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Endophytic fungi and arbuscular mycorrhizal (AM) fungi are important components of grassland ecosystem. Endophytes can reduce colonization rates of their host plants by AM fungi. In this study, Achnatherum sibiricum, infected by Epichloe sibiricum (Es) or E. gansuensis (Eg), was adopted as experimental material. The effect of Epichloe endophyte culture filtrate, root exudates and aqueous extracts from the leaves (including fresh and dead leaves) on the spore germination rates of AM fungi (Glomus mosseae and Glomus etunicatum) were evaluated. The results showed that culture filtration of Epichloe endophyte significantly inhibited the germination rate of AM fungi spores. Root exudates of infected plants only significantly inhibited the germination of G. etunicatum spores, and such effect was not related to the endophytic species. The leaf aqueous extracts had no significant effect on the germination rate of G. mosseae spores. Only the aqueous extract of Es-infected dead leaves significantly reduced the spore germination rate of G. etunicatum. In natural ecosystem, Epichloe endophytes are normally internally hosted in plants, which may affect the spore germination of AM fungi by affecting the root exudates of the host plants. [ABSTRACT FROM AUTHOR]

We used Achnatherum sibiricum, a native grass as test material and application of methyl jasmonate (MJ) to simulate herbivory, and compared the growth and physiological characters of en- dophyte-infected (EI) and endophyte-free (EF) plants. The results showed that MJ treatment significantly decreased the shoot growth, but significantly increased the concentrations of defensive substances such as total phenolic and lignin, and decreased the size of aphid population. Endophyte infection significantly increased the tiller number, total phenolic and lignin contents in the shoot. As for shoot biomass and total phenolic in the root, they were affected by MJ treatment. Without MJ treatment, no significant differences were found in shoot biomass or root phenolic content whether the plants were infected by endophyte or not. With MJ treatment, the shoot biomass was significantly lower and the shoot phenolic content was significantly higher in EI plants than in EF plants. Endophyte infection significantly increased resistance of the host plant to aphids, and the beneficial effect was enhanced by MJ treatments, after three applications with MJ, there were no aphids on EI plants. Overall, endophyte infection could alter the allocation pattern of the host plant between growth and defense, and MJ treatments further strengthened the defensive ability of the host plant at the cost of growth. [ABSTRACT FROM AUTHOR]

Caraganaspecies are commonly distributed in desert regions. We hypothesized that the photosynthetic traits of desertCaraganaspecies could acclimated well to the desert environments, which are characterized by high temperature, intense radiation, and low moisture. To test our hypothesis, we studied the responses of photosynthesis to light, temperature and humidity, and fluorescence parameters of fourCaraganaspecies from desert region and oneCaraganaspecies from steppe region in Inner Mongolian Plateau. The desertCaraganaspecies had higher light compensation point, light saturation point, optimum temperature for photosynthesis, and lower optimum relative air humidity for photosynthesis than the steppeCaraganaspecies, and their net photosynthesis rates (Pn) were higher under high temperature, intense sunlight, and low humidity. The nonphotochemical quenching efficiency(NPQ)and minimal fluorescence(Fo)of the desertCaraganaspecies were higher, and the values of maximum fluorescence(Fm), maximum quantum yield(Fv/Fm), relative quantum yield (ΦPSII), and photochemical quenching coefficient (qP) were lower, except forC. korshinskii. The electron transport rate (ETR) of the desertCaraganaspecies was greater or similar to that ofC. microphylla.In summary, the photosynthetic traits of the desertCaraganaspecies acclimated well to desert environment, although such acclimation might be still not sufficient. The order of photosynthetic acclimation of the four species to desert environment is:C. korshinskii > C. stenophylla > C. tibetica > C. roborovskyi. [ABSTRACT FROM AUTHOR]

Epichloë species and their anamorphic relatives in genus Neotyphodium are fungal symbionts of grasses ubiquitously existing in temperate regions all over the world. To date, 13 Epichloë species and 22 Neotyphodium species have been formally described, based on morphological characters and phylogenetic analyses. Leymus chinensis (Poaceae) is a dominant grass native to the Inner Mongolia steppe of China. Previously, it was reported to harbor endophytes, but little was known about these endophytes. To investigate their diversity and taxonomy, 96 fungal isolates were obtained from three field populations of L. chinensis. The isolates were classified into three morphotypes based on morphological characters and phylogenetic analyses of sequences of genes for β-tubulin ( tubB), translation elongation factor 1-α ( tefA), and actin ( actG). The dominant morphotype, morphotype I, was identified as a choke disease endophyte, Epichloë bromicola. This broadened the host range and phylogenetic definition of E. bromicola. [ABSTRACT FROM AUTHOR]

Plant calcium (Ca) is composed of dissociated Ca2+ and easily soluble, slightly soluble, and hard soluble combined Ca salts. The hard soluble Ca salts can often engender Ca crystals. To understand the Ca status in different growth form plants in salinized habitats, 54 plant species were sampled from the salinized habitats in Tianjin, with the Ca crystals examined by microscope and the Ca components determined by sequential fractionation procedure. More Ca crystals were found in 38 of the 54 plant species. In 37 of the 38 plant species, drusy and prismatic Ca oxalate crystals dominated, whereas the cystolith of Ca carbonate crystal only appeared in the leaves of Ficus carica of Moraceae. The statistics according to growth form suggested that deciduous arbors and shrubs had more Ca oxalate crystal, liana had lesser Ca oxalate crystal, and herbs and evergreen arbors had no Ca oxalate crystal. From arbor, shrub, liana to herb, the concentration of HCl-soluble Ca decreased gradually, while that of water soluble Ca was in adverse. The concentration of water soluble Ca in herbs was significantly higher than that in arbors and shrubs. This study showed that in salinized habitats, plant Ca crystals and Ca components differed with plant growth form, and the Ca oxalate in deciduous arbors and shrubs played an important role in withstanding salt stress. [ABSTRACT FROM AUTHOR]