Alfalfa, tall fescue, ryegrass, and celery, some of which were inoculated with the AM fungus Glomus intraradices, were compared for their contributions to phenanthrene (PHE), pyrene (PYR), and dibenzo( a,h)anthracene (DBA) dissipation in spiked soil. A pot experiment was conducted in which PAHs extracted from soil and plant, quantity of PAH degraders, and plant biomass were evaluated. The results showed that biodegradation was the dominant removal mechanism for PAHs from soil while PAH accumulation in the plant tissue was negligible. PAH dissipation varied with the plant species and decreased with the increase of PAH molecular weight. The four plant species displayed a positive effect on PHE dissipation, and alfalfa improved PYR and DBA dissipation. AM fungi significantly increased plant biomass, phosphorus uptake, and PHE removal rate in planted treatments. Plant biomass and PAH degraders showed a weak linear relationship with PAH dissipation, indicating that there might be other important factors influencing PAH dissipation.
The objective of this investigation was to study the effects of three Glomus species: G. etunicatum, G. intraradices and G. versiforme on the development of verticillium wilt in cotton plants. Results indicated that the influence of arbuscular mycorrhizal fungi as a biocontrol agents were different among three Glomus species. In diseased cotton plants colonized by G. etunicatum, the disease index was lower than others and also, higher colonization percentage was relevant to these plants. On the other hand, the establishment of mycorrhizal symbiosis and development of structure of AMF were reduced when both symbiotic and pathogenic fungi infected the same root. In addition, the symptoms of veticillium wilt were diminished too. These results revealed that the beneficial effects of mycorrhiza could alleviate the pathogenic effects of V. dahliae and also a competitive interaction existed between these pathogenic and symbiont fungi.
The arbuscular mycorrhizal (AM) status of plants colonizing an area affected by leakage of salty water (Barycz near Kraków, Poland) was studied in 2000 and 2001. The occurrence of plants typical for soils of increased salinity was observed. Among the 13 examined plant species 7 were mycorrhizal. The abundance of mycorrhizal plant populations was increased in the second year of study. Strains of 4 species of AMF, including Glomus caledonium, G. claroideum, G. geosporum and G. intraradices were isolated using trap cultures. On the basis of morphological characters the presence of G. tenue was detected in plant roots of several species from the study area. The efficiency of mycorrhizal colonization and arbuscule formation by two strains of G. geosporum isolated from a saline area and a strain of G. intraradices from unaffected sites was tested in an experiment carried out on Plantago lanceolata cultivated on substrata of different salinity levels. The increase in mycorrhizal parameters with growing salt content was observed in the case of strains originating from the salt-affected area. At the highest salt level these strains formed better developed mycorrhiza than the strain from the non-saline site, suggesting a better adaptation of the strains from the saline area. The data on vitality (alkaline phosphatase test) of intraradical AM fungi gave a clearer picture than those obtained by the conventional aniline blue staining.
Annexins belong to a family of multi-functional membrane- and Ca2+-binding proteins. The characteristic feature of these proteins is that they can bind membrane phospholipids in a reversible, Ca2+-dependent manner. While animal annexins have been known for a long time and are fairly well characterized, their plant counterparts were discovered only in 1989, in tomato, and have not been thoroughly studied yet. In the present review, we discuss the available information about plant annexins with special emphasis on biochemical and functional properties of some of them. In addition, we propose a link between annexins and symbiosis and Nod factor signal transduction in the legume plant, Medicago truncatula. A specific calcium response, calcium spiking, is an essential component of the Nod factor signal transduction pathway in legume plants. The potential role of annexins in the generation and propagation of this calcium signal is considered in this review. M. truncatula annexin 1 (MtAnn1) is a typical member of the plant annexin family, structurally similar to other members of the family. Expression of the MtAnn1 gene is specifically induced during symbiotic associations with both Sinorhizobium meliloti and the mycorrhizal fungus Glomus intraradices. Furthermore, it has been reported that the MtAnn1 protein is preferentially localized at the nuclear periphery of rhizobial-activated cortical cells, suggesting a possible role of this annexin in the calcium response signal elicited by symbiotic signals from rhizobia and mycorrhizal fungi.
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