Fotosintesi dinamica: modellizzazione e valutazione tramite esperimenti a livello di foglia e popolamento

Photosynthesis has become a target to improve global food production since the increase in population is demanding an increase in plant productivity. Therefore, photosynthesis has been intensively studied in latest years, but mostly in the laboratories in steady state conditions, whereas plants are normally exposed to variable environmental conditions. Obtaining instantaneous gas exchange data in dynamic conditions has become fundamental as measurements at steady state and their related models may overestimate total carbon (C) plant uptake. The combination of mathematical models and experiments in dynamic conditions may enhance the understanding of the responses of plants to fluctuating environments and can be used to make predictions on how photosynthesis would respond to non-steady state conditions. In this thesis, I have studied dynamic photosynthesis under fluctuating light conditions. The studies have been mainly performed on two soybean varieties, a green wildtype Eiko and a chlorophyll deficient mutant MinnGold. Chlorophyll deficient plants have been proposed as a strategy to mitigate climate change since they can increase global surface albedo. Nevertheless, contrasting results in terms of yield have been reported when compared to their wildtypes. To unravel the different mechanisms of responses of these varieties we first built a growth chamber system able to perform long-term instantaneous gas exchange measurements in dynamic light conditions. The plants grown in these conditions have been analyzed both at leaf level (combining gas exchange and fluorescence data) and at canopy level. Furthermore, we developed a System Dynamics photosynthetic model of leaves exposed to fluctuations of light. The model explained well the photosynthetic responses of these two varieties to fluctuating and constant light conditions and allowed us to make relevant conclusions on the different dynamic responses of the two varieties. Finally, we also performed electrophysiological analysis under fluctuating light conditions to correlate voltage induced differences with photosynthetic responses. In conclusion, all the different projects had the common aim to unravel the responses of green and white leaves under fluctuating light conditions to fill the gap between controlled experimental data and canopy level field data.

Photosynthesis has become a target to improve global food production since the increase in population is demanding an increase in plant productivity. Therefore, photosynthesis has been intensively studied in latest years, but mostly in the laboratories in steady state conditions, whereas plants are normally exposed to variable environmental conditions. Obtaining instantaneous gas exchange data in dynamic conditions has become fundamental as measurements at steady state and their related models may overestimate total carbon (C) plant uptake. The combination of mathematical models and experiments in dynamic conditions may enhance the understanding of the responses of plants to fluctuating environments and can be used to make predictions on how photosynthesis would respond to non-steady state conditions. In this thesis, I have studied dynamic photosynthesis under fluctuating light conditions. The studies have been mainly performed on two soybean varieties, a green wildtype Eiko and a chlorophyll deficient mutant MinnGold. Chlorophyll deficient plants have been proposed as a strategy to mitigate climate change since they can increase global surface albedo. Nevertheless, contrasting results in terms of yield have been reported when compared to their wildtypes. To unravel the different mechanisms of responses of these varieties we first built a growth chamber system able to perform long-term instantaneous gas exchange measurements in dynamic light conditions. The plants grown in these conditions have been analyzed both at leaf level (combining gas exchange and fluorescence data) and at canopy level. Furthermore, we developed a System Dynamics photosynthetic model of leaves exposed to fluctuations of light. The model explained well the photosynthetic responses of these two varieties to fluctuating and constant light conditions and allowed us to make relevant conclusions on the different dynamic responses of the two varieties. Finally, we also performed electrophysiological analysis under fluctuating light conditions to correlate voltage induced differences with photosynthetic responses. In conclusion, all the different projects had the common aim to unravel the responses of green and white leaves under fluctuating light conditions to fill the gap between controlled experimental data and canopy level field data.