Continuous sensing of water status in the root zone of wheat plants reveals features of circadian-dependent water uptake under mild water deficit

• Diurnal root water uptake oscillations can be followed with dielectric soil sensors • Low frequency watering in pots shows water uptake rates regulated by circadian rhythm • Plants under drought sustain day-to-day water uptake when water availability declines • Installing soil water sensors in the pot root zone is very valuable in stress studies Drought studies mostly rely on field capacity ( FC ) to maintain an imposed soil water deficit. However, they frequently overlook in situ water availability changes, hindering full understanding of soil water uptake by plants. Soil water potential ( Ψ S ) may cover the limitation of relying solely on a defined percentage of FC . We conducted a pot experiment in which wheat growth stage- and diurnal-dependent water dynamics was concurrently and continuously monitored using volumetric water content ( VWC ) and Ψ S sensors. Low-frequency fertigation in alternate days was applied to maintain mild water deficit (65% FC ) with a mean Ψ S value of −16.1 kPa. The combined installation of VWC and Ψ S sensors in the potted root zone disclosed fine features of diurnal oscillations in water uptake rate, endogenously controlled by the plant circadian rhythm, with a maximum rate ratio of five between daytime and nighttime. Flag leaves showed 20% decrease in both biomass and area, while proline content increased 60%. Osmotic adjustment favoured keeping daytime stomatal conductance, photosynthesis and WUE . At milk development, day-to-day root water uptake remained unchanged between two consecutive days despite lower water availability every second day. A decline in Ψ Leaf between consecutive days led to nitrate accumulation. At maturity, grain yield and plant biomass showed parallel reductions in ca. 40%, reflecting the difference in water use between water treatments. This approach connecting soil water availability with the plant’s circadian-dependent root water uptake using VWC and Ψ S sensors went beyond their conventional use and is recommended to explore plant adaptation to water deficit.