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Geothermal alteration fields are very prohibitive environments, limiting vegetation establishment and growth. In the present study, the ecological specialisation of the pioneer plant Calluna vulgaris (L.) Hull was investigated, assuming that its ability to survive in geothermal habitats derives from a fine regulation of morpho-physiological traits. Mature leaves of C. vulgaris were sampled from plants close to a fumarole (near), and from plants living at a distance of some metres (intermediate) or ~1 km (distant) from a fumarole. Along the sampling sites, a gradient of soil-pH and temperature values occurred, with near plants facing the highest soil temperature and the lowest soil pH. A regulation of constitutive morpho-anatomical and physiological traits in response to different stress levels occurred. A progressive reduction of leaf exposed surface and hair density and mucilages, combined with a gradual increase of oxidative stress levels, of phenols and ascorbate, was observed from distant to near plants. Near plants showed an increase in stomatal density and in lignin and cuticle thickness, and the highest activity of ascorbate peroxidase. Except for high glutathione concentrations, in distant plants antioxidant machinery was consistently less active. The apparent morphological and physiological plasticity demonstrated in the present research contributed to the capability of these plants to tolerate the prohibitive, highly changing environmental conditions of the geothermal field

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This study focused on crop plant response to a simultaneous exposure to biosolid and TiO at micro-and nano-scale, being biosolid one of the major sink of TiO 2 nanoparticles released into the soil environment. We settled an experimental design as much as possible realistic, at microcosm scale, using the crop Pisum sativum. This experimental design supported the hypotheses that the presence of biosolid in the farming soil might influence plant growth and metabolism and that, after TiO 2 spiking, the different dimension and crystal forms of TiO 2 might be otherwise bioavailable and differently interacting with the plant system. To test these hypotheses, we have considered different aspects of the response elicited by TiO 2 and biosolid at cellular and organism level, focusing on the root system, with an integrative approach. In our experimental conditions, the presence of biosolid disturbed plant growth of P. sativum, causing cellular damages at root level, probably through mechanisms not only oxidative stress-dependent but also involving altered signalling processes. These disturbances could depend on non-humified compounds and/or on the presence of toxic elements and of nanoparticles in the biosolid-amended soil. The addition of TiO 2 particles in the sludgeamended soil, further altered plant growth and induced oxidative and ultrastructural damages. Although non typical dose-effect response was detected, the most responsiveness treatments were found for the anatase crystal form, alone or mixed with rutile. Based on ultrastructural observations, we could hypothesise that the toxicity level of TiO 2 nanoparticles may depend on the cell ability to isolate nanoparticles in subcellular compartments, avoiding their interaction with organelles and/or metabolic processes. The results of the present work suggest reflections on the promising practice of soil amendments and on the use of nanomaterials and their safety for food plants and living organisms.