Abstract
Cool season vegetables such as carrot, garland chrysanthemum, komatsuna, pea, Japanese radish, radish, spinach, turnip and Welsh onion were grown in hydroponics for 4 weeks. The solution temperatures of the three plots were regulated and the solution temperature of one plot was not regulated so as to maintain the solution temperatures to about 15°, 20°, 25° and 30°C. The effects of solution temperatures on root and shoot growth were investigated.
1. The optimum solution temperatures for root elongation varied in plant kinds used. The temperatures at the end of experiment were from 13° to 25°C. The optimum temperatures for spinach (13.3°C) and pea (13.7°C) were the lowest and those for Japanese radish (18.1°C), carrot (19.3°C), komatsuna (19.9°C), Welsh onion (19.9°C), radish (20.2°C) and turnip (20.2°C) were moderate high, and for garland chrysanthemum (24.7°C) was the highest.
2. When root elongation was measured weekly, the optimum temperatures for root elongation in some vegetables had a tendency to decline a little as they grew. Those kinds of plants were spinach, pea, Japanese radish, carrot, Welsh onion, radish and turnip.
3. Estimated optimum temperatures for root elongation calculated from the correlation between the mean solution temperatures and maximum root length varied also in plant kinds used. The values for pea and spinach were the lowest and those for radish, Welsh onion, garland chrysanthemum, komatsuna, Japanese radish and turnip were moderate high, and for carrot was the highest.
4. Increase of root dry weight was also affected by the solution temperatures. The optimum temperatures for root growth at the end of experiment used were from about 13° to 25°C. The values for spinach and pea were the lowest and those for komatsuna, Welsh onion, garland chrysanthemum, radish, turnip and carrot were moderate high, and for Japanese radish was the highest.
5. There was a significant correlation between leaf area and root growth; root fresh weight and maximum root length.
