Kazumi Maeda

Occurrence and Its Mechanism of Single Stand Emergence by Unshelled-Seed Sowing of Peanut (Arachis hypogaea L.)

In field experiment conducted using dormancy released unshelled-seeds of cv. Chico peanut, ssp. fastigiata, the single stand emergence by apical seed occurred in high percentage. When unshelled-seeds were sown horizontally and dosal suture down and 2 cm in depth without compaction of covered soil, the pods, which contain apical seed cotyledons and rooted basal seed, penetrated above ground. Consequently, apical seeds epicotyl grew alone while basal seed died due to drying. Unshelled-seeds sown 5 cm in depth and covered with packed soil induced similar apical seed emergence, but the pods were at the position initially sown in the soil. The same single stand emergence also occurred by naturally dormancy-broken fruits of large-seeded cultivars in the field, but the pods had moved to the below of crusted soil surface. These results suggest the existence of a mechanism which induces a priority of apical seed in emergence over basal seed by the time lag in natural dormancy breaking within a fruit. Thinner pericarp of the beak of pod will serve it by an easiness to dehisce. This may be a mechanism to control the competition among the individual plants emerged from geocarpic fruits developed closely together around a mother plant under natural growing conditions. Shallow sowing of unshelled-seeds with less soil resistance for emergence seemed to enhance the occurrence of single stand emergence.

Morphological Studies on the Root Nodules of Leguminosae. : III. Peanut (Arachis hypogaea, L.).

Generally, the origin of the root nodule of peanut plant develops in the cortex at the base of the lateral root. According to this investigation, it was found that there was no connection between the location of root nodules and the radiating direction of the protoxylem in the central cylinder of the lateral root. The process of the infection of root nodule bacteria may be divided as follows. (1) Infection through epidermis {root hairs. other epidermal cells.} (2) Infection through broken epidermis {broken epidermis caused by the lateral root. other broken epidermis.}