水稲種子根の培養,とくに糖の種類, 濃度および供給方法が根の生育に及ぼす影響

抄録

The effects of sugar supply on the growth and development of rice root were studied by means of the following two methods for the culture of isolated seminal root provided with scutellum: one was the ordinary "floating culture" in which the whole explant was bathed in the culture solution containing sugar and the inorganic salts of White modified, another was Raggio-Raggio's "bi-media culture" in which the scutellum end of the explant was placed into sugar-containing agar medium and the root portion was bathed in the inorganic salts solution (fig.1). Sugars used were sucrose, D-glucose and D-fructose. Comparing two methods of culture in the growth responses of cultured root to different sugars at various concentrations in medium, the following points were noted. At the first, glucose was the best sugar source for the growth of root in both the culture. Secondly, the optimum concentration of glucose for root growth was distinctly lower in "floating culture" (4 percent) than in "bi-media culture" (7 percent), and the highest concentration of glucose permitting root to grow without any noticeable growth injuries was also lower in the former (4 percent) than in the latter (11 percent). Thirdly, fructose was injurious for root growth even at thc low concentration of 1 percent in "floating culture", while, in "bi-media culture" it supported root growth as well as glucose and sucrose. At the last, the morphological differences were reveald between the root of "floating culture" and that of "bi-media culture" maintaining each on the optimum concentration of glucose. The former, compared with the latter, had dense and developed branching secondary-root as well as thick seminal root, but had sporadic and restrained root hair on root axis. Since these characteristics of the root of "floating culture" in growth responses to sugar and in morphology were considered to be the effects of unnatural manner of sugar feeding, then it might be suggested that "floating culture" was less suitable method of culture for the study of root morphogenesis than "bi-media culture". On the growth responses of cultured root to the concentration of glucose or sucrose in medium, the data obtained in this study led to the conclusion that the higher the sugar concentration, the greater the length and the diameter of the seminal root as well as the density and the total length of the branching secondary-root, if the sugar concentration in medium was below the optimum, irrespective of the method of culture