The aim of this study was to provide new insights into how intraspecific variability in the response of key functional traits to drought dictates the interplay between gas-exchange parameters and the hydraulic architecture of European beech (Fagus sylvatica L.). Considering the relationships between hydraulic and leaf functional traits, we tested whether local adaptation to water stress occurs in this species. To address these objectives, we conducted a glasshouse experiment in which 2-year-old saplings from six beech populations were subjected to different watering treatments. These populations encompassed central and marginal areas of the range, with variation in macro- and microclimatic water availability. The results highlight subtle but significant differences among populations in their functional response to drought. Interpopulation differences in hydraulic traits suggest that vulnerability to cavitation is higher in populations with higher sensitivity to drought. However, there was no clear relationship between variables related to hydraulic efficiency, such as xylem-specific hydraulic conductivity or stomatal conductance, and those that reflect resistance to xylem cavitation (i.e., Ψ₁₂, the water potential corresponding to a 12% loss of stem hydraulic conductivity). The results suggest that while a trade-off between photosynthetic capacity at the leaf level and hydraulic function of xylem could be established across populations, it functions independently of the compromise between safety and efficiency of the hydraulic system with regard to water use at the interpopulation level.

This work outlines an experimental and theoretical investigation of the effect of molybdenum (Mo) doping on the oxygen vacancy formation and photocatalytic activity of TiO₂. Analytical techniques such as x-ray diffraction (XRD), Raman, x-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) were used to probe the anatase to rutile transition (ART), surface features and optical characteristics of Mo doped TiO₂ (Mo–TiO₂). XRD results showed that the ART was effectively impeded by 2 mol% Mo doping up to 750 °C, producing 67% anatase and 33% rutile. Moreover, the crystal growth of TiO₂ was affected by Mo doping via its interaction with oxygen vacancies and the Ti–O bond. The formation of Ti–O–Mo and Mo–Ti–O bonds were confirmed by XPS results. Phonon confinement, lattice strain and non-stoichiometric defects were validated through the Raman analysis. DFT results showed that, after substitutional doping of Mo at a Ti site in anatase, the Mo oxidation state is Mo⁶⁺ and empty Mo-s states emerge at the titania conduction band minimum. The empty Mo-d states overlap the anatase conduction band in the DOS plot. A large energy cost, comparable to that computed for pristine anatase, is required to reduce Mo–TiO₂ through oxygen vacancy formation. Mo⁵⁺ and Ti³⁺ are present after the oxygen vacancy formation and occupied states due to these reduced cations emerge in the energy gap of the titania host. PL studies revealed that the electron–hole recombination process in Mo–TiO₂ was exceptionally lower than that of TiO₂ anatase and rutile. This was ascribed to introduction of 5s gap states below the CB of TiO₂ by the Mo dopant. Moreover, the photo-generated charge carriers could easily be trapped and localised on the TiO₂ surface by Mo⁶⁺ and Mo⁵⁺ ions to improve the photocatalytic activity.

We investigated the hydraulic architecture of young olive trees either self-rooted or grafted on rootstocks with contrasting size-controlling potential. Clones of Olea europea L. (Olive) cv ‘Leccino’ inducing vigorous scion growth (Leccino ‘Minerva’, LM) or scion dwarfing (Leccino ‘Dwarf’, LD) were studied in different scion/rootstock combinations (LD, LM, LD/LD, LM/LM, LD/LM and LM/LD). Shoots growing on LD root systems developed about 50% less leaf surface area than shoots growing on LM root systems. Root systems accounted for 60–70% of plant hydraulic resistance (R), whereas hydraulic resistance of the graft union was negligible. Hydraulic conductance (K = 1/R) of LD root systems was up to 2.5 times less than that of LM root systems. Total leaf surface area (A_L) was closely and positively related to root hydraulic conductance so that whole-plant hydraulic conductance scaled by A_L did not differ between experimental groups. Accordingly, maximum transpiration rate and minimum leaf water potential did not differ significantly among experimental groups. We conclude that reduced root hydraulic conductance may explain rootstock-induced dwarfing in olive.