Abstract
To clarlify the role of main stem against the establishment of canopy or the productive structure of dry matter of peanut individuals of two cultivated varieties differing plant type, Chiba shoryu, Spanish type (E) and Chiba handachi, Virginia Bunch type (SP); two treatments, continuous defoliation and excision of main stem apex, were done at the various growth stages under the greenhouse condition. In the peanut plant showing weak or no apical dominance of main stem in early growth stage, branch formation was disturbed in large degree in variety SP, much branched type, than variety E, fewer branched type, by the inhibitory treatments of main stem growth such as the removal of apex or continuous defoliation at the beginning of the development of individual "stem-system". General responses in the vegetative and reproductive growth in the treated plants, especially, the total and each organ's dry matter production and yield of matured fruits, may be shown as the summarized scheme (fig.5). As already reported by the author (1970), the occupying ratio of main stem's leaves in the individual assimilation system at the stage of maximum leaf quantity is very small, compared with that in the early growth stage when the main stem's leaves largely contribute to the growth as the major assimilative organ of the plant. However, with the further progress of canopy growth, the growth of main stem is disturbed by the rapid increasing of lateral branches and their leaves. And the main stem gradually loses the role and becomes "parasitic" due to the fall of its contribution to the individual growth, formation of ineffective flowers in some varieties, and promotion of self-shading. In such a sense, it may be suggested that the main stem of the plant of Virginia type varieties contribute for longer period to the individual dry matter production through the establishment of "stem-system" than the one of Spanish or Valencia type varieties.
