Javier Villegas

Root colonisation by the arbuscular mycorrhizal fungus Glomus intraradices alters the quality of strawberry fruits (Fragaria × ananassa Duch.) at different nitrogen levels

BACKGROUND Arbuscular mycorrhizal fungi (AMF) increase the uptake of minerals from the soil, thus improving the growth of the host plant. Nitrogen (N) is a main mineral element for plant growth, as it is an essential component of numerous plant compounds affecting fruit quality. The availability of N to plants also affects the AMF-plant interaction, which suggests that the quality of fruits could be affected by both factors. The objective of this study was to evaluate the influence of three N treatments (3, 6 and 18 mmol L(-1)) in combination with inoculation with the AMF Glomus intraradices on the quality of strawberry fruits. The effects of each factor and their interaction were analysed. RESULTS Nitrogen treatment significantly modified the concentrations of minerals and some phenolic compounds, while mycorrhization significantly affected some colour parameters and the concentrations of most phenolic compounds. Significant differences between fruits of mycorrhizal and non-mycorrhizal plants were found for the majority of phenolic compounds and for some minerals in plants treated with 6 mmol L(-1) N. The respective values of fruits of mycorrhizal plants were higher. CONCLUSION Nitrogen application modified the effect of mycorrhization on strawberry fruit quality.

Performance of two valuable species, Pinus pseudostrobus and Eysenhardtia polystachya, in a low fertility soil mediated by mycorrhizal fungi and fertilization

Abstract Interspecific relationships are fundamental to maintain ecological processes, and are particularly important for the recovery of plant cover in severely degraded sites. An experiment was set up to evaluate pairs of Pinus pseudostrobus–Eysenhardtia polystachya plants, the first inoculated with Pisolithus tinctorius and the second inoculated with P. tinctorius and/or Rhizophagus intraradices, plus inoculation controls, and phosphorus fertilization. Growth and biomass were measured as response variables. For the pines, only height and number of branches responded to factors directly applied to the tree: fertilization and inoculation with Pisolithus tinctorius. However, these variables also responded to inoculation of the legume with Rhizophagus intraradices, implying an indirect effect on the pine plant. Furthermore, this indirect effect was significant for pine biomass accumulation. Fertilization had a positive and significant effect for the legume plants increasing the values for almost all of the variables (apart from branch length) but for some variables the simultaneous presence of both mycorrhizal fungi was detrimental. Different combinations of fertilization and inoculation benefit growth of the pines and the legumes. When environmental restoration of production systems is considered, either conditions favoring the legume can be achieved (if protection of the soil in the short-term is desirable), or conditions favoring the pines can be implemented (if favoring the tree species is preferable).

Biological effects of carbon nanotubes generated in forest wildfire ecosystems rich in resinous trees on native plants

Carbon nanotubes (CNTs) have a broad range of applications and are generally considered human-engineered nanomaterials. However, carbon nanostructures have been found in ice cores and oil wells, suggesting that nature may provide appropriate conditions for CNT synthesis. During forest wildfires, materials such as turpentine and conifer tissues containing iron under high temperatures may create chemical conditions favorable for CNT generation, similar to those in synthetic methods. Here, we show evidence of naturally occurring multiwalled carbon nanotubes (MWCNTs) produced from Pinus oocarpa and Pinus pseudostrobus, following a forest wildfire. The MWCNTs showed an average of 10 walls, with internal diameters of ∼2.5 nm and outer diameters of ∼14.5 nm. To verify whether MWCNT generation during forest wildfires has a biological effect on some characteristic plant species of these ecosystems, germination and development of seedlings were conducted. Results show that the utilization of comparable synthetic MWCNTs increased seed germination rates and the development of Lupinus elegans and Eysenhardtia polystachya, two plants species found in the burned forest ecosystem. The finding provides evidence that supports the generation and possible ecological functions of MWCNTs in nature.