Spring composition of xylem sap of apple [Malus] with respect to amino-nitrogen and mineral elements at two root temperatures
1981
Tromp, J. | Ovaa, J.C. (Research Station for Fruit Growing, Wilhelminadorp (Netherlands))
Apple rootstocks M.7 low in reserve nitrogen (N) were given N once early in the spring and were then kept in a greenhouse (18 deg C) at root temperatures of about 8 deg and 18 deg C. Xylem sap was sampled every 2-7 days for 2 months starting at bud-break, and was analysed for the minerals potassium (K), calcium (Ca), and magnesium (Mg) and for the amino compounds asparagine, aspartic acid, glutamine, glutamic acid, and arginine. For the mineral elements the importance decreased in the order K, Ca, Mg. The Ca/K ratio was mostly somewhat higher at 8 deg than at 18 deg. Asparagine plus aspartic acid were always the predominating amino compounds, but at the low root temperature the ratio of asparagine plus aspartic acid to glutamine and glutamic acid was clearly lower. Similarly, the arginine concentration was lowest at the root temperature of 8 deg.
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