Study of the absorption and distribution characteristics of 15N-urea applied to leaves of nectarine planted in greenhouse

This research was carried out in a greenhouse in 2005.Mature trees of Zaohongzhu nectarine/wild peach were fertilized in spring with 15N-labelled urea via leaf,and the nitrogen absorption and distribution characteristics were studied using isotope 15N.The uptake of 15N by leaves mainly occurred during the first 6 hours following application of urea.The mean rate of absorption during this period was 0.204 mg/(gh).The content of 15N in leaves peaked 24 hours after urea application and then decreased,whereas 15N content in younger leaves and new shoots peaked 48 hours and 15N content in older leaves was very low. Moreover,15N content in different tissues followed this order: treated leaves younger leaves new shoots older leaves.At the end of the experiment(168h),however,mobility of urea-derived N varied with different organs: treated leavesyounger leavesnew shootsolder leaves.The result suggested that the distribution of absorbed N was mainly translocated to the younger leaves and new shoots.Thus foliar application of N accelerated growth and formation of newly organs.15N absorption was greatest in leaves with both abaxial and adaxial leaf surface treatments,followed by abaxial leaf surface treatment and adaxial leaf surface treatment.Applying foliar 15N-urea during morning resulted in greater absorption of 15N than in the afternoon or at noon.It is clear that mature trees of Zaohongzhu nectarine could rapidly absorb urea applied to leaves and maximum N absorption from foliar urea sprayed to both abaxial and adaxial leaf surfaces in the morning.