems of herbicidal toxicity, tolerant N2 fixing and phosphate solubilizing bacterial strains were isolated and identified. Among 20 bacterial isolates, Azotobacter sp. strain AZ1 survived 2400, 3200, and 1600 μg/mL while Bacillus sp. strain PSB2 tolerated up to 1600, 2400 and 1600 μg/mL glyphosate, quizalofop and metribuzin, respectively. Under in vitro conditions, these bacterial strains secreted IAA, siderophores, exopolysaccharides, ammonia and transformed inorganic P into organic P even under herbicides stress. SEM and CLSM images revealed a clear toxic impact of herbicides on bacterial cells above tolerance limit. Phytotoxicity to greengram plants increased with increasing concentrations of herbicides. Herbicide tolerant Azotobacter strain AZ1 and Bacillus sp. strain PSB2 when used as inoculant, substantially reduced the herbicidal toxicity to greengram. For instance, strain AZ1 increased the length of roots (10%) and shoot (6%), dry biomass of root (28%) and shoot (6%), different symbiotic parameters like nodule number (6%), nodule dry biomass (8%), LHb (15%), photosynthetic pigments and seed yield (39%), whereas, Bacillus sp. strain PSB2 enhanced the measured parameters by 12%, 13%, 23%, 21%, 4%, 6%, 22%, 5% and 27%, respectively relative to positive control (1444 μg/kg glyphosate). Additionally, proline in shoot tissues declined rapidly in bio-inoculated plants. Conclusively, the microbial cultures resulted in better management of herbicidal toxicity to greengram plants. And hence, Azotobacter sp. strain AZ1 and Bacillus sp. strain PSB2 could be recommended for use as an effective and inexpensive microbial inoculant/biofertilizer to augment the production of greengram in herbicide contaminated soils.

Effect of zinc and boron on yield, nutrient content and quality of blackgram (Vigna mungo L.)

An experiment was carried out in sandy loam soil at M. G. C. G. Vishwa Vidyalaya Farm, Chitrakoot during kharif of 2013. The objectives were to evaluate the effect of zinc (Zn) and boron (B) on the yield, nutrient content and quality of blackgram [Vigna radiata (L.) Wilczek] and to find out the optimum dose of Zn and B for yield maximization. There were four levels of zinc (0, 10, 20 and 30 kg/ha) and boron (0, 2.0 kg/ha one spray with boric acid and 2 kg/ha two sprays with boric acid) along with a blanket dose of N20 P40 K20 kg/ha. The experiment was laid out in factorial randomized block design with three replications. Results showed that the application of 30 kg zinc/ha and boron 2 kg/ha with two foliar sprays resulted in highest grain yield with their interaction effect on grain yield (8.98 q/ha) as well as all growth, yield, quality and nutrients uptake parameters. The lowest value of symbiotic traits, yield parameters, quality and uptake status were recorded under control treatments. Increasing dose of zinc and boron increased the all parameters.

Studies on impact of nutrient management and tillage practices on yield attributes and yield on gram – maize cropping sequence

Awareness to wards soil health and food quality has forced to find out a suitable and eco-friendly nutrient management system of crop production. Integrated nutrient management system found suitable on yield of cereal crops, but has least impact on leguminous crops. To study the impact of nutrient management practices and tillage practices was studied at the farm of Department of Soil Science, CSKHPKV, Palampur during 2013-16 gram-maize cropping sequence. The organic management with conventional tillage was found to be significantly superior with rest of the treatment combinations on yield attributes, symbiotic parameters and yield of gram in all the three years. The major constraints to grow gram at Palampur was the attack of root rot disease. The disease incidence was reduced through organic nutrient management with conventional tillage. The yield attributes and yield of maize was better in integrated management in organic management in second year. The conventional tillage in both the years registered significant impact on yield and yield attributes of maize.

Symbiotic Parameters, Growth, Nutrient Uptake as Influenced by Biofertilizers under Conservation Agriculture Practices

A field experiment was conducted during rainy season 2014 and 2015 at Research Farm of the Punjab Agricultural University, Ludhiana, Punjab, India to study the effect of conservation agriculture practices (Happy Seeder sowing, Straw Chopper + Zero Tillage and Conventional tillage) and biofertilizers [Bradyrhizobium and plant growth promoting rhizobacteria (PGPR)] on growth, symbiotic parameters and productivity of soybean. The results showed that Happy Seeder sowing and Straw Chopper + Zero Tillage sowing improved the emergence count, leaf area index, photosynthetic active radiation interception, plant height of soybean and symbiotic traits (number and dry weight of nodules and leghaemoglobin content). Highest pods plant−1 and 100-seed weight were recorded in Happy Seeder sowing, followed by Straw Chopper + Zero Tillage sowing and conventional sowing. Based on the mean of two years, Happy Seeder sowing recorded 14.6 and 17.0% higher seed yield than Straw Chopper + Zero Tillage sowing and conventional sowing, respectively. Total nitrogen, phosphorus and potassium uptake were significantly higher in Happy Seeder sowing than the other planting methods. Single and dual inoculation of Bradyrhizobium and PGPR did not influence the growth parameters, symbiotic traits, yield attributes, biological, straw and seed yields, nutrient uptake and protein content of soybean significantly. Therefore, retention of crop residues with zero tillage (Happy Seeder sowing) proves to be the best planting method for sustainable productivity of soybean.

Bio-Efficacy of different herbicides in greengram under irrigated condition of middle Gujarat

A systemic field study on bioefficacy of different herbicides in greengram (Vigna radiata L.) under irrigated condition of Gujarat and its residual effect on succeeding mustard crop was conducted during Kharif 2014 and 2015 at AAU, Anand. Among the tested options, hand hoeing at 20 and 40 days after sowing (DAS) and pre-emergence (PE) application of imazethapyr + pendimethalin ready mix (RM) at 1000 g/ha proved their supremacy in achieving highest seed yield (1.45 and 1.43 t/ha) with highest B:C of 2.91 & 2.88, respectively These treatments provided season long control of weeds with the weed control efficiency (WCE) of 93% and 89%, respectively. Moreover, post-emergence (PoE) application of imazethapyr 70 and 80 g/ha or imazethapyr + imazamox ready mix (RM) 80 g/ha provided excellent WCE of more than 85%, but posed their negative impact on symbiotic parameters such as nodule number, plant dry weight and secured lower net return. Treatment receiving pre-emergence application of imazethapyr 80 g/ha was only found superior to achieve all profits with low input cost but did not control weeds effectively. Additionally, imazethapyr and its ready mix combination irrespective of dose did not show any residual effect to succeeding mustard crop.

The dynamic equilibrium and simulation of mobile internet platform innovation ecosystem

Purpose The purpose of this paper is to build a symbiotic evolution model to analyze the symbiotic modes and dynamic equilibrium of mobile internet platform innovation ecosystem (MIPIE) in order to explore its evolutionary path. Design/methodology/approach From a symbiosis theory perspective, the authors studied the dynamic evolution stages and symbiotic mode of MIPIE. By adopting logistic model, the symbiotic evolution model of MIPIE is established. After calculating the steady conditions and equilibrium point of this model, numerical simulation was done with MATLAB software to illustrate the impact of symbiotic parameters on evolution path in this ecosystem. Findings The symbiotic evolution mode of MIPIE experienced parasitism, commensalism to asymmetric mutualism, and symmetry mutualism or independence. In given conditions, the dynamic evolution of MIPIE eventually tends to a steady equilibrium point. The evolutionary consequence of innovative subjects is not only determined by the natural growth rate, but symbiotic modes can also affect the evolutionary path. Different symbiotic modes result in different evolutionary paths. Practical implications Improved understanding of symbiosis in MIPIE could help policy makers to promote value co-creation and dynamic interests balance while facilitating the cooperation of others for successful platform ecosystem management. Originality/value The logistic model introduced here bridge theory and practice while establishing a stronger link between symbiosis theory and platform ecosystem management.

Experimental Study of Fluid Phase Equilibrium Along Thermodynamically Optimized Interface of a Stored Liquid Container

This experimental study presents the thermal optimization of a storage container partially filled with liquid (water) with an ullage region above the liquid composed of water vapor and air. The basic purpose of this thermal optimization was to qualitatively explore the design conditions that minimize the heat leaks from the storage tank to the external environment at a lower temperature than the liquid in the storage container. Two symbiotic physical parameters—interfacial mass transfer and the entropy generated by the system—influence the thermal performance of the storage container. These two symbiotic physical parameters were simultaneously considered when optimizing the system. The mass transfer estimation involved the determination of (i) the liquid–vapor interfacial temperature, (ii) the fractional concentration of the evaporating liquid present in the gaseous state, and (iii) the surface area of the liquid–vapor interface. The entropy of the system was estimated separately by considering the entropy of the diabatic saturated liquid and the ullage vapor. A synergistic objective function was subsequently composed based on the penalty involved in deviation from the individual optima, thus determining a holistic optimum. The results show that stored liquids exhibit better second-law efficiency in open containers than in containers that are closed by a lid. The primary factor that influences this optimum is the lid condensation that occurs in closed containers at the 50% filling level.

Response of lentil (<italic>Lens culinaris</italic> Medikus) to phosphorus-A review

Lentil (<italic>Lens culinaris</italic> Medikus) is an old world legume and probably one of the first plant species to be domesticated. Lentil is mainly cultivated in rainfed agro-ecosystems, where majority of soils are low to medium in available phosphorus (P), so lentil responds well to phosphorus fertilization. Higher phosphorus application stimulates the plant to increase the main root as well as lateral root length which enables the plant to take large volume of water from deeper soil layers. The symbiotic parameters i.e. nodulation, nodule dry weight and leghaemoglobin content are positively influenced by phosphorus application. Proper supply of phosphorus lengthens the lentil phenology i.e. maturity period, moreover it also influences the physiological parameters i.e. harvest index, leaf area index, net assimilation rate and crop growth rate. The optimum phosphorus application enhances the yield attributes such as number of pods per plant, grains per pod and 1000-grain weight, resulting in high production. Lentil occupies a unique position in the world of agriculture by virtue of its high protein content. Adequate supply of phosphorus increases the protein concentration and protein developing parameters i.e. albumins, globulins and prolamins. Higher phosphorus fertilization stimulates the plant to capture molybdenum (Mo) element from soil which is an important component of the nitrogenase enzyme and also manipulates the soil N and organic carbon status to maintain the soil fertility. Phosphorus application makes the plant resistant against diseases i.e. root rot, collar rot and wilt by morphological and physiological changes.

Development and field evaluation of liquid inoculants with native <i>Bradyrhizobial</i> strains for peanut production

A critical process in the leguminous crops cycles is biological nitrogen fixation (BNF). Application of inoculants with N fixing bacteria is economically and environmentally favourable. The aim of this work was to select competitive native peanut microsymbionts, evaluate their survival in inoculant support and assess their impact on peanut (Arachis hypogaea L.) production under field conditions at Córdoba province in Argentina. The efficient N fixing Bradyrhizobium sp. J-81 and Bradyrhizobium sp. J-237, previously obtained from peanut nodules in the region of Cordoba, Argentina, were evaluated. In microcosm assays, plants inoculated with these isolates demonstrated better symbiotic parameters than those inoculated with reference strains. Different bacterial growth media and inoculant stabiliser solutions were evaluated. Balanced medium and arabic gum stabilising solution had optimal bacterial growth and the highest bacterial concentration and viability, respectively. Inoculation with either inoculants resulted in 44% greater peanut pod yield at Pizarro compared to the non-inoculated plants, although no significant differences were found with respect to commercial inoculants treatments.Keywords: Arachis hypogaea, Argentina, biological nitrogen fixation

Synergetic effect of Rhizobium sp. and Piriformospora indica on bioenhancing activity, symbiotic parameters and grain yield in pigeon pea (Cajanus cajan L.)

The synergetic effect of Rhizobium sp. (Cajanus) and Piriformospora indica on bioenhancing activity, symbiotic parameters and grain yield of pigeon pea was evaluated. Nine genotypes were raised during kharif, 2013 at the Experimental Farm, HAU, Hisar (India). Rhizobium sp. and P. indica, alone or co-inoculated, along with untreated control were assessed for response of genotypes to these organisms on various metric traits. Significant differences among the genotypes for the studied traits indicated beneficial effect of both the organisms. Among the treatments, P. indica inoculation alone was most effective for most of the characters followed by dual inoculation of P. indica and Rhizobium. But for symbiotic traits the performance of Rhizobium alone was better than dual inoculation or P. indica alone. The genotypes Manak, Paras, UPAS 120, Pusa 991 and AH09–47 performed better with respect to symbiotic, growth and yield parameters. Hence, these genotypes could be used as parents in hybridization programme for genetic improvement of pigeon pea.

Symbiotic functioning, structural adaptation, and subcellular organization of root nodules from Psoralea pinnata (L.) plants grown naturally under wetland and upland conditions in the Cape Fynbos of South Africa.

In the Cape Fynbos of South Africa, Psoralea pinnata (L.) plants occur naturally in both wetland and well-drained soils and yet effectively fix N2 under the two contrasting conditions. In this study, nodule structure and functioning in P. pinnata plants from the two habitats were evaluated using light and transmission electron microscopy (TEM), as well as the 15N natural abundance technique. The results showed that, structurally, fully developed P. pinnata nodules were spherical in shape with six components (namely, lenticels, periderm, outer cortex, middle cortex, inner cortex, and a central bacteria-infected medulla region). Morphometric analysis revealed 44 and 84% increase in cell area and volume of wetland nodules compared to those from upland. The percentage area of nodules occupied by the middle cortex in wetland nodules was twice that of upland nodules. As a result, the size of the medulla region in wetland nodules was significantly reduced compared to upland nodules. Additionally, the average area of medulla occupied by intercellular air spaces in wetland nodules was about five times that of upland nodules (about 431% increase in wetland over upland nodules). TEM data also showed more bacteroids in symbiosomes of upland nodules when compared to wetland nodules. However, isotopic analysis of above-ground plant parts revealed no differences in symbiotic parameters such as N concentration, ∂15N and %Ndfa between wetland and upland P. pinnata plants. These results suggest that, under limiting O2 conditions especially in wetlands, nodules make structural and functional adjustments to meet the O2 demands of N2-fixing bacteroids.