Japanese Journal of Tropical Agriculture

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The effects of gibberellin A₃ on the leaf sheath elongation of the floating rice, var. Co. 64 and the non-floating rice, var. Puka Sula Ponean, Norm No. 22 and Tanginbouzu were compared. The effect of submerging treatment on the growth of the shoots and on the amounts of endogenous gibberellin-like substances was also examined in both types of rice plants under the ordinary and the submerged conditions.
The results obtained were as follows:
1) Application of gibberellin A3 markedly stimulated the leaf sheath elongation in all rice seedlings. The promotion was more striking in the non-floating rices than in the floating rice.
2) Under the ordinary condition the plant height and fresh weight of the shoot in the floating rice plants were larger than those in the non-floating rice plants. Under the submerged condition the elongation of the shoot was promoted in both types of rice plants. The promotion in the floating rice plants was more remarkable than that in the non-floating rice plants.
3) In both types of rice plants, gibberellin-like substances active for the rice seedling test and the rice endosperm test were found at Rf 0.17-0.30 and Rf 0.40-0.55, respectively, on the chromatogram with ammonical iso-propanol. Amount of the former in the floating rice plant was larger than those in the non-floating rice plants, and increased by submerging treatment. The amount of the latter in the floating rice plant is also larger than that in the non-floating rice plants under both ordinary and submerged conditions
4) The above results suggest that the growth habit of the floating rice plant may be in parts ascribed to larger amounts of gibberellin-like substances in its tissue.

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1) With the seeds and plants of Paraguay origin and those collected or raised at Izu, studies on the propagation of Stevia rebaudiana were carried out.
2) The seeds collected at Izu showed germination of 50-86%; on the other hand, germination of a sample of Paraguay seeds was 30%. In each case, the seed tended to germinate regularly during a short period.
3) Reproduction by tip cutting was also recognized to be very successful.

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1) With the plants introduced from Paraguay and those raised at Izu from the seeds of Paraguay origin, studies on the growth and stevioside content of Stevia rebaudiana were carried out.
2) Although the plant showed active growth under relatively high temperature conditions, it also tended to considerably be resistant to cold, and seemed to winter over in warmer districts with seldom frost even in Japan.
3) Stevioside was found to be richest in the leaves, and very little in the stem. About 6% of stevioside was seen in the leaves harvested at Izu, whereas a leaf sample of Paraguay origin showed 7.6% stevioside.

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