Abstract
Nitrogen (N) is essential for preserving green leaf area in wheat during the late growth phases and for postponing senescence. This research examined foliar N uptake, translocation, and redistribution in stay-green (YM66) and early-senescent (WM6) wheat plants treated with (15)N-labeled urea applied to flag leaves before and after anthesis. The redistribution of absorbed (15)N was observed during the grain-filling phase. Post-anthesis, YM66 exhibited a larger green leaf area and higher chlorophyll content compared to WM6 and demonstrated superior foliar (15)N uptake at both administration periods. At maturity, 51-56% of the absorbed (15)N before anthesis was detected in the grain, but 19-30% and 18-25% were retained in the leaves and stems, respectively. After post-anthesis treatment, 40-48.7% of absorbed (15)N was remobilized to the grain, whereas the majority remained in vegetative tissues. The data indicate that grain N in both genotypes primarily originates from N assimilated before anthesis, and that the stay-green genotype shows improved foliar N uptake and redistribution during grain filling. The results offer a physiological insight into N dynamics linked to differing senescence behaviors in wheat.