Evaluation of the photosynthetic efficiency of sweet sorghum under drought and cold conditions

Sweet sorghum, a C4 crop of tropical origin, is gaining momentum as a multipurpose feedstock to tackle the growing environmental, food and energy security demands. Under temperate climates sweet sorghum is considered as a potential bioethanol feedstock, however, being a relatively new crop in such areas its physiological and metabolic adaptability has to be evaluated; especially to the more frequent and severe drought spells occurring throughout the growing season and to the cold temperatures during the establishment period of the crop. The objective of this thesis was to evaluate some adaptive photosynthetic traits of sweet sorghum to drought and cold stress, both under field and controlled conditions. To meet such goal, a series of experiments were carried out. A new cold-tolerant sweet sorghum genotype was sown in rhizotrons of 1 m3 in order to evaluate its tolerance to progressive drought until plant death at young and mature stages. Young plants were able to retain high photosynthetic rate for 10 days longer than mature plants. Such response was associated to the efficient PSII down-regulation capacity mediated by light energy dissipation, closure of reaction centers (JIP-test parameters), and accumulation of glucose and sucrose. On the other hand, when sweet sorghum plants went into blooming stage, neither energy dissipation nor sugar accumulation counteracted the negative effect of drought. Two hybrids with contrastable cold tolerance, selected from an early sowing field trial were subjected to chilling temperatures under controlled growth conditions to evaluate in deep their physiological and metabolic cold adaptation mechanisms. The hybrid which poorly performed under field conditions (ICSSH31), showed earlier metabolic changes (Chl a + b, xanthophyll cycle) and greater inhibition of enzymatic activity (Rubisco and PEPcase activity) than the cold tolerant hybrid (Bulldozer). Important insights on the potential adaptability of sweet sorghum to temperate climates are given.

Experiments on Pro-Sociality and Environmental Issues

The thesis comprises three essays that use experimental methods, one about other-regarding motivations in economic behavior and the others on pro-social behavior in two environmental economics problems. The first chapter studies how the expectations of the others and the concern to maintain a balance between effort exerted and rewards obtained interact in shaping the behavior in a modified dictator game. We find that dictators condition their choices on recipients' expectations only when there is a high probability that the the recipient will not be compensated for her effort. Otherwise, dictators tend to balance the efforts and rewards of the recipients, irrespective of the recipients' expectations. In the second chapter, I investigate the problem of local opposition to large public projects (e.g. landfills, incinerators, etc.). In particular, the experiment shows how the uncertainty about the project's quality makes the community living in the host site skeptical about the project. I also test whether side-transfers and costly information disclosure can help to increase the efficiency. Both tools succesfully make the host more willing to accept the project, but they lead to the realization of different types of projects. The last chapter is an experiment on climate negotiations. To avoid the global warming, countries are called to cooperate in the abatement of their emissions. We study whether the dynamic aspect of the climate change makes cooperation across countries behaviorally more difficult. We also consider inequality across countries as a possible factor that hinders international cooperation.

Energy-efficient Communication and Estimation in Wireless Sensor Networks

This thesis focuses on the energy efficiency in wireless networks under the transmission and information diffusion points of view. In particular, on one hand, the communication efficiency is investigated, attempting to reduce the consumption during transmissions, while on the other hand the energy efficiency of the procedures required to distribute the information among wireless nodes in complex networks is taken into account. For what concerns energy efficient communications, an innovative transmission scheme reusing source of opportunity signals is introduced. This kind of signals has never been previously studied in literature for communication purposes. The scope is to provide a way for transmitting information with energy consumption close to zero. On the theoretical side, starting from a general communication channel model subject to a limited input amplitude, the theme of low power transmission signals is tackled under the perspective of stating sufficient conditions for the capacity achieving input distribution to be discrete. Finally, the focus is shifted towards the design of energy efficient algorithms for the diffusion of information. In particular, the endeavours are aimed at solving an estimation problem distributed over a wireless sensor network. The proposed solutions are deeply analyzed both to ensure their energy efficiency and to guarantee their robustness against losses during the diffusion of information (against information diffusion truncation more in general).