Abstract
Using hydroponics, we have analyzed the growth and nutrition absorption of three commercial cabbage cultivars (Brassica oleracea L. cv. Kogetsu, Syunrai 500, YR Ryokuhou), under five different concentrations of Hoagland's culture solution (×1/8, 1/2, 1, 2 and 8 in concentration). During the first 20 d after planting, the growth and nitrogen concentration fluctuated against different nutrition levels for all cultivars examined. The most sensitive was 'Syunrai 500' the most tolerant was 'Kogetsu' and moderate was 'YR Ryokuhou.' There were no significant differences in the mineral (P, Mg and K) concentrations among the cultivars. The amount of Ca ion absorbed, however, was lower when plants were cultured under high nutrition conditions, and the optimum concentration which yielded the highest amount of Ca in a plant was different among the cultivars. Root development, length and unit fresh weight (g m^<-1>), was also influenced by the concentration of culture solution. To delineate closely the root system of each cultivar, we observed underground distribution patterns of roots in a specially equipped "root box." The roots of 'Kogetsu' were well developed, while those of 'Syunrai 500' and 'YR Ryokuhou' were very poor and moderate, respectively. The characteristics for growth and nutrition absorption of cultivars is discussed in connection with development of root systems.
