Indici Plant-Based per la determinazione ed il monitoraggio dello stato funzionale delle piante in un contesto di cambiamento climatico

Climate change is increasingly exposing perennial fruit crops to water scarcity, recurrent heat waves, and high atmospheric evaporative demand, particularly in Mediterranean environments. Under these conditions, the sustainability of orchard systems depends both on irrigation strategies capable of responding to plant water status and on the availability of plant material able to maintain functional performance under combined water and thermal stress. Although these objectives address distinct agronomic and biological questions, they rely on a common physiological basis. This PhD thesis investigates plant functional status as an integrative framework for interpreting plant responses to abiotic stress. The work focuses, in parallel, on the development of plant-based approaches for irrigation monitoring and on the phenotypic characterization of genotype-dependent responses to water limitation. A plant-centred perspective is adopted, in which stomatal conductance, photosynthetic activity, stem water potential, canopy thermal behaviour—expressed as the leaf-to-air temperature difference (ΔT)—indices derived from chlorophyll fluorescence, and an index linked with carboxylation (PKO/KC) are considered interconnected descriptors of plant functioning under stress conditions. The thesis is structured as an article-based dissertation. A comprehensive review defines the conceptual background, examining the limitations of soil- and climate-based irrigation approaches and the methodological constraints associated with the use of plant-based indicators relying on fixed thresholds. Within this framework, plant functional status is defined as a dynamic and context-dependent property emerging from the coordination among multiple physiological processes, rather than as a single measurable trait. A field experiment on almond under regulated deficit irrigation evaluates plant-based indicators and indices as tools to diagnose changes in plant functional status in response to progressive water limitation under orchard field conditions. A comparative field study on grapevine applies the same functional framework to a second perennial crop, supporting its applicability across species. In parallel, a controlled phenotyping experiment on almond is conducted within a dedicated phenotyping platform to assess genotype-dependent variability in functional responses to water stress. The study includes the cultivars Filippo Ceo, Ferragnès, Texas, and Tuono, allowing the comparison of contrasting physiological strategies under controlled environmental conditions. Overall, the thesis shows that plant-based indices, when interpreted within an integrative and context-aware physiological framework, can support both irrigation monitoring and the functional characterization of plant material under climate change. By combining field experimentation, controlled phenotyping, and conceptual analysis, the work contributes to the development of plant-centred approaches for the management of perennial fruit crops in increasingly water-limited environments.