Abstract
The purpose of this study was to grope the hormonal requirements for the differentiation of complete plantlet from hypocotyl and hypocotyl callus of Cucumis sativus L.cv. 'Shinko Fushinari No.10'. At first, segments of hypocotyl (1 cm) in young seedling were inoculated on the agar media (MURASHIGE & SKooG's basal medium) with various combinations of auxin (NAA) and cytokinin (BA) concentration. Subsequently, half of the cultures were untouchedly cultured on the same media, not transferring hypocotyl callus to another medium. The callus formed from other half hypocotyl were transferred to another media, that is two kinds of media with 1.0ppm BA alone and in the absence of NAA and BA, being di-vided into the small mass the size of an adzuki bean. Callus formation from hypocotyl required alternative or both addition of auxin and cytokinin at O.1ppm or higher levels of concentration, although callus was favourably fcrmed for the most part. Root formation was observed at the media with the combination of O-10.0ppm NAA and O-1.0ppm BA and the ratio of root formation generally increased as BA concentration becomed lower. On the other hand, shoot formation was observed at a low frequency on the media with BA concentration either higher than or equal with NAA concentration, that is, with the combination of O-1.0ppm NAA and 1.0ppm BA. However, only a few of the shoots continued to develop and one complete plantlet was finally obtained at the medium with O.O1ppm NAA and 1.Oppm BA. Shoot formation from the transferred callus was observed at a low frequency only when calluses produced on the medla wlth the combinatron of O.O1-1Oppm NAA and 1.Oppm BA were transferred to the two kinds of media for redifferentiation. It appeared from this result, as lettuce and tomato, that whether shoot was formed from callus or not was destined by the relative concentration between auxin and cytokinin in the medium for callus induction. Complete plantlets were obtained at a low frequency on the meium in the absence of NAA and BA. Root formation was Observed only when shoot vv-as L0rmed on the media in the absence of NAA and BA.
