The research projects coordinated by Prof. Nardini span from basic understanding of plant physiological processes related to water uptake and transport, to applied topics in the fields of forest ecology. Functional traits assuring efficiency and safety to plant water transport systems are studied with a combination of biophysical, molecular and ecological tools. Controlled experiments and field surveys are used to investigate how plant water balance is affected by different environmental parameters, and how plants cope with reductions in water availability.
Mechanisms of drought-induced tree mortality: from physiological bases to ecological consequences
Ongoing climate warming is leading to increased frequency and intensity of heat and drought waves in several areas of the globe. One of the consequences of these extreme climatic events is tree die-off in forests. Tree mortality implies a reduction of net primary productivity and a conversion of forest ecosystems from net carbon sinks to net carbon sources, with impacts on climate at a regional scale, modifications of competitive processes, and consequences on ecosystem biodiversity and stability. 
We currently investigate the physiological mechanisms linking drought to tree die-off. Prolonged/intense drought causes a progressive decrease of plant water potential leading to xylem embolism and blockage of root-to-leaf water transport, plant desiccation and death ('hydraulic failure'). On the other hand, stomatal closure to prevent xylem embolism causes a halt of photosynthesis leading to progressive depletions of reserves on non-structural carbohydrates and impairment of plant metabolism ('carbon starvation'). We seek for connections between plant water and carbon metabolism, and in particular to the role of carbon starvation into the impairment of the plants' ability to recover from drought stress via energy-dependent xylem refilling. We are currently investigating the species-specific roles of hydraulic failure and carbon starvation in tree decline and recovery capability, as a function of stress intensity and duration. We also aim at quantifying the species-specific critical stress levels inducing increased mortality risk and eventual increase of vulnerability to successive drought events.
The hydraulic engineering of the Angiosperm leaf
The intricate and delicate network of leaf veins is a wonderful example of evolutionary engineering, and leaf vasculature has always fascinated scientists, as well as artists. From a functional viewpoint, this complex plumbing system is designed to efficiently deliver water to photosynthetic cells, thus replacing the huge amount of water that plants lose to the atmosphere during the transpiration process. In fact, large water losses are unavoidably coupled to stomatal opening and CO2 diffusion from the atmosphere into the leaf interior, which is crucial to fuel photosynthetic processes.
We investigate the structure/function relationships between the architecture of the vein system and leaf hydraulics. We are particularly interested in the responses of leaf hydraulic conductance to different environmental factors, and specifically to drought stress. We analyze the relationships between leaf hydraulic efficiency and safety, investigating basic mechanisms underlying the loss of leaf hydraulic conductance under stress conditions, and the processes allowing eventual recovery upon stress release. We are also very interested in the trade-offs between leaf construction costs, hydraulic safety and efficiency, and the ecological consequences in terms of plants competitiveness and distribution in different habitats, ranging from local to regional and global spatial scales.
We use anatomical, biophysical and molecular tools to investigate leaf hydraulics, and we also apply basic knowledge to the development of screening criteria to identify drought-resistant genotypes of different woody crops.
Functional and mechanistic traits promoting invasion by alien plants
The invasion of natural habitats by alien plants is one of the most important threats to biodiversity conservation and ecosystem stability at regional and global scales, and is of particular concern because it can alter several biogeochemical and hydrological processes of fundamental importance. 
Our understanding of the fundamental ecophysiological mechanisms promoting invasion by alien species is still limited. Despite large efforts devoted to identify functional traits related to invasiveness of alien plants, most studies dealing with this topic have focused on traits relatively easy to measure, but often without clear mechanistic linkages with plant physiological performance. However, ‘mechanistic’ traits clearly associated with physiological processes hold better promise to provide meaningful information on fitness and performance of invasive plants compared to native ones. Among these, traits related to plant water relations and hydraulics are very interesting for studies focused on invasive plants, because the efficiency of root-to-leaf water transport is one of the factors most closely correlated to leaf gas exchange rates, maximum net photosynthesis, competition for water and relative growth rates.
We are currently measuring several mechanistic traits in alien plants, comparing these values with those found in native and outcompeted species. We aim to identify the set of mechanistic traits promoting invasion by alien plants in different native habitats.
