Home About us Contact
|
Home About us Contact | ||
|
|
||
Maize Roots (maize + root)
Selected AbstractsDifferent portions of the maize root system host Burkholderia cepacia populations with different degrees of genetic polymorphismENVIRONMENTAL MICROBIOLOGY, Issue 1 2000Luigi Chiarini In order to acquire a better understanding of the spatial and temporal variations of genetic diversity of Burkholderia cepacia populations in the rhizosphere of Zea mays, 161 strains were isolated from three portions of the maize root system at different soil depths and at three distinct plant growth stages. The genetic diversity among B. cepacia isolates was analysed by means of the random amplified polymorphic DNA (RAPD) technique. A number of diversity indices (richness, Shannon diversity, evenness and mean genetic distance) were calculated for each bacterial population isolated from the different root system portions. Moreover, the analysis of molecular variance ( amova) method was applied to estimate the genetic differences among the various bacterial populations. Our results showed that, in young plants, B. cepacia colonized preferentially the upper part of the root system, whereas in mature plants, B. cepacia was mostly recovered from the terminal part of the root system. This uneven distribution of B. cepacia cells among different root system portions partially reflected marked genetic differences among the B. cepacia populations isolated along maize roots on three distinct sampling occasions. In fact, all the diversity indices calculated indicated that genetic diversity increased during plant development and that the highest diversity values were found in mature maize plants, in particular in the middle and terminal portions of the root system. Moreover, the analysis of RAPD patterns by means of the amova method revealed highly significant divergences in the degree of genetic polymorphism among the various B. cepacia populations. [source] Constructing life-tables for the invasive maize pest Diabrotica virgifera virgifera (Col.; Chrysomelidae) in EuropeJOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2006S. Toepfer Abstract:, The western corn rootworm (Diabrotica virgifera virgifera LeConte, Col.; Chrysomelidae) is an alien invasive species in Europe. It is a univoltine species with eggs that overwinter in the soil and larvae that hatch in spring. Three larval instars feed on maize roots, which can cause plant lodging and yield loss of economic importance. Adults emerge between mid-June and early August and can reduce yields through intensive silk feeding. In order to provide a thorough understanding of the population dynamics of this invasive pest species in the invaded European region, complete age specific life-tables were constructed in two maize fields in southern Hungary assessing the significance of natural mortality factors acting on D. v. virgifera populations. This information provides a rational basis for devising sustainable integrated pest management programmes, in particular, by enabling the identification of vulnerable pest age intervals for the timely application of various management tools. The life-table for D. v. virgifera in Europe resulted in a total mortality of about 99% from the egg stage in the autumn to the emergence of adult females in the following year (KTotal = 2.48), which is comparable with North America. The highest reduction of D. v. virgifera numbers resulted from the mortality in first instar larvae (94% marginal death rate) and from the unrealized fecundity (80%). However, only the variation in mortality between years can change the generational mortality and thus influence population growth. High variation in the marginal death rate between fields and years was found in the second and third instar larval stages, and in the overwintering egg stage. These mortality factors therefore have the potential to cause changes in the total generational mortality. Furthermore, the life-table suggested that a high fecundity could compensate for a high generational mortality and would lead to population increase. [source] Improvement of Cupressus atlantica Gaussen growth by inoculation with native arbuscular mycorrhizal fungiJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2007L. Ouahmane Abstract Aims: The study aimed to determine whether inoculation with native arbuscular mycorrhizal (AM) fungi could improve survival and growth of seedlings in degraded soils of Morocco. Methods and Results: Soil samples were collected from the rhizosphere of Cupressus atlantica trees in the N'Fis valley (Haut Atlas, Morocco). AM spores were extracted from the soil, identified and this mixture of native AM fungi was propagated on maize for 12 weeks on a sterilized soil to enrich the fungal inoculum. Then C. atlantica seedlings were inoculated with and without (control) mycorrhizal maize roots, cultured in glasshouse conditions and further, transplanted into the field. The experiment was a randomized block design with one factor and three replication blocks. The results showed that a high AM fungal diversity was associated with C. atlantica; native AM fungi inoculation was very effective on the growth of C. atlantica seedlings in glasshouse conditions and this plant growth stimulation was maintained for 1 year after outplanting. Conclusions: Inoculation of C. atlantica with AM fungi increased growth and survival in greenhouse and field. Significance and Impact of the Study: The data indicate that use of native species of AM fungi may accelerate reforestation of degraded soils. Further studies have to be performed to determine the persistence of these mycorrhizae for a longer period of plantation and to measure the effects of this microbial inoculation on soil biofunctioning. [source] Western corn rootworm (Diabrotica virgifera virgifera LeConte) population dynamicsAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2009Lance J. Meinke Abstract 1,The western corn rootworm Diabrotica virgifera virgifera LeConte is a major insect pest of field maize, Zea mays L. Larvae can cause substantial injury by feeding on maize roots. Larval feeding may destroy individual roots or root nodes, and reduce plant growth, stability, and yield. Costs associated with managing corn rootworms in continuous maize are annually one of the largest expenditures for insect management in the United States Corn Belt. 2,Even though D. virgifera virgifera has been studied intensively for over 50 years, there is renewed interest in the biology, ecology, and genetics of this species because of its ability to rapidly adapt to management tactics, and its aggressive invasive nature. 3,This article provides a comprehensive review of D. virgifera virgifera population dynamics, specifically: diapause, larval and adult development, seasonality, spatial and temporal dynamics at local and landscape scales, invasiveness in North America and Europe, and non-trophic interactions with other arthropods. 4,Gaps in current knowledge are identified and discussed especially within the context of challenges that scientists in North America and Europe are currently facing regarding pest dynamics and the need to develop appropriate management strategies for each geographic area. [source] Physiological characteristics of selenite uptake by maize roots in response to different pH levelsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 3 2010Lianhe Zhang Abstract In selenite solutions, H2SeO3, HSeO, and SeO<$>_3^{2-}<$> are in equilibrium in proportions that vary with solution pH. The physiological characteristics of selenite uptake were studied with excised roots of maize (Zea mays L.) seedlings at pH 3.0, 5.0, and 8.0. The results showed that 0.10 mM 2,4-dinitrophenol (DNP), 1.0 mM sodium fluoride (NaF), and a temperature of 4°C inhibited selenite uptake by maize roots by 16%, 20%, and 23% at pH 3.0, by up to 80%, 79%, and 78% at pH 5.0, and by 5%, 9%, and 16% at pH 8.0. Hence, selenite may enter roots at pH 5.0 in an energy-dependent manner, in contrast to pH 3.0 and 8.0. The uptake kinetics for selenite were determined for excised roots of maize, and the curves were linear at pH 3.0 and 8.0, but saturated at pH 5.0, showing that carrier-mediated uptake of selenite occurred at pH 5.0, but not at pH 3.0 or 8.0. Further studies showed that HgCl2 and AgNO3 inhibited selenite uptake separately by 81% and 76% at pH 3.0 and indicated that selenite was absorbed by maize roots through aquaporins at pH 3.0. At pH 8.0, anion-channel inhibitors only inhibited a small fraction of selenite uptake, indicating that the major absorption pathway of SeO<$>_3^{2-}<$> species into roots was not absorbed passively through anion channels, but might involve other processes. According to these results, it is proposed that selenite uptake occurs via different mechanisms depending on its species in solution in response to pH levels. [source] Uptake and apoplastic retention of EDTA- and phytosiderophore-chelated chromium(III) in maizeJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 6 2007Bülent E. Erenoglu Abstract Increasing the mobilization and root uptake of chromium (Cr) by synthetic and plant-borne chelators might be relevant for the design of phytoremediation strategies on Cr-contaminated sites. Short-term uptake studies in maize roots supplied with 51CrCl3 or 51Cr(III)-EDTA led to higher apoplastic Cr contents in plant roots supplied with 51CrCl3 and in Fe-sufficient plants relative to Fe-deficient plants, indicating that Fe stimulated co-precipitation of Cr. Concentration-dependent retention of Cr in a methanol:chloroform-treated cell-wall fraction was still saturable and in agreement with the predicted tendency of Cr(III) to precipitate as Cr(OH)3. To investigate a possible stimulation of Cr(III) uptake by phytosiderophores, Fe-deficient maize roots were exposed for 6 d to Cr(III)-EDTA or Cr(III)-DMA (2'-deoxymugineic acid). Relative to plants without Cr supply, the supply of both chelated Cr species in a subtoxic concentration of 1 µM resulted in alleviation of Fe deficiency,induced chlorosis and higher Cr accumulation. Long-term Cr accumulation from Cr(III)-DMA was similar to that from Cr(III)-EDTA, and Cr uptake from both chelates was not altered in the maize mutant ys1, which is defective in metal-phytosiderophore uptake. We therefore conclude that phytosiderophores increase Cr solubility similar to synthetic chelators like EDTA, but do not additionally contribute to Cr(III) uptake from Cr-contaminated sites. [source] Herbicidal cyanoacrylates with antimicrotubule mechanism of actionPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2005Stefan Tresch Abstract The herbicidal mode of action of the new synthetic cyanoacrylates ethyl (2Z)-3-amino-2-cyano-4-ethylhex-2-enoate (CA1) and its isopropyl ester derivative CA2 was investigated. For initial characterization, a series of bioassays was used indicating a mode of action similar to that of mitotic disrupter herbicides such as the dinitroaniline pendimethalin. Cytochemical fluorescence studies including monoclonal antibodies against polymerized and depolymerized tubulin and a cellulose-binding domain of a bacterial cellulase conjugated to a fluorescent dye were applied to elucidate effects on cell division processes including mitosis and microtubule and cell wall formation in maize roots. When seedlings were root treated with 10 µM of CA1 or CA2, cell division activity in meristematic root tip cells decreased within 4 h. The chromosomes proceeded to a condensed state of prometaphase, but were unable to progress further in the mitotic cycle. The compounds caused a complete loss of microtubular structures, including preprophase, spindle, phragmoplast and cortical microtubules. Concomitantly, in the cytoplasm, an increase in labelling of free tubulin was observed. This suggests that the herbicides disrupt polymerization and microtubule stability, whereas tubulin synthesis or degradation appeared not to be affected. In addition, cellulose labelling in cell walls of root tip cells was not influenced. The effects of CA1 and CA2 were comparable with those caused by pendimethalin. In transgenic Arabidopsis plants expressing a green fluorescent protein-microtubule-associated protein4 fusion protein, labelled arrays of cortical microtubules in living epidermal cells of hypocotyls collapsed within 160 min after exposure to 10 µM CA1 or pendimethalin. Moreover, a dinitroaniline-resistant biotype of goosegrass (Eleusine indica (L) Gaertn) with a point mutation in ,-tubulin showed cross-resistance against CA1 and CA2. The results strongly indicate that the cyanoacrylates are a new chemical class of herbicide which possess the same antimicrotubule mechanism of action as dinitroanilines, probably including interaction with the same binding site in ,-tubulin. Copyright © 2005 Society of Chemical Industry [source] Spatial coordination of aluminium uptake, production of reactive oxygen species, callose production and wall rigidification in maize rootsPLANT CELL & ENVIRONMENT, Issue 7 2006D. L. JONES ABSTRACT Aluminium (Al) toxicity associated with acid soils represents one of the biggest limitations to crop production worldwide. Although Al specifically inhibits the elongation of root cells, the exact mechanism by which this growth reduction occurs remains controversial. The aim of this study was to investigate the spatial and temporal dynamics of Al migration into roots of maize (Zea mays L.) and the production of the stress response compound callose. Using the Al-specific fluorescent probe morin, we demonstrate the gradual penetration of Al into roots. Al readily accumulates in the root's epidermal and outer cortical cell layers but does not readily penetrate into the inner cortex. After prolonged exposure times (12,24 h), Al had entered all areas of the root apex. The spatial and temporal accumulation of Al within the root is similarly matched by the production of the cell wall polymer callose, which is also highly localized to the epidermis and outer cortical region. Exposure to Al induced the rapid production of reactive oxygen species and induced a significant rigidification of the cell wall. Our results suggest that Al-induced root inhibition in maize occurs by rigidification of the epidermal layers. [source] Non-invasive quantification of endogenous root auxin transport using an integrated flux microsensor techniqueTHE PLANT JOURNAL, Issue 6 2010Eric S. McLamore Summary Indole-3-acetic acid (IAA) is a primary phytohormone that regulates multiple aspects of plant development. Because polar transport of IAA is an essential determinant of organogenesis and dynamic tropic growth, methods to monitor IAA movement in vivo are in demand. A self-referencing electrochemical microsensor was optimized to non-invasively measure endogenous IAA flux near the surface of Zea mays roots without the addition of exogenous IAA. Enhanced sensor surface modification, decoupling of acquired signals, and integrated flux analyses were combined to provide direct, real time quantification of endogenous IAA movement in B73 maize inbred and brachytic2 (br2) auxin transport mutant roots. BR2 is localized in epidermal and hypodermal tissues at the root apex. br2 roots exhibit reduced shootward IAA transport at the root apex in radiotracer experiments and reduced gravitropic growth. IAA flux data indicates that maximal transport occurs in the distal elongation zone of maize roots, and net transport in/out of br2 roots was decreased compared to B73. Integration of short term real time flux data in this zone revealed oscillatory patterns, with B73 exhibiting shorter oscillatory periods and greater amplitude than br2. IAA efflux and influx were inhibited using 1- N -naphthylphthalamic acid (NPA), and 2-naphthoxyacetic acid (NOA), respectively. A simple harmonic oscillation model of these data produced a correlation between modeled and measured values of 0.70 for B73 and 0.69 for br2. These results indicate that this technique is useful for real-time IAA transport monitoring in surface tissues and that this approach can be performed simultaneously with current live imaging techniques. [source] | |||||||||||||