Seasonal patterns of root nodule growth, endophyte morphology, nitrogenase activity, and shoot development in Myrica gale

1982 ◽  
Vol 60 (6) ◽  
pp. 746-757 ◽  
Author(s):  
Christa R. Schwintzer ◽  
Alison M. Berry ◽  
Lynn D. Disney
Keyword(s):  
Root Nodule ◽  
Nitrogenase Activity ◽  
Shoot Development ◽  
Infected Tissue ◽  
Actinorhizal Plants ◽  
Seasonal Patterns ◽  
Cortical Cells ◽  
Myrica Gale ◽  
Nodule Biomass ◽  
Infected Cells

Myrica gale L. populations growing in central Massachusetts were observed throughout the ice-free season. Nitrogenase activity appeared in mid-May shortly after budbreak, was at its maximum between late June and mid-August, and disappeared in late October after all leaves had fallen. Growth of overwintering nodules began in early May and was largely complete by mid-July. Most nodules (88%) lived for 3 years or less and 61% of the nodule biomass present in autumn was produced during the current season.Colonizing hyphae of the Frankia sp. endophyte were seen throughout the year in partially expanded cortical cells near the nodule lobe apex. Vesicles first appeared in mature cortical cells coincident with the onset of nitrogenase activity in mid-May, occupied the bulk of the infected tissue during the summer, and disappeared as nitrogenase activity ceased in late October. Evidence is presented that the vesicles are the site of nitrogenase activity and are newly produced each season in freshly formed nodule lobe tissue. Sporangia frequently formed in mature infected cells in nodules at one site but were rare at another. The processes described here in M. gale are probably typical of winter-deciduous actinorhizal plants.

Host–endophyte interactions in effective and ineffective nodules induced by the endophyte of Myrica gale

1983 ◽  
Vol 61 (11) ◽  
pp. 2898-2909 ◽  
Author(s):  
Kathryn A. VandenBosch ◽  
John G. Torrey
Keyword(s):  
Nitrogenase Activity ◽  
Root Nodules ◽  
Seedling Development ◽  
Nodule Development ◽  
Nodule Formation ◽  
Cortical Tissue ◽  
Intercellular Spaces ◽  
Cortical Cells ◽  
Myrica Gale ◽  
Infected Cells

Suspensions of crushed root nodules of Myrica gale containing the actinomycete Frankia induced nodule formation on roots of seedlings of M. gale and Comptonia peregrina grown in nutrient water culture. Nodules formed on M. gale were normal in structure and exhibited nitrogenase activity (measured as acetylene reduction) and provided the necessary nitrogen for seedling development. These effective nodules showed typical external and internal structure with the endophyte developing both vesicles and sporangia within cortical cells of the host tissue. Small nodules formed on C. peregrina representing the primary nodule stage. They lacked nitrogenase activity and were termed ineffective. Vesicles failed to develop within these ineffective nodules. However, sporangia were formed in infected cells and within intercellular spaces of the nodule cortical tissue. In addition, prominent amyloplasts occurred in infected cells of the ineffective nodules, a feature lacking in effective nodules. Exogenously supplied combined nitrogen increased seedling growth but did not improve nodule development or endophyte morphogenesis in the ineffective nodules.

Response of respiration and nitrogenase activity in Datisca glomerata (Presl.) Baill. to changes in pO2

1999 ◽  
Vol 77 (9) ◽  
pp. 1367-1372 ◽  
Author(s):  
John D Tjepkema ◽  
Gangyi Du ◽  
Christa R Schwintzer
Keyword(s):  
Pisum Sativum ◽  
Gas Phase ◽  
Nitrogenase Activity ◽  
Root Systems ◽  
Actinorhizal Plants ◽  
Diffusion Resistance ◽  
Turn On ◽  
Pisum Sativum L ◽  
Oxygen Protection ◽  
Infected Cells

Respiration and nitrogenase activity by root systems of Datisca glomerata (Presl.) Baill. decline rapidly after exposure to C2H2. We measured C2H2 reduction and CO2 evolution to determine whether this decline is due to a variable barrier to O2 diffusion and to examine the nature of O2 regulation in these nodules. Changes in pO2 between 16 and 30 kPa during the decline had only small effects on respiration and nitrogenase activity. Thus the decline is not due to an increase in resistance to O2 diffusion. In contrast, in peas (Pisum sativum L.) nitrogenase activity was strongly reduced when the pO2 was lowered from 20 to 16 kPa during the decline. In Datisca there was little difference in nitrogenase activity when measurements in He-O2 mixtures were compared with Ar-O2 mixtures, showing that there is no gas phase limitation on diffusion. Therefore the major diffusion resistance in Datisca nodules is in the infected cells. We propose that this resistance is in the vesicles of Frankia and that the vesicles represent a series of compartments that vary in the degree to which nitrogenase is protected from O2. As pO2 increases or decreases, various compartments turn on and off keeping the overall rate of nitrogenase activity and respiration nearly constant.Key words: actinorhizal plants, Datisca glomerata, Frankia, nitrogenase, oxygen protection, Pisum sativum.

Effective and ineffective root nodules in Myrica faya

1976 ◽  
Vol 194 (1116) ◽  
pp. 285-293 ◽  
Keyword(s):  
Root Nodules ◽  
Light And Electron Microscopy ◽  
Nodule Formation ◽  
Culture Solution ◽  
Myrica Gale ◽  
Main Site ◽  
Myrica Faya ◽  
Modern Methods ◽  
Infected Cells ◽  
Nodule Endophytes

In cross-inoculation trials, inocula containing the nodule endophytes of Myrica gale, M. cerifera, M. cordifolia and M. pilulifera respectively were applied to the roots of young plants of M. faya Ait. growing in nitrogen-free culture solution. All four inocula induced nodule formation, and except where the M. gale inoculum had been used the nodules were of effective type and enabled the plants bearing them to grow nearly as well as other M. faya plants associated with the normal endophyte. The nodules induced by the M. gale endophyte were very numerous, but remained small and fixed no significant amount of nitrogen, and were thus ineffective. Light and electron microscopy showed that in the effective nodules induced by the normal endophyte or by that of M. cordifolia , the endophyte was confined to a layer 1-2 cells deep near the middle of the nodule cortex, and that in respect of the width of the hyphae and their production of club-shaped internally subdivided vesicles, the endophytes resembled closely those in the nodules of the few other species of Myrica that have been studied by modern methods of microscopy. In ineffective nodules the disposition of the infected cells was unchanged, but within the cells only a sparse development of the endophyte was observed, and no vesicles were found. The finding that nodules lacking vesicles showed little or no fixation is consistent with other evidence that the vesicles normally produced by non-legume nodule endophytes are the main site of nitrogen fixation.

Seasonal pattern of energy use, respiration, and nitrogenase activity in root nodules of Myrica gale

1983 ◽  
Vol 61 (11) ◽  
pp. 2937-2942 ◽  
Author(s):  
Christa R. Schwintzer ◽  
John D. Tjepkema
Keyword(s):  
Energy Cost ◽  
Energy Use ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Seasonal Pattern ◽  
Uptake Ratio ◽  
Experimental Conditions ◽  
Myrica Gale ◽  
Net Production ◽  
N Requirement

Annual CO2 evolution, H2 evolution, and C2H2 reduction were measured in root nodules from a vigorous Myrica gale stand in a Massachusetts peatland at 3-week intervals in 1980. Nodule activity was approximately the same under the experimental conditions (excised nodules reducing C2H2) as in nature (attached nodules reducing N2) and the CO2 evolution to O2 uptake ratio averaged 1.07. Nitrogenase activity was first detectable in late May, reached its maximum [Formula: see text] in mid-July, and disappeared in late October. The seasonal pattern of CO2 evolution was similar except that it continued at low rates when nitrogenase activity was absent. Hydrogen evolution was barely detectable. The energy cost of nitrogen fixation, expressed as the molar CO2:C2H4 ratio, was relatively low [Formula: see text] throughout the period of substantial nitrogenase activity and had a mean annual value of 4.9. Annual N2 fixation was estimated to be 2.8 g N m−2year−1, contributing about 33% of the annual N requirement measured in 1979. Annual C use by nodules was about 21.0 g C m−2 year−1. If this C were available for additional net production, it would increase it by about 5.5%.

Early symptom development in lodgepole pine seedlings infected with Endocronartium harknessii

1990 ◽  
Vol 68 (2) ◽  
pp. 270-277 ◽  
Author(s):  
Eric A. Allen ◽  
P. V. Blenis ◽  
Y. Hiratsuka
Keyword(s):  
Pinus Contorta ◽  
Rust Fungus ◽  
Infected Tissue ◽  
Cortical Cells ◽  
Subsequent Formation ◽  
Early Symptom ◽  
Pine Seedlings ◽  
Endocronartium Harknessii ◽  
Periderm Formation ◽  
Lignin Deposition

Six-week-old Pinus contorta seedlings were inoculated with spores of the western gall rust fungus Endocronartium harknessii. Of 660 seedlings inoculated, 174 showed early symptoms and were sampled for histological observation in the 7 weeks following inoculation. Pigmentation of epidermal cells was the first externally visible response to infection, generally occurring 14–28 days after inoculation. Developing symptoms were extremely variable, ranging from little or no visible response to severe necrosis. The appearance of external symptoms was largely due to changes occurring in underlying infected cortical cells such as the production of phenolic compounds, necrophylactic periderm, or necrotic tissue. Intercellular lignin deposition was observed in infected tissue and was thought to be associated with necrophylactic periderm formation. Suppression of normal exophylactic periderm development was evident in virtually all infected tissue zones. Infection of the vascular cambium occurred as early as 21 days after inoculation and resulted in the subsequent formation of distorted xylem tracheids typical of gall tissue.

Field nodules of Alnus incana ssp. rugosa and Myrica gale exhibit pronounced acetylene-induced declines in nitrogenase activity

1997 ◽  
Vol 75 (9) ◽  
pp. 1415-1423 ◽  
Author(s):  
Christa R. Schwintzer ◽  
John D. Tjepkema
Keyword(s):  
Time Course ◽  
Nitrogenase Activity ◽  
Alnus Incana ◽  
Partial Recovery ◽  
Myrica Gale ◽  
Open Flow ◽  
Peak Rate ◽  
Flow Through ◽  
Speckled Alder ◽  
Initial Peak

The time course of acetylene reduction was examined in field nodules of speckled alder (Alnus incana ssp. rugosa (Du Roi) Claus.) and sweet gale (Myrica gale L.) with an open flow-through system. When detached speckled alder nodules were measured in the laboratory, there was an initial peak rate of nitrogenase activity between 2 and 3 min followed by pronounced declines to 50% of the peak rate (early summer) and 66% (late summer) at 9 min, after which there was little further change. Speckled alder nodules measured in the field while still attached to the plant also had a peak rate between 2 and 3 min. Most sweet gale nodules had a peak rate at 2–3 min and a sharp decline to 27% at 21 min followed by a partial recovery to 49% at 60 min. The time courses of field nodules of speckled alder and sweet gale were comparable with those of intact, growth chamber grown seedlings. The initial peak rate is the most accurate measure of nitrogenase activity and the only reliable way to measure this is with an open, flow-through system. We describe a simple, inexpensive, flow-through system for use in the field. Key words: acetylene-induced decline, Alnus incana ssp. rugosa, actinorhizal plants, Myrica gale, nitrogen fixation, nitrogenase activity.

scholarly journals Dark Green Islands in Plant Virus Infection are the Result of Posttranscriptional Gene Silencing

2001 ◽  
Vol 14 (8) ◽  
pp. 939-946 ◽  
Author(s):  
Carolyn J. Moore ◽  
Paul W. Sutherland ◽  
Richard L. S. Forster ◽  
Richard C. Gardner ◽  
Robin M. MacDiarmid
Keyword(s):  
Gene Silencing ◽  
Plant Virus ◽  
Infected Tissue ◽  
Common Symptom ◽  
Yellow Virus ◽  
Posttranscriptional Gene Silencing ◽  
Heterologous Virus ◽  
Infected Cells ◽  
Dark Green ◽  
Lines Of Evidence

Dark green islands (DGIs) are a common symptom of plants systemically infected with a mosaic virus. DGIs are clusters of green leaf cells that are free of virus but surrounded by yellow, virus-infected tissue. We report here on two lines of evidence showing that DGIs are caused by posttranscriptional gene silencing (PTGS). First, transcripts of a transgene derived from the coat protein of Tamarillo mosaic potyvirus (TaMV) were reduced in DGIs relative to adjacent yellow tissues when the plants were infected with TaMV. Second, nontransgenic plants coinfected with TaMV and a heterologous virus vector carrying TaMV sequences showed reduced titers of the vector in DGIs compared with surrounding tissues. DGIs also were compared with recovered tissue at the top of transgenic plants because recovery has been shown previously to involve PTGS. Cytological analysis of the cells at the junction between recovered and infected tissue was undertaken. The interface between recovered and infected cells had very similar features to that surrounding DGIs. We conclude that DGIs and recovery are related phenomena, differing in their ability to amplify or transport the silencing signal.

Ontogenèse des nodules caulinaires du Sesbania rostrata (légumineuses)

1984 ◽  
Vol 62 (5) ◽  
pp. 982-994 ◽  
Author(s):  
E. Duhoux
Keyword(s):  
Sesbania Rostrata ◽  
Cortical Cells ◽  
Root Cortex ◽  
Central Mass ◽  
Intracellular Release ◽  
Infection Threads ◽  
Bacterial Penetration ◽  
Infected Cells ◽  
Determinate Growth

Stem nodules of the legume Sesbania rostrata are ovoids, contain chlorophyll and have determinate growth. They possess a large central mass of infected cells. Stem mamillae are regularly arranged in vertical files along the stem and develop into nodules when they are infected by a specific Rhizobium. Each nodule arises from the development of an infected region of the incipient root cortex. The infection in S. rostrata has been shown to proceed in four sequential stages. Some of them have never been shown to occur in other legumes: (i) bacterial penetration takes place in degenerated (dead) cortical cells; (ii) proliferation of the bacteria occurs in the intercellular cavities and initiates a meristematic nodule; (iii) protusion of infection threads at first occurs intercellularly and then intracellularly from the cavities; (iv) finally there is an intracellular release of Rhizobia by an endocytotic process.

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