Co-Authors:
Klein, I., Institute of Horticulture, Volcani Center, Agricultural Research Organization, P.O.B. 6, Bet Dagan 50250, Israel
Zilkah, S., Institute of Horticulture, Volcani Center, Agricultural Research Organization, P.O.B. 6, Bet Dagan 50250, Israel
Abstract:
Solution retention by avocado (Persea americana cv. Fuerte) and apple (Mallus domestica Burkh. cv. Anna) leaves was measured by weight gain of detached leaves after dipping them in solutions of two surfactants and by analysis of various concentrations of urea retained at zero time on surfaces of attached leaves. Linear regression equations were calulated, relating leaf area and retention of solution. The slope of the equation represents the retention of solution on the leaf surface, and its intercept represents the value retained on the leaf margin. Solution retained on leaf surface was 2.5–2.6 and 5.4–6.4 mg/cm2 for ‘old’ avocado and apple leaves, respectively. Retention on the serrated leaf margin of the apple was greater than on the smooth margin of the avocado. The abaxial leaf surfaces retained approximately 62% and 83% of the total solution retained by the avocado and the apple leaves, respectively. The rate of urea uptake was proportional to the applied concentration and reached in avocado 65–85% within 2–5 days and over 90% in apple within 2 days. The rate of urea uptake by avocado was similar on ‘Young’ and ‘old’ leaves, similar from either Triton X-100 or L-77 surfactants, and similar through abaxial and adaxial surfaces. The nitrogen enrichment from foliar application of urea was related to retention and threshold of phytotoxicity rather than to rate of uptake. Older leaves of avocado showed some phytoxicity to 4% urea. Young leaves were damaged by repeated 2% application and flowers by 0.5–1.0%. The actual nitrogen enrichment in avocado, which could be predicted accurately from measurement of urea retention, was 43% following three successive applications of 3% urea in 12 days. © 1986, Taylor & Francis Group, LLC. All rights reserved.
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