The effect of some factors on the content of nitrate and nitrite in lettuce leaves grown with the nutrient film
technique. II. Effect of light and growth regulators in conditions of NPK fertilization discontinued before
J. Myczkowski*, S. Rożek*, W. Sady**, T. Wojtaszek**
**Chair of Plant Physiology
**Institute of Vegetables and Ornamental Plants
**Faculty of Horticulture, Agricultural University
**29 Listopada 54, 31-425 Kraków, Poland
The investigation concerned the complex effect of light conditions, growth
regulators, and NPK fertilization discontinued before harvesting, on the
content of nitrates and nitrites in greenhouse lettuce leaves.
A comparison of the results with data from the first part of the work, in which the NPK fertilization
was applied throughout the vegetation period, allowed the effect of
modified fertilization on the investigated nitrate metabolism and yields
of plants to be determined.
It was shown that discontinuance of NPK fertilization considerably reduced the content of
nitrates, which on the day of harvesting varied from 5.5-21.5 mg g-1
dry weight of lettuce leaves. The effect of the modified fertilization
distinctly dominated over that of growth regulators and light conditions.
During the growth and development of plants there appeared a tendency to
an inhibited activity of nitrite reductase and a considerable variation in
the content of nitrites in the lettuce leaves. Yields of lettuce were not reduced.
Myczkowski J., Rożek S., Sady W., Wojtaszek T., 1990. The effect of some factors on
the content of nitrate and nitrite in lettuce leaves grown with the
nutrient film technique. II. Effect of light and growth regulators in
conditions of NPK fertilization discontinued before harvest. Folia Horticulturae II/1: 7-16.