Details

Autor(en) / Beteiligte

• Lea-Cox, J.D. (NASA, Kennedy Space Center, FL.)
• Syvertsen, J.P

Titel

Nitrogen uptake by Citrus leaves

Ist Teil von

• Journal of the American Society for Horticultural Science, 1995-05, Vol.120 (3), p.505-509

Erscheinungsjahr

1995

Link zum Volltext

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• We studied whether foliar-applied N uptake from a single application of low-biuret 15N-urea or K15NO3 to citrus leaves was affected by N source, leaf age, or whole-shoot N content. In a glasshouse experiment using potted 18-month-old Citrus paradisi (L.) 'Redblush' grapefruit trees grown in full sun, 2- and 6-month-old leaves on single shoots were dipped into a 11.2 g N/liter (1.776% atom excess 15N-urea) solution with 0.1% (v/v) Triton X-77. Two entire trees were harvested 1.5, 6, 24, and 48 hours after 15N application. Uptake of 15N per unit leaf area was 1.6- to 6-fold greater for 2-month-old leaves than for older leaves. The largest proportion of 15N remained in the treated leaf, although there was some acropetal movement to shoot tips. In a second experiment, 11.2 g N/liter (3.78% atom excess) urea-15N and 3.4 g N/liter (4.92% atom excess) 15KNO3 solutions of comparable osmotic potential were applied to 8-week-old leaves on 5-year-old 'Redblush' grapefruit field-grown trees of differing N status. Twenty-four percent of the applied 15N-urea was taken up after 1 hour and 54% after 48 hours. On average, only 3% and 8% of the K15NO3 was taken up after 1 and 48 hours, respectively. Urea increased leaf N concentration by 2.2 mg N/g or 7.5% of total leaf N after 48 hours compared to a 0.5 mg N/g increase (1.8% of total leaf N) for KNO3. Foliar uptake of 15N from urea, however, decreased (P 0.05) with increasing total shoot N content after 48 hours (r2