Lettuce, spinach, cabbage, chinese cabbage (pe-tsai), celery, seri (
Oenanthe javanica DC.), garland chrysanthemum, and japanese honewort (
Cryptotaenia japonica Hassk.) were grown in solution culture in order to compare their growth and accumulation of ammonium-and nitrate-nitrogen, using NO
3, NO
3+NH
4 (1:1), NH
4, NO
3+NO
2 (1:1), and NO
2 as nitrogen sources. The experiment consisted of 4 kinds of treatment conditions where 2 levels of nitrogen concn (2meq/
l designated as low-N and 12meq/
l as high-N) and 2 levels of solution pH (5 and 7) were combined. Plants were grown under different treatments for about 3 weeks.
1. When plants were supplied with NO
3, the growth of vegetables, in general, was excellent and plants showed normal appearance with healthy leaves except seri which showed somewhat yellowish-green color leaves.
2. In general, leaf vegetables fertilized with NO
3+NH
4 grew well under all treatment conditions. Plant growth of the NO
3+NH
4 treatment was almost equal to, or better than that of the NO
3 treatment. In seri, especially, the growth of NO
3+NH
4 treated plants was sometimes 30 to 40% better than that of NO
3 treated plants.
3. In comparison with NO
3, the growth of spinach and chinese cabbage was most markedly inhibited with NH
4, and cabbage also showed restricted growth in NH
4. However, the growth inhibition in seri and lettuce was little. When plants were cultured with NH
4, a relatively close relationship was observed between growth response and leaf NH
4-N concn, i.e., low NH
4-N concn was detected in leaves of healthy plants, and high NH
4-N concn was detected in leaves of injured plants.
4. Under NO
3+NO
2 or NO
2 nutrition, seri and lettuce showed the most marked growth reduction of all the leaf vegetables. But the tolerance of garland chrysanthemum and celery to NO
2 seemed to be relatively high. They showed about 80% of the growth of the NO
3 plants under low-N treatment.
5. When plants were cultured with NO
3 nutrition, concn of NO
3-N in leaves of tested plants varied with plant species. Even under low-N treatment, concn of NO
3-N in leaves of seri, celery, lettuce, and chinese cabbage was higher than 1.0% on a dry weight basis. Under high-N treatment, concn of NO
3-N in leaves of tested plants was also high and, in general, was higher than 1.2%. In particular, that of celery and chinese cabbage was over 2.0% on a dry weight basis.
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