水稲節間の伸長機構に関する研究 第5報 茎切片を用いた伸長試験法

抄録

In this experiment, a japonica type of rice (Oryza sativa L., cv. "Sasanishiki") was used. 1. Twenty seeds each were sown equal distance on a circumference (10 cm diameter) in Wagner's pots (1/5000 a). They were grown under field conditions. All the tillers were removed every two or three weeks in order to obtain uniformity among the main stems. At the panicle initiation stage, the pots were transfered into the outdoor phytotrons at 25°/20°C (day/night) until harvest. 2. The plants were harvested when the distance between the auricles of the last two leaves (_⊿L in Fig.2) reached 4 to 8 cm. In this boot stage, there was a close relationship between the second internodes (2IN) length and _⊿L (Fig. 1). 3. The harvested shoots were held up to a light in order to identify the node (1N) position through the sheath (2LS). 4. The stem segments (5 cm long) were excised from the bottom of the 2IN. The excised segments included the surrounding leaf sheath (2LS), the 2IN and 1 cm of the top of the third internode (31N) as shown in Fig. 3- (1). Upon excising, all the segments were immersed in a 0.1% sodium hypochlorite solution for 20 seconds, then vigorously cleansed in distilled water several times. 5. Ten segments were placed vertically in glass tubes, each having 5 ml of test solutions containing various concentrations of growth regulators. Ten segments were also placed vertically in the grooves of the rectangular staining jars as shown in Fig. 3- (2). Because of the equal spacing of the grooves in these jars, this approach aided in greater experimental accuracy. And they were incubated for 2 to 3 days at 30°C in either darkness or light. Net changes in the length of 2IN of each segments were measured after the incubation period. 6. It was shown that the growth increment of 2IN by gibberellic acid (y axis) depended on the initial length (age) of the 2IN segments (x axis) as shown in Fig.4. This bioassay will provide helpful information concerning growth regulation of rice internodes.