Tb and θ50 values facilitated model development of the thermal niche for in situ germination of R. persicifolia. These experimental approaches may be applied to model the natural regeneration patterns of other species growing on Mediterranean mountain waterways and of physiologically dormant species, with overwintering cold stratification requirement and spring germination.

Morphophysiological dormancy was investigated in seeds of Ribes multiflorum Kit ex Roem et Schult. ssp. sandalioticum Arrigoni, a rare mountain species endemic to Sardinia (Italy). There were no differences in imbibition rates between intact and scarified seeds, suggesting a lack of physical dormancy, while methylene blue solution (0.5%) highlighted a preferential pathway for solution entrance through the raphe. Embryos were small at seed dispersal, with an initial embryo:seed ratio (E:S) of ca. 0.2 (embryo length, ca. 0.5 mm), whereas the critical E:S ratio for germination was three times longer (ca. 0.6). Gibberellic acid (GA(3), 250 mg · l(-1)) and warm stratification (25 °C for 3 months) followed by low temperature (<15 °C) enhanced embryo growth rate (maximum of ca. 0.04 mm · day(-1) at 10 °C) and subsequent seed germination (radicle emergence; ca. 80% at 10 °C). Low germination occurred at warmer temperatures, and cold stratification (5 °C for 3 months) induced secondary dormancy. After radicle emergence, epicotyl emergence was delayed for ca. 2 months for seeds from three different populations. Mean time of epicotyl emergence was affected by GA(3) . Seeds of this species showed non-deep simple (root) - non-deep simple (epicotyl) morphophysiological dormancy, highlighting a high synchronisation with Mediterranean seasonality in all the investigated populations.

No abstract

Sardinia was known as an important mine pole in Europe during his history. Still after decades from mine closure, 75.000.000 m 3 of mine waste, rich in heavy metals, were left abandoned causing a huge environmental legacy on the mine district area. Consequently, cost effective remediation is required. In this frame, phytoremediation is considered a feasible candidate. This research was focused on Helichrysum microphyllum subsp. tyrrhenicum, which is pioneer in xeric soils with low-functions, like mine tailings. The aim of this study was to evaluate its ability to extract heavy metals from mine soils and accumulate them in plant tissues and its suitability for phytostabilization. Sundry samples of soil, roots and epigean organ were collected through field sampling and analysed in order to obtain metals concentration and mineralogical characteristics. Our results indicate that this species tolerates high concentration of zinc, lead and cadmium, behaving as a species suitable for phytostabilization.

Environmental contamination due to human activities is a worldwide problem that has led to the development of different remediation techniques, including biotechnological approaches such as phytoextraction and phytostabilization. These techniques take advantage of pioneer plants that naturally develop tolerance mechanisms to survive in extreme environments. A multi-technique and multi-disciplinary approach was applied for the investigation of Helichrysum microphyllum subsp. tyrrhenicum samples, bulk soil, and rhizospheres collected from a metal-extreme environment (Zn-Pb mine of Campo Pisano, SW Sardinia, Italy). Zinc, Pb, and Cd are the most abundant metals, with Zn attaining 3 w/w% in the rhizosphere solid materials, inducing oxidative stress in the roots as revealed by infrared microspectroscopy (IR). X-ray diffraction (XRD), scanning electron microscopy (SEM), and chemical analysis coupled with synchrotron radiation-based (SR) techniques demonstrate that quartz, dolomite, and weddellite biominerals precipitate in roots, stems, and leaves, likely as a response to environmental stress. In the rhizosphere, Zn chemical speciation is mainly related to the Zn ore minerals (smithsonite and hydrozincite) whereas, in plant tissues, Zn is primarily bound to organic compounds such as malate, cysteine, and histidine molecules that act as metal binders and, eventually, detoxification agents for the Zn excess. These findings suggest that H. microphyllum subsp. tyrrhenicum has developed its own adaptation strategy to survive in polluted substrates, making it a potential candidate for phytostabilization aimed at mitigating the dispersion of metals in the surrounding areas.