ABSORPTION, TRANSLOCATION, AND DISTRIBUTION FROM UREA APPLIED IN AUTUMN TO LEAVES OF YOUNG POTTED APPLE (MALUS DOMESTICA) TREES.

Authors: DONG, SHUFU - PACIFIC AGRI-FOOD RSRCH; CHENG, LAILIANG - DEPT OF HORT - CORNELL U; Scagel, Carolyn; FUCHIGAMI, LESLIE - DEPT OF HORT/OSU UNIV.

Submitted to: Tree Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2002
Publication Date: 11/15/2002
Citation: Dong, S., Cheng, L. Scagel, C.F., Fuchigami, L.H. Absorbtion, Tranlocation, And Distribution From Urea Applied In Autumn To Leaves Of Young Potted Apple (Malus docmestica) trees.

Interpretive Summary: Absorption, translocation and distribution of nitrogen (N) from foliar urea application in the autumn were studied with one-year-old potted Fuji/M26 apple trees. In early October, leaves on trees were painted with 15N enriched urea or with water as control. Four trees were harvested before the treatment and the baseline levels of total N and amino acids were determined. Four trees from each treatment were harvested at 2, 4, 7, 10, 15 and 20 days after foliar urea application. Total N, amino acids and 15N content of leaves, bark, xylem, shank, and roots were analyzed to monitor the urea-N uptake and mobilization. Uptake of urea-N from foliar application occurred primarily in the first two days after application. The average rate of absorption during these two days was 29.01mg.cm-2.d-1. Amino acids in leaves, bark and roots significantly increased immediately after foliar urea application in comparison to controls. The highest levels of amino acids in leaves and bark occurred four days after application, while the highest levels of amino acids in roots occurred 10 days after application. The total 15N content in leaves peaked 2 days after urea application then decreased, and 15N content in roots and bark increased throughout the experiment. Total 15N content in xylem and shank was very low. Leaves absorbed 34.6% of applied urea N and 63.6% of absorbed N was translocated out of leaves within 20 days after urea application. Our results suggest that urea-N was converted into amino acids in leaves after the foliar application in the autumn, and roots and bark were the main storage tissues of N from the foliar applied urea

Technical Abstract: Absorption, translocation and distribution of nitrogen (N) from foliar urea application in the autumn were studied with one-year-old potted Fuji/M26 apple trees. In early October, leaves on trees were painted with 3% 15N enriched urea (10% 15N atom abundance) or with water as control. No 15N solution was allowed to contact bark or soil during the painting process. Four trees were harvested before the treatment and the baseline levels of total N and amino acids were determined. Four trees from each treatment were harvested at 2, 4, 7, 10, 15 and 20 days after foliar urea application. Total N, amino acids and 15N content of leaves, bark, xylem, shank, and roots were analyzed to monitor the urea-N uptake and mobilization. Uptake of urea-N from foliar application occurred primarily in the first two days after application. The average rate of absorption during these two days was 29.01mg.cm-2.d-1. Amino acids in leaves, bark and droots significantly increased immediately after foliar urea application in comparison to controls. The highest levels of amino acids in leaves and bark occurred four days after application, while the highest levels of amino acids in roots occurred 10 days after application. The total 15N content in leaves peaked 2 days after urea application then decreased, and 15N content in roots and bark increased throughout the experiment. Total 15N content in xylem and shank was very low. Leaves absorbed 34.6% of applied urea N and 63.6% of absorbed N was translocated out of leaves within 20 days after urea application. Our results suggest that urea-N was converted into amino acids in leaves after the foliar application in the autumn, and roots and bark were the main storage tissues of N from the foliar applied urea.