In this research I'm investigating how the photosynthesis and transpiration of plants changes depending on the CO2 level under which plants have grown up. I think this question is very important to answer because plants play and important role in hydrological cycle and the carbon cycle. Plants influence these cycles at a global scale because they assimilate carbon by photosynthesis and simultaneously transpire water through microscopically small stomatal pores in their leaves (see the image below). This role becomes even more intriguing when you consider that the current rise in atmospheric CO2 concentrations has a direct effect on the transpiration and photosynthesis of plants. The extent to which plants influence global fluxes of water and carbon are recognized as key uncertainties in climate change predictions.
Short-term versus long-term responses
Plants respond to the daily changes in light, temperature and moisture by dynamically opening and closing their stomata. These responses allow plants to regulate the fluxes of water and CO2 through their leaves. For example, many plants close their stomata during drought to prevent untimely desiccation. Plants also adjust the number and size of the stomata on their leaves to CO2 concentrations under which they grow up. However, we lack clear understanding of the coordination between these short-term and long-term responses and how they may influence photosynthesis and transpiration in future climates with elevated CO2.
Drought stress and rising CO2
In my latest experiment I'm investigating how plants cope with drought stress under different CO2 levels. My expectation is that plants will take more risk in terms of drying out under low CO2 and less risk under higher CO2.
For this experiment I'm growing two genotypes of the plant Bittersweet (Solanum dulcamara) under three different CO2 levels, representing past, current and future predicted CO2 levels. For this experiment I use special growth chambers in which CO2 concentrations can be controlled. The difference between plants grown at low and high CO2 concentrations is visible in the image above.
On the plants we perform detailed measurements of leaf gas exchange and the opening state of the stomata. Soil water status is continuously measured with special sensors developed by researchers from Wageningen University. The leaves will be sampled for detailed analysis of their anatomical characteristics after the experiment. The combination of these measurements will learn us more about how the ongoing rise in atmospheric CO2 concentrations influences plant responses to drought.