Internode lengths and other characters were measured with the 33 “Daikoku” type dwarfs, 43 of the other type dwarfs, 22 normal rices and 5 giant rices. Heritability and phenotypic and genetic correlation coefficients were estimated from those data. Then it was attempted to clarify the characteristics of the dwarf rice and the significance of using it in rice-breeding program.
In the rice varieties of late maturity, the panicle initiation is preceded by the beginning of internode elongation with varying degrees. The internodes which elongate after the panicle initiation increase in length from the lower internodes to the upper ones in a geometrical progression. On the contrary, the length of internodes which elongate before the panicle initiation does not show this trend or regularity and remains rather constant. The internode distribution pattern of the former is indicated by the regression coefficient of logarithmic internode length to the node order and is related to other agronomic traits.
The time of onset of nucleic acid syntheses and mitosis have been determined especially in the first leaf meristem of germinating barley seed. These cells in the dormant barley seed remain at G1 and the synchronization of cell division is attained by proceeding them simultaneously to S phase with the seed soaking.
Thirty-three F1 hybrids of rice were examined to discuss the degree of heterosis and its phenomenon. The degree of heterosis was high in grain yield and number of spikelets per panicle. In grain yield 8 of 33 combinations exceeded their higher parent. Norin 22×Araki, which had the highest combining ability, exceeded higher parent by 50%.
The relation between pollen stage and the plantlet formation and the process of embryogenesis from pollen grain were studied by using two varieties of Nicotiana tabacum. Haploid plantlets were induced from immature pollen grains in uninuclear to early binuclear stage and no plantlet was formed in tetrad stage in both varieties. In the process of embryoid fcrmation from immature pollen grain, it was clarified that the vegetative nucleus played the main part of embryogenesis and the generative nucleus rarely divided. Two types of cell division were also observed, one of which had clear cell walls and the other had not. The cause of these phenomena were discussed.
In order to clarify the mode of inheritance of resistance to bacterial wilt disease, gene analysis was performed with fifteen crosses among Japanese domestic, burley and flue-cured tobacco cultivars by the artificial inoculation method using temperature tank. Presence of Rps gene controlling the resistance was made clear, and the existence of polygenes and the close association of resistance with white burley character were inferred. By the combination of these genetic factors, the hereditary phenomena in wilt resistance of domestic cultivars may be approximately explained.