Enhancement of short-term nitrogen uptake by greenhouse roses under intermittent N-deprivation

A recirculating nutrient solution system was utilized to study the effect of intermittent N deprivation on N uptake by mature Royalty rose over the course of one flowering cycle.Plants received a nutrient solution lacking N for 4, 8 or 16 days, after which one containing NO₃–N (0.75 mM) was supplied for 4 days. N-deprivation resulted in a 2–3 fold increase in N uptake rate compared to control plants supplied continuously with N. The magnitude of this deprivation-enhanced N uptake was not affected by either the duration of N-deprivation or the plant developmental stage. Over the course of the flowering cycle, the total cumulative N uptake by the plants was 95, 66, and 44% of the control plants in the 4, 8 and 16-day deprivation treatments, respectively. A characteristic diurnal pattern of N uptake occurred in both N-starved and control plants. Uptake oscillated between minimum rates in the morning and maximum rates in the evening, the latter occurring 4–6 hr after the maximum rate of transpiration.