浮萍科植物ノ生育ニ對スルモリブデンノ意義

抄録

When Lemnaceae plants are cultured in the nutrient solution containing nitrate as nitrogen source, molybdenum is necessary in a minute concentration for their healthy growth. If this element is omitted, chlorosis and other necrotic symptoms appear. In the case of Spirodela polyrhiza moreover an accumualation of anthocyan happens. The minimum concentration of molybdenum necessary for the growth is 10^-10mol. Molybdenum in the concentration 10^-3mol shows the harmful effects on the plant growth. The pH-value of the nutrient solution decreases to 4, 0 during the culture, when NH₄NO₃ is used as nitrogen source. In a NH₄NO₃-culture lacking in Mo, the plants die in high acidity at last, while in the nutrient solution containing this element in a minute amount the plant growth continues, if not healthy, and after a certain period the pH-value remains unchanged 4, 2. This difference depends upon the fuction of molybdenum, which favours the nitrate assimilation at high acidity. In a Mo-deficient plant body nitrate accumulates in remarkable amount. From this fact it seems protects that molybdenum has to do with the nitrate reduction, and protects the plant from the injury caused by the nitrate accumulation. In Spirodela polythiza and Lemna sp. the Mo-deficiency causes the formation of flower buds. Tungsten shows the similar physislogical function for the Lemnaceae plants as described in the case of molybdenum, but tungsten is required for this purpose in a higher concentration than the latter element.