Anna Füzy

Mycorrhizal symbiosis effects on growth of chalk false-brome (Brachypodium pinnatum) are dependent on the environmental light regime

AMF (arbuscular mycorrhizal fungi) colonization of the grass chalk false-brome (Brachypodium pinnatum (L.) P. B.) was studied in selected habitats under spatially different light regimes: (a) shade condition under oak trees, (b) half shade in a shrubby area and (c) full-sun conditions on unshaded grassland. This study assessed the variations in AMF colonization of the grass dependent on the light supply in field habitats. Soil, root and shoot samples were collected four times during the vegetation period (in June, July, September and October). Root colonization, root and shoot biomass as well as soil water content were determined. The highest rate of AMF colonization was detected in June under half-sun and full-sun conditions, where about 50% of the roots were colonized. The average amount of arbuscules was less than 20% in the roots at the three sites, with the highest number of arbuscules in June, under half-sun and full-sun conditions, however, not under the trees. Overall, best mycorrhizal colonization occurred during summer, and its rate decreased in autumn. This tendency inversely correlated with the amount of precipitation, and thus with the water content of soils. The high colonization rate of the examined root samples, and also its seasonal fluctuation, might reflect the importance of the symbiosis where inorganic nutrients and water are the growth-limiting factors. The marginal AMF colonization of chalk false-brome under shade conditions indicates that plants do not use AMF under all stress conditions. When low light limits photosynthesis and thus growth of the plants, they dispense with the colonization of AMF in order to save the expenditure of organic carbon.

Effect of Arbuscular Mycorrhizal Fungi on the Growth and Polyphenol Profile of Marjoram, Lemon Balm, and Marigold.

The aim of this study is to examine the effect of arbuscular mycorrhizal fungi (AMF) colonization on biomass, polyphenol profile, and content of economically important herbs. A pot experiment was performed with marjoram, lemon balm, and marigold applying a commercially available AMF mixture for inoculation. Major polyphenols were identified using HPLC-UV-ESI-qTOFMS on the basis of their UV-vis and mass spectral characteristics, and selected ones were quantified. We showed that AMF can provide different services for each herb. Marjoram had the highest level of fungal colonization (82 M%) followed by lemon balm (62 M%) and marigold (17 M%). AMF inoculation significantly increased the biomass of marjoram (1.5-fold), the number of marigold flowers (1.2-fold), and the yield of rosmarinic acid and lithospermic acid isomers of marjoram (1.5-fold) and lemon balm (1.2-fold). Therefore, the quantity and quality of plant material could be improved by the application of optimized AMF inoculum.

Simultaneous monitoring of electrical capacitance and water uptake activity of plant root system

Abstract Pot experiments were designed to test the applicability of root electrical capacitance measurement for in situ monitoring of root water uptake activity by growing cucumber and bean cultivars in a growth chamber. Half of the plants were inoculated with Funneliformis mosseae arbuscular mycorrhizal fungi, while the other half served as non-infected controls. Root electrical capacitance and daily transpiration were monitored during the whole plant ontogeny. Phenology-dependent changes of daily transpiration (related to root water uptake) and root electrical capacitance proved to be similar as they showed upward trends from seedling emergence to the beginning of flowering stage, and thereafter decreased continuously during fruit setting. A few days after arbuscular mycorrhizal fungi-colonization, daily transpiration and root electrical capacitance of infected plants became significantly higher than those of non-infected counterparts, and the relative increment of the measured parameters was greater for the more highly mycorrhizal-dependent bean cultivar compared to that of cucumber. Arbuscular mycorrhizal fungi colonization caused 29 and 69% relative increment in shoot dry mass for cucumbers and beans, respectively. Mycorrhization resulted in 37% increase in root dry mass for beans, but no significant difference was observed for cucumbers. Results indicate the potential of root electrical capacitance measurements for monitoring the changes and differences of root water uptake rate.

Mycorrhizal colonisation can be altered by the direct and indirect effect of drought and salt in a split root experiment

Introduction Technical literature data about the effects of saline or sodic soil on the rates of arbuscular mycorrhizal fungal (AMF) colonisation are rather controversial. Salt was reported to inhibit mycorrhizal colonisation, spore germination, hyphal elongation and spore-forming activity (Juniper and Abbott 1993), while on the contrary several halophytes are reported to be heavily colonized by AMF at salt affected sites (Hildebrandt et al. 2000). This relative paradoxon can be partly explaind by the manner of the plant-endomycorrhyza symbiosis: a halophyte macrosymbiont host with the microsymbiont endomycorrhiza partner can better tolerate the suboptimal or extreme conditions. The stressbuffer effect of some beneficial microbes in this respect was reported by Biro et al. (2000). To maintain the symbiosis by the macrosymbiont host can be a „profitable investment”, where the assimilates, carbohydrates are generally refunded with macroand micronutrients by the fungi. The increased plant acquisition capacity or the limitation of salt uptake are all important conditions of the symbiosis in poor quality salt affected soils (Ruiz-Lozano and Azcon 2000; Marschner 1998). After thesese findings, our hypothesis is that the enhancement of mycorrhizal colonisation in the saline soils can be the result of a communication process between the macroand microsymbiont partners. As a consequence of this the salt adaptation mechanisms of the halophytes can be related by the incresed mycorrhizal colonisation (Fuzy et al. 2006). Our aim in this study was to demonstrate this hypothesis in a split-root experiment, where the direct effects of the rhizosphere towards the mycorrhiza fungi can be well separated from the plant-mediated physiological actions. Stress-factors, such as the salt and the drought were examined, which are known to be the most prominent plant-growth-retardation reasons at the salt affected sites.

METABOLIC ACTIVITY AND GENETIC DIVERSITY OF MICROBIAL COMMUNITIES INHABITING THE RHIZOSPHERE OF HALOPHYTON PLANTS

A preliminary study was conducted to compare the community level physiological profile (CLPP) and genetic diversity of rhizosphere microbial communities of four plant species growing nearby Kiskunság soda ponds, namely Böddi-szék, Kelemen-szék and Zab-szék. CLPP was assessed by MicroResp method using 15 different substrates while Denaturing Gradient Gel Electrophoresis (DGGE) was used to analyse genetic diversity of bacterial communities. The soil physical and chemical properties were quite different at the three sampling sites. Multivariate statistics (PCA and UPGMA) revealed that Zab-szék samples could be separated according to their genetic profile from the two others which might be attributed to the geographical location and perhaps the differences in soil physical properties. Böddi-szék samples could be separated from the two others considering the metabolic activity which could be explained by their high salt and low humus contents. The number of bands in DGGE gels was related to the metabolic activity, and positively correlated with soil humus content, but negatively with soil salt content. The main finding was that geographical location, soil physical and chemical properties and the type of vegetation were all important factors influencing the metabolic activity and genetic diversity of rhizosphere microbial communities.

Estimation of am fungal colonization - Comparability and reliability of classical methods

The characterization of mycorrhizal status in hosts can be a good indicator of symbiotic associations in inoculation experiments or in ecological research. The most common microscopic-based observation methods, such as (i) the gridline intersect method, (ii) the magnified intersections method and (iii) the five-class system of Trouvelot were tested to find the most simple, easily executable, effective and objective ones and their appropriate parameters for characterization of mycorrhizal status. In a pot experiment, white clover (Trifolium repens L.) host plant was inoculated with 6 (BEG144; syn. Rhizophagus intradices) in pumice substrate to monitor the AMF colonization properties during host growth. Eleven (seven classical and four new) colonization parameters were estimated by three researchers in twelve sampling times during plant growth. Variations among methods, observers, parallels, or individual plants were determined and analysed to select the most appropriate parameters and sampling times for monitoring. The comparability of the parameters of the three methods was also tested. As a result of the experiment classical parameters were selected for hyphal colonization: colonization frequency in the first stage or colonization density in the later period, and arbuscular richness of roots. A new parameter was recommended to determine vesicule and spore content of colonized roots at later stages of symbiosis.

Application of Electrical Capacitance Method for Prediction of Plant Root Mass and Activity in Field-Grown Crops

The root electrical capacitance (CR) method is suitable for assessing root growth and activity, but soil water content (SWC) strongly influences the measurement results. This study aimed to adapt the method for field monitoring by evaluating the effect of SWC on root capacitance to ensure the comparability of CR detected at different SWC. First a pot experiment was conducted with maize and soybean to establish CR–SWC functions for the field soil. Ontogenetic changes in root activity were monitored under field conditions by simultaneously measuring CR and SWC around the roots. The CR values were normalized using SWC data and experimental CR–SWC functions to obtain CR*, the comparable indicator of root activity. The effect of arbuscular mycorrhizal fungi (AMF) inoculation on the CR* and biomass of field-grown soybean was investigated. The pot trial showed an exponential increase in CR with SWC. CR–SWC functions proved to be species-specific. CR showed strong correlation with root dry mass (R2 = 0.83–0.87). The root activity (CR*) of field-grown crops increased until flowering, then decreased during maturity. This was consistent with data obtained with other methods. AMF inoculation of soybean resulted in significantly higher CR* during the late vegetative and early flowering stages, when destructive sampling concurrently showed higher shoot biomass. The results demonstrated that the root capacitance method could be useful for time course studies on root activity under field conditions, and for comparing single-time capacitance data collected in areas with heterogeneous soil water status.

Mikrobiális anyagcsere aktivitás-mintázat és mikorrhiza gomba kolonizáció elemzése három szikes tó melletti talaj rizoszférában

A szikes talajok szelsőseges vizhaztartasuk, nagy sotartalmuk es alkalikus kemhatasuk miatt az előlenyek alkalmazkodasat alaposan probara teszik. A talaj mikrobialis kozosseg katabolikus aktivitas mintazatat hasonlitottuk ossze harom szikes to, a Boddi-szek, a Kelemen-szek es a Zab-szek (Felső-Kiskunsagi szikes tavak) partkozeli vegetaciojanak rizoszferajaban az iszaptol a zsiokason es a mezpazsiton keresztul a homoki legelőig. Felteteleztuk, hogy a szikes jellegben es a novenyzetben meglevő kulonbsegek a mikrobialis kozossegre is hatast gyakorolnak. Kezdeti eredmenyeink azt mutattak, hogy a szubsztrat hasznositasi mintazat alapjan az egyes mintak jol elkulonultek egymastol. Az alaprespiracio elsősorban a talaj humusztartalmaval mutatott szoros osszefuggest. A katabolikus aktivitas mintazatokat 5 szubsztrat alapjan a gazkromatografias SIR meressel a pH es EC, mig 15 szubsztrat alapjan mikrorespiracioval a pH es humusztartalom szignifikansan befolyasolta, a novenyzet kozvetlen hatasa kevesbe volt igazolhat...

Reviews of: “Rangeland and Animal Production in Arid Lands: A State of Knowledge, as of 2006”, “The Biology of Deserts by David Ward” and “Salt-Affected Soils of Russia. Shishov, L. L. and E. I. Pankova (eds.)”

Secheresse (http://www.revue-secheresse.fr) is one of the important journals specializing in holistic studies of semi-arid and arid areas. In spite of being a francophone journal, it publishes papers from all over the world. The editor, Professor Le Houérou (hn.le-houerou@club-internet.fr) is an independent consultant, who has published several papers in our journal and worked for our Board of Editors. There are 37 scientific contributions in the special edition totaling 376 pages. 40% of the papers are written in English, 20% in Spanish, and 40% in French. After the introductory section, containing a paper by the thematic editor, the following chapters are found. The part “Regional Contributions,” is divided into subchapters of continents. The chapter ‘Africa’ has 10 papers. The effect of soil texture on the occurrence of woody plants is shown by indicating typical occurrence on the texture triangle at 150–330, 300–450, and 450–600mm/year precipitation ranges in the paper of Hiernaux and Le Houérou. After analyzing previous trials aimed at regenerating rangelands in the Sahel, Toutain et al. suggest a four-step procedure: “i) stop the causes of degradation, ii) reach a wide consensus among rangeland users on the limits for the area to be improved and as to how regeneration should be implemented, iii) select the technologies and soil profile modifications adapted to the soils; iv) protect the area a sufficient number of years for the regeneration process to become spontaneous.” The chapter ‘Asia’ contains nine papers. Johnson, Sheehy, and Miller authored two papers, one on Mongolian, and another on Tibetan rangelands. Gintzburger, Le Houérou, and Saïdi authored one on Near East-West Asia and another one on Middle Asia. There are two papers in the chapter ‘North America’. Huntsinger and Starrs presented a biogeographical assessment of grazing in all of arid North America. Herrick et al. urges the use of standardized methods for monitoring arid and semi-arid rangelands. The chapter ‘South America’ consists of five papers on Argentine, Chilean, Andean, and Brazilian (two papers) pastoralism.