Spatiotemporal responses of wheat and pea roots to fluctuations in soil physical conditions

Sammanfattning: Penetration resistance and the oxygen level vary in the soil, and a root will face fluctuations in these physical properties during development. The aim of this study was to understand how pea (Pisum sativum L.) and wheat (Triticum aestivum L.) roots are affected in fluctua-tions of soil penetration resistance, the oxygen concentration in soil air and a combination of those. Root growth rate and root diameter were quantified during six days of growth in rhizoboxes. Root growth was recorded in intervals of 20 minutes using automated time-lapse imaging and the diameter was measured in images from a flatbed scanner. The roots were subjected to increased penetration resistance, hypoxic conditions or a combination of those two times during the growing period, with a release of the physical stress in between. Pea and wheat showed different but consistent patterns in root growth rate. Both pea and wheat responded with a decrease in root growth rate when subjected to physical stress. The difference was that pea had an increase, and recovered, in root growth rate upon the release of the stress, while wheat did not. Regarding the diameter, the results had an inconsistent pattern and did not fully correspond with previous studies. The ability of pea roots to recover in root growth rate upon release of physical stress implies that pea roots can reach deeper in the soil than wheat roots after facing fluctuations in pene-tration resistance and oxygen concentration.