Time series soil-shoot-roots of two contrasting wheat root systems

Associations of plants species having contrasted root architecture can have a beneficial impact on the overall crop productivity. However, combining multiple plants species into a single crop creates practical challenges for the farmer. Another more practical solution is to combine cultivars of a same species with contrasted root systems. For instance, combining deep and shallow root systems may provide multiple advantages creating a more resilient and durable agro-ecosystem against water deficit. In the CROP project (Combining ROot contrasted Phenotypes for more resilient agro-ecosystem, funded by the German BMBF), we will focus on the plant species winter wheat (Triticum aestivum) for its economic importance and its susceptibility to future climate modifications. We evaluate if the two cultivars, UPQ12 and UPQ15 (developed at Hickey lab, University of Queensland, Australia; see for details (Rambla et al., 2022)), having different root insertion angle values (110 and 66°, respectively), lead to shallower and deeper root systems, respectively. These cultivars were obtained from the Hickey lab (University of Queensland, Australia).
These two contrasted wheat root cultivars are studied in this experiment. Thirteen PVC columns (diameter = 8 cm, height = 45cm) were filled with silty loam soil from one testing site of the Research Center Julich, located in Selhausen (50.8659 N, 6.4471 E). The columns received two seeds each and were afterwards installed in a climate chamber (20°C day, 18°C night, 50% RH, 1000 μmol m−2s−1 of PAR from 6am to 8pm). The mean initial soil gravimetric water content (θsoil) was of 0.40 cm3 cm−3. Water was added twice a week to keep the θsoil value between 0.30 cm3 cm−3 to 0.44 cm3 cm−3. Fertiliser (7% Nitrate, 19% Ammonium) was added at 6 and 34 days after sowing (stage two leaves and tillering, respectively) in liquid solution supplied at a rate of 3 kg m−2. At 28, 35, 42 and 49 Days after Sowing three of the soil columns were randomly selected to extract the root systems from the soil columns segmented in 5 layers of 9cm. Soil samples from each layers were sampled and stored in a freezer at −20◦C. Shoot parts of the plant growing on these columns were also sampled at the same time. After sampling, stems and leaves were stored in a freezer at −20◦C The roots were then stored in 30% Ethanol solutions to be scanned (Expression 10000XL Model J181A; EPSON, Japan). The images were analyzed using the WinRhizo™ (Regent Instruments Inc., Quebec, Canada) software package for the determination of the total root length, surface and volume in each soil layers and per 100 μm diameter class of these soil layers. The Total Nitrogen content (TN) and Non Purgeable Organic Carbon content (NPOC) are respectively assed with the standard protocoles (soil extraction then analysed with Shimadzu© TOC 5050A).