| Research Abstract |
The growth habit of soybean plants rapidly came to be clear after the proposal of strategy based on Phytomer-concept. The aim of this study is to obtain the fundamental informations of diagnostic characters of soybean growth in terms of the identification of the raceme order(RO).
According to the observation of flowering and shedding in soybean plants(c. v. Tatisuzunari), the percentage of the shedding buds, flowers and pods reached 5, 28 and 66 % respectively. The flower shedding was especially increased by shading of light. The flowering took place in the short duration of 20 days after the initiation stage, however, the shedding lasted for fairly long period, ranging from the stage shortly after flowering initiation to the ripening stage. The following five stages were able to describe the inherent transition of RO : Stage-1, flower shedding in lower RO ; Stage-2, flower shedding in higher RO ; Stage-3, pod shedding in lower RO together with flower shedding in lower RO ; Stage-4, pod
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shedding in higher RO together with flower shedding in higher RO and pod shedding in lower RO ; Stage-5, pod shedding in lower and higher ROs. To examine the relationship among individual ROs, the experiment of flower removal was conducted. The amount of flowers, podding ratio and 100-seeds weight in higher RO was risen by the removal of lower RO right after flowering. Flower removal in lower RO at two weeks after flowering initiation derived increasing flower number and podding ratio in higher RO, therefore the seed weight in this plot reached 82% of that in the control. These results suggest that flowers in higher RO functionated as organs compensating the lack of the sink size in lower RO. The flower removal in higher RO derived rises of podding ratio and seed weight in lower RO, consequently it is suggested that floral organs in lower RO show the compensatory function unless the sink size of higher RO is adequate. It may be also suggested that there existed tight interactions among floral organs in lower RO.
According to the above investigations, it can be described that RO on soybeans is essential mechanism for stability of seed yield. The diagnosis will be enabled by means of observing the state of floral organs at each growth stages. Less
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