The relation between root hair infection by Rhizobium and nodulation in Trifolium and Vicia

1962 ◽  
Vol 156 (962) ◽  
pp. 122-137 ◽  
Keyword(s):  
Root Formation ◽  
Relative Rate ◽  
Lateral Roots ◽  
Root Hairs ◽  
Strain Differences ◽  
Nodule Formation ◽  
Low Concentrations ◽  
Rate Of Increase ◽  
Infection Threads ◽  
Root Hair Infection

The infection of the root hairs of young seedlings of twelve species of Trifolium and of Vicia hirsuta was examined. The amount of infection (numbers of hairs containing infection threads) at 2 weeks varied much between species of host and was less affected by bacterial strain ; host and strain differences were independent. In most hosts a high proportion of infections did not result in nodule formation. The relative rate of increase in numbers of infected hairs was constant before nodulation began. The duration of this pre-nodulation phase of exponential increase in infection, but not its rate, differed between species. Nodulation (and lateral root formation) caused an abrupt lowering of the initial rate of infection. Post-nodulation infection also increased exponentially. Low concentrations of nitrate nitrogen delayed nodulation and increased the number of hairs infected. Infected hairs were not randomly distributed along the root, infection beginning at a few well-separated points. Later infections occurred near these primary foci to give zones of infection which then spread up and down the root. The positions of nodules or lateral roots were not related to the primary foci of hair infection.

Investigation of a non-nodulating cultivar of Pisum sativum

1976 ◽  
Vol 54 (14) ◽  
pp. 1633-1636 ◽  
Author(s):  
T. L. Degenhardt ◽  
T. A. Larue ◽  
E. A. Paul
Keyword(s):  
Pisum Sativum ◽  
Rhizobium Leguminosarum ◽  
Root Hairs ◽  
Infection Process ◽  
Nodule Formation ◽  
Temperature Sensitive ◽  
Infection Threads

A non-nodulating cultivar of Pisum sativum cv. Afghanistan was studied to characterize the nature and location of the non-nodulating factor. Nodule formation was not temperature sensitive. Rhizobium leguminosarum could exist in the rhizosphere. Root secretions did not decrease nodulation in adjacent normal plants, nor did the proximity of normal plants promote nodulation. Infection threads formed in the root hairs, but nodules were not formed. The infection process apparently aborted, resulting in the formation of swellings on areas of the root where nodulation would normally occur. Grafting experiments indicate that the factor preventing nodulation is in the root and is not translocated from the cotyledon or plant top.

scholarly journals Nod Factor Perception During Infection Thread Growth Fine-Tunes Nodulation

2007 ◽  
Vol 20 (2) ◽  
pp. 129-137 ◽  
Author(s):  
Jeroen Den Herder ◽  
Celine Vanhee ◽  
Riet De Rycke ◽  
Viviana Corich ◽  
Marcelle Holsters ◽  
...  
Keyword(s):  
Light And Electron Microscopy ◽  
Cortical Cell ◽  
Root Hairs ◽  
Infection Thread ◽  
Bacterial Invasion ◽  
Nodule Formation ◽  
Nodulation Factors ◽  
Polysaccharide Synthesis ◽  
Infection Threads ◽  
Surface Polysaccharide

Bacterial nodulation factors (NFs) are essential signaling molecules for the initiation of a nitrogen-fixing symbiosis in legumes. NFs are perceived by the plant and trigger both local and distant responses, such as curling of root hairs and cortical cell divisions. In addition to their requirement at the start, NFs are produced by bacteria that reside within infection threads. To analyze the role of NFs at later infection stages, several phases of nodulation were studied by detailed light and electron microscopy after coinoculation of adventitious root primordia of Sesbania rostrata with a mixture of Azorhizobium caulinodans mutants ORS571-V44 and ORS571-X15. These mutants are deficient in NF production or surface polysaccharide synthesis, respectively, but they can complement each other, resulting in functional nodules occupied by ORS571-V44. The lack of NFs within the infection threads was confirmed by the absence of expression of an early NF-induced marker, leghemoglobin 6 of S. rostrata. NF production within the infection threads is shown to be necessary for proper infection thread growth and for synchronization of nodule formation with bacterial invasion. However, local production of NFs by bacteria that are taken up by the plant cells at the stage of bacteroid formation is not required for correct symbiosome development.

scholarly journals Phylogeny and Expression of NADPH Oxidases during Symbiotic Nodule Formation

Agriculture ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 179 ◽  
Author(s):  
Jesús Montiel ◽  
Citlali Fonseca-García ◽  
Carmen Quinto
Keyword(s):  
Developmental Stages ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Root Hairs ◽  
Nodule Formation ◽  
Nadph Oxidases ◽  
Mutualistic Interaction ◽  
Infection Threads ◽  
Multistep Process ◽  
Regulation Of Activity ◽  
Respiratory Burst Oxidase

The mutualistic interaction between gram-negative soil bacteria and the roots of legumes leads to the establishment of nodules, where atmospheric nitrogen is fixed. Nodulation is a multistep process with numerous essential players. Among these are reactive oxygen species (ROS), which are mainly generated by Nicotinamide Adenine Dinucleotide Phosphate (NADPH) oxidases. In plants, these enzymes are known as respiratory burst oxidase homologs (RBOHs). In legumes, these proteins are encoded by a multigene family with members that are differentially expressed in various tissues and organs at distinct developmental stages. RBOHs have critical roles at several stages of nodulation: in the early signaling pathway triggered by nodulation factors in the root hairs, during both the progression of infection threads and nodule ontogeny, and in nitrogen fixation and senescence. Data from the literature along with the analysis conducted here imply that legumes use different RBOHs for different stages of nodulation; these RBOHs belong to the same phylogenetic subgroup, even though they are not strictly orthologous. Accordingly, the regulation of activity of a given RBOH during the nodulation process probably varies among legumes.

Lateral root formation and nutrients: nitrogen in the spotlight

2021 ◽  
Author(s):  
Pierre-Mathieu Pélissier ◽  
Hans Motte ◽  
Tom Beeckman
Keyword(s):  
Signaling Pathways ◽  
Root System ◽  
Root Development ◽  
Lateral Root ◽  
Molecular Mechanisms ◽  
Root Formation ◽  
Lateral Roots ◽  
Nutrient Use Efficiency ◽  
Lateral Root Formation ◽  
Lateral Root Development

Abstract Lateral roots are important to forage for nutrients due to their ability to increase the uptake area of a root system. Hence, it comes as no surprise that lateral root formation is affected by nutrients or nutrient starvation, and as such contributes to the root system plasticity. Understanding the molecular mechanisms regulating root adaptation dynamics towards nutrient availability is useful to optimize plant nutrient use efficiency. There is at present a profound, though still evolving, knowledge on lateral root pathways. Here, we aimed to review the intersection with nutrient signaling pathways to give an update on the regulation of lateral root development by nutrients, with a particular focus on nitrogen. Remarkably, it is for most nutrients not clear how lateral root formation is controlled. Only for nitrogen, one of the most dominant nutrients in the control of lateral root formation, the crosstalk with multiple key signals determining lateral root development is clearly shown. In this update, we first present a general overview of the current knowledge of how nutrients affect lateral root formation, followed by a deeper discussion on how nitrogen signaling pathways act on different lateral root-mediating mechanisms for which multiple recent studies yield insights.

scholarly journals Organ Regeneration on Excised Roots of Chondrilla Juncea and Its Chemical Regulation

1972 ◽  
Vol 25 (4) ◽  
pp. 691 ◽  
Author(s):  
NP Kefford ◽  
OH Caso
Keyword(s):  
Root Formation ◽  
Bud Formation ◽  
Endogenous Factors ◽  
Chemical Regulation ◽  
Synthetic Auxins ◽  
Organ Regeneration ◽  
Low Concentrations ◽  
Standard Assay ◽  
Gibberellin Treatment ◽  
Regulation Of Regeneration

The effects of endogenous factors (plant age, section length, and section location) and environmental factors (temperature and mineral nutrition) upon organ regeneration on isolated root sections of Ohondrilla juncea L. were used to develop a standard assay system for the study of the chemical regulation of regeneration. Bud and root formation and its polarity in the presence of a variety of regulators alone and in combinations were observed quantitatively. Bud numbers were increased by auxin (low concentrations), cytokinin, and gibberellin treatments. High concentra� tions of auxin inhibited bud formation and this effect was reversed by antiauxin, cytokinin, or gibberellin. Adenine did not counteract auxin� induced bud inhibition but adenine and N�6�benzyladenine did counteract inhibition induced by the purine antagonist 2,6�diaminopurine. Numbers of regenerated roots were increased by auxin treatment and reduced by cytokinin and gibberellin treatment. On control and auxin� treated sections, bud formation was strongly polar and proximal and cytokinin and gibberellin treatments lessened the polarity. Growth retardants inhibited regeneration. Of a number of synthetic auxins tested, 2,4.dichlorophenoxy. acet.O.methylhydroxamic acid and 4�amino.3,5,6.trichloropicolinic acid were the most effective inhibitors of bud formation.

scholarly journals Wpływ kwasu 2-chloroetanofosfonoiuego (Ethrel) na ukorzenianie się zdrewniałych sadzonek czarnych porzeczek [Effect of 2-chloroethylphosphonic acid (Ethrel) on the rooting of the blackcurrant hardwood cuttings]

2015 ◽  
Vol 26 (2) ◽  
pp. 229-235 ◽  
Author(s):  
Janusz Lipecki ◽  
Jan Selwa
Keyword(s):  
Root Formation ◽  
Harmful Effect ◽  
Inflorescence Development ◽  
Complete Cessation ◽  
Low Concentrations ◽  
High Concentrations

The effect of Ethrel on root formation in the blackcurrant (cv. Blacksmith) hardwood cuttings was investigated in five different periods of the year. Low concentrations of Ethrel (up to 250 ppm) stimulated rooting, whereas higher concentrations (above 250 ppm) had a harmful effect on root formation. It is suggested that ethylene can act as a rooting promoter (when low concentrations of Ethrel were used) or as rooting inhibitor (when Ethrel was used in high concentrations). Complete cessation of the inflorescence development was observed in cuttings treated with Ethrel at 100 ppm and higher concentrations.

scholarly journals H2O2 Is Required for Optimal Establishment of the Medicago sativa/Sinorhizobium meliloti Symbiosis

2007 ◽  
Vol 189 (23) ◽  
pp. 8741-8745 ◽  
Author(s):  
Alexandre Jamet ◽  
Karine Mandon ◽  
Alain Puppo ◽  
Didier Hérouart
Keyword(s):  
Medicago Sativa ◽  
Plant Cell ◽  
Sinorhizobium Meliloti ◽  
Root Hairs ◽  
Symbiotic Interaction ◽  
Infection Threads ◽  
Cell Layers

ABSTRACT The symbiotic interaction between Medicago sativa and Sinorhizobium meliloti RmkatB ++ overexpressing the housekeeping catalase katB is delayed, and this delay is combined with an enlargement of infection threads. This result provides evidence that H2O2 is required for optimal progression of infection threads through the root hairs and plant cell layers.

scholarly journals Overexpression of OsPIN2 Regulates Root Growth and Formation in Response to Phosphate Deficiency in Rice

2019 ◽  
Vol 20 (20) ◽  
pp. 5144
Author(s):  
Huwei Sun ◽  
Xiaoli Guo ◽  
Fugui Xu ◽  
Daxia Wu ◽  
Xuhong Zhang ◽  
...  
Keyword(s):  
Root Growth ◽  
Growth And Development ◽  
Plant Root ◽  
Lateral Roots ◽  
Root Hairs ◽  
Phosphate Deficiency ◽  
P Deficiency ◽  
Auxin Distribution ◽  
Seminal Roots ◽  
Underlying Mechanisms

The response of root architecture to phosphate (P) deficiency is critical in plant growth and development. Auxin is a key regulator of plant root growth in response to P deficiency, but the underlying mechanisms are unclear. In this study, phenotypic and genetic analyses were undertaken to explore the role of OsPIN2, an auxin efflux transporter, in regulating the growth and development of rice roots under normal nutrition condition (control) and low-phosphate condition (LP). Higher expression of OsPIN2 was observed in rice plants under LP compared to the control. Meanwhile, the auxin levels of roots were increased under LP relative to control condition in wild-type (WT) plants. Compared to WT plants, two overexpression (OE) lines had higher auxin levels in the roots under control and LP. LP led to increased seminal roots (SRs) length and the root hairs (RHs) density, but decreased lateral roots (LRs) density in WT plants. However, overexpression of OsPIN2 caused a loss of sensitivity in the root response to P deficiency. The OE lines had a shorter SR length, lower LR density, and greater RH density than WT plants under control. However, the LR and RH densities in the OE lines were similar to those in WT plants under LP. Compared to WT plants, overexpression of OsPIN2 had a shorter root length through decreased root cell elongation under control and LP. Surprisingly, overexpression of OsPIN2 might increase auxin distribution in epidermis of root, resulting in greater RH formation but less LR development in OE plants than in WT plants in the control condition but levels similar of these under LP. These results suggest that higher OsPIN2 expression regulates rice root growth and development maybe by changing auxin distribution in roots under LP condition.

Cluster root formation by Gymnostoma papuanum (Casuarinaceae) in relation to aeration and mineral nutrient availability in water culture

1990 ◽  
Vol 68 (12) ◽  
pp. 2564-2570 ◽  
Author(s):  
Suzanne Racette ◽  
Isabelle Louis ◽  
John G. Torrey
Keyword(s):  
Root Growth ◽  
Root Formation ◽  
Phosphorus Deficiency ◽  
Lateral Roots ◽  
Critical Factor ◽  
Mineral Nutrient ◽  
Cluster Roots ◽  
Phosphorus Level ◽  
Water Culture ◽  
Cluster Root

The term cluster root is used to refer to a dense cluster of determinate lateral roots (rootlets), in preference to the terms proteoid root and proteoid-like root used by other authors. Cluster roots are often formed by the actinorhizal plant Gymnostoma papuanum. In water culture, cluster root formation by G. papuanum was influenced by aeration, phosphorus level, and nitrogen source. Aeration was a critical factor, with nonaerated rooted cuttings having far fewer cluster roots than aerated ones. Phosphorus deficiency was the single nutrient deficiency that led to increased cluster root formation. Seedlings, grown under conditions of either low (0.8 mg∙L−1) or no phosphorus, responded by devoting a greater portion of root growth to the production of cluster roots, with no overall reduction in root growth for 6 weeks. The response to varying phosphorus level was modified by providing nitrogen in different forms. Supplying nitrogen as ammonium resulted in low levels of cluster root formation. Supplying nitrate to nodulated seedlings led to an increase in cluster root formation in comparison with plants that depended solely upon dinitrogen fixation by Frankia. Greatest cluster root formation occurred on plants grown in aerated water cultures supplied with nitrate and with little or no phosphorus. Key words: Gymnostoma papuanum, cluster roots, proteoid roots, phosphorus deficiency.

scholarly journals Glutamate, calcium ion-chelating agents and the sodium and potassium ion contents of tissues from the brain

1970 ◽  
Vol 116 (2) ◽  
pp. 181-187 ◽  
Author(s):  
I. Pull ◽  
H. McIlwain ◽  
R. L. Ramsay
Keyword(s):  
Calcium Ion ◽  
Chelating Agents ◽  
Potassium Ion ◽  
Low Concentrations ◽  
Rate Of Increase ◽  
Other Substances ◽  
Ion Contents ◽  
Bicarbonate Solutions ◽  
The Brain ◽  
Sodium And Potassium

1. Salts of l-glutamate added to cerebral tissues maintained in glucose–saline–bicarbonate solutions cause the Na+ content of the tissues to increase rapidly and K+ to be lost. Entry of 22Na+ also is accelerated by l-glutamate and this acceleration is inhibited by low concentrations of tetrodotoxin. 2. Tissue Na+ content and its rate of increase after the addition of l-glutamate are affected by the Ca2+ of incubation media. 3. Very rapid and extensive entry of Na+ to the tissue is caused by EDTA, and a moderate entry by citrate and ATP. Calculations of the concentration of free Ca2+ in media after these additions indicate that Na+ entry is sometimes associated with low Ca2+ concentration, but that other substances, especially l-glutamate, act without greatly diminishing Ca2+ concentration. 4. Experiments with 2,4-dinitrophenol and valinomycin are also reported and aspects of the Na+ entry formulated and discussed.

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