The Rhizotron system



In special cassettes – the rhizotrons – root growth can be observed. A total of 360 of these cassettes provide insights into the "hidden half", the concealed underground part of the plants.

In the only five-centimeter-wide boxes, the roots grow along a transparent, yet light-shielded disc. The rhizotrons are automatically drawn in by two imaging towers throughout the entire growth period, and in these, the plants with their roots are not only photographed with state-of-the-art, high-resolution cameras but are also supplied with water and nutrients.

This allows researchers to gain important insights into what remains hidden in the soil: From the images taken daily, root characteristics such as length and thickness, number and arrangement of branches, as well as the orientation of the individual parts are derived.











































The container system

In up to 108 containers (each 1 m³ in volume), plants grow in stands like in small experimental plots in the open field. In this part of the PhenoSphere, the environmental conditions can be set to be particularly variable and extensive. This allows not only the regulation of soil temperature and water content in the vessels but also the variation of the composition and structure of the 1-meter-thick soil. The capture of plant characteristics is done from above using a PhenoCrane system with various cameras and sensors.

The layering of the soil in the containers corresponds to reality in the field – humus layer followed by loess, sand, and gravel, as well as drainage. The soil temperature can also be controlled, and natural temperature gradients can be created. Water supply is controlled through drip irrigation. Systems for capturing root growth in the containers are also planned, for example, through cameras in plastic tubes.

























































The “PhenoCrane”

The plant characteristics – the phenotype – are recorded in the container system with the “PhenoCrane”. This is an automated recording platform that can move in three axes and can approach any container. It is equipped with RGB cameras, a 3D scanner, and a hyperspectral scanner, as well as an imaging system for capturing the kinetics of chlorophyll fluorescence for dynamic measurement of photosynthesis.





































The lighting

With the lighting, various weather scenarios can be played out. Sunrises and sunsets, as well as the changing light conditions with clouds in the sky, can be simulated. A mix of discharge lamps, six different colored LED types (cool white, dark blue, blue, cyan, red, and deep red), as well as UV(A) tubes cover the light spectrum from 350 nm. The side walls are mirrored for even illumination of the compartments.











































The Wind

In the container system of the PhenoSphere, wind can also be simulated, triggering the associated movement of the plants. In each of the two compartments of the container system, there are ten fans, five on each side. They can blow air alternately in opposite directions.



















































Automation vs. Handwork

State-of-the-art camera systems, automated processes - and yet hard manual labor is also necessary for the operation of the PhenoSphere. For example, in the preparation of experiments in the rhizotrons. It takes more than a week to fill all 360 root boxes with soil. Each rhizotron requires ten kilograms. The soil must be filled into the narrow opening between the two plates. Once filled, a rhizotron weighs 20 kilograms. Up to 1.5 tons of soil is filled in multiple layers per container, which is equipped with soil sensors at different depths.

But manual labor is not only required when filling the rhizotrons and containers. Sowing or planting and harvesting are also carried out manually, specific to the experiment.

Scientific and technical staff from the working groups "Automated Plant Phenotyping", "Heterosis", "Technology" and "Experimental Field and Horticulture" work hand in hand here.





















Container System

In an initial extensive series of experiments in the container system, two different weather scenarios were simulated, showing that the growth and development progress of plants from very different corn varieties closely matches that of a nearby field, whose weather patterns were simulated in the PhenoSphere.

The findings obtained in the PhenoSphere are also significant for breeding progress, as demonstrated by the collaborative project AVATARS. At its core, it addresses the question of what makes rapeseed plants resilient to adverse weather events such as drought or heavy rainfall, which are becoming increasingly common in times of climate change.

Finally, the interactions between genetic material and environmental factors that are responsible for the production of good or poor quality seeds are being investigated. This primarily concerns their vitality and germination capacity, which are crucial for a good emergence of one of our most important crops.

In search of solutions, the project partners are taking new approaches. The goal is to process the enormous amounts of data using new techniques such as Virtual Reality (VR) and to spark interest in plant research among students with this new medium.