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Composition of tomatoes and tomato products in antioxidants (WG1) page 44
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fruits (-10% out of 300 mg/kg fresh matter); high nitrate supply was associated with high fruit
production, but with low ascorbic acid content; on the contrary, the nitrate supply after the
onset of ripening influenced neither fruit production nor acid ascorbic content (Somers et al,
1951). Working on cvs. Marglobe and Stokesdale, Murneek et al.(1954) observed that with
increasing nitrogen supply there was a decrease in vitamin C concentration in the fruit and
that differences due to nitrogen supply may be slight when the tomato crop is grown under a
prevailing low light intensity but considerable in the presence of bright sunlight (250 to 320
mg/kg in ripe fruit). In field and pot trials established by Neubert (1959), high N-applications
(160 or 320 kg N/ha) were followed by a decrease of vitamin C content in ripe fruits (up to -
25 or -30% according to the seasons), bound to the existence of monosaccharides which were
also decreased, due to a concurrency coming from the increased synthesis of N-compounds
and organic acids, in spite of an enlarged surface of assimilation. Dastane et al.(1963)
obtained tomatoes (var. Pusa Ruby) from field experiments in winter and summer on a sandy
loam medium fertility soil; fruit vitamin C content was not influenced by increasing nitrogen
supply (45 to 135 kg N/ha) with a tendency to decreasing in winter (21.5 mg/100ml juice
against 24 in summer). Kaniszewski et al.(1987) demonstrated on cv. New Yorker cultivated
in field that increasing nitrogen fertilization (preplant and/or top dressing at the rates 37.5, 75,
75 + 75, 150, 150 + 75, 225 and 150 + 150 kg N ha -1 ) reduced fruit vitamin C concentration
(3136, 2723, 2494, 2218, 2169, 2068, 1786 mg/kg dry matter respectively) while yield
increased. According to Müller and Hippe (1987), in tomato fruits the vitamin C content
(variations from 300 to 450mg/kg fresh matter) was inversely correlated with the N supply
(pot culture in a mixture of sand and soil) and there was only very small amounts of
dehydroascorbic acid present. Montagu et al.(1990) cultivated tomatoes in pots filled with
peaty loam soil. Various forms (nitrate, ammonium, compost, blood and bone) of nitrogen
were applied at four rates (0, 150, 300, 600 kg N/ha). Fruit vitamin C content decreased
almost linearly from about 320 mg/kg fresh matter to about 230-250 mg/kg fresh matter when
N applied increased from 0 to 600 kg/ha. A general review from Mozafar (1993) reports that
increased application of nitrogen fertilizers has been shown to decrease the content of
ascorbic acid in many plants; there are also reports indicating that nitrogen fertilizer may have
no effect or may even increase the content of vitamin C; there are both types for tomato but
nitrogen fertilizers, especially at high rates, often seem to decrease the concentration of
vitamin C in tomato fruit. However, urea sprays (6 applications on foliage at fortnight
intervals) on field grown tomato “Marglobe” increased vitamin C content from 200 to 240
mg/kg (Varma, 1970) and in sandy soils, fresh fruit vitamin C content was increased with the