Valutazione dell'evoluzione della componente fenolica di Olea Europaea durante l'intero ciclo di maturazione del frutto

This PhD thesis is related to the evolution of phenolic composition of olive fruit to demonstrate the relationship between the raw material sources and the compounds responsible for the healthy and sensory properties of virgin olive oil, and to investigate the mechanisms involved in the synthesis and/or in the degradation of the phenolic fraction. On the basis of phenolic compositions of twelve Italian olive cultivars (Bianchella, Canino, Coratina, Dolce di Andria, Dritta, Frantoio, Leccino, Moraiolo, Nocellara del Belice, Nocellara Etnea, Rosciola and Tendellone) analysed, some significative qualitative and quantitative differences were observed. The main results were utilized, during the following analysis of the genetic expressions of olive cultivars, to determine the genes directly involved in the synthesis and the degradation of the phenolic fraction during the different fruit ripening stages. On the basis of the results about the evolution of phenolic compounds of olive drupes a research program aimed to identify the genes involved in the biosynthesis pathways of fruit secoiridoids, was developed by the CNR-Institute of Plant Genetics, Perugia.

Parameter estimation in a growth model for a biological population

The motivating problem concerns the estimation of the growth curve of solitary corals that follow the nonlinear Von Bertalanffy Growth Function (VBGF). The most common parameterization of the VBGF for corals is based on two parameters: the ultimate length L∞ and the growth rate k. One aim was to find a more reliable method for estimating these parameters, which can capture the influence of environmental covariates. The main issue with current methods is that they force the linearization of VBGF and neglect intra-individual variability. The idea was to use the hierarchical nonlinear model which has the appealing features of taking into account the influence of collection sites, possible intra-site measurement correlation and variance heterogeneity, and that can handle the influence of environmental factors and all the reliable information that might influence coral growth. This method was used on two databases of different solitary corals i.e. Balanophyllia europaea and Leptopsammia pruvoti, collected in six different sites in different environmental conditions, which introduced a decisive improvement in the results. Nevertheless, the theory of the energy balance in growth ascertains the linear correlation of the two parameters and the independence of the ultimate length L∞ from the influence of environmental covariates, so a further aim of the thesis was to propose a new parameterization based on the ultimate length and parameter c which explicitly describes the part of growth ascribable to site-specific conditions such as environmental factors. We explored the possibility of estimating these parameters characterizing the VBGF new parameterization via the nonlinear hierarchical model. Again there was a general improvement with respect to traditional methods. The results of the two parameterizations were similar, although a very slight improvement was observed in the new one. This is, nevertheless, more suitable from a theoretical point of view when considering environmental covariates.

Effects of temperature and acidity on Mediterranean benthic calcifiers, in the face of globale climate change

The Mediterranean Sea is expected to react faster to global change compared to the ocean and is already showing more pronounced warming and acidification rates. A study performed along the Italian western coast showed that porosity of the skeleton increases with temperature in the zooxanthellate (i.e. symbiotic with unicellular algae named zooxanthellae) solitary scleractinian Balanophyllia europaea while it does not vary with temperature in the solitary non-zooxanthellate Leptopsammia pruvoti. These results were confirmed by another study that indicated that the increase in porosity was accompanied by an increase of the fraction of the largest pores in the pore-space, perhaps due to an inhibition of the photosynthetic process at elevated temperatures, causing an attenuation of calcification. B. europaea, L. pruvoti and the colonial non-zooxanthellate Astroides calycularis, transplanted along a natural pH gradient, showed that high temperature exacerbated the negative effect of lowered pH on their mortality rates. The growth of the zooxanthellate species did not react to reduced pH, while the growth of the two non-zooxanthellate species was negatively affected. Reduced abundance of naturally occurring B. europaea, a mollusk, a calcifying and a non-calcifying macroalgae were observed along the gradient while no variation was seen in the abundance of a calcifying green alga. With decreasing pH, the mineralogy of the coral and mollusk did not change, while the two calcifying algae decreased the content of aragonite in favor of the less soluble calcium sulphates and whewellite (calcium oxalate), possibly as a mechanism of phenotypic plasticity. Increased values of porosity and macroporosity with CO2 were observed in B. europaea specimens, indicating reduces the resistance of its skeletons to mechanical stresses with increasing acidity. These findings, added to the negative effect of temperature on various biological parameters, generate concern on the sensitivity of this zooxanthellate species to the envisaged global climate change scenarios.

Reproduction of Mediterranean zooxanthellate and azooxanthellate scleractinian corals along environmental gradients

Despite extensive studies focus mainly on sexual reproductive characteristics in tropical scleractinian species, there is limited knowledge on temperate regions. The Mediterranean is a biodiversity hotspot under intense pressure from anthropogenic impacts. Climatic models further predict that the Mediterranean basin will be one of the most impacted regions by the ongoing warming trend. This makes it a potential model of more global patterns to occur in the world’s marine biota, and a natural focus of interest for research on climate. The present research contributed to increase data on reproductive modes and sexuality of temperate scleractinian corals, highlighting their developmental plasticity, showing different forms of propagation and different responses to environmental change. For the first time, sexuality and reproductive mode in Caryophyllia inornata were determined. An unusual embryogenesis without a clear seasonal pattern was observed, suggesting the possibility of an asexual origin. Sexual reproduction of Astroides calycularis was governed by annual changes in seawater temperature, as observed for other Mediterranean dendrophylliids. Defining the reproductive biology of these species is the starting point for studying their potential response to variations of environmental parameters, on a global climate change context. The results on the influence of temperature on reproductive output of the zooxanthellate (symbiosis with unicellular algae) Balanophyllia europaea and the non-zooxanthellate Leptopsammia pruvoti suggest that the latter may be quite tolerant to temperature increase, since the zooxanthellate species resulted less efficient at warm temperatures. A possible explanation could be related to their different trophic system. In B. europaea thermal tolerance is primarily governed by the symbiotic algae, making it more sensitive to temperature changes. On the contrary, the absence of symbionts in L. pruvoti might make it more resistant to temperature. In a progressively warming Mediterranean, the efficiency on scleractinian reproduction could be influenced in different ways, reflecting their extraordinary adaptability.