Siegfried Jahnke

Learn More
Unravelling the factors determining the allocation of carbon to various plant organs is one of the great challenges of modern plant biology. Studying allocation under close to natural conditions requires non-invasive methods, which are now becoming available for measuring plants on a par with those developed for humans. By combining magnetic resonance(More)
Roots are vital to plants for soil exploration and uptake of water and nutrients. Root performance is critical for growth and yield of plants, in particular when resources are limited. Since roots develop in strong interaction with the soil matrix, tools are required that can visualize and quantify root growth in opaque soil at best in 3D. Two modalities(More)
Both structural and functional properties of belowground plant organs are critical for the development and yield of plants but, compared to the shoot, much more difficult to observe due to soil opacity. Many processes concerning the belowground plant performance are not fully understood, in particular spatial and temporal dynamics and their interrelation(More)
Diffusion of CO2 inside leaves is generally regarded to be from the substomatal cavities to the assimilating tissues, i.e. in the vertical direction of the leaf blades. However, lateral gas diffusion within intercellular air spaces may be much more effective than hitherto considered. In a previous work it was demonstrated that, when 'clamp-on' leaf chambers(More)
Gas exchange is generally regarded to occur between the leaf interior and ambient air, i.e. in vertical (anticlinal) directions of leaf blades. However, inside homobaric leaves, gas movement occurs also in lateral directions. The aim of the present study was to ascertain whether lateral CO2 diffusion affects leaf photosynthesis when illuminated leaves are(More)
Carotenoid turnover was investigated in mature leaves of Arabidopsis (Arabidopsis thaliana) by 14CO2 pulse-chase labeling under control-light (CL; 130 mmol photons m s) and high-light (HL; 1,000 mmol photons m s) conditions. Following a 30-min 14CO2 administration, photosynthetically fixed C was quickly incorporated in b-carotene (b-C) and chlorophyll a(More)
Noninvasive imaging sensors and computer vision approaches are key technologies to quantify plant structure, physiological status, and performance. Today, imaging sensors exploit a wide range of the electromagnetic spectrum, and they can be deployed to measure a growing number of traits, also in heterogenic environments. Recent advances include the(More)
Non-invasive and rapid determination of plant biomass would be beneficial for a number of research aims. Here, we present a novel device to non-invasively determine plant water content as a proxy for plant biomass. It is based on changes of dielectric properties inside a microwave cavity resonator induced by inserted plant material. The water content of(More)
We demonstrate a dedicated design of microwave cavity resonators mainly developed for high-throughput phenotyping systems of plants. Based on simulations, the field distribution of the TM010 mode inside the resonators was modified to achieve an electric field, which is homogeneously distributed in the horizontal plane and oriented in the vertical direction.(More)