ACTA AGRONOMICA TOMUS 33. (A MTA AGRÁRTUDOMÁNYI KÖZLEMÉNYEI, 1984)

1984 / 1-2. szám - JUHÁSZ, O.-KOZMA, P.-POLYÁK, D.: Nitrogen status of grape-vines as reflected by the arginine content of the fruit

4 JUHÁSZ et al. KOZMA—POLYÁK (1973) studied the effects of 18 quantitative combina­tions of NPK on the productivity of vine and the chemical composition of leaf in the variety Olaszrizling using a culture pot system (KOZMA—POLYÁK 1968). On the basis of leaf analysis it was found that a rise in the N, Р and К levels of the soil increased the N, P and К contents of the leaves, while at certain P and К levels of the soil the nitrogen content in the leaves rose in response to increasing rates of N application. However, for a large number of samples the total nitrogen determina­tion is a relatively slow and time-consuming procedure. The determination of the nitrate nitrogen content of the vine petiole — also suggested for use as an indicator of the nitrogen status of vine (COOK 1961) — has similar limiting factors. A number of authors have studied the effect of nitrogen fertilization on the free amino acid content in various organs of the grape-vine (STOEV et al. 1966, DITTKICH et al. 1970, KLIEWER—COOK 1971, DORER—MALNARIC 1978). The authors give contradictory opinions on whether an unambiguous correla­tion exists between the nitrogen level of the soil and the free amino acid content of the grapes. The present paper aimed to examine under field conditions, and as a function of the course of ripening, whether changes in the nitrogen supply of the vine were reflected by the free amino acid and arginine contents of the fruit. Material and method The varieties Vitis vinifera L. cv. Rizlingszilváni, ev. Ezerjó, cv. Hárslevelű and cv. Olasz rizling were chosen for the experiments. Before the plantation of the vine cultivars (at Szigetcsép in 1966) 600 kg K20, 200 kg P206 and 100 kg N/ha were added to the sandy soil which was poor in humus. For Rizling­szilváni the experiment was carried out in a 5 X 200 m2 plot and from 1973 onwards the vines were supplied with additional potassium (200 g K20/M2) and nitrogen (100 g N/m2) (POLYÁK 1974). From the vines of untreated and treated cultivars samples were taken every two weeks from the middle of July until the vintage for a period of three years (1976 —1978). The culsters of grapes were washed with running water, then dried between layers of blotting paper. The juice was pressed out of the grapes using a fruit centrifuge and, after settling, was centrifuged for 10 minutes at 8000 rpm for further purification. The must samples were preserved with merthiolate applied at a concentration of 0.005% and were stored in air­tight 1-litre bottles at 0 °C until the chemical analysis began. 1. The total nitrogen content of the must samples was determined by Kjeldahl's method (BAILEY 1967). 2. Prior to the free amino acid analysis the proteins were removed from the samples by alcohol precipitation (KLIEWER 1968) and ultrafiltration (MOLNÁR 1972). Free amino acids from the samples were identified on a Fixion 50X8 layer containing cation exchange resin (DÉVÉNYI—ZOLTÁN 1970) according to the method of DÉVÉNYI et al. (1971). The chromatograms were evaluated by video-densitometry (DÉVÉNYI 1976). The quantitative evaluation of free amino acids was carried out with an automatic amino acid analyser. The analyses were performed in three replications and evaluated statistically. Acta Agronomica Academiae Scientiarum Hungaricae 33. 1984

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