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
2 5 NITROGEN STATUS OF GRAPE-VINES Results 1. Changes in the total nitrogen content Changes in the total quantity of nitrogen during maturation showed nearly the same trend in all three years and in each variety examined. Rizlingszilváni contained the largest and Olasz rizling and Hárslevelű the smallest quantities of total nitrogen (37—47 mg/100 ml and 27—33 mg/100 ml, respectively) of all the vine varieties examined. In the growth period of the green fruit the nitrogen content of the grape juice increased, reaching a concentration of 44.95 mg/100 ml in 1976, 48.03 mg/100 ml in 1977 and 41.63 mg/100 ml in 1978 when averaged over the varieties. On colouring the grapes lost some of their total nitrogen content, which then either rose again or did not substantially change until the completion of ripening. This fluctuating change in the total amount of nitrogen is caused by the increase or decrease in inorganic (ammonia, ammonium, nitrate) and organic (amino acids, peptides) nitrogen compounds translocated into the green fruit during maturation. With regard to the effect of nitrogen fertilizer, there was no great difference in the total nitrogen content of the must of untreated and treated Fig. 1. Changes in the total free amino acid content of must samples in various untreated and treated vine varieties during maturation (1977) Acta Agronomica Academiae Scieniiarum Hungaricae 33, 1984