Photosynthetic gas exchange of Tomato (Solanum lycopersicum) in Fluctuating Light Intensity

In order to achieve high yields and year-round production, tomato (Solanum lycopersicum) production in greenhouses requires an extensive light integral. In northern countries, such as the Netherlands, year-round tomato production is impossible without inputs of artificial lighting. To save energy and money, it is of interest to investigate strategies that rely on dynamically modulating the intensity of artificial lighting. This can be achieved by using LEDs which, unlike the currently used high-pressure sodium (HPS) lamps, can be switched on and off frequently without considerable loss of efficiency and potential lifetime. In order to assess the quantitative effect that light fluctuations have on tomato leaf photosynthesis, photosynthesis under non-steady state conditions must be characterised. In this poster, we present combined gas exchange and chlorophyll fluorescence measurements of tomato (cv. Cappricia) leaf photosynthesis during gain and loss of photosynthetic induction. Different kinetic phases can be distinguished that could reflect limitations by RuBP- regeneration capacity, Rubisco activation state and stomatal opening and closing. These processes are activated in light and deactivated in the dark; their activation takes less time than their deactivation. We intend to combine these measurements with enzyme activity assays at a range of combinations of CO2 concentration, temperature and vapour pressure deficit to assess dynamic behaviour of photosynthetic gas exchange under conditions relevant to current greenhouse cultivation. The results will be fed into a crop growth model to explore novel lighting strategies