Possible mode of action of Azospirillum brasilense strain Cd on the root morphology and nodule formation in burr medic (Medicago polymorpha)

1990 ◽  
Vol 36 (1) ◽  
pp. 10-14 ◽  
Author(s):  
Eli Yahalom ◽  
Yaacov Okon ◽  
Amos Dovrat
Keyword(s):  
Root Morphology ◽  
Ethylene Production ◽  
Azospirillum Brasilense ◽  
Specific Activity ◽  
Root Tip ◽  
Nodule Formation ◽  
Shikimate Dehydrogenase ◽  
Medicago Polymorpha ◽  
Burr Medic ◽  
Nodule Initiation

The mechanism(s) involved in the effect of Azospirillum brasilense strain Cd on root susceptibility to nodulation was studied in medic seedlings grown in pouches. The number of nodules above the position of the root-tip mark at the time of inoculation and the position of the uppermost nodule were used as parameters for determining the rate of nodule initiation. Cell-free extracts and culture supernatants prepared from Azospirillum and the cytokinin benzyladenine (10−9 M) significantly increased the number of nodules formed above the root-tip mark when applied together with Rhizobium compared with those formed with Rhizobium alone. The application of indoleacetic acid did not cause an increase in the number of nodules. In the absence of Rhizobium, exposure to Azospirillum at a concentration of 109 cfu/mL or to compounds excreted by the bacteria into the growth medium caused a 40% increase in endogenous ethylene production by the roots. A less concentrated inoculum did not increase ethylene production. Inoculation with Azospirillum significantly increased the specific activity of the enzymes glucose-6-phosphate dehydrogenase, L-phenylalanine ammonia-lyase, and shikimate dehydrogenase compared with roots inoculated with Rhizobium alone. Key words: Azospirillum, Rhizobium, Medicago polymorpha, root morphology, nodule initiation.

High phosphorus concentrations in seed of wheat and annual medic are related to higher rates of dry matter production of seedlings and plants

1988 ◽  
Vol 28 (6) ◽  
pp. 765 ◽  
Author(s):  
MDA Bolland ◽  
MJ Baker
Keyword(s):  
Triticum Aestivum ◽  
Field Experiment ◽  
Western Australia ◽  
Dry Matter ◽  
Field Experiments ◽  
Medicago Polymorpha ◽  
P Concentration ◽  
Pot Experiments ◽  
Matter Production ◽  
Burr Medic

Seed of 2 cultivars of wheat (Triticum aestivum) and 1 burr medic (Medicago polymorpha) with increasing phosphorus (P) concentrations (wheat 1.4-3.7 g P/kg dry matter, medic 3.3-7.9 g P/kg dry matter) were collected from field experiments with variable levels of applied superphosphate (wheat 0- 577 kg P/ha, medic 0-364 kg P/ha) in south-western Australia. These seeds were used in further experiments to examine the effect of seed P concentration on the subsequent dry matter (DM) production of seedlings and plants in 3 glasshouse pot experiments and 1 field experiment. Seed of the same size (wheat, 35 mg/seed; medic, 3.6 mg/seed) but with increasing P concentration produced substantially higher DM yields in the absence or presence of freshly applied superphosphate P up to 28-35 days after sowing in the pot experiments and 67 days after sowing in the field experiment.

scholarly journals Dark Septate Endophyte Improves Drought Tolerance of Ormosia hosiei Hemsley & E. H. Wilson by Modulating Root Morphology, Ultrastructure, and the Ratio of Root Hormones

Forests ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 830 ◽  
Author(s):  
Yan Liu ◽  
Xiaoli Wei
Keyword(s):  
Water Stress ◽  
Drought Stress ◽  
Host Plant ◽  
Drought Resistance ◽  
Root Morphology ◽  
Stress Conditions ◽  
Root Tip ◽  
Root Weight ◽  
Root Cells ◽  
Water Capacity

Dark septate endophytes (DSEs) are known to help host plants survive drought stress; however, how DSEs enhance host plant drought resistance under water stress conditions remains unclear. The objective of this study was to inoculate Ormosia hosiei seedlings with a DSE strain (Acrocalymma vagum) to investigate the effects of DSE inoculation on root morphology, ultrastructure, and the endogenous hormone content under drought stress conditions and to elucidate the drought resistance mechanism involved in the DSE–host-plant association. The inoculated seedlings were grown under three different soil water conditions (well watered—75% field water capacity, moderate water—55% field water capacity, or low water—35% field water capacity) for 114 days. Fresh root weight, root volume, root surface area, root fork, and root tip number were significantly higher in inoculated seedlings than in noninoculated seedlings. Furthermore, the root architecture of the inoculated seedlings changed from herringbone branching to dichotomous branching. Mitochondria and other organelles in root cells of inoculated seedlings remained largely undamaged under water stress, whereas organelles in root cells of noninoculated seedlings were severely damaged. The abscisic acid (ABA) and indole-3-acetic acid (IAA) content and IAA/ABA ratio of inoculated seedlings were significantly higher than those of noninoculated seedlings, whereas the content of gibberellic acid (GA) and the ratios of GA/ABA, zeatin riboside (ZR)/ABA, and ZR/IAA in inoculated seedlings were lower than those of noninoculated seedlings. DSE inoculation could help plants adapt to a drought stress environment by altering root morphology, reducing ultrastructural damage, and influencing the balance of endogenous hormones, which could be of great significance for the cultivation and preservation of the O. hosiei tree.

Effect of rhizobia and soil nitrate on the establishment and functioning of the soybean symbiosis in the field

1984 ◽  
Vol 35 (2) ◽  
pp. 149 ◽  
Author(s):  
DF Herridge ◽  
RJ Roughley ◽  
J Brockwell
Keyword(s):  
Soil Depth ◽  
Root Nodules ◽  
Xylem Sap ◽  
Progressive Increase ◽  
Rhizobium Japonicum ◽  
Nodule Development ◽  
Initial Increase ◽  
Nodule Formation ◽  
Mineral N ◽  
Nodule Initiation

The symbiosis of the root-nodules of Bragg soybean [Glycine max (L.) Merrill] and the relative dependence of the plants on symbiotic and soil sources of N were evaluated in an experiment conducted on a vertisol which was high in organic- and mineral-N, free of Rhizobium japonicum, and where poor nodulation was characteristic of inoculated, new sowings. Effective inoculant containing R. japonicum strain CB 1809 was sprayed into the seed bed at three rates of application (10-fold intervals). Increasing rates of inoculant led to greater numbers of rhizobia in the rhizosphere and in the soil, and to improved nodulation. Uninoculated plants did not nodulate. High soil NO-3 (30 �g N/g, top 30 cm) did not prevent prompt, abundant colonization of rhizospheres by the bacteria from the inoculant, but nodule initiation was delayed and nodule development was retarded until 42 days after sowing. There was an acceleration in nodule formation and development between 42 and 62 days which coincided with a depletion of NO-3 from the top 60 cm of the soil profile. Nodulated and unnodulated soybeans took up NO-3 at similar times and rates to a soil depth of 90 cm; only unnodulated plants utilized soil NO-3 below 90 cm. Vacuum-extracted stem (xylem) exudate was sampled from plants throughout growth and analysed for nitrogenous solutes. The proportion of ureide-N relative to total-solutes-N in xylem sap was used as an index of symbiotic N2-fixation. The initial increase in concentrations of ureides coincided with the period of accelerated nodule formation and development between 42 and 62 days. Thereafter, there was a progressive increase in ureide concentrations in nodulated plants, and the levels were related to rate of inoculation, extent of nodulation, and to the decline in concentrations of soil NO-3. Ureide concentrations in unnodulated plants remained low throughout. The quantities of NO-3-N and �-NH2- N in xylem sap were not related to nodulation. The differences between treatments in terms of whole-plant N and grain N were less than predicted from the symbiotic parameters. This indicated that soybeans compensated for symbiotic deficiencies by more efficient exploitation of soil N and/or by more efficient redistribution of vegetative N into grain N, and that nodulation and soil NO-3 were interactive and complementary in meeting the N requirements of the crop.

Variation in pheno-morphological and agronomic traits among burr medic (Medicago polymorpha L.) populations collected in Sicily, Italy

2010 ◽  
Vol 61 (1) ◽  
pp. 59 ◽  
Author(s):  
D. Graziano ◽  
G. Di Giorgio ◽  
P. Ruisi ◽  
G. Amato ◽  
D. Giambalvo
Keyword(s):  
Field Experiments ◽  
Agronomic Traits ◽  
Phenotypic Diversity ◽  
Natural Populations ◽  
Environmental Parameters ◽  
Farming Systems ◽  
Livestock Farming ◽  
Medicago Polymorpha ◽  
Large Variability ◽  
Burr Medic

The present study assessed the diversity of pheno-morphological and agronomic traits among 31 natural populations of burr medic (Medicago polymorpha L.) from different environments throughout Sicily, and analysed the patterns of phenotypic diversity in relation to the environmental parameters of each collection site. Three commercial cultivars (Cavalier, Santiago, and Anglona) were also included in the study as check cultivars. Two field experiments were performed in 2005–06 in a hilly area of the Sicilian inland. Principal components analysis (PCA) was performed on the sites using geographic, climatic, and pedological data to assess the differences in types of collection sites. PCA was also performed on the accessions using pheno-morphological and agronomic data to establish the importance of different traits in explaining multivariate polymorphisms. Sicilian burr medic populations showed highly significant inter-population differences for all of the recorded pheno-morphological and agronomic traits, and several populations had agronomic attributes that were more pronounced than those of the check cultivars. PCA did not clearly differentiate the accessions according to their habitats of origin, but in some cases, accessions from the same habitat had a tendency to stay together. Populations from drier and warmer habitats flowered earlier and were less productive than those from wetter and colder ones. The large variability in both pheno-morphological and agronomic traits among Sicilian populations may be valuable when searching for suitable M. polymorpha material to exploit in pastures and crop–livestock farming systems in the Mediterranean region.

scholarly journals Water-Specific Imaging

2021 ◽  
pp. 3-37
Author(s):  
Tomoko M. Nakanishi
Keyword(s):  
Water Vapor ◽  
Neutron Beam ◽  
Specific Activity ◽  
Water Solution ◽  
Physiological Activity ◽  
Metal Vapor ◽  
Root Tip ◽  
Soil Culture ◽  
Water Culture ◽  
Spatial Image

AbstractOur first target was water, namely, how to obtain a water-specific image nondestructively. Using a neutron beam, we could visualize water-specific images of plants, including roots and flowers, which were never shown before. Each image suggested the plant-specific activity related to water.We briefly present how to acquire the image and what kind of water image is taken by neutron beam irradiation. We present a variety of plant samples, such as flowers, seeds, and wood disks. It was noted that neutrons could visualize the roots imbedded in soil without uprooting. When a spatial image of the root imbedded in soil was created from many projection images, the water profile around the root was analyzed. Then, fundamental questions were raised, such as whether plants are absorbing water solution or water vapor from the soil, because there was always a space adjacent to the root surface and hardly any water solution was visualized there. The roots are in constant motion during growth, known as circumnutation, and it is natural that the root tip is always pushing the soil aside to produce space for the root to grow. If the roots are absorbing water vapor, then the next question is about metals. Are the roots absorbing metal vapor? Since we tended to employ water culture to study the physiological activity of plants, the physiological study of the plants growing in soil was somewhat neglected. Later, when we could develop a system to visualize the movement of element absorption in a plant, there was a clear difference in element absorption between water culture and soil culture.

Studies on alfalfa mosaic virus infection of burr medic (Medicago polymorpha) swards: seed-borne infection, persistence, spread and effects on productivity

1992 ◽  
Vol 43 (3) ◽  
pp. 697 ◽  
Author(s):  
RAC Jones ◽  
DA Nicholas
Keyword(s):  
Mosaic Virus ◽  
Seed Yield ◽  
Alfalfa Mosaic Virus ◽  
Primary Source ◽  
Medicago Polymorpha ◽  
Daily Growth ◽  
Infected Seed ◽  
Burr Medic ◽  
Seed Yields ◽  
Healthy Seed

During 1988-90, burr medic (Medicago polymorpha) cvv. Circle Valley, Serena and/or Santiago were grown in field trials in which plots were sown with healthy seed or seed that carried varying levels of infection with alfalfa mosaic virus (AMV). Seed-infected plants were the primary source for subsequent virus spread by aphids. Levels of AMV infection normally reached 80-100% in swards sown with infected seed whether they were mown, grazed or not defoliated, most spread occurring late in the growing season. Infection of harvested seed was often less than in seed sown. However, in self-regenerated grazed swards AMV spread earlier and infection in harvested seed was up to 10 times greater than in seed before regeneration. In two trials sown in 1988, plots were mown or left uncut; AMV infection decreased herbage yields by 13-35% while seed yields were decreased significantly (by 7-30%) in one of the two trails. When one of these trials was cropped with barley in 1989 but allowed to regenerate in 1990 and grazed, herbage yield fell by 5-15% and seed yield by 2-29% due to AMV infection. In a trial sown in 1989 in which some plots were grazed and others not, AMV infection decreased herbage and seed yields by 27-32% and 21-29% respectively. In a similar grazing trial sown in 1990, AMV infection decreased herbage daily growth rates by 16-42% and seed yield sometimes by as much as 32%. Seed harvested from plots sown with infected seed was normally smaller than seed from plots sown with healthy seed. AMV-infected swards were established in 1987, allowed to regenerate in 1988-91 and grazed. With cvv. Circle Valley and Serena, AMV was readily detected each year in foliage and was also found in seeds.

Long-term patterns of seed softening in some annual pasture legumes in a low rainfall environment

1992 ◽  
Vol 32 (3) ◽  
pp. 331 ◽  
Author(s):  
GB Taylor ◽  
MA Ewing
Keyword(s):  
Subterranean Clover ◽  
Soil Surface ◽  
Trifolium Subterraneum ◽  
Medicago Polymorpha ◽  
Pasture Legumes ◽  
Burr Medic ◽  
Growing Environment ◽  
Simulated Field ◽  
Favourable Environment

Annual rates of seed softening were determined from 4 lines of burr medic (Medicago polymorpha), 1 barrel medic (M. truncatula), and 1 subterranean clover (Trifolium subterraneum) grown at Merredin in the 1 year. Measurements were also made on one of the lines of burr medic grown in 2 other environments, Gnowangerup and Eneabba, in the same year. Burrs were placed on the soil surface at Merredin and the numbers of residual hard seeds determined each year for up to 5 years in this one environment. Patterns of softening of seeds from the same seed populations were also determined in a laboratory oven with a diurnal temperature fluctuation of 60/15�C. In the field, the softening rates of the 5 medics grown at Merredin were similar, averaging 21% of the original seeds each year for the first 4 years. Seeds of the burr medic grown in a more favourable environment at Eneabba were much slower to soften (averaging 14%); hence, hardseededness in these medics was influenced more by the growing environment than by genotype. More than half of the seeds of subterranean clover softened in the field over the first summer, with declining annual proportions thereafter. There were clear differences between the clover and medics in both pattern and rate of seed softening. The lower seed-softening rate of medics than of subterranean clover was more favourable for ley systems involving frequent cropping, especially in low rainfall areas. Treatment of seeds at 60/15�C simulated field softening for subterranean clover well but produced misleading results for the medics.

Comparative phosphate requirements of yellow serradella (Ornithopus compressus) burr medic (Medicago polymorpha var. brevispina) and subterranean clover (Trifolium subterraneum)

1990 ◽  
Vol 30 (4) ◽  
pp. 507 ◽  
Author(s):  
BH Paynter
Keyword(s):  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Medicago Polymorpha ◽  
P Content ◽  
Shoot Production ◽  
Ornithopus Compressus ◽  
Burr Medic ◽  
Total Plant ◽  
Greater Curvature ◽  
Total Seed

The phosphate (P) requirements of burr medic (Medicago polymorpha) on marginally acidic, medium-textured soils and yellow serradella (Ornithopus compressus) on acidic, light-textured soils in the low rainfall (<400 mm) wheatbelt of Western Australia are not known. The hypothesis that yellow serradella, subterranean clover (Trifolium suhrerraneum) and burr medic have the same external requirement for applied P was tested in a glasshouse trial on 2 P-deficient soils. Species were compared on an equal total seed weight and similar maturity length basis. It was found that yellow serradella required less soil applied P to achieve 90% maximum shoot production or total plant (shoots + roots) growth and had a greater curvature co-efficient from fitted Mitscherlich functions than either subterranean clover or burr medic. Burr medic was the most responsive to applied P and had the largest external requirement for applied P. These differences in external P requirements were related to differences in ability of the 3 legumes to absorb P and to transport it to their shoots and were not due to differences in internal efficiency of the shoots. Yellow serradella was able to take up more P (total plant P content) per g roots than subterranean clover, and subterranean clover more than burr medic. The same relationship applied to the translocation of absorbed P from roots to shoots.

scholarly journals Enhanced Nodulation and Nodule Development by nolR Mutants of Sinorhizobium medicae on Specific Medicago Host Genotypes

2014 ◽  
Vol 27 (4) ◽  
pp. 328-335 ◽  
Author(s):  
Masayuki Sugawara ◽  
Michael J. Sadowsky
Keyword(s):  
Sinorhizobium Meliloti ◽  
Regulatory Protein ◽  
Selective Advantage ◽  
Nodule Development ◽  
Nodule Formation ◽  
Wild Type ◽  
Nod Factor ◽  
Transcriptional Regulatory ◽  
Sinorhizobium Medicae ◽  
Nodule Initiation

The nolR gene encodes a negatively acting, transcriptional regulatory protein of core Nod-factor biosynthetic genes in the sinorhizobia. Although previous reports showed that nolR modulates Nod-factor production and enhances nodulation speed of Sinorhizobium meliloti on alfalfa, there have been no reports for the symbiotic function of this gene in the S. medicae–Medicago truncatula symbiosis. Here, we constructed an nolR mutant of S. medicae WSM419 and evaluated mutant and wild-type strains for their nodulation ability, competitiveness, host specificity, and density-dependent nodulation phenotypes. When the mutant was inoculated at low and medium population densities, it showed enhanced nodule formation during the initial stages of nodulation. Results of quantitative competitive nodulation assays indicated that an nolR mutant had 2.3-fold greater competitiveness for nodulation on M. truncatula ‘A17’ than did the wild-type strain. Moreover, the nodulation phenotype of the nolR mutant differed among Medicago genotypes and showed significantly enhanced nodule development on M. tricycla. Taken together, these results indicated that mutation of nolR in S. medicae positively influenced nodule initiation, competitive nodulation, and nodule development at later nodulation stages. This may allow nolR mutants of S. medicae to have a selective advantage under field conditions.

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