Abstract
Following the study reported in the first paper of this series, some observations were made on the flower-bud differentiation, flowering and fruiting of “Issun” broad bean (a large seeded variety) at the Awa Branch of Chiba Agricultural Experiment Station in 1955-56.
The first sign of flower-bud differentiation was observed in middle November, 38 days after the planting or 15-20 days after the average daily temperature failed below 15°C. The plants had two or more fully developed leaves at that time. Although, as a rule, flower buds were observed earlier on the branches developed in early stage, they were slightly retarded on the main stems and the first laterals.
Once differentiated, flower buds developed rapidly and formed pollen mother cells in the end of December. Then they suspended their development during the winter till the end of February, when they resumed their active growth to blooming.
While the first blooming occurred on the third branch, the largest number of flowers and pods were obtained on the sixth branch. When branches were thinned to six per plant, the blooming was accelerated and numbers of flowers and pods were increased on the remaining branches.
This fact seemed to show that there was a competition for nutrients among the branches. Relatively low productivity of the branches developed earlier was due to their susceptibility to winter injury. High productivity of the branches of rather higher orders seemed to owe to the fact that they developed when the internal conditions were most favorable and took dominance over the other branches.
