Root Hair Surface Research Articles

Germination Behavior and Geographical Information System-Based Phenotyping of Root Hairs to Evaluate the Effects of Different Sources of Black Soldier Fly (Hermetia illucens) Larval Frass on Herbaceous Crops.

Insect larval frass has been proposed as a fertilizer and amendment, but methods for testing its effects on plants are poorly developed and need standardization. We obtained different types of black soldier fly (Hermetia illucens) frass via the factorial combination of (a) two insect diets, as follows: G (Gainesville = 50% wheat bran, 30% alfalfa meal, 20% maize meal) and W (43% sheep whey + 57% seeds); (b) two frass thermal treatments: NT = untreated and T = treated at 70 °C for 1 h. We tested the effects on the germination of cress (Lepidium sativum L.) and wheat (Triticum durum Desf.) by applying 1:2 w:w water extracts at 0, 25, 50, 75 and 100% concentration. Standardizing frass water content before extraction affected chemical composition. Frass extracts showed high electrical conductivity (8.88 to 13.78 mS cm-1). The W diet was suppressive towards Escherichia coli and showed a lower content of nitrates (e.g., WNT 40% lower than GNT) and a concentration-dependent phytotoxic effect on germinating plants. At 25% concentration, germination indices of G were 4.5 to 40-fold those at 100%. Root and shoot length and root hair area were affected by diet and concentration of frass extracts (e.g., root and shoot length in cress at 25% were, respectively, 4.53 and 2 times higher than at 100%), whereas the effects of the thermal treatment were few or inconclusive. On barley (Hordeum vulgare L.) grown in micropots on a silty loam soil, root mass was reduced by 37% at high extract concentration. A quick procedure for root hair surface area was developed based on the geographic information system (GIS) and may provide a fast method for incorporating root hair phenotyping in frass evaluation. The results indicate that below-ground structures need to be addressed in research on frass effects. For this, phyotoxicity tests should encompass different extract dilutions, and frass water content should be standardized before extraction in the direction of canonical procedures to allow comparisons.

Heavy metal accumulation and distribution in Phragmites australis seedlings tissues originating from natural and urban catchment.

The retention of heavy metal (HM) was studied in root and rhizomes (BLG), stems (ST), and leaves (LF) of Phragmites australis (common reed) seedlings collected from different locations, differing in the scale of anthropogenic interference. The analysis includes the reference samples of sediments in uncontaminated lake Garczonki and contaminated roadside ditch in Cieplewo. The concentrations of Zn, Cu, Pb, Cd, Ni, and Cr were analyzed in plant tissues and sediments using the atomic absorption spectrometry and inductively coupled plasma mass spectrometry. The general assessment of sediments collected in the Garczonki lake showed a good environmental status; while in the roadside ditch in Cieplewo, the sediments were considerably polluted with HM. In the first stage of plant growth, all of the analyzed HMs are mainly inhibited by BLG system. The decreasing trend of elements was as follows: BLG > ST > LF. The organs followed different decreasing trends of HM concentration; the trend Zn > Cu > Ni > Cr > Pb > Cd was found in ST and LF for the Garczonki lake seedlings and for BLG and LF for the roadside ditch in Cieplewo seedlings. Zn showed the highest concentration, while Cd the lowest concentration in each of the examined organs. The bioaccumulation factor indicated the higher mobility of HM in seedlings in the Garczonki lake than in the roadside ditch in Cieplewo. The morphological studies suggest the good state and health of seedling from both sites; however, the reduction of root hair surface was observed for the roadside ditch seedlings. The anatomical studies present changes in the size of the nucleus and count of chloroplasts in LF. No reaction on HM contamination sediments in the seedlings from the roadside ditch in Cieplewo in the aerenchyma was noted. Potentially, both types of seedlings can be used to decontaminate environments rich in HM. However, the level of HM absorbed by seedlings (in the first stage of growth) should be considered due to the behavior in the target phytoremediation site.

Examination of nanoparticulate phosphate rock as both a liming agent and phosphorus source to enhance the growth of spinach in acid soil

ABSTRACT To examine the effect of nanoparticulate phosphate rock (NPR) as both a liming agent and phosphorus source in a tropical acid soil. The study examined five rates of NPR (0, 250, 500, 1000, or 2000 kg ha−1), which supplies 30, 60, 120 or 240 kg P ha−1, in a randomized complete pot experiment design with 3 replications. The pots of soil were incubated in a climate-controlled greenhouse for 21 days and then spinach was grown for 49 days. Soil parameters (pH, available P and exchangeable acidity), spinach parameters (leaf area, root hair surface area, root length and dry matter yield) and the effectiveness of NPR dissolution were estimated. The soil and plant parameters and the effective NPR dissolution all increased to the same degree at 1000 and 2000 kg NPR ha−1. Therefore, the use of 1000 kg ha−1 was most economically justified. Although, NPR has been appeared as an effective liming agent and phosphorus source in tropical acid soil. However, a regular application of NPR and further research for economic comparison between NPR and both of lime and superphosphate, as well as the original PR, will be needed.

An endophytic microbe from an unusual volcanic swamp corn seeks and inhabits root hair cells to extract rock phosphate

In the animal microbiome, localization of microbes to specific cell types is well established, but there are few such examples within the plant microbiome which includes endophytes. Endophytes are non-pathogenic microbes that inhabit plants. Root hairs are single cells, equivalent to the nutrient-absorbing intestinal microvilli of animals, used by plants to increase the root surface area for nutrient extraction from soil including phosphorus (P). There has been significant interest in the microbiome of intestinal microvilli but less is known about the root hair microbiome. Here we describe a bacterial endophyte (3F11) from Zea nicaraguensis, a wild corn discovered in a Nicaraguan swamp above rock-P lava flowing from the San Cristobal volcano. Rock-P is insoluble and a major challenge for plants. Following seed coating and germination on insoluble-P, the endophyte colonized epidermal surfaces, ultimately colonizing root hairs intracellularly. The endophyte promoted root hair growth and secreted acids to solubilize rock-P for uptake by a larger root hair surface. The most interesting observation was that a seed-coated endophyte targeted and colonized a critical cell type, root hair cells, consistent with earlier studies. The endophyte maintained its targeting ability in two evolutionary divergent hosts, suggesting that the host recognition machinery is conserved.

Root hair formation in rice (Oryza sativa L.) differs between root types and is altered in artificial growth conditions.

Root hairs are important sites for nutrient uptake, especially in P limiting conditions. Here we provide first insights into root hair development for the diverse root types of rice grown under different conditions, and show the first in situ images of rice root hairs in intact soil. Roots of plants grown in upland fields produced short root hairs that showed little responsiveness to P deficiency, and had a higher root hair density in the high P condition. These results were reproducible in rhizoboxes under greenhouse conditions. Synchrotron-based in situ analysis of root hairs in intact soil further confirmed this pattern of root hair formation. In contrast, plants grown in nutrient solution produced more and longer root hairs in low P conditions, but these were unequally distributed among the different root types. While nutrient solution-grown main roots had longer hairs compared to upland field-grown main roots, second order lateral roots did not form any root hairs in nutrient solution-grown plants. Furthermore, root hair formation for plants grown in flooded lowland fields revealed few similarities with those grown in nutrient solution, thus defining nutrient solution as a possible measure of maximal, but not natural root hair development. By combining root hair length and density as a measure for root hair impact on the whole soil-grown root system we show that lateral roots provided the majority of root hair surface.

Microtubule array formation during root hair infection thread initiation and elongation in the Mesorhizobium-Lotus symbiosis

Nuclear migration during infection thread (IT) development in root hairs is essential for legume-Rhizobium symbiosis. However, little is known about the relationships between IT formation, nuclear migration, and microtubule dynamics. To this aim, we used transgenic Lotus japonicus expressing a fusion of the green fluorescent protein and tubulin-α6 from Arabidopsis thaliana to visualize in vivo dynamics of cortical microtubules (CMT) and endoplasmic microtubules (EMTs) in root hairs in the presence or absence of Mesorhizobium loti inoculation. We also examined the effect of microtubule-depolymerizing herbicide, cremart, on IT initiation and growth, since cremart is known to inhibit nuclear migration. In live imaging studies of M. loti-treated L. japonicus root hairs, EMTs were found in deformed, curled, and infected root hairs. The continuous reorganization of the EMT array linked to the nucleus appeared to be essential for the reorientation, curling, and IT initiation and the growth of zone II root hairs which are susceptible to rhizobial infection. During IT initiation, the EMTs appeared to be linked to the root hair surface surrounding the M. loti microcolonies. During IT growth, EMTs dissociated from the curled root hair tip, remained linked to the nucleus, and appeared to surround the IT tip. Lack or disorganized EMT arrays that were no longer linked to the nucleus were observed only in infection-aborted root hairs. Cremart affected IT formation and nodulation in a concentration-dependent manner, suggesting that the microtubule (MT) organization and successive nuclear migration are essential for successful nodulation in L. japonicus by M. loti.

Structural interaction between GFP-labeled diazotrophic endophytic bacterium Herbaspirillum seropedicae RAM10 and pineapple plantlets 'Vitória'

The events involved in the structural interaction between the diazotrophic endophytic bacterium Herbaspirillum seropedicae, strain RAM10, labeled with green fluorescent protein, and pineapple plantlets ‘Vitória’ were evaluated by means of bright-field and fluorescence microscopy, combined with scanning electron microscopy for 28 days after inoculation. After 6 hours of inoculation, H. seropedicae was already adhered to the roots, colonizing mainly root hair surface and bases, followed by epidermal cell wall junctions. Bacteria adherence in the initial periods occurred mainly in the form of solitary cells and small aggregates with pleomorphic cells. Bacteria infection of root tissue occurred through the cavities caused by the disruption of epidermal cells during the emergence of lateral roots and the endophytic establishment by the colonization of intercellular spaces of the cortical parenchyma. Moreover, within 1 day after inoculation the bacteria were colonizing the shoots. In this region, the preferred sites of epiphytic colonization were epidermal cell wall junctions, peltate scutiform trichomes and non-glandular trichomes. Subsequently, the bacteria occupied the outer periclinal walls of epidermal cells and stomata. The penetration into the shoot occurred passively through stoma aperture followed by the endophytic establishment on the substomatal chambers and spread to the intercellular spaces of spongy chlorenchyma. After 21 days of inoculation, bacterial biofilm were seen at the root hair base and on epidermal cell wall surface of root and leaf, also confirming the epiphytic nature of H. seropedicae.

Root Colonization by Pseudomonas sp. DSMZ 13134 and Impact on the Indigenous Rhizosphere Bacterial Community of Barley

Over the last few decades, the ability of rhizosphere bacteria to promote plant growth has been considered to be of scientific, ecological, and economic interest. The properties and mechanisms of interaction of these root-colonizing bacteria have been extensively investigated, and plant protection agents that are based on these bacterial strains have been developed for agricultural applications. In the present study, the root colonization of barley by Pseudomonas sp. DSMZ 13134, that is contained in the commercially available plant protection agent Proradix, was examined using the fluorescence in situ hybridization method with oligonucleotide probes and specific gfp-tagging of the inoculant strain in combination with confocal laser scanning microscopy. In the first phase of root colonization, the inoculant strain competed successfully with seed and soil-borne bacteria (including Pseudomonads) for the colonization of the rhizoplane. Pseudomonas sp. DSMZ 13134 could be detected in all parts of the roots, although it did not belong to the dominant members of the root-associated bacterial community. Gfp-tagged cells were localized particularly in the root hair zone, and high cell densities were apparent on the root hair surface. To investigate the impact of the application of Proradix on the structure of the dominant root-associated bacterial community of barley, T-RFLP analyses were performed. Only a transient community effect was found until 3 weeks post-application.

Soybean metabolites regulated in root hairs in response to the symbiotic bacterium Bradyrhizobium japonicum.

Nodulation of soybean (Glycine max) root hairs by the nitrogen-fixing symbiotic bacterium Bradyrhizobium japonicum is a complex process coordinated by the mutual exchange of diffusible signal molecules. A metabolomic study was performed to identify small molecules produced in roots and root hairs during the rhizobial infection process. Metabolites extracted from roots and root hairs mock inoculated or inoculated with B. japonicum were analyzed by gas chromatography-mass spectrometry and ultraperformance liquid chromatography-quadrupole time of flight-mass spectrometry. These combined approaches identified 2,610 metabolites in root hairs. Of these, 166 were significantly regulated in response to B. japonicum inoculation, including various (iso)flavonoids, amino acids, fatty acids, carboxylic acids, and various carbohydrates. Trehalose was among the most strongly induced metabolites produced following inoculation. Subsequent metabolomic analyses of root hairs inoculated with a B. japonicum mutant defective in the trehalose synthase, trehalose 6-phosphate synthase, and maltooligosyltrehalose synthase genes showed that the trehalose detected in the inoculated root hairs was primarily of bacterial origin. Since trehalose is generally considered an osmoprotectant, these data suggest that B. japonicum likely experiences osmotic stress during the infection process, either on the root hair surface or within the infection thread.

Plasmodiophora brassicae in its Environment

Plasmodiophora brassicae Wor. is viewed in this article from the standpoint of a highly evolved and successful organism, well fitted for the ecological niche that it occupies. Physical, chemical, and biological components of the soil environment are discussed in relation to their effects on the survival, growth, and reproduction of this microbe. It is evident that P. brassicae is well equipped by virtue of its robust resting spores for survival through many seasonal cycles. Germination is probably triggered as a result of signals initiated by root exudates. The resultant motile zoospore moves rapidly to the root hair surface and penetration and colonization follow. The short period between germination and penetration is one of greatest vulnerability for P. brassicae. In this phase survival is affected at the very least by soil texture and structure; its moisture; pH; calcium, boron, and nitrogen content; and the presence of active microbial antagonists. These factors influence the inoculum potential (sensu Garrett, 1956) and its viability and invasive capacity. There is evidence that these effects may also influence differentially the survival of some physiologic races of P. brassicae. Considering the interaction of P. brassicae with the soil environment from the perspective of its biological fitness is an unusual approach; most authors consider only the opportunities to destroy this organism. The approach adopted here is borne of several decades spent studying P. brassicae and the respect that has been engendered for it as a biological entity. This review stops at the point of penetration, although some of the implications of the environment for successful colonization are included because they form a continuum. Interactions with the molecular and biochemical cellular environment are considered in other sections in this special edition.

Derivation of a macroscopic model for nutrient uptake by hairy-roots

In this article the process of nutrient uptake by a single root branch is studied. We consider diffusion and active transport of nutrients dissolved in water. The uptake happens on the surface of thin root hairs distributed periodically and orthogonal to the root surface. Water velocity is defined by the Stokes equations. We derive a macroscopic model for nutrient uptake by a hairy-root from microscopic descriptions using homogenization techniques. The macroscopic model consists of a reaction-diffusion equation in the domain with hairs and a diffusion-convection equation in the domain without hairs. The macroscopic water velocity is described by the Stokes system in the domain without hairs, with no-slip condition on the boundary between domain with hairs and free fluid.

Interactions between diazotrophic bacteria and mycorrhizal fungus in maize genotypes

Some diazotrophic bacteria can fix nitrogen biologically in gramineous host plants. Generally, gramineous plants are also associated with mycorrhizal fungi, that can improve mainly plant P uptake. Among the factors affecting plant-microbe interactions, the plant genotype plays an important role. This study evaluates the effect of diazotrophic bacteria and an arbuscular mycorrhizal fungus (AMF), on five genotypes of maize (Zea mays L.), in relation to plant biomass, shoot N and P concentrations, and fine root morphological traits. The experimental design was entirely randomized in a factorial 5 × 4 × 2 arrangement, i.e., five maize genotypes (hybrids C333B, AS3466, and PREMIUM, and the inbreed lines lg40897-1 and lg40505-1), three diazotrophic bacteria (Azospirillum lipoferum, A. amazonense, and Burkholderia sp.) in addition to a control without bacterial inoculation, co-inoculated or not with the AMF Glomus clarum. The non-mycorrhizal plants inoculated with Azospirillum exhibited the highest N concentrations. The lines lg40897-1 and lg40505-1 showed higher P concentrations as compared to the hybrids, mainly when colonized by AMF. The higher levels of mycorrhizal colonization (90%) occurred in the C333B and lg40897-1 genotypes, which also exhibited a greater root diameter. Mycorrhiza increased shoot and root biomass, besides root traits as total length, specific length, total surface, and incidence of root hairs in all genotypes. In addition, mycorrhiza also stimulated the root colonization by diazotrophic bacteria. The bacteria did not affect root morphological traits and mycorrhizal colonization.

In-situ analysis of pectic polysaccharides in seed mucilage and at the root surface of Arabidopsis thaliana.

Pectic polysaccharides are a complex set of macromolecules of the primary cell wall matrix with distinct structural domains. The biosynthesis, organisation and function of these domains within cell wall matrices are poorly understood. An immersion immunofluorescence labelling technique was developed for the in-situ analysis of pectic polysaccharides at the surface of seeds and seedlings of Arabidopsis thaliana (L.) Heynh., and used to investigate the occurrence of pectic homogalacturonan (HG) and rhamnogalacturonan-I (RG-I) epitopes. Seed mucilage appeared to consist of two regions: a highly methyl-esterified HG was a major component throughout the mucilage, while an inner region with relatively low porosity was stabilized by calcium-based HG cross-linking. The small size and transparency of Arabidopsis roots allowed the occurrence of pectic HG and RG-I epitopes at root surfaces to be directly determined on whole-mount preparations. Pectic epitopes were not distributed evenly over root surfaces and were notably absent from lateral root apices and from the surface of root hairs. The use of defined antibody probes in the immersion immunolabelling protocol will be useful for the analysis of the influence of growth conditions and genetic factors on pectic polysaccharides in Arabidopsis.

K+ transport by Arabidopsis root hairs at low pH

Mechanisms underlying changed K + uptake by plantsat low pH need to be deciphered. One possibility is that K+ acquisition is under the strict control of plasmamembrane potential (E m ), which,in turn, is affected by external pH. To test this hypothesis, we used themicroelectrode ion flux measurement (MIFE ) technique tostudy net K + and H +fluxes near Arabidopsis root hairs at different externalpH, KCl concentrations and clamped Em . Lowering the solution pH led to strong H+ influx, K + efflux andsignificant E m depolarisation.Addition of K + to the bathing media causedsignificant net K + uptake when external pH wasover the range 5.5–6.0. At external pH below 5.0, however, correlationbetween K + availability and net K+ uptake was negative. To explain this apparentparadox, measurements of net K + and H+ fluxes from the root hair surface were performedconcurrently with E m clamped at different values above and below the restingpotential (approx. –180 mV). Our data revealed a strong dependence ofnet K + flux on the clamping voltage. Clamping atvalues more negative than the resting potential caused a significant increasein K + uptake into the root hair; clamping at lessnegative values (–20 and 0 mV) caused significant net K+ efflux from the cell. Qualitatively similarresults were observed for net H + flux. Ourobservations indicate direct control of K + flux bychanging E m , and suggest thatE m depolarisation could be themain reason for the observed K + efflux at low pH.

In vivo fluorescence correlation microscopy (FCM) reveals accumulation and immobilization of Nod factors in root hair cell walls.

Fluorescence correlation microscopy (FCM) is a new single-molecule detection technique based on the confocal principle to quantify molecular diffusion and concentration of fluorescent molecules (particles) with sub-micron resolution. In this study, FCM is applied to examine the diffusional behaviour of fluorescent Nod factor analogues on living Vicia sativa root hairs. Three recently described Nod factors with a fluorescent acyl chain (Goedhart et al. Biochemistry 1999, 38, 10898-10907) were used. Plasmolysis of fluorescently labelled root hairs showed that the Nod factors are predominantly located in the cell wall, as hardly any fluorescence could be detected in the plasma membrane. After Nod factor-induced root hair deformation, the new outgrowth was not labelled, indicating a lack of migration of Nod factors to the newly synthesized cell wall. In agreement, FCM showed a > 1,000-fold reduction of molecular mobility of the fluorescence Nod factors upon binding to the cell wall. In addition, FCM demonstrated that Nod factors, when exogenously applied in aqueous solution at 10 nM, markedly concentrate in the cell wall of root hairs (up to 50-fold). The feasibility of applying FCM for the study of living plant cells as well as the implications of our results for the perception of Nod factors are discussed.

Methanotrophic Bacteria in the Rhizosphere of Trichloroethylene-Degrading Plants

ABSTRACT The presence and density of methanotrophic bacteria has been shown to play an important role in the bioremediation of trichloroethylene (TCE). This article describes the methanotrophic bacterial densities in rhizosphere soils from two areas of the Department of Energy's Savannah River Site in Aiken, South Carolina. A direct fluorescent antibody (DFA) technique was evaluated to determine the presence of methanotrophic bacteria in roots and rhizospheres from vascular plants. The first site, the Miscellaneous Chemical Basin (MCB), was contaminated with a mixture of chemicals, including chlorinated solvents. The second site will be potentially affected by outcropping of TCE-contaminated groundwater. Significantly higher numbers of methanotrophic bacteria were observed with DFA in rhizosphere soils and on roots of Lespedeza cuneata and Pinus taeda (that previously showed higher rates of 14C-TCE mineralization) compared with nonvegetated soils. In addition, viable and heterotrophic microbial counts were consistently higher in rhizosphere soils and on plant roots compared with nonvegetated soils. Therefore, the presence of these plant species may enhance 14C-TCE mineralization by selectively increasing the microbial population in the root zone. Methanotrophic bacteria were directly observed by DFA in soils, on the surface of root hairs, within plant roots, and in higher densities associated with mycorrhizal fungi. These experiments provide further evidence that specific types of bacterial interactions with vegetation in the rhizosphere may play an important role in remediation of TCE-contaminated soils and groundwater.

Specific Localization of Arabinogalactan-Protein Epitopes at the Surface of Maize Root Hairs

Specific Localization of Arabinogalactan-Protein Epitopes at the Surface of Maize Root Hairs

Root hairs and phosphorus acquisition of wheat and barley cultivars

Root-soil contact is an important factor for uptake of a less mobile soil nutrient such as phosphorus (P) by crop plants. Root hairs can substantially increase root-soil contact. Identification of crop cultivars with more and longer root hairs can, therefore, be useful for increasing P uptake in low input agriculture. We studied the root hairs of wheat (Triticum aestivum L. cvs. Kosack, Foreman, Kraka) and barley cultivars (Hordeum vulgare L. cvs. Angora, Hamu, Alexis, Canut) in relation to P depletion from the rhizosphere in three soils of different P levels (0.45, 1.1 and 1.6 mmoles P kg−1 soil; extracted with 0.5 M NaHCO3). Root hairs were measured in solution culture having nutrients and concentration similar to soil solution. Root hairs of Kraka were much longer (1.27 ± 0.26 mm) and denser (38 ± 3) hairs mm−1 root) than those of Kosack which had shorter (0.49 ± 0.2 mm) and fewer (24 ± 3) hairs mm−1 root) root hairs. Root hairs increased root surface area (RSA) of Kraka by 341%. The increase with Foreman was 142% and with Kosack it was 95%. For winter barley, the length (1.1 ± 0.3 mm) and density (30 ± 1 hairs mm−1 root) of root hairs of Hamu differed from root hair length (0.52 ± 0.18 mm) and density (27 ± 1 hairs mm−1 root) of Angora. Root hairs of spring barley cultivars differed in length (Canut 1.0 ± 0.24 mm; Alexis 0.64 ± 0.19 mm) but not in density (Canut 31 ± 1, Alexis 30 ± 2 hairs mm−1 root). Root hair diameter (12 ± 1µm) did not differ among the cultivars. Root hairs increased RSA of Canut by 245%, Hamu by 237%, Alexis by 143% and Angora 112%. The variation in root hair parameters of the cultivars was related to quantity of P depleted from rhizosphere. The correlation (R2) between the root hair lengths of wheat cultivars and the quantity of P depleted from the rhizosphere soil (Q) was (0.99***) in low-P, (0.85***) in medium-P and (0.78**) in high-P soil. The values of (R2) between the root hair surface areas of wheat cultivars and Q were (1.00***) in low-P, (0.74**) in medium-P and (0.66**) in high-P soil. Similar high values of R2 were found for barley. These results show that the variation in root hairs of cereal cultivars can be considerable and it can play a significant role in P acquisition, especially in low-P soils.

Role of Ca 2+ in Bradyrhizobium japonicum Strain 273 Attachment Ability and Accumulation on Soybean Root Surface

Summary Ca2+ limitation in the cultivation medium of Bradyrbizobium japonicum strain 273 and in Hellriegel's nutrient solution led to optimal bacterial growth and to greater accumulation and attachment of the bacterium to the root hair surface. With the increase of Ca2+ in the medium the bacterial attachment ability and their quantity on the root surface were reduced. Optimal nodule formation in soybean plants required 127 µM Ca2+ in the nutrient medium. The problem concerning differences between Bradyrbizobium japonicum and Rhizobium leguminosarum attachment and accumulation caused by Ca2+ is discussed.

INTERACTION BETWEEN THE ECTOMYCORRHIZAL FUNGUS PISOLITHUS TINCTORIUS AND ROOT HAIRS OF PICEA MARIANA (PINACEAE)

The ectomycorrhizal fungus Pisolithus tinctorius interacts with roots of Picea mariana to form a typical mantle and Hartig net. Hyphae alter their growth pattern when in contact with susceptible root hairs in the mycorrhizal infection zone and grow acropetally, gradually covering the length of the hair to form a mantlelike structure. Initial contact with the hair may be influenced by a fibrillar material on the root hair surface. Although many root hairs become surrounded by fungal hyphae, they are not penetrated, and therefore are not entry points for this symbiotic fungus.