Characteristics of molybdenum absorption and translocation in soybean plants

Investigations on the absorption and translocation of molybdenum (Mo) in soybean plants (Glycine max) grown in the field were conducted, and the following results were obtained.Up to the flower-bud-appearing stage, little absorption of Mo was detected.The Mo accumulation in the nodules may thus be highly dependent on the Mo contained in the seeds during the early growing period, and it can be said that the Mo contained in the seeds may play an important role in the early plant growth and probably in the nitrogen fixation by nodules.After the middle of June, the soybean plants began to absorb soii-Mo, and the Mo concentrations.in all the plant parts increased, especially in the nodules.During the podfilling stage, the Mo concentrations in the roots and pod shells decreased rapidly, whiie, in contrast, that in the seeds Increased.The Mo concentrations in the nodules, stems and leaves did not decrease so much, probably indicating negligible translocation to the seeds from these organs.Soybean seeds collected from various sites in Japan and Brazil were analyzed for their essential micro-elements.The Mo concentrations in the seeds from Hokkaido were very low.The Mo concentrations increased with decreasing geographic latitude of the sites up to the central part of the main island of Japan.However, there was no significant trend in the variation in Mo concentrations in seeds from the southwest of Japan.There was no such trend for Mn, Fe, Cu and Zn.Various soybean seeds having different maturing habits were grown in an experimental field, and the harvested seeds were analyzed for their concentrations of essential micro-elements.The seeds of earlier maturing varieties had lower Mo concentrations, while the late maturing ones had high Mo concentrations.There was no such relationship for Mn, Fe, Cu and Zn.Based on these observations, it is concluded that the Mo concentrations in soybean seeds may depend more on the maturing habits than on the soil conditions, except in cases where the plants are grown in Mo deficient soils.