Diurnal regulation of rice N uptake ability under interrupted N supply

Plants take up nitrogen (N) both day and night. The diurnal variation in N uptake results from interactions between aboveground and belowground tissues. We examined the long-term effects of interrupted N supply (day only or night only) under hydroponic conditions to test whether plant acclimatisation response to the interrupted N supply differs by day or night. Seedlings experienced 32 days under daytime-fed (DF), night-time-fed (NF), or continuous (CT) N supply. The root N uptake rate (NUR) differed between DF and NF from day 3 of treatment, after which NUR was significantly increased (by up to 82%) in DF and NF plants. The increased NUR during each half-day did not fully compensate for lost access to N during the other half-day, resulting in lower N accumulation by the end of the treatment. The reduction was smaller in DF plants than NF plants. The underlying mechanism of diurnal variation of N uptake is discussed in terms of transpiration demand and gene expression in roots.

Automated summary

Plants uptake nitrogen both day and night, but the acclimation response differs between interrupted nitrogen supply during the day and during the night. The increased nitrogen uptake rate during each feeding period does not fully compensate for the lost access to nitrogen, resulting in lower nitrogen accumulation by the end of the treatment. The reduction is smaller in plants with interrupted daytime nitrogen supply compared to plants with interrupted nighttime nitrogen supply.